Quick update
So I went to track tonight for some more test and tune. Really to gather more data on how far I can push the launch with the tbrake to try and hit a new pb tonight.

I did some static testing in the pits to see how high boost level I could potentially launch at using the fake tbrake, launch control and spool shot to build boost while the tbrake and launch control is active. With the launch control rpm at only 3500 rpm and with the spool shot activated prior to launch, say roughly 5 to 6 tenths and 160psi tank pressure, and the gtx3576 .82 churbo, I was able to build nearly 30psi just sitting there before I let off the gas.

Im just using crude bleed type boost control, so that is going to have to go in favor of more computer control of boost at launch and down track. So with the knowledge of that static test and seeing how much boost I could potentially launch at, I knew I had a lot left on the table in so far as 60' was concerned, and that directly correlates to quicker et.'s. I also knew there is no way these stock axles would hold a 30psi launch. I would have to test with somewhat less than that, but more than what I launched with when I ran the 6.56 et. in order to improve on that time.

SSSSoooo..... On my first pass I tried to time the spool shot to where I could launch at roughly 15 psi. I overshot that by a few psi apparently and left at almost 19psi according to the log. Both axles let go immediately after launch lol..... I am going to have to address the axles and rear setup in order to go quicker. Im leaning towards insane axles as thats the easy button, but may be best to bite the bullet and swap the whole deal. Just getting axles may just push the weak link downstream a bit. Gonna call insane axles next week and think on it a bit.

I will say the stock axles have done ok to recent. It looks like they have a hard limit of mid 6.50s in the 1/8th with an automatic transmission, would be slower than that with a manual Im sure. Anyone on here know if anyone has gone quicker with stock axles and rear?

Yes, replacing axles will push the weak link to somewhere else. The question is where, and does that weak link fall within your output.

I would have thought the auto would be kinder to axles/transmissions generally, compared to a manual?

yes the automatic would generally be more gentle due to the cushioning effect of the converter. When I wrote lower, I meant slower. skipped the s LOL. edited original to correct

Lower/Slower works either way :) Sorry to hear about your axles.

No worries. It was inevitable that this would have to be addressed sooner or later.

I'm actually anxious to make a decision on how to proceed and get this junk back together soon as possible for further testing of tbrake and launch setup with high boost.
I fully expect to immediately pick up at least a tenth, more likely two tenths, in the 1/8th when/if I can launch at 20-25 psi and have it hold together and hook. I think this may be the last piece of the puzzle to eventually reach my ultimate goal of 6.30s in the 1/8th I had originally planned for this junk.

I would really like to do a narrowed solid axle and 4 link setup, but doubt that will happen. I will have more information after I speak with the insane axles folks. However even if after speaking with them and if they say their axles will hold up I'm still concerned about the differential. I never wheel hop and if it does break traction and spin, its still smooth and doesnt hop, so I hope that can preserve the diff. If the insane axle folks say they will hold I'll likely try them just to get back together and test at track asap. The other alternative will take a fair amount of time and money.

It would be great if someone could chime in who has actually actually tested those axles at a drag strip to see what they are capable of in the real world.

Just ordered a set of Insane Shafts 500hp axles. Sure hope I didnt just throw away $700.. Insane shafts has mixed reviews so that concerns me a bit. However a fellow who owns valiants racing locally says he uses them on his s2000 he races and he is happy with them, so I figured I would pull the trigger.

Hopefully these axles will hold up well enough to launch with at least 15psi. I have a modification to my spool shot system I plan to try that should allow me to quickly come up on my launch control rpm when on the tbrake and have an adjustable boost level to use for launch. Even with the insane axles I'll likely limit boost at launch to maybe 15-17 psi, unless they hold that level well enough over time that I get confident I can add more.

Static testing of the tbrake at the track indicates I can launch at around 30psi if I can get a driveline to hold it. Sooo... I may change my mind on not doing a 4 link solid axle. I hate to spend the money and effort, but that would make this a pretty gnarly ride for what it is. If I could launch at 30psi that should put wheels in the air a bit.:)

https://cimg1.ibsrv.net/gimg/www.mia...dd464dc416.jpg

Three broken axles.. All broke on the mid shaft. Top two broke on diff side immediately at launch testing tbrake and launch control. I was trying to leave off tbrake what was apparently almost 19psi according to log.
Bottom one broke on wheel side while carrying a passenger at the track but launching as I usually had done prior with no problems.

When Insane axles come in Ill take measurements and compare.

The insane shaft axles showed yesterday. I also had time to install, which I did.
I measured the middle of the mid shaft of both the insane axles and stock. The Insane axle were .965" whereas the stock were .954" best i could tell. The insane shafts dont neck down nearly as much in the boot area so definitely a little thicker there, but I couldn't measure due to boot. So most of the strength difference would have to be in the materials rather than size. The Insane shafts are supposed to be chromemoly, not sure on stock.

A new setup I am also testing is incorporating the spool shot system to be able to fire on the launch control and tbrake setup to get up on the staging rpm and boost level quickly. I am using the speedyefi ecu to control it. However Im using the nitrous map settings to control the spool solenoid for launch control. I have yet to use the nitrous at the track and now that I am breaking driveline parts not sure if I ever would. So I took off the nitrous setup to free up that map in order to control the spool solenoid. The car has already trapped at darn near 110mph in the 1/8th, so I think it makes enough power to reach my goal without it anyways.
I did a couple street tests on that system. Even took video of it if yall are interested. The setup works well, just need to do more testing and tuning with it a bit as it overshoots my target launch boost level a bit. The target boost level should be tunable now, but Im trying to keep launch boost below about 14-15psi until Im confident these new axles will hold more.

FWIW, I am measuring .965" on my MSM axles.
The MSM's are documented to be stronger on the diff side, but I see you are mainly breaking them on the wheel side.
It would be interesting to know if the MSM axle necks down less than the standard axle on the wheel side.

edit. Just took another look at the car, and the MSM axle appears to get thicker approaching the boot on the wheel side. Is this the case for the standard axle?
https://cimg8.ibsrv.net/gimg/www.mia...7b1f7b1c88.jpg

I have the stock axles pictured above in post 127. You can see where they neck down. That is used as an outer locating shoulder for the boot, then another raised shoulder for the inside of the boot, then necking down again for remainder of the axle. The raised portion you are showing may be the outer locating shoulder for the boot. I assume the msm and regular axles are the same material? I believe the stock axles are 1040 whereas the Insane shafts are supposedly 4340. So any real strength advantage (should they be believed) would be due to material rather than that minor difference in size. However Im not that confident on these shafts to really push them to the maximum I can now launch at, likely will try to keep launch under 15 psi so I can re-sell them later if I dont break them. I am planning to doing a rear swap later, just need to decide what direction to go.

