1990 open "mod" class build.
 

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https://youtu.be/heMwnmDl1F8




Trackday fun


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There is a local class in my autocross region we call (STM) Street tire mod. The rules are only 140tw tires or higher. It's pretty much a "run what ya brung" class. We are usually the largest class at each event with 15+ people registered regularly.

I got this car spring break my senior year of college (Spring 2014). I decided to build a dedicated car for STM while keeping it marginally street legal (because tow rigs are expensive).

I placed 3rd in my region in STM my first year out with the car. I have gone through 3 different suspension setups and have cut weight in almost every place I could find it, while keeping the car "streetable". I drive it to and from events and some of our mountain roads, although it's a bit unsafe on the road.

Car started with life with a crank wobbling 1.6L. I did the "Loctite 660" fix. The wobble didn't stop, but it didn't pull anymore timing so I raced it like that. The motor still made good power but short nose crank problems. So I picked up a ~100k mile 93 long nose crank engine locally. Everyone hates the 1.6 so you can get them really cheap.

1990 Miata crankshaft wobble fixed. - YouTube

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Water temp, oil pressure, Innovate LC-2 (getting prepped for MS2)
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Finding more weight to trim. Getting a bit unsafe for street stuff though.
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Heading to Miata's at the Gap this year was a pretty fun time.
A quick run with a 2015 WRX, STI, and M3 at "Miata's at the Gap". - YouTube

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My buddy with his ITB 4ag AE86. Lots of time and goodies in that thing.
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My buddy with his E30 on Deal's Gap. He has been first in our class for the past 2 years.
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Halfway through the autocross season a deal came up on some suspension.

Out with the old...
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In with the new...
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First autocross felt pretty good with it but going from a 4.30 gear to a 4.10 really killed the powerband of the car. It got a bit better once I got the Megasquirt dialed in a bit more for 93 octane. The midrange felt much better but the car needs more power.

Ended up getting a trophy position.
https://www.miataturbo.net/attachmen...ine=1449509641

Then I decided that the open diff life was getting kinda lame. So I built a clutch type RX-7 diff with 94 half shafts and a 7" open diff carrier housing.



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Now time for the Turbokitten lyfe...

This is Curly's old kit.

SR20 T25
ARTech manifold/downpipe/testpipe
Most all oil/water lines
TSE hardware
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Cheap XTD clutch, PP, and light flywheel. Probably going to make all sorts of bad noises.
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Mounted the MS with some rivnuts. Next to my distribution block I build for the gauges making it a bit easier to remove/troubleshoot.
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The car currently.
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My little work space. Not perfect but works alright for what I need.
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Here is my Youtube channel where I do most of my updates. Trying to give a bit back to the community by doing some "How to" videos.

I will say that this place has been a great resource, explicitly the Race Prep section. A lot of big talent on this forum and some great free data. I don't know how much further I will end up taking this car, but I plan on seam welding the chassis, shimming my diff, building a cage for it and then doing some HPDE events.

Unless you are planning on eating the reserved posts today, they are pointless to do. There is only a certain time limit that users can go back and edit posts.

Thanks, didn't know that. :likecat:

Why did you not adjust pinion depth to get a better pattern. That pattern is really far towards the toe. And that's the coast pattern you were looking at. Not the drive side pattern.

I don't want to remove the pinion at all honestly. It has a crush sleeve in it and I don't want to pay for all those parts yet. I may do it down the road if I break what I currently have but after 400 miles and 3 autocross events I have yet to have a problem out of it.


What I plan on doing this off season is to break it back down, shim it up, and then I will reevaluate the wear pattern. With used parts getting a proper patter while keeping proper backlash is going to be pretty difficult, if not impossible, with my tools and knowledge. I have very little money in the build and keeping it that way is a plus. This car saw 1854 miles this year, it will probably be similar next year as well.

You just need a lot of shims, and a lot of patience to get the right pattern. I'm in the middle of rebuilding my ford 9 inch, and it sucks.

Adding power wont help either.

These are a bit different in that they don't use shims to adjust the ring gear "chunk". You have these large inset screws that you move. It's pretty difficult but great that I don't need copious amounts of shims around.

