COPs
 

Alright well i figured i would take on installing COPs as I was getting pretty significant breakup on the dyno around 6300 RPM. Went for the Toyota COPs and followed a combination of a few threads on here and the FM big spark kit instructions (since I'm running Hydra). Car fired up on the first crank thankfully. I'm running the COPs as sequential direct fire. good news is Im no longer getting the misfire/breakup at 6300 RPM. Bad news is I'm getting noticeable misfire elsewhere in the rev range. Most noticeably around 4500 RPM. Doesn't seem to happen every time but happens enough to be an issue. The hope was the cops would solve these issues not create them.

Im running the general dwell settings recommended by Jason and most everyone else. My plugs are gapped to .040. I did not use a capacitor or an extra ground strap. I did wire cylinders 1 and 4 and 2 and 3 individually to their cooresponding 12v and ground connectors on the original ignition harness.

Here are some install pictures as this is a build thread after all.

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Wait a minute. ...where's the pic with the hold down bracket?

no idea what that is.

UPDATE:
misfire issue resolved. turns out two of the coilpacks I bought had cracked boots and were filled with some kind of crud/build up inside the boot. This must have been shorting out the spark. Replaced the boots and cleaned the coils. Added some dielectric grease to the plug porcelain and misfires disappeared.

decided to take the car to the strip to try it out. Never done drag racing before and figured why not. For those interested in a sound clip on the exhaust, this should do it. The video was my first attempt. I was never really able to get the launching down smooth but it was still a good time regardless. Car did pretty well considering its got 205k on the clock with a homebrew turbo kit. best time was a 14.1 at 101. Time slip for proof. the car should be able to see 13's with a better driver.

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Alright looking for some input on boost spike. The research I have done to this point seems to show that boost spike with these small t25s and MBCs is a pretty common thing. Now how much that spike is seems to vary. I see around a 3 psi spike currently when punching it from higher RPM. If i do a pull from something like 2.5k rpm, the spike is more subtle (2 psi perhaps). Most logs I have show spike to 14.1 and settle around 11-11.5. Here is what I have tried so far to limit the spike:

- Tried different MBCs (Ebay, Grainger, Hallman RX)
- MBC sourced from just before TB
- MBC sourced from just after compressor outlet
- Tried two wastegates (both from SR20 T25s)
- Changed the position of the wastegate to get as close as i can to where it was positioned before it was clocked
- Changed the wastegate preload from pretty tight to not very tight
- Multiple boost leak tests.

None of these really did much. Sourcing form closer to the compressor seemed to help slightly. Likely because of shorter hose length to the MBC and being sourced closer to the compressor.

I would like to be able to turn up the boost a little but I don't want to be spiking to 15+ psi just to see a steady 12psi. I should have the tuning and fuel to deal with it but would prefer to limit/eliminate the spike.

Options I am considering:
Try a different wastegate. Maybe something with a 10 psi spring so that the MBC doesn't need as much resistance to achieve 12 psi. I could get a fancy turbosmart adjustable internal wastegate but that thing costs more than the turbo itself.
Accept the fact the turbo is going to spike and just make sure I have the right timing and fuel to deal with it.

I cant seem to think of any cause for the spike at this point besides the turbo spooling so quickly that boost overshoots before the MBC has a chance to let some pressure into the wastegate. However, i know there are a ton of people on here using this turbo and I have to imagine not everyone has boost spike issues. Let me know if there are other things I should be looking for or if not, what route you would take to address the spiking.

I might have an extra EBC that is sitting on an EFR housing if you have the capability of running it in Hydra. You're 20 minutes away.

Ive heard EBC is a pain in the ass on 2.6, and 2.7 for that matter. That being said, I wouldn't mind playing around with it and see for myself.

Any other thoughts? I didn't want to make a separate thread about this but I'm thinking this question may be getting lost in here.

Definitely attempt to use EBC if you can. Any porting to the turbo?

I ported the WG slightly when i rebuilt it.

Do you have a picture of your port job? Do you know what wastegate boost pressure is for the two wastegates you tried? DIY Arduino EBC??

no picture, wastegate boost pressure is 6-7 psi

When i started working on this Miata I never had any intentions of doing anything with the sound system, but like most other "i dont need that" things, i ended up wishing I had a little more. Turbo sounds are great, but there are other times where music is nice to have as well. Car had a head unit and I put in some old 6.5 2 way speakers i had from a sound system on my old car.

I also had my old subwoofer set up that I pulled out of my daily driver. Figured, why not throw a sub into the miata and try to round out the sound, especially since i already had pretty much everything. During this I realized that I have had that Alpine amp for 14 years. In the tradition of keeping cost low, i decided to build a box. This was my first attempt building a sub box and i think it came out pretty decent. I wanted to try to leave myself some trunk space so I built the face of the box at an angle.

The project cost me about $30 in total and Im glad i did it. Music just always sounds so much better with a subwoofer in the system. I didn't like the idea of adding weight to the car but the box, sub and amp weighed in at about 25 pounds so I'm not too worried about that. I also stuffed the box with polyfil to help it with the smaller volume of the box.

Hi there dude.