Hello Fellows. I went to the track last friday on tnt night to test these insane shafts axles. I had a buddy with me as a passenger and it was a hot day so knew would be no pb's. Was really just for axle testing. Good news is looks like these axles may hold a pretty decent launch, should be better than the stock axles in my opinion so far. Bad news is now that I have launch control, pre-spool for launch and fake tbrake, it looks like i may be uncovering the fuel pump pickup if fuel level gets down to about 3/8th of a tank or below. I went to track with about 1/2 tank of fuel and made 7 passes, each getting a little more aggressive on launch. Once I started to leave with higher boost I experienced significant power loss immediately after launch with simultaneous very lean condition. My best pass of the night was a 6.63 1/8th mile with a passenger. That was i think my third pass. I attached a couple dragy screenshots for the 0-60mph data on a couple passes that clearly shows the dip in the g forces after the launch when the fuel sloshes to the back of the tank. the 2.66 0-60 shot was from my 6.63 pass. You can see the dip in g force from fuel pressure loss after the launch on that run, but it recovered pretty quickly and still ran ok for the conditions and a passenger. The other screen shot is from a pass a little later in the day when fuel level was slightly lower and I left with more boost and launched much more aggressively. The fuel slosh issue was very bad on that pass and can clearly be seen in the attached 0-60 g force data. On that pass It launched hard and then almost died, and was very slow to recover.

The solution to correct is either going to be better baffling in the tank and being sure to have more fuel in the car, Switching to a fuel cell or adding a surge tank, Or something I just came across that appears very interesting. It is called "hydramat" and is made by holley. I will likely go with additional baffling initially. I looked into the tank again and have some ideas on how I want to baffle it for drag racing. However if that doesnt produce the result I need I may go with the hydramat. I think I want to keep the stock tank and dont really want to change to a fuel cell or add surge tank setup, so I think one of those prior two solutions will be my best option.
https://cimg8.ibsrv.net/gimg/www.mia...4cbe9efeaf.png
https://cimg0.ibsrv.net/gimg/www.mia...63bc3a9c9f.png

Hydramat has been covered on here, From (bad) memory, expensive and some other draw back I can't remember. Search is your friend ...

Yep. You are right. It has been covered on here apparently, and is pricey. I've run rear sump fuel cells and external pumps in the past when I drag raced in the late 80s through early 90s but never heard of hydramat before though so thought I would mention it. I suppose it was a development after I got out of racing first time around. I just recently saw a video of hydramat in action and was impressed with it. I didnt notice at the time of my earlier post the date on the video LOL....

Just read your entire thread, great stuff with the compressed air spool!
Love DIY experimentation, even better when you have data to back up the changes.

Your car has to be one of the quicker stock rear suspension miatas out there at the strip?

Thanks! It does ok for what it is.

I'm not sure if its quickest stock rear or not. I haven't seen one quicker, but that doesn't mean someone hasn't gone quicker. Would be interesting if one has gone quicker with stock rear and could post it up!

I love this idea, been musing about it for weeks
 

It's a great idea but I was wondering to myself though, what about a half butterfly like the VICS system, but between the turbo and manifold flanges. Ecu operated servo controlled gas velocity adjustment to make up for the lack of exhaust gas volume. If it worked in conjunction with an exhaust cut out you could coax those extra psi. Especially if you got an oversized manifold and an adapter to a smaller turbo and adjusted the cam sprockets to take away overlap. Before I stumbled upon this I was hoping to one day try and set variable cam timing, variable intake, and an exhaust cut out to be run by the ecu to maximize an na motors potential. If all that and a variable exhaust gas velocity system were used in conjunction with an oversized turbo every thing could be adjusted on the fly by the ecu to chase spool in the low rpms and peak power in the high rpms. Garage 4age has some awesome videos of a non bp dohc motor being dyno'd with many possible mods combo'd and altered.

The first part of your statement you are basically describing a quick spool valve. They tend to work best with a divided housing. Some people have good results with them, others, not so much. My friend that goes down the track with me occasionally owns a turbo lancer on which he ran a quick spool valve for a while. He wound up taking his off as it didn't work as well as anticipated for him.

Well went to the track last night to attempt to get a new personal best with this junk. Broke one of these insane shaft axles on the first pass. Crap!!!
Guess I got a little greedy on the launch LOl.... Apparently a transbrake, and lots of boost at the launch is just too much for these puny parts, who would have thought... Oh well. We will now test their warranty to see if I can get a replacement axle. Doubtful, but we will see. I will report back what they decide to do. In the meantime I will pop a stock axle back in for now while I figure out whats next for this pile.

Last two pages of this thread have massive carnage occurring in the driveline...
It looks like the damage started up after you solved your spark issues and changed from a 4.1 to a 4.3
So, you slightly improved power and changed gearing (which increased torque on the drive line parts).
I'd change BACK to the 4.1 or lower if I wanted to stay with the IRS.
What RPM are you running at the finish line in what gear?

Want to go faster? a solid rear axle is in your future...
If you fix the issue with the axles then something else will end up failing.
What are you using for a drive shaft? I'd worry about it.
Are you already running drive shaft and 1/2 shaft "loops"?
You should. You're breaking them!
At some point (ET) those pieces are a requirement at most dragstrips.
I think you're there already.

You're turning into Pat you know. This is not a bad thing.
Where I'd have fun with that car is on the street. Some wannabe pulls up next to you at a light in a brand-new Vette/Lambo/Ferrari and gets his lunch eaten by what looks like a crap box Miata.
That would be fun!
Even better if his significant other is sitting in the right seat...

Hey Ninja

Yeah the 4:30 has a little more torque multiplication than the 4:10s for sure. However the carnage really stepped up after doing a tbrake and launch control to try and leave with significant boost. Its just too much of a shock for these axles. I've switched between these two ratios in the past with no breakage, but I was foot braking before which was much less an initial hit.

I would have to go back and look at some logs to see exactly what rpm I cross the line at with both gears. I cross near the top of 3rd gear rpm wise, the 4;10 may be a couple hundred lower, but either is a pretty good ratio for me at the track.

I am required to have a safety loop for the driveshaft, actually any car on slicks is supposed to have that.

I've been debating going a narrowed solid axle, and may in the future. My friend with the drag barretta has really been pushing me in that direction. He even offers help as he does professional level fabrication. If I do all that i would likely do a turbo smallbock or an turbo ls engine.