This was my first diff I had built and I agree, adding power is not going to help prolong the life of the diff. The shimming I plan to do is to achieve more preload. I will probably make another video on that process.

I mean shims for the pinion. You get a crush sleeve eliminator and shims to set pinion depth.

Interesting, do you know a link of anyone doing that with the Miata? I did a good amount of research but it didn't extend very far outside of Miata/RX7 based forums or searches.

Weir Performance - Solid Pinion Spacer Kits

First link google popped up.

I know @Leafy set up his diff himself.

Getting the right pattern is heavily dependent on pinion depth. Thats why your pattern was so far towards the toe. Backlash just moves it towards/away from the root.

Oh, I was meaning a "how to" on setting it. I am sure someone makes the parts. That is pretty affordable though. If it is something I may be able to do in my shop I probably will.

Yup did, way easier with the shims than trying to uncrush a crush sleeve of you go too far. Still a pita and I wouldn't even consider doing it unless you're going to 3.63 gears. Just buy the ratio you want in the housing and then you don't have to paint anything. Just swap the lsd and set the backlash and preload. Avoid touching the pinion depth unless you're putting in a gear ratio that you can't already buy in a matching housing.

This is generally the answer I got whenever I looked up adjusting the pinion depth. I am sure a shop with more experience could do it but I didn't want to pay anyone and I sure don't want to mess with something that isn't broken.

I will try and get a better wear pattern when I go back for stacking some shims in the clutch packs.

I planned on buying some .010 copper sheet and just making shims out of it. I have read people using soda cans and stuff but I want to try and keep similar metals together in the diff and the "crush washers" look to be copper.

I figured out how to set the pinion depth and preload by reading about other diffs and applying it to mine and reading the fsm. I think the crush sleeve eliminator kit was worth the 70 bucks it costs to avoid dealing with the crush sleeve. For my case I ended being in the middle of two shim sizes, so it still involved a bunch of taking apart and putting it back together. But I didn't need any of the depth shims, the gears all tend to be cut to the same pinion depth so the shim just stays with the housing.

Finally got a bit of time to get new fluids in and start the car. The coolant reroute and new radiator really keep temps down. Ambient was about 56*F and the coolant gauge hung around 170*F until I idled it up for about a minute. Really impressed with the cooling over stock.

The lightweight flywheel is almost comical with how responsive the throttle is now. I am sure it's going to be interesting.

Needs moar accel enrich tuning.


Also sounds kinda funny. Misfire or something?

I have no idea. Is it possible to have the CAS 180* out? I thought it was just because of the stupid light flywheel in the car now. I also don't have the front mount hooked up. I also didn't have my laptop on me to change any settings. I'm still waiting to send in my injectors for cleaning and flow match before I drive the car.

What's stupid light? I have a fidanza (lightest 1.8 available) and it sounds normal, just revs faster.

Check spark/fuel with ouput test mode.

In the video the car was idling around around 200-400 rpm. It would hardly register on my gauge cluster. I honestly don't think anything is wrong with the the car. That was just what it sounds like with 1 bolt in the downpipe and low idle. The solid mounts are going to be ridiculous though, gonna hold out for some used AWRs or something.

The flywheel is 9.5lbs.

Didn't realize it's that low. Makes sense.

That will be fun. I think mine is 8.3 lbs. Will be for sale soon though.

Christ, that is light! Do you hate it or are you moving to a clutch that isn't supported by it?

Love it. Going twin disc

Ah shit, I just dropped my diff off at the trans shop. Is there any benefit or reason why the stock distance piece is inferior to a solid pinion spacer kit? I mean, I'm not going to do hard launches or don't really plan on drag racing (as I'm scared for my transmission already).

Should I have invested in this before handing off an OSGiken to the builder?

In theory the stock piece can smoosh from the thrust load on the pinion. I dont know of anyone who's specifically autopsied a diff failure that hard and posted about it, but from looking briefly at some 1.6 failures that looks like a contributing factor.

So got the car running pretty good on wastegate pressure. Going to the 460CC injectors has been somewhat a pain. The idle was fine but after 180 degrees on the coolant the pulse width was set incorrectly so the car would stall. It did that to me right in a super busy intersection.