Love the build! As for your boost spike i was getting similar with my external gate on my RX-7.
I found that because the lines are so long it takes half a second or so to fill the actuator. like you say it was slightly better when closer to the turbo.
Now ive changed all my lines to ID 6mm hose. This has cured it. im using a turbosmart MBC although i think ill be going back to my greddy OLED after i sussed this out.
Im hard lined also. i was 1/4 lines but the wall thickness made them 3.6mmID ive changed to 3/8 copper pluming tubing with compression fittings. 6.8mm ID.

Good luck

Thanks for the advice, I was thinking that could be an issue as well. I tried to go with bigger tube but the next size up would not work with the MBC fittings or the boost source fitting. The tubing that came with the hallman seemed slightly bigger than what I had before which i think is about as big as i can go with the current fittings. It seems to me like its just the combination of delay in MBC opening plus time to fill the waste gate. Perhaps I can come up with larger fittings and larger line but there may be a few other things i mess with first.

So i was never a big fan of my wastegate solution. It worked, but it looked ghetto as hell. I happened to come across another thread someone made detailing their waste gate solution on an sr20 turbo (https://www.miataturbo.net/diy-turbo...0-turbo-89713/) and figured id give it a go as well. picked up the same bracket, pulled the compressor housing and drilled and tapped some 6mm holes. I positioned mined slightly different and did not need to use an angled wastegate arm. I did have to cut the waste gate rod and rod end slightly as the distance is very short. All said and done i think it came out great. Looks so much cleaner than my old setup.

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Thought Id give a little update. Like most of the people on here i couldn't leave well enough alone. some of you may have seen the less than stellar results i got back when i sent my rx8 injectors to be cleaned and flowed. I bought a set of "re manufactured" ones and although they flowed within tighter tolerance, all their characteristics differed from the ones I had (color, static rate and dynamic rate). I felt they were probably some cheap knock off so i said screw it returned them and went with a set of Flow Force 640cc injectors. They are overkill for my current needs but at least I know they are top quality and flow matched.
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Then I said screw it, if i have bigger injectors i might as well try to make more power (that's not entirely true but it certainly helped me justify the purchase). I picked up a new GT28R from the S15 Silvia. Its essentially a GT2560 with some coating on the turbine housing, iconel turbine wheel and a divider built into the turbine housing. It was also couple hundred cheaper than a GT2560.
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during the install i noticed my down pipe had cracked at the flange which appears to have been a common problem with these VERY old FM/Begi down pipes. I also started getting some boost creep as i figured the small bellmouth portion wasn't allowing the waste-gate to dump out enough air. the pipe was also 2.25 inches fo the first couple feet which is not ideal. I weighed the options and went to Abe from Artech to have him custom make me a down pipe to mate to my existing system. I went with 2.5in as thats the size of the rest of my system. It did take a good amount of time before Abe got to my downpipe but as most know, his work is amazing. Even better, he actually managed to get the downpipe to link right up to my custom exhaust based solely on pictures i sent him. Its pretty amazing actually.
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Here is the old vs new.
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In a month or so Ill likely take it back to the dyno to do more spark tuning. My hope is to see this car make around 240whp

Dyno!
 

Alright just got back from the dyno. Very happy with the results. This was done on Ptuning's Dyno Dynamics. The tuner there said its generally around 10-12% lower than a Dynojet depending on the car. I wasn't there for the numbers but I wanted a point of reference since my first tune was on a Dynojet.

Our baseline run put down 204whp and the run we finished with made 228 whp. boost peaked around 12.5 and tapered to 11 by redline. Turns out I had two pretty good boost leaks. Hopefully that eliminates the drop off.

Splitter
 

I decided to make a splitter for my car. I haven't done anything to it in a while and was looking for something to do. First and foremost I did this as a cosmetic thing. If it has some positive effect on down force that's great but that's not the reason I made it. I looked at making it from more expensive materials like plastic or alumilite but ultimately chose to just try making one out of plywood to see if i even liked it. I didn't want to go crazy with it. I was looking for something that stuck out somewhere between the two Track Dog splitters. I also didnt want to use turnbuckles as i thought they were too a bit too "ricey" given this is a cosmetic thing.

I'll be honest, I'm not thrilled that i used plywood on my car, especially when it was not made as a performance minded modification. However, I do think it came out pretty good. Id like to hear your opinions. My feelings will not be hurt if you think its ghetto.

First step was to remove the R lip and create an outline on the sheet of plywood. I used 1/4 plywood for this. It was around $20. then i cut it out with a jigsaw and sanded the edges. Next. i drilled holes in the lip and the splitter. I also wanted to mount the splitter to something more structural than just the flimsy R lip. I made two brackets out of aluminum that mount the the tow hook bolting points. Hopefully this provides more support at speed when hitting things, etc.

I then painted it using two cans of rustoleum bed liner paint. I'm hopeful this will keep out the moisture. I almost never drive the car in the rain (not my daily) so that should help. The texture of the paint does mask the fact that its wood vs plastic or some other material.

Then I mounted everything and finished off the front with some door edging trim from autozone.

Uhm........can I copy your splitter?