I'm trying to figure a cheap/easy way out to keep me from going to deep into this thing. If I do the above the cheap part will be out the window LOL, but it will be much, much faster.

I generally won't race this on the street, except at my test spot. I actually did race a cammed ls truck and an older zrx1100 there. Beat them both.

My wife wouldnt be caught dead in this junk LOL...

Maybe check that the cv axles were perfectly straight and level between the diff and hubs at launch. They are supposedly strongest during the times when the joints are straight. But then again, you aren't breaking the joints.

Yep breaking the actual shafts. Never had a problem the joints. I attached a pic of the broken insane shaft. I just emailed them pics and a return form. Lets see if they warranty.
https://cimg3.ibsrv.net/gimg/www.mia...d7d51d5413.jpg

I'm investigating potentially using two left side 88-91 929 axles with early 1.8 stubs with spacers between the stub and axle. I will have to source some na fc rx7 hubs as well apparently.

It looks like using 929 axles and spacers is an upgrade in the rx7 community, maybe even over the turbo axles. https://silhouettepower.com/collecti...37073959911588

Just to catch y'all up on axle conundrum.

Still haven't heard back from the insane shafts folks. I've emailed them a couple times their rma form, sales receipt and pics of broken axle, no reply yet. I've also called and left a voicemail, no reply to that either.

The currently car has 1 stock, 1 insane axle. If I do get a replacement from them I will be selling the Insane shaft axles. I do feel they were stronger, just not enough so for what I'm trying to do.

So moving on to improving them. I got in a couple left side 929 axles. Now those puppies are looking strong! The axle shaft is 28mm as does not neck down anywhere, even going into the cv race. In fact I pulled off one of the boots to have a look into the cv joint. the axle actually steps up larger to go into the cv race. The cv joint are also significantly larger. Since I have so many broken shafts and a broken insane shaft I can look into where the boot areas would be and measure the areas where those axles step down to measure the minimum diameters since that is where they've been breaking. The stock axles neck down to about 22mm, the insane shaft necks down to about 23mm. The 929 axle is 28mm minimum. So if I can pull this off with as minimum expense as possible I should be a huge upgrade.

Now for the challenge. These axles use an rx7 style stub shaft. No biggie, I just picked those up along with a rx7 carrier and axles for $100 from a cool sort of local fellow.
These axles are too short by about 3/4" or so. Also the centering ring on the 929 axle is a little larger than needed to fit into the rx7 stubs. Im assuming the spacer made by sillouettepower accounts for that. I emailed them to confirm before I order but no reply as of yet. there is a chance a may have to spin my own spacers. Not a huge deal though. I can figure that part out if need be. The good thing about swapping to these axles is I can swap to a turbo 2 style diff and carrier later if need be, the outboard stuff will be done.

Also these require a 28 spline rx7 style hub. This is where it gets interesting. I emailed Martin at monster miata asking him about possibly broaching some miata hubs with the 28 spline rx7 style spline. That guy actually took the time to pick up the phone and call me if you can believe that! Talk about customer service!! Well it turns out he actually has those on the shelf. So I ordered two. If I decide to move forward on any other swaps to the rear, he will be the first one I check in with before spending any big bucks.

Below is a pic of the size difference of the 929 axle vs the insane axle. The insane axle is slightly larger than the stock axle as well, though just barely. Howevre notice the difference in the size of the outer cv! stock is on the right.
https://cimg3.ibsrv.net/gimg/www.mia...6672676171.jpg

No clue where your alignment is at currently, but I wonder how much of that you would be able to make up just by setting all of the eccentrics to pull the control arms to maximum inboard position.

Not nearly enough.
In fact I had to extend the top arms to get positive camber so tires will be flat at launch. Also I'm still gathering parts and taking measurements. It could need as much as an inch spacer. Also need to adapt to different centering dimensions since I'm using the na rx7 stubs as opposed to the t2 stubs., that can be accomplished in the spacer as well. The t2 stubs would have the same centering dimensions as the 929 axles. Good chance I will order two 5" x 1" aluminum lathe stock and make them. Cheap and easy enough.

The new fuse will likely be the stubs, differential or driveshaft joints. After looking at these axles I find it extremely unlikely the axle will break before those other things. If I start breaking stubs or differential I'll address going to t2 diff or something else.. I'm only looking to pick up a couple tenths though, so hopefully those fuses don't blow before then.

Lots more axle info:
So I got the spacers made, larger 28 spline hubs and everything needed to convert to 929 axles
https://cimg1.ibsrv.net/gimg/www.mia...15b8576997.jpg

I installed them in the car and took for a rip. I noticed a slight vibration at heavy load so jacked up car and ran on jackstands to observe if spacers were machined true and center, they were not as evidenced in video clip Dang it!! If its not one thing its another LOl...
Time to regroup a bit.
Since I now have 28 spline hubs I can no longer use miata axles, but fc rx7 axles bolt right in, so that's what's on the car now. I also have a couple spare rx7 axles too. I have a lot of measurements of various axles I have on hand in pics below. It looks as rx7 axles are potentially a little stronger than miata axles as evidenced in pics. The miata axles neck down to ~22mm inside the boot areas going into the cv joints. The rx7 axles look to be between 24-25 in the boot area going into cv so the shaft should be a little stronger. I have been breaking the miata axles in the narrower area where it necks down. The rx7 cv joints are larger as well so the cv joints should be stronger too. However I have yet to fail a cv joint, just the axle shafts themselves.. Hopefully these rx7 axles will get me by while I decide if I want to remake the spacers to use the 929 axles with the miata diff or just save the 929 axles for when I do a ford 8.8 conversion or for a turbo2 differential setup to use them with. Apparently the 929 axles are stronger than the turbo2 axles according to sillouettepower.
https://cimg3.ibsrv.net/gimg/www.mia...e130f1c75c.jpg

Below are pics of the 929 axles and measurements
https://cimg9.ibsrv.net/gimg/www.mia...59fdde8c15.jpg
https://cimg1.ibsrv.net/gimg/www.mia...f35b411e5b.jpg
https://cimg3.ibsrv.net/gimg/www.mia...808137d58c.jpg
https://cimg5.ibsrv.net/gimg/www.mia...d5f8a90ac0.jpg
https://cimg7.ibsrv.net/gimg/www.mia...27ebe87b7b.jpg



Below is pic of 929 spline size vs miata (I removed the sensor ring for install as it interfered with spindle)
https://cimg5.ibsrv.net/gimg/www.mia...f4cfdbf168.jpg




