Nice work!
Those bolt heads don't interfere with the converter?

Thats a good observation. They do get close, but they do clear.

Also a huge shout out to all the professional machinist out there. That is a very underrated talent! I've just scratched the surface and come to realize its not easy.

Hello Fellows
I thought I would post up a couple vids showing factory converter pilot runout vs the new adapter. The factory stuff I quess has more tolerance as to runout than we sometimes like to think. Had more than I thought it would anyways.

https://www.youtube.com/shorts/YGnlh9Tg-_w

https://www.youtube.com/shorts/6XGeEM0dqkg

hello fellows quick update.
The local track I normally go to hasn't been open much this year so its kind of killed my motivation to get driveline swap done rapidly. I have the transmission, converter, and adapter done and ready to go I think. I've been collecting some of the smaller parts as well. Will be doing the driveshaft next.

The car is still up and running with the jatco until I have everything done to swap over. That way I can still take the car out and beat on it while collecting swap parts.

One thing I did recently was add a flex sensor. I have been wanting to do flex fuel for a while just to play with that. Car has been exclusively e85 for years and will likely remain that mostly, but will be cool to test different percentages of ethanol.
The flex sensor did allow me to do something which is beneficial with my injectors. That is to adjust fueling based on fuel temperature. I'm running a high amp draw walbro 525 pump with a return setup, so it adds some heat to the fuel. Particularly an issue on very hot days and lowish fuel volume in the tank and longer drives. The sep 1500 injector coils combined with the natural lowering of fuel density with heat made the car get leaner at idle and light cruise as fuel got hotter. I saw fuel temps well over 140f after about 25-30 minutes on 90f+ days. The problem I noticed with the speeduino is when you adjusted the fuel temperature correction to make idle and cruise afr's correct as fuel got hot, it made it too rich at heavy load. The speeduino fuel temp correction adjusted the whole pulse width rather than just low pulse widths. So to correct that issue I went into the coding to make it adjust just the deadtime value rather than whole pulse width. That way any fuel temp correction would have a much greater effect at low loads and not so much at high loads.

Below were the changes to coding under "corrections" in speeduino. This change did more of what I was looking for with fuel temp correction.

This was original line of code:



This is after change:

Oh no. Not your track cutting back the schedule too, dang!

Hello fellows. Its been a while so if figure I would update. My local track has been closed for a good portion of the year and only in the last couple weeks decided to open back up. I haven't done much with the car since track has been closed, but now that they appear to be open for the time being at least its got me thinking on this hoopty again. I have a good portion of the c4 swap stuff collected or built. However since track has been only open occasionally I may be second quessing swapping the c4 stuff over into the car. The jatco has a 4th gear which is nicer on the street over the c4. I will hang onto all the c4 stuff and maybe continue with swapping it over later. Especially if the track is going to be open regularly, but until I see that happen I think I may try and develop the jatco a little more. I have several of them with 2 being built and modified already. I am going to go back into one of them while its out and further strengthen by adding even more clutches to the packs. I've already added 2 additional clutches over the stock count to the pack used for 3rd and the forward drum as well. now that I have a lathe I can machine to fit even more. I have also gone back into one of the valve bodies to do an actual real trans brake. What I had done prior was what I have been calling a fake transbrake (sloppy mechanics style forcing 3rd gear). It work well and allowed stall speed about 1000-1100 rpm higher than the 2800 rpm I could get without it before it started to push through the brakes. With the fake brake I could get about 3800-3900 rpm before pushing through the brakes.

However this one on car now is a real trans brake and locks 1st and reverse together. This required some valve body mods which I am detailing in case any other fools out there want to try this... LOL...... I have to do some testing to see which one I prefer most as I can now set up to do either way. I do think ill need to add a bump box with this transbrake, which is something I didnt need with the fake brake, but I do think the real t-brake will allow even higher rpm launch, which should perform better. If I get axles and diff to hold that is. I'll likely be converting to the 929 axles very soon and may look into doing a little more diff strengthening as well to see how far I can take it too before deciding to do 8.8 or not.