I have also noticed that VEAL does not play well for my idle. I have to lock the cells or it will put my VE so low that the car won't start back up again. Warm up Enrichment I still have to play with as well since the car just starts dumping fuel on a hot start.

Still, logs look alright and once I got my Time based EAE going tip-in got much better. Still some fine tuning left.

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Think I am going to try a center exit exhaust on the car.
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I also mounted my Kirkey to the floor. Short video of how I did it. Overall content with it, but it needs some adjustment. I think a quick release would make live easier with the seat mounted the way it is.





Manual boost controller suck...
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Good to see that turbo living again!

Car seems really well though out. Little things like that distribution block you made will make your life so much easier in the future.

Don't use veal for idle. It will do weird things

Thanks for the compliment. It's been a really fun project in my free time.

I got some soot around the exhaust manifold (between the head and manifold to be more specific) and I am not sure if I should try another gasket or to use some high temp cooper based RTV. I feel like the flange is just not super flat anymore, which was to be expected, but what did you use when the kit was on your car? Super happy with the turbo overall. Even on the little 1.6L it feels like I will have no more excuses being a second off the top guys this season, but tires are going to be used at a quicker rate for sure. :rofl:


Once I figured out how to lock the cells things got easier. VEAL has been a great tool for the other stuff though. I watched all those Megameet videos and they do a great job explaining MS2/3 to you. Do you have anymore literature or better yet subscribe to anyone on YT that covers it. I've already watched which really helped a lot, but I would love more info on open-loop, EAE, WUE, ect...

Ready to trash this MBC.

https://www.miataturbo.net/attachmen...ine=1455148962

I just need to find out how to wire it in on my DIYPNP. I thought I needed the mod kit for some reason but the microsquirt on my MS board seems to take care of it, doh.

Awesome build, really like the Rx7 clutch diff idea.
Any reason you went that route rather then the torsen?

Mostly cost and availability. I've only got $275 in this diff and just a Torsen chunk goes for around $500. I need to get in and shim the clutches for more preload, it's a bit weak factory if I'm honest.

Electronic Boost Controller in and working pretty well. I have it hooked to a switch in the car that will let me stop a constant 12v supply to the valve and open it to just run wastegate pressure. With the EBC working I get a pretty solid 12-13 psi pull that brings the power to a much more linear usage. It's a nice gradual pull which really lends itself to autocross.

I made a video of the install, how I did it, some footage of the install and a log of 2-4th gear pull. Really happy with this modification and I think every car should have it.

Didn't watch the vid but typically you wanna interrupt the signal line (ground), not the 12v. Otherwise you'd want to run an inline fuse or relay to prevent the switch from frying things.

Interesting, I thought that was for high current stuff. I used the blue power plug in the engine bay which goes through the fuse box so I assumed it would be fine.

It's just good practice. You switch ground, not power.

Good to know. Future modifications will be ground switched. Thanks dudes. :likecat:

Yeah that's what most use for the timing light. If you're really JDM you'll have a tiny cap that clips over it.

For the record switching 12v is fine, but too much on/off might blow the switch or fuse, which will really only leave you on waste gate, this isn't your fuel pump or anything.

Yeah, that is what I used for setting time as well, I put a spade connector on it so I can just quickly disconnect it if I have to run my timing light. It had the blue cap on it at one point but I have since lost it. :(

Thanks for the knowledge, I wish I was as electrically savvy as I am mechanically. Car pulls great on 13psi btw, very happy overall with this turbo/kit.

Finally closed on our house so now I get more time to wrench on the car. For the past 2 years I have borrowed garage space and was only able to really work on the car during the weekends. Now I get to work on some more long term modifications. Aero modifications, probably a single stage paint or wrap job, and some welding work. Really looking forward to try some things on this car.

https://www.miataturbo.net/attachmen...ine=1456155918

Nice garage!!

Thanks man. Need to make some bench space and start moving my tools into it. Not really looking forward to that process. Probably going to take it on this weekend. Car is going to take a back seat for awhile since it's running pretty well and autocross is about to start up.