Below are miata axles
https://cimg7.ibsrv.net/gimg/www.mia...eb4b846686.jpg
https://cimg9.ibsrv.net/gimg/www.mia...c43992b06f.jpg
https://cimg1.ibsrv.net/gimg/www.mia...56a064d2e6.jpg
https://cimg2.ibsrv.net/gimg/www.mia...de913d668b.jpg
https://cimg1.ibsrv.net/gimg/www.mia...ffb38e174f.jpg




Below are fc rx7 axles
https://cimg7.ibsrv.net/gimg/www.mia...d0edb00264.jpg
https://cimg9.ibsrv.net/gimg/www.mia...d55491c523.jpg
https://cimg1.ibsrv.net/gimg/www.mia...d160128187.jpg
https://cimg4.ibsrv.net/gimg/www.mia...369db7fb97.jpg
https://cimg6.ibsrv.net/gimg/www.mia...5e9c87fd73.jpg


I am hoping to have everything in hand to do a 8.8 swap or t2 swap by the end of the year to get it done while track is shut down. I really want to start testing using some nitrous at the track, but the weak driveline has been stopping me. Hopefully that will be corrected beginning of the year as well as some weight reduction. Should get some pretty solid passes in if can lose a couple hundred lbs, stronger rear and spraying 50-100hp worth n2o eventually.

I would just like to start this off with HOLY COW. I have an NB Miata with an auto and there is hardly any information online about auto Miata's with turbos. I've been trying to gauge how i could do it for so long and you sir have been a godsend. After spending the last 30 minutes of this reading i do have to ask. What are you using for engine management? I may have missed it in one of the posts but I absolutely want to go this direction. I also wanted to know how you felt about the auto that came in the NB miatas (Aisin 03-70le i believe). Thank you for all the help : )

I am using a "fishdog" from speedyefi. It uses an ua4c board made by wmtronics.

The transmissions I run are the early jatcos. I have never been into an aisin transmission so cant help you much there. Pat ran that transmission for a while before switching to a c4 so you may want to ask his thoughts.

I have heard a lot about this pat person but have yet to find a way to contact him. Could you point me in the right direction? Also that's awesome information about that ECU. If I'm not incorrect, you are using the transmission that came in NA miata automatics. From what ive heard those are controlled by a unit in the stock ecu and are not a separate module. Does the Speedyefi control the transmission in your build?

PS: Sorry if these questions are stupid im still learning about miata autos haha

Just send him a private message through this forum or ask a question on one of his threads. He will respond to you eventually. I know he ran the Aisin transmission before swapping to a c4, but was not happy with it. However he did not really pursue building it up either. He just stepped up to a big boy transmission.

The transmissions I run are very heavily modified throughout and are basically manualized, so mostly don't rely on ecu for shifting. I shift manually all but first to second shift. I do use an ecu map to control first to second solenoid, but all else is manual in so far as shifting gears goes. I only use first gear at the track and on slicks. Street driving is all manual shifting no ecu control.

The na miata 94-97 use the factory ecu and a tcu for transmission control, but I believe the ones prior to 94 are all hydraulic with the exception of the lock up solenoid which is controlled by the ecu. You could use one of those transmission and use a simple switch for lock up in 4th gear. Its not rocket science, but automatics are complex and do require you study up if you plan on building one successfully.

I dont know what you are trying to achieve, but your stock automatic may hold 250hp or so as it is. That is if its in good shape and you don't cook it.

Don't expect to duplicate my results though unless you really know what you're doing in so far as going into the transmission.

Being fully honest i didnt think putting a turbo on an auto Miata was possible. Every time I asked in a forum places people just told me "manual swap it". Which yes this is the easier route, but personally I have to drive my car in stop and go traffic ALOT and dont want to destroy my left foot LOL. And i appologize for not explaining it better, i mostly was excited to see hope. My goal is nothing crazy as its my daily. Its a 2003 NB Miata with an auto and I want to put a turbo on it to run at a max 200 wheel hp. To start i dont even want to go that crazy. But i guess talking with you was my first step in learning about miata autos as there is so little information present online. I'm not trying to duplicate the spooling system you have, for now I just want to go with a basic automatic turbo Miata. I know a lot about engines but little to nothing about how transmissions work. I should probably start by learning that LOL. If I do have questions would you be willing to answer some? You seem like an amazingly experienced mechanic that I could learn lots from :) If not I understand completely people have lives to life :P

If you are only looking for 200hp and your engine and tranny in good shape I would just go for it with what you have personally. For easy management you could run an aftermarket ecu in parallel with factory setup. You could use the aftermarket ecu for fuel and ignition and factory for everything else

@Kango , you are looking for @patsmx5 .

IIRC, there is a modulator (externally accessed part) from another transmission that allows the Mazda automatic to hold more torque.

DNM

Hey Dnm. Thanks for linking right to Pat. I didnt think to do that. I assumed he had already been to some of Pats' threads.

Are you referring to a vacuum modulator? I dont think his tranny uses a vacuum modulator. I could be wrong since I've never personally laid hands on one of these things.
However, I did look up the tranny used for the 2001-2005 miatas. It looks like it uses a throttle cable for pressure control. That can be adjusted slightly for more pressure but at the expense of harsher shifting when just putzing around. At his projected power level i wouldnt bother doing anything to the transmission. It should be fine if its in good shape.
If the info and schematics I found are correct I see a couple positives and negatives if wanting to build this transmission for something more serious, Like 400- 500hp.
It does use 4 pinion planets, which should be ok for 400 or so. The valve body uses separator plate with orifices that can be modified for faster filling and draining of the packs for faster shifting. However the issue I see is that it would not be easy to add to clutch frictions and steels count in any of the packs. It doesnt look to use cushion plates which can be removed to make room in the packs for more frictions and the retaining plates dont look thick enough to do a lot of machining to make room. I suppose if you could locate some thinner steels and adjust pack clearance by slightly machining retaining plates it might be doable?? Again, since I havent seen or been into one of these in person, take the above with a grain of salt lol... I could be wrong.
Probably best though if one is considering bigger power with this tranny to just follow Pats lead and look elsewhere.

https://cimg6.ibsrv.net/gimg/www.mia...fb2ea9f040.jpg


Well snap!! All this transmission talk last few post jinxed me LOL..... Glad I found this before it totally let go. This thing lives right by my leg. I should really get a blanket on this thing.

Direct drum developed a crack. Most likely started on one of my trips at the dragstrip trying to launch at high boost with the transbrake and launch control when the axles started breaking. Once the crack started it likely just propagated from there. Looks like I will be foot braking this as before until I decide how I want to proceed. Car ran a best of 6.57 at 108 and change foot braking, but not much left on the table to get off the line harder. With the transbrake I feel I had some performance left to be tapped into, but the driveline parts just couldn't handle the shock of the instant hit of power application. For now the tranny is repaired and back in the car. All is well again.

