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...