Been a bit slow the past month or so with the house and the car running pretty good. Some light tuning here and there but mostly just looking forward to racing the car this season. I did pick up something recently that I plan on making a video for. This is the start of converting the car to E85.

https://www.miataturbo.net/attachmen...ine=1459436237

Picked up some Avanti S1 Storms in a 15x9 and some Rival S 225/45/15s. Wow what a difference the extra tire made. The difference is stopping power was pretty apparent as I was really early on the brakes almost everywhere. Ended up top 10 raw time and 4th fastest street tire car out. I love these Rivals. I would have gone with an re71 if they made them in a 225 but I think these are just as fast as an re71 in a 205. Huge difference in launching the car as well. My old Toyo R1Rs I couldn't launch past 3k or I would just roast them. I tried that with the Rivals and just bogged off the line. My region is hosting a nationals tour at Bristol Motor Speedway in a few weeks and I am really excited to see how I do against some of the competition.

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Found a bit of time to make a small heat shield on the car. Was also running into a very strange lean condition driving the car. My target AFRs are a bit rich and I was seeing 12.1: climbing up to 16:1 above 4500 RPM and 10 PSI. It just out of nowhere started to happen. So I did a fresh air calibration on my LC-2 and that still didn't change much except my doubt on the sensor failing. So I decided to change the fuel filter and, bingo, AFRs on target. Love this LC-2 and being able to calibrate it. I would have my doubts in other units that were calibration free.

https://www.miataturbo.net/attachmen...ine=1462829041

So I thought I knew how a PCV system worked until I joined this forum. I can't believe how massive the topic seems to be and how argued it is. So with that out of the way...

Here is my inexpensive catch can that I ripped off from this guy, and then found others doing the same thing on here. Overall super simple and very inexpensive. The only real issue with it seems to be getting the petcock to close since it's designed to close under pressure and it will be seeing vacuum. I've got a small motorcycle petcock that I am probably going to use in the future but for now a small washer inside keeps the seal at all times until a better solution can be found.

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My region was host to the SCCA match tour at Bristol Motor Speedway this weekend. The class I run doesn't have any national PAX time so it was set up as a local event as well. The cars in SSM,SM/SMF and XP were pretty crazy. I really have no desire to participate at that level so I will probably start getting the car up to safety for some track time. The event was really enjoyable and the pace was extremely quick for the amount of cars we had.

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I also got to see how well my catch can setup was working. This was after 150 miles and 6 autocross runs. Honestly it smelt pretty heavily of fuel so I am wondering if I need a check valve in the return hose to the intake manifold. My oil doesn't smell like it's contaminated with fuel when I open the valve cover fill port or dip stick. Just assume it's some fuel being forced in under boost.

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The head of TECH was a guy I've been racing with for a while, so during other run heats he let me get on the scales.

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All sorts of cutting wheel mods, no passenger seat, no hardtop or window glass, and 3/4 tank of fuel. Cross weights are a bit off from the scales being on a slight incline.
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So the Bristol event made me realize a few things.

1. I am never going to compete at this high of a level.
2. Considering 1 I am now going to try and prep up the car for some HPDE and some street miles.

With that I think my car needs to start with a small bit of aero modifications.

First I plan to build a spoiler and see how that balances the car. Trying different AOA and seeing how it feels or if any results come from it. BlackBird Fabworx sells a very nice one for around $300. It has also been proven by a few people on their local tracks. I've read one guy credit the spoiler to a 3 second difference in lap times over a 1:20s course.. Not sure how legitimate that claim is but other stories also come up with some significant gains. Not one to spend copious amounts of money I decided to make my own. I am already about $50 into materials but I bought enough to build 2 since I'm sure I'll mess something up.

So here is where I am currently at.