However I have some decisions to make. Should I keep everything as is and try to be satisfied with a best transbrake run (so far) of 6.56 at 109.8 (not likely I can control myself lol)? Should I sell it and move on to the next one? Keep the miata engine and swap out driveline for stronger stuff?

Sad thing is years ago before I swapped out the 5 speed to the jatco I had a c4 I built up and planned on going with. I also had the jatco to use for the bellhousing. When I opened up the jatco I noticed the clutches and drums were very similar sized, so I thought to myself, Self you can build this puppy up for the easy button, which I did. I then sold the c4 when it looked like the jatco will hold. The jatco did well for years until I recently decided to go crazy with a transbrake setup looking for more.

However the main issue with the jatco is there is no aftermarket support for stronger hard parts,, whereas the c4 is still supported. The jatco you are stuck using factory hard parts. The jatco may hold ~500ish hp for a couple years though if modded but with no transbrake. I've never dynoed my car nor do I care to, but wallace race calculator has me between 520-530hp based off best 1/8th mile trap and est weight. I would think the jatco would live a pretty long life if built similar, but at a lower hp level, say maybe 400ish, in case anyone else out there is eyeing these things for their projects.

The problem with the c4 is build-able cores are getting a little harder to find locally. If I keep the miata and the bp engine I will most likely wind up using a c4 and ford rear, but not 100% sure I wont swap everything in the future, including the engine.

Or go on a drastic weight reduction endeavor with the miata and see how quick that will get you.
I am currently attempting to take 200 lbs out of my miata kart to bring it down to 1,750 lbs.

Maybe. Right now its back together as it was. I most likely will keep the car as I've had it for so long and had a lot of fun with it. Undecided how far I want to try and take it though and if Im staying with the miata engine or not.

If you get to 1750 you should fly. Thats really light.

https://imgflip.com/i/71rv0k

FWIW I have an auto from a 2003 sitting in a box. I modded it a bit to shift faster and hold more power. I'd say it's good to 300whp. I got it to hold about 350whp by developing some electronics to limit torque on gear changes. Less fun but more fast. Would sell for very cheap if you're interested.

As mentioned, I now run a Ford C4 Auto which is a lot stronger, but it was stupid expensive to get finished. But it works really well for how I use it.

Small update..
Went to the track last friday for tnt to beat on the car a bit. Track was not really prepped since the following saturday was basically a 28 tire race which they dont really do much prep, if any at all. Tire spin was an issue for me. Best pass I had to peddle a couple times to only a 6.94. This was also on lower boost and launch rpm to try and preserve driveline parts a while longer.

I am still tentatively planning to 8.8 swap in the near future to start cranking the power and launch aggression in this junk back up. Need to do some maintenance on the rear bushings as well. Mine are energy suspension about 5 years or so and apparently wearing out. I was getting some tire rub in the upper forward portion of the wheel wells. The wheels are biasing forward under heavy power. I checked all the rear suspension stuff for cracks/looseness, everything looked good that I could see. I also need to limit the amount of rear squat at heavy load when launching to help with tire clearance, keeping tires planted flat and axles at less of an angle.

Its been a while since I tinkered with this junk miata so I messed with it a little this weekend. I was going to build a cheap header for it, likely still will eventually. However when I got the cast ebay manifold off I looked at it and decided to try a few ideas to improve on it first. The pic below is the before pic. It was mostly as cast but slightly radiused ports from when I first got it and installed a number of years ago. Of course it also has the pipe for the spool shot system.
https://cimg8.ibsrv.net/gimg/www.mia...adab9bef7c.jpg


After looking it over I decided to open it up and shaped it a bit to closer match the gasket area. Its hard to see in the pic but I also welded in a center divider. The divider goes from where the wastegate pipe is welded up to about half way up the open area where the turbo mounts. I would have liked to have brought the divider all the way to fill the entire cavity, but i couldn't do that due to the inlet from the spool shot system. The idea behind adding the center divider is to help add a little bit of a barrier to try and mitigate some of the cylinder dilution of exhaust gasses during overlap of the exhaust valves between cylinders 1/3 and 2/4.

And yes, I know this is cobbled junk and the work is crude, but the idea is to test these things without spending a huge amount of time unless it is absolutely necessary.

I got all this done and put car back together to test. I only got to do a couple short pulls at my test spot today due to some people in the area, but the manifold mods appear to have made a positive change. It seems to spool a little better and may have slightly improved power. I need to do more testing to confirm results but it definitely didn't hurt.

https://cimg4.ibsrv.net/gimg/www.mia...d77a383808.jpg


I also want to give a huge shout out to 208 fab. He cut me a great deal on a ford 8.8 diff. I hope to have that ready to go in by the end of the year.

Nice work. I am using this manifold and initially considered porting it. So very interested in hearing your take on the results.
I see these manifolds are back down in price, $74 for the T3 version. IIRC at one point they were $120 or so.

BTW, I saw this video recently, on using the data from Draggy to load virtual dyno. Thought it might interest you.

Thanks. I haven't done any more follow up testing to get solid data on any performance improvement. My initial impressions were positive. I did add a divider in addition to some opening it up. The dragstrip will be back open early march so should know for sure then. I have a couple more mods to the manifold I may try as well. Its cheap junk so I have no reservations about cutting or welding on it.

The dragy to virtual dyno is very interesting, Thanks for linking that.

I doubt that I will personally bother with doing all that for a couple reasons. First i'm not sure how accurate it will be with my setup due to there being not necessarily any direct correlation between engine speed and wheel speed when accelerating hard from a very low speed when in say third gear for example. The converter is very torque dependent in so far how high it will stall. Lets say in a scenario where Im accelerating full throttle from 25 mph in third gear and am using the spool shot system. If using the spool shot I could very well be at full boost (35 psi for example) before 40 mph and the engine speed would very likely be at or near 6000 rpm even at that low wheel speed due to converter slippage. The engine speed would just basically hang at roughly that rpm while the car is accelerating. Once the turbine speed in the converter gets closer to the impeller speed the percentage of slip starts to reduce and the engine speed starts to increase as the turbine and impeller get closer to being more coupled. In other words in a real world test for me going full throttle from 25-110 mph and in third gear the whole time The rpm might hang out going from 6000rpm at 40 mph to maybe just 6200 at 80 and only after 80ish to 110ish engine speed going from 6300 to 7300 lets say. Im not sure how accurate such a graph on vitual dyno would be in that scenario.
Secondly in my mind trap speed is king insofar as measuring hp vs weight, more importantly how efficiently one is using whatever hp they have available.
For me personally trap speed data when at the track and time to speed data from the dragy when street testing give me a good indication of power vs weight changes. The E.T. and 60' data from the track tells me how quickly im able to start applying whatever power I have available.