Below are required valve body mods for transbrake. This is ONLY applicable to the valve bodies as used in the 94-97 miata jatcos with shift solenoids. After these mods are done to activate the transbrake the 2-3 shift solenoid is de-powered through a momentary switch and relay while the shifter is in low and car is in first gear. This effectively locks 1st and reverse together while those conditions are met.

Many other valve body mods were done prior. I'm not detailing all those, just the latest to do transbrake.


below is the channel that leads to the back side of the 2-3 shift valve which needs to be blocked.

https://cimg2.ibsrv.net/gimg/www.mia...859a47c672.jpg




below is where i blocked a portion of the channel with lead solder.

https://cimg3.ibsrv.net/gimg/www.mia...7e0950120b.jpg





below shows where a relief hole needs to be drilled on the back side of the 2-3 shift valve.

https://cimg7.ibsrv.net/gimg/www.mia...97181570b7.jpg




below is after hole was drilled.

https://cimg1.ibsrv.net/gimg/www.mia...2c816329b1.jpg

This is really interesting. I've thought about wanting to do something similar with my megasquirt but since I don't run an ethanol sensor, I've not had any chance to do it. As someone who likes to drive their car year-round, I'd often have to mess with the tune in the winter and summer to get the AFRs back where I wanted them. That or run really aggressive EGO settings. I've been messing with microprocessors a whole lot recently in college so I think I might finally start looking into this, however, doesn't MS use another language whereas Speeduino is C++? Regardless, very cool and motivating. :likecat:

Thanks for looking out for the rest of us fools! :bowrofl:

Hey Soth you thinking on doing one of these transmissions?

Newaza, I mean, I have been thinking about this for a long time now. I don't think it will be on my current car but I keep seeing autos for sale. I think if I want to win some money or a Wally, I need to consider building an auto. I almost picked up one of the Jatcos a while back but the guy flaked and was offering to give it to me afterward, but the drive was too long.
At some point I will likely do something similar, it's all just hypothetical now though. That being said I am probably one of us fools who tries this one day.
That post was hilarious and cracked me up :rofl: just thinking about even.

Can someone out there identify this manifold? At first glance I thought it was an ebay manifold. However I've never seen an ebay manifold like that with the wastegate port. Its t3 flange but a few details in the pics make me think I may not be an ebay manifold.
https://cimg8.ibsrv.net/gimg/www.mia...8551cc877c.jpg

Could this be an old begi?

begi s2 is my guess!
because begi is in the file name.

No thats just what I named it when I saved the pic on my computer. LOL... I have two pics saved as begi1 and begi2. I uploaded begi2.

I just named the pics that to make them easy for my to find to upload, not to be a head fake of any sort.. After looking at some pics of some begi manifolds I thought it could be one but not sure. Hoping someone out there with more knowledge than me on these would confirm.

OOOppppss!!! Well above manifold is identified.. Sadly Its for a honda, and unfortunately I own it. A guy on fb listed this with a bunch of miata parts. He claimed it was for a 1.8 miata. The above pic is one he sent me and I saved on my computer. When I went to go get it the other day there was also an older 280z there. I started looking over the 280 and just snatched up the manifold without really even looking at it. Dang it!! Moral of this story fellers is maybe take a second or two to look at something when you buy it. Oh well. I got it for almost nothing so maybe I will toss it or maybe I will modify it and use it to test. I have a factory header I can cut the flange off of and make the honda manifold work. Geezz sometimes I just want to kick my own butt! lol..

Anyone on here have one of these they can part with? Its a ford 8.8 axle inner stub in 31 spline.



https://cimg6.ibsrv.net/gimg/www.mia...d4bd34318c.jpg

Hello Fellows. Just figured I would do a quick post to update.