The proof of concept with some scrap aluminum stock I had.
https://www.miataturbo.net/attachmen...ine=1463783267

Mock up of the larger version using the same turn buckel (Home Depot, claimed 150lbs load capable) and some 1.5 x 1.5 x 1/8th inch aluminum L stock.
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About 18 inch height cardboard. Probably going to go about 14 inches with the poly-carbonate.
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Here is the final version, now 2 more to go. It's a lot easier when you can use the original as a template but it's still pretty time consuming.
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Progress continues. Now is the time to get the poly-carbonate for it. I want to keep around 2 inches of space around the outside of the supports. I am hoping that 3/16 thickness will be adequate for the job. Really happy with the final product but mounting is going to be tricky. I am thinking about using some blind rivets (nutserts) in the trunk for ease of install. I think some M6 inserts will be fine for strength...and that's the largest manderal I have. lol

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Lowest AOA
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Still some minor finish work to do on it but pretty happy overall. I am using 1/8th Lexan right now and plan to transfer the template over to another sheet of 1/4" that I picked up. This is about the max AoA I can achieve with the current design. I picked up a ton of Lexan from a dude out in the boonies on Craigslist, so I will have plenty of material to play around with.

The mounting was a bit tricky and I would have liked to get it further back. I think the next one will be 8 to 10 runners with 12-14 inch supports. I may need better hardware for that though.

https://www.miataturbo.net/attachmen...ine=1464470471

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Went to the local 1/8th mile track a couple weeks ago. I set up launch control, kinda, found some strange bugs within my wiring harness that I need to track down but, I can still get it to work as long as I hit my lights on, odd. The best time I was able to run was a 9.3@76mph. The car has more in it for sure but it being an autocross car I don't want to set up the boost controller for max torque and have it set up to feed power more like a naturally aspirated motor. I find the car much easier to drive fast that way. No in car video but I did have my wife shoot a run with my buddies bolt on STU 350Z.


I also got to test out my spoiler this weekend over a 2 day event. I didn't change anything from Bristol last month except the spoiler and launch control. I ended up winning my class by .8 of a second and was top 5 in RAW time. The car was absolutely fucking flying. I had people asking me all sorts of questions about the spoiler and wanting a ride. I was the second fastest car on street tires and only differed from the full STX prep FRS by .057 seconds. He is also racing PRO and has been autocrossing for over 10 years. I am sure my car has more in it with a more seasoned driver. I want to do a few other aero mods but I may wait until the off season since the car feels so neutral right now and it's winning.

5th down
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Spent the morning building a shift boot. Did this very inexpensively.

Another fun time with Miata's at the Gap. Ended up being the lead this time with nothing fun to chase. :(

Started to get some bends and marks on my turbo water inlet fitting from the engine moving so much in the engine bay. I can't really justify nice supermiata mounts or the drop mounts offered by Blackbird Fabworx so I went with an inexpensive engine damper option. It's cheap and may help my mounts last longer or, at the very least, keep my engine from hitting the engine chassis.

I have some cheap-ish mounts in the works, stay tuned. Did you ever get those coils mounted? We have a brackets and wire for those now.

I need to get a duckbill made for mine, assuming it doesn't unbalance the car as I cant run a splitter. But I see you don't so...

I haven't done the coils yet. I was going to do them with my injectors and fuel pump for E85. I just want to do it all at once during the off season. Right now the car is winning and easy to drive. I don't want to upset it, lol.

Already have the bracket you all are offering, but the wiring I may be interested in. I don't see them listed on the website, can you link me more details?

The spoiler didn't unbalance the car for autocross and high 3rd gear mountain runs but some tracks it could if the speeds are were high enough, the crazy amounts of drag at high AoA would limit top speed for sure. I also don't run a rear bar, largest RB front bar on a 440/300 Bilstein HD setup. The car is about as budget as you can get while still being competitive on street tires.


*Edit
Can't get the video to embed, not sure what has changed since the last time I posted.

saw first post of your thread and immediately hated you. there are very few guys I hate more than that rx7 guy

but

then I kept reading. and you're actually doing things right. so all is well again and you get a +cat :)

I thought you might have had the bracket already, couldn't remember. Ignition wires, not to be confused with harness. Theres too many variations in how people install them and between each chassis, but I suppose I can come up with some sort of 4 coil pigtail, hmmmmm....

In any case I see you have the stock LS2 truck harness. There is a certain sort of oragami you can perform on that harness to make it fit our bracket without cutting it apart.


Im sure these picture will provide you, in great detail, everything you need to know about the folding process :)
before
https://cimg5.ibsrv.net/gimg/www.mia...b29b6d85c2.jpg


after
https://cimg6.ibsrv.net/gimg/www.mia...178834c5ab.jpg