More ebay manifold butchery!!
Those last couple mods on the ebay manifold seemed to net a slight improvement. Had to richen mixture so it likely flowed better. So I figured what the heck. Lets pull this junk manifold back off and look for more improvement. If I ruin it no biggie. I opened up the top portion of the runners leading to 1 and 4 and grafted on some tubing going to the top portion of the plenum. Intuitively it seems as though this should further improve. I just need to test to verify and get some solid performance data. I once again had to richen a bit, so it likely helped as well Look beyond the crudeness... thats the way I roll on this junk LOL....

If these last round of changes to the manifold show an improvement and the casting holds up after the hackery Ill likely just keep this manifold on the car. I may eventually pull it back off to spend a little time blending and smoothing inside for flow, but that would be about it.

https://cimg2.ibsrv.net/gimg/www.mia...c210208fe1.jpg

https://cimg6.ibsrv.net/gimg/www.mia...fe380f4117.jpg

https://cimg2.ibsrv.net/gimg/www.mia...89ccc29685.jpg

Making some more changes to hopefully save weight and further improve performance of car.
I will be testing a pretty novel idea for building boost on the tbrake without using the spool shot system. I was using two steel air tanks totaling about 9-10 gallons capacity. I swapped those for a 7 gallon aluminum tank to save weight. However less capacity means I would rather not use spool shot to build boost on the tbrake. Saving the spool shot for actual launch. Im testing out some other ideas to build significant boost at a relatively low rpm when on the tbake.

On the manifold.
So did you block the runners from where 1 and 4 normally hit the flow from 2 and 3 and force them into the new section you added?
If so, then I would expect that to make a real difference.
Can you quantify what improvements were made on each modification a little further?

On the first go around I added a shaped barrier in the bottom portion of the middle of the manifold between 2 and 3. You can kind of see it in the pics although the pics arent the best. When I did the top runners I also added a bit of a short, curved "lip" on the exits on one side of the ports of 2 and 3 to try and discourage dilution between 1 and 2 as well as 3 and 4, but cant see in the pics.

For the merged top runners i opened up and removed top sections of the manifold to "siamese" the new runner additions if that makes sense. It likely does flow more at this point since I've had to add a good bit of fuel to get mixture as it was before I started modifying it. However I dont have enough solid dragy data to quantify any exact performance improvement yet. My initial impressions are if I pull it off once more to do more interior runner clean up and shaping is that it will be good enough for me not to bother swapping to a header. Everything is already built around this so even if its not quit as good as a long runner header it will be good enough for me. If/when I pull it back off to clean up I will try and take better pics. I am going to build a 3 1/2" downpipe to run at the track in the future I think. Would be nice to get rid of that full exhaust system weight plus multiple other benefits to doing larger open downpipe at the track. My exhaust is all v band so not hard to remove for the track.

Just came across this. I believe he is still on a mazda bp based engine. 8.09 in the 1/4 mile. As Jesse lee Peterson would say, AMAZING!!!!

Hello fellows another quick update.
So I've been doing dragy testing in the 40-80mph range that i normally do when testing mods and unfortunately the gains from the manifold mods are too small to be consistently measured in that short speed range in terms of acceleration improvements. Bummer! I was hoping for more. It may show some slight gains in the 1/8th mile since its a much longer speed and time frame. The only thing I can say for certain is it required a little more fuel up top to get afr to match prior, which should mean a little more power.
I also just changed crank wheel to 36-1 and ground off the two close teeth on the cam wheel for sequential with speeduino. I was running sequential with the stock 99-05 trigger but had some spark latency. I made up for the latency in other ways but didnt like doing that and wanted to get rid of the latency. It appears that the new wheel setup timing is rock solid with no perceptible spark lag so I no longer have to trick any spark maps or other ways to make up the latency as I did prior. Unfortunately speeduino doesn't yet have a place for latency compensation as does megasquirt. I really want to start doing some nitrous testing this year to see how it compares at the track to spool shot for spooling turbo at launch and really wanted a little more stable timing with no tricks to be on the safe side. If i do start testing nitrous at launch and can get similar results to spool shot I may eventually remove the spool shot setup. The spool shot setup has been a big winner on this car and is a MAJOR contributor to its overall performance, and is great on the street since the "shots" are free, but the baggage is weight unfortunately. After watching Pat I'm starting to eyeball some weight reduction a little more seriously.

I hope the nitrous will get you off the compressed air and you do start shedding some weight. I bet your car would be in the low 6's in short order.

OOps!!! Got a little greedy at my test spot. Good thing I had walking shoes on LOL....Broken input shaft.

https://cimg3.ibsrv.net/gimg/www.mia...97ff8fab6a.jpg

Just picked up a core c4 transmission to build up. I guess y'all can see where this is going LOL...

I wont build it to the level of Pats transmission though. I'll likely build it to hold a comfortable 600hp or so level at my weight. I will also likely pick up another c4 to build up in anticipation of a higher level down the road. Hard parts are available for these things to hold some pretty serious hp levels (for a miata anyways). The c4 has some other advantages over the jatco as well. For one it is quite a bit lighter, secondarily it consumes less power, both of those should help performance to some degree.

https://cimg8.ibsrv.net/gimg/www.mia...1101762753.jpg

I did put my spare transmission back in the car for the time being. I also went ahead and repaired the one with the broken input shaft, so its ready to go as well.

The ford transmission should be ready to go in a couple months. I'm not sure if I will go ahead and convert the tranny over then or just wait until the end of the year and do the rear then as well. I'm actually kind of looking forward to doing the c4 now. That was actually my original plan years ago before I went with the Jatco. Oh well, at least the jatco was nice on the street due to the 4th gear.

That's cool. Will you build it yourself or have a shop do it?
What will you do for an adapter plate?

Build it myself of course. These older transmissions are actually quite easy to do. Dealing with all the bushings is the only real pain. Besides, I'm waaayyy too cheap to pay someone LOL..