The track was open for the first weekend of the year so I took hooptie out to play a bit. I was just doing a little t-n-t to try out tbrake since I haven't actually tried this latest version. What I used prior was what I would call a fake tbrake, sloppy mechanics style. This version is a real tbrake that locks 1st and reverse.
It works very well. I just need to devise a method of "bumping in" with it. I got a good dragy video and will also post the timeslip that went with it.
Dragy video

timeslip (disregard reaction time. Was just there to test tbrake setup and new launch strategy.)
https://cimg7.ibsrv.net/gimg/www.mia...38cf951849.jpg

Log that goes with
https://cimg6.ibsrv.net/gimg/www.mia...8db678900a.jpg


The tbrake setup is working really well and may be one of the keys to getting quicker times. You can see I only launched at ~3600 rpm and 6 psi, so I was EXTREMELY conservative on launch. I did run ~180psi tank pressure, which spooled the turbo quickly. I think the key to (possibly) picking up another tenth or two will be to launch with more rpm, boost, and even more tank pressure.

Frickin killer man! That shows a ton of potential.

Hello fellows bringing yall up to speed on a few things I tested and will be testing soon as well.

First is the c4 conversion. Well to try and sum it up, I installed the c4, drove it a couple weeks, basically hated driving it on the highway with 26" tall tires and 4.30 gear so put all the jatco stuff back in LOL.... A few more details on this.

So In late january/early february of this year I didnt have a lot going on and had some downtime. I figured well, since I have time I may as well convert to the c4 setup since I already had most of the stuff made to convert at that point, so that's what I did. I cobbled together an adapter out of steel plates to adapt rear of transmission to front of ppf, (basically copied what Pat did early on) and threw everything in to convert over to c4 setup. I had been hesitant to go forward with this conversion due to concerns of converter and driveshaft balance since I had no real way to effectively balance those parts, I could measure runout as I was building the parts and got the tolerances tight so wasn't too concerned about that, just balance. Was concerned about gearing too, but figured I could live with it for a while. Boy was I wrong on that one LOL. After putting it together and driving I had no detectable vibrations so I must have gotten pretty lucky on the balance side of things. The gearing? well that was another story. It was aweful for highway driving. I knew it would be as I had a street/strip car in the past with 4.56 gears and 28" tall tires, but I was a much younger man then LOL....
When I decided to do a hard pull with the c4 setup I thought I was getting some slippage in third gear or blowing through the converter a bit, so I pulled everything out to check. In reality and looking back it was early february when I was doing this so roads were cold and it was likely just spinning tires. The real truth be told I was just looking for an excuse to pull it out and convert back to the jatco setup since the basically suitable for race only gearing with the c4 and 4:30 gears and I REALLY didnt feel like doing a rear swap at that point. I decide at that point to pop that jatco back in to push it a little further since the track is only open occasionally and I still street drive this thing. If I ever do a rear swap in this I may revisit the c4 setup since it is mostly plug and play at this point, plus I feel pretty good about the runout and balance of the converter adapter setup now.

I have been back on the jatco bandwagon since 2nd week of february and haven't looked back.

Below is a pic of a conversion driveshaft I adapted. I turned down a weld yoke on my lathe to fit the miata driveshaft tube and measured runout while welding it up.

https://cimg6.ibsrv.net/gimg/www.mia...1f27ff4513.jpg

Below is a pic of the rear of transmission adapted ppf as installed in the car. Basically copied Pat on this one.

https://cimg9.ibsrv.net/gimg/www.mia...dd3f7202c8.jpg

As of mid february car is set up with Jatco tranny, 4;30 gears welded open diff, rx7 axles and broached hubs to fit larger rx7 axles. That was the setup on the previous post I did with the dragy video. If going forward I start breaking the rx7 axles I will put the 929 axles in since I redid the adapters for those and I think they will work now, heck I may eventually try them anyways just to see.
I am rocking a real transbrake setup with the jatco now and am testing a new launch strategy of leaving off the transbrake with only a moderate rpm/boost level but using greater air pressures to ramp up boost faster at actual release of tbrake and launch. That was strategy used in the prior post with the dragy vid. I used about 180ish psi on that one. Next time at track I'll be testing maybe up to 200psi.