Dont need an adapter plate. The jatco bellhousing only takes a little modification to bolt on in place of the ford bh, Thats why I went with a c4. I would prefer a powerglide since i have used them in the past and its among the lightest, lowest power loss automatic out there suitable for drag racing in a light car, but it would be more of a challenge to adapt.
the c4 tranny does require a custom converter, driveshaft, mounts, shifter, yada-yada,,,,all thats really no biggie. The custom torque converter can get a little pricy, but on my first go around I think I have a cheap solution i may try for that too.

Quick update. Bellhousing is finished. Pic below is it sitting on the ford c4 pump with bolt going through new holes for correct orientation. I epoxied in a centering ring cut from a thin strip of what i think is 21 gauge steel. This finished product is a very snug fit.

https://cimg1.ibsrv.net/gimg/www.mia...f4329080e7.jpg

Next step is to build the transmission.
I pulled the transmission apart to see condition and what parts were needed. Also to try and determine why it was originally taken out of service since this was bought as needing rebuild. The tranny looked really good internally except the forward drum clutch pack shows significant wear. Upon disassembly of the forward drum I found the cause. The belleville spring was broken. pic below shows damage.
https://cimg9.ibsrv.net/gimg/www.mia...8183678a50.jpg
https://cimg0.ibsrv.net/gimg/www.mia...d43602ba4f.jpg

The track opened back up yesterday as well for the first time this year. I decided to take the car up there to play a bit. I made 3 passes. Since the car has been breaking so much drive line stuff as of late I decided to take out a few pounds of boost and launch with very low rpm and very low boost. Naturally the car was not going to be very fast but I just wanted to go play a bit. My first two passes were against a acura with a turbo k24 that the owner said dynoed over 600hp. Since he was front wheel drive and on drag radials, not slicks, he wasnt really competitive. I beat him by a lot both times. Unfortunately my third pass was lined up with a well set up smallblock powered s10 pickup on big slicks, so I lost my self control on the original plan to launch at low rpm and no to low boost. Once I realized I was going to run him I enabled the spool shot system which on this particular tune in the ecu was already mapped to try and launch at around 15-17psi and about 3800 rpm. Well it launched at around that and proceeded to break something in the rear suspension. I havent been under the car yet but I suspect it cracked the subframe somewhere near one of the lower control arm mounts. I was getting rear steering. Oh well, no biggie. All this just gives me more incentive to hurry up and finish the driveline with strong stuff so I can throw some real power at this hooptie. Im hoping that after I do the tranny and rear to be able to start throwing some nitrous at this thing to eventually possibly dip into the high 5s in the 1/8th.
On a positive note I did get a dragy video of my first pass. I have never done a dragy video so thought this was pretty cool and should share. This was my first pass against the honda. You cant see him due to phone camera angle, but you can hear him right before the launch rev up and go on two step. You never hear him after that because he just basically spun and fell way back. Again keep in mind this is low boost (for me anyways) and now real rpm or boost at launch, so this pass is naturally going to be slower than usual. Now that I know how to do dragy overlay videos y'all can expect some more in the future, but with much quicker times. This pass was only a 7.05. the car has run in the 6.50s, but breaks driveline stuff half the time trying to get there or go faster. Fixes happening soon!!

The dragy video can be trimmed so that not so much after the finish line is played and you can change what increments are measured ie the 1000ft and 1/4 mile don't have to be displayed.
I look forward to more dragy video.

Quick update and maybe even a laugh...

Transmission is done. Replaced all broken parts and built with red clutches and adding an extra clutch in the direct drum by using thinner steels and sanding pressure plate for clearance. I replaced the intermediate servo with a "h" servo. That gives holding surface area very close to the "c" servo most aftermarket units are based on. It is also converted to full manual, no automatic function.
Next step will be figuring out a converter solution. I have a couple ideas that I will be exploring soon in that regard, but if they don't pan out I guess i'll have to break down and spend the money on a custom converter.
https://cimg0.ibsrv.net/gimg/www.mia...979c025e75.jpg



Tanks and compressor taken out for now, maybe permanent, maybe not. There is about 40ish pounds difference between what I removed so far and a full nitrous bottle.

https://cimg6.ibsrv.net/gimg/www.mia...8074eae5e6.jpg


I removed most of the spool shot stuff so I can start testing the nitrous for rapid spool at launch when at the track. I have street tested a 50 shot against the spool shot system to compare boost rise over time. The spool shot does spool the turbo faster than a 50 shot so I now have slightly larger jets, likely equivalent to maybe a 60 shot to test. I may go a little larger later. Since the tanks and compressor aren't in the car I will be forced to use the nitrous now to spool turbo. Its really about time to start using it and gathering test data for spool at the track. I have it configured to fire at launch when brake is released and shut off when 250kpa is reached, so will just be using at launch to spool turbo for now. Once all the driveline stuff is eventually done I will start to stage the nitrous to add power down track as well as launch. Junk should be pretty quick at that point.


Anyhoooo The track was open for tnt last friday so I wanted to get to the track for a couple reasons. One, to test the 60 shot for boost rise at launch. Secondly to get yall some better numbers on the dragy overlay video now that I know how to do it. Last time I was too much of a sissy chicken boy and was too conservative at launch for trying to preserve driveline parts. On the 7.05 pass it looks like I left at only 3300 or so rpm and a pip squeak 4-5 psi. I was going to get a little more gnarly for y'all and go ahead and try to bust out a 6.50 something in the 1/8th and maybe a mid 2 something for 0-60 and get it on the dragy overlay. I know about what boost and rpm level I need to launch at to achieve those numbers now and was going to go for it for yall. 50-50 Yall would have gotten to see me break something and coast down the track though lol....
Well last friday I loaded up the car and left for the track. About 2 or 3 blocks away I realized I forgot to throw the spare trailer tire in the back of the truck, but I figured, be a man and press on, so being the manly man that I am, I pressed on..... The track is about an hour from my house. I picked up a buddy who lives at about the halfway point to go with. Below is about 5 minutes from his house after picking him up..LOL
https://cimg6.ibsrv.net/gimg/www.mia...8488e37294.jpg
Needless to say didnt make it to the track. I just limped back to buddies house and left trailer there. Went back saturday to change tire and bring trailer back home. Got 4 tires coming and going to build an attachment on the trailer to hold spare so this doesnt happen again.

Sucks about the flat, better luck next time!

Update time
Finally got the converter solution done... I think LOL...
I bought an 8" c4 converter from a fellow racer. The converter flashed to about 5000 rpm for him behind a 347 smallblock ford. It was in a maverick that ran in the 6.20s at around 108mph.
I had to cut off the ford mounting pads and figure out how to adapt it to mount a c4 transmission to a mazda engine using the mazda bellhousing. The tranny and bellhousing I did prior.

I mocked up a mazda block and crank to the ford c4 pump and modified bellhousing to get measurements and figure out the easiest solution for me. Below is a pic of my mockup setup
https://cimg8.ibsrv.net/gimg/www.mia...9e649d994a.jpg

I came up with a plan to do a simple pilot bushing adapter to have machined in steel to weld onto and over original ford pilot. In the meantime I was talking to a friend who just happened to have an old lathe he inherited from his Dad that was just taking up storage space and he wanted it gone. I picked it up for $200 and replaced the motor with a 1hp harbor freight unit as well as getting new drive belts. The lathe is an ancient southe bend 8 jr, but all the critical stuff is still in good condition. They used to build stuff to last back in those days for sure!

I had a friend 3d print what I thought would work for a pilot adapter. After test fitting the plastic model and seeing it would work I chucked some steel stock in my new toy and started spinning away.
https://cimg2.ibsrv.net/gimg/www.mia...0f928f188a.jpg
https://cimg6.ibsrv.net/gimg/www.mia...68bcd954e0.jpg

After tack welding over the original ford pilot I had to come up with some ways to try and determine if pilot was true after welding. Although I got a large 4 jaw chuck the came with the lathe the converter body would not quite clear the ways. So I just mounted on some v blocks and checked in that manner as well as putting it in mock up set up. While testing on the v blocks I was getting about .003 indicated runout, which I feel is acceptable. More on this in a bit.

https://cimg1.ibsrv.net/gimg/www.mia...dfe0fd394f.jpg
https://cimg6.ibsrv.net/gimg/www.mia...35e9faed8f.jpg

next I had to build some mounting pads to bolt to the flex plate. I went with 3 as the converter had 3 "bosses" originally in the body so it was easier to do with 3. If 3 mounting pads is good enough for 1000+hp chevy's its good enough for me.
I built 3 pads with the proper spacing to mount in 3 of the 6 holes in a 99 model flex plate. After welding those up and the pilot as well I mocked up to measure the runout of the face of the mounting pads. I got .004 so pretty good on that too.
Below is a pic of mock up pad measurements.
https://cimg8.ibsrv.net/gimg/www.mia...164cdb4fe7.jpg

After all that was done I bolted just to the flexplate to measure runout at the pump hub. When I initially bolted it together I was getting runout of 8-9 thou, after it was bolted together a while it seemed to reduce to around 6-7 thou. Thats evidently pretty good too. Out of curiosity i mocked up a stock miata converter to measure pump hub runout. It was almost 15 thou, so I must be golden on that. The factory flexplates have about 25 to 30 thou face runout before a converter is bolted up, I measured 2 of them. So the flexplate runout will influence the pump hub runout until the pump hub is supported by the hub bushing in the pump.
Below is a pic measuring pump runout.

https://cimg5.ibsrv.net/gimg/www.mia...2a98e3eca0.jpg

At this point I am calling the converter and transmission done. My only concern, and its only a slight concern, is the converter balance. When I built the mounting pads I adjusted the weights to each other within a couple grams. The unknown is the welds weight. the welds are all equally ugly so hopefully they all weigh roughly the same, or at least close enough.

For now the converter and tranny assembly will be just sitting pretty for a while.

https://cimg9.ibsrv.net/gimg/www.mia...7402b31014.jpg


Next will be getting the shifter, rear tranny mount and driveshaft done. Hopefully all that is completed in the next few months. I plan to build or collect all the parts and swap over at one time so I can keep car to continue to drive and race as is until then.

Got to decide what I want to do about the rear setup before doing driveshaft though. One good thing about having the lathe now is I was able to redo the adapters for the 929 axles, I think they may work now, so I am leaning to keeping rear and adapting the 929 axles, at least for a while anyways. Since I have the axles I may as well.

Well my OCD kicked in and I did a thing LOL..... Spoke with Pat and he mentioned that FTI likes no more than .001" runout on the converter pilot. I initially felt that the pilot I had welded on to the front of converter was good, and it very likely was based off of runout measurement on the pump side of converter. However after thinking about it further I really didn't like the v block way I measured the pilot after welding as It did not really directly measure runout at very end of pilot. Sooooo,, I cut the weld and removed the pilot adapter I welded onto the front of the converter and devised a way to build an adapter to register off original pilot on the converter and bolt to back of crank to register into crankshaft side. Doing this way I can directly measure runout at very end of pilot adapter.

Below are pics of the new adapter I built. I was able to achieve less than .001 runout this way directly measured.

https://cimg8.ibsrv.net/gimg/www.mia...169dd93669.jpg
https://cimg2.ibsrv.net/gimg/www.mia...3824fb524b.jpg
https://cimg4.ibsrv.net/gimg/www.mia...691488ea72.jpg
https://cimg6.ibsrv.net/gimg/www.mia...18d1ca815b.jpg


However there are two issue with this one that I do not like. One is I had to make it out of 2 pieces since I didn't have any stock big enough to make it out of one piece. Secondly the wall thickness I feel is too thin on the converter side. If the bolts ever loosen or if the flexplate ever cracks, which I've had happen before on a nitrous sbc,The pilot needs to be sturdy enough to hold converter in place. I made the o.d. of that side that size so I could fit in a socket for the flexplate to crank bolts, but I feel now too thin. So I ordered some steel stock large enough to make out of 1 piece and will be full height thickness on the converter side. I'll just use longer bolts to mount onto crank. This should be last iteration as I know it will be true and extremely strong to hold in center should flexplate ever fail

After making the converter pilot adapter in above post I decided to redo it in a much stronger fashion. The new design is machined out of one solid piece of 12l14 steel. This one is plenty strong to hold the converter pilot centered if the flexplate ever breaks. After bolting it up to my mock up block I was able to get around a thousandth runout measuring at the register for the converter pilot. I am pleased with this one and finally calling it done and moving on to next part.

https://cimg5.ibsrv.net/gimg/www.mia...a2e483f334.jpg
https://cimg8.ibsrv.net/gimg/www.mia...4566559f4d.jpg
https://cimg5.ibsrv.net/gimg/www.mia...71d1cc6378.jpg

My one and only concern with this adapter is I had to source some 40mm long 12mmx1.0 flywheel bolts to work with the adapter. These bolts are for a honda!!! I cant believe I'm reduced to honda parts. Whenever I get all these parts collected/built and swap over to c4 tranny I'm only hoping I don't wake up the next morning and all the sudden my junk is 20 decibels louder and somehow sprouts some goofy looking giant wing off the back LOL.......

Lol you cracked me up with that!
Bwaaaaaaaaahhhhhh