Well that catches yall up on the transmission conversion I tested early in the year, but never did a post on it. Now on to a couple things Ill be testing soon.

On the prior post with the dragy vid I was running a peak boost of 35ish psi. With the level of timing ran and at that boost level the car will trap 107-108ish mph. I have trapped a little over 109mph over some prior testing, but that took 38ish psi to get there. Not much extra juice for that amount of extra squeeze, so it seems turbo is getting maxed out. This is a gtx3576 sized turbo. It seems from all the testing I've done with it is that the sweet spot for it is in the low to mid 30s range. So in looking for ways to improve compressor efficiency It seems a couple things could help move the compressor map up and to the right a tad. One is straightening vanes and another is pre-turbo water injection. In order to quickly and easily test both those ideas I had a friend 3d print me something I could test just the vanes or both the vanes and water at same time.

https://cimg1.ibsrv.net/gimg/www.mia...8350ebdef7.jpg
https://cimg2.ibsrv.net/gimg/www.mia...612b53284f.jpg
https://cimg3.ibsrv.net/gimg/www.mia...bda57d9839.jpg

I have this device on the car now, but not yet plumbed with water, so will be just testing the vanes at first.

A couple other things I want to test involve possible engine efficiency improvements. I've read about the exhintake deal and see mixed results with that. It is an easy thing to test so I just did that conversion. No data yet as I havent taken the car out to my test spot to get in some 40-80 pulls with the dragy. The only definitive results so far is slightly less Idle vacuum. I may turn down an offset bushing for the cam dowel to allow me to test advancing or retarding the cam a bit as well.
I have also been doing a little to modify that honda header with the miata flange on my extra engine on a stand, but will be a while before I get that on the car. Not expecting much improvement with these few things, just hoping for anything consistently measurable on the 40-80 testing.

Of course I still have to test the nitrous at the track too. I have still yet to try that at the track. That is guaranteed gains and may test that soon with a 35hp jet just at launch to see what it does.

Tell me more about the RX7 axle swap.

Hey 208. You will need a set of miata hubs that are broached for the larger 28 spline rx7 style axles. You can get those from Martin at monster miata. The 929 axles use that 28 spline rx7 style hub too. The factory miata hub spline is smaller at 26 splines. After that you just need to source a couple na fc rx7 axles and be sure to get the inner stub shafts. Once you have all that they pop right in easy peasy!
Be sure to get the na rx7 axles and not the turbo ones. Although the hub side 28 spline count is the same on the na and turbo axles, the turbo axle stubs where they go into the diff are different and wont work in the miata diff. The na rx7 stubs will work in the miata diff.

The stock nb miata axles neck down to around 22mm on both ends on the area inside the rubber bellows where they go into the cv joints. On all the miata axles I broke those necked down areas are where the axles failed. The rx7 axles measure between 24-25mm in those areas inside the bellows. So they should be a good bit stronger since gaining at least 2mm diameter in that area, plus the hub side spline area is significantly larger. How much stronger are the rx7 axles over the miata stuff? I dont yet have an answer for that since I havent broken an rx7 axle yet. However I do plan to push them harder going forward so may find out..

Honestly though since you are a miata cart and I think you told me once you were around 1900lbs the stock miata axles may serve you well.. but if you do start breaking them and feel you need just a little more axle strength, these rx7 axles may be just the ticket for a reasonable expense. I picked up 4 complete rx7 axles and a rx7 rear for $100 and I think the broached hubs were around $250, these might be more now though due to bidenflation. However its still not a huge investment for what looks like a decent axle upgrade.