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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 09-24-2016, 11:24 PM   #41
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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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Old 09-25-2016, 06:08 AM   #42
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Wait a minute. ...where's the pic with the hold down bracket?
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Old 09-25-2016, 11:24 AM   #43
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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.

Last edited by kmo25; 09-27-2016 at 10:44 PM.
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Old 11-22-2016, 02:08 PM   #44
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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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Old 12-14-2016, 08:05 AM   #45
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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.
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Old 12-14-2016, 08:29 AM   #46
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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.
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Old 12-14-2016, 08:50 AM   #47
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Quote:
Originally Posted by psyber_0ptix View Post
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 *** on 2.6, and 2.7 for that matter. That being said, I wouldn't mind playing around with it and see for myself.
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Old 12-15-2016, 10:19 AM   #48
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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.
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Old 12-15-2016, 12:02 PM   #49
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Definitely attempt to use EBC if you can. Any porting to the turbo?
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Old 12-15-2016, 12:46 PM   #50
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I ported the WG slightly when i rebuilt it.
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Old 12-15-2016, 04:21 PM   #51
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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??
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Old 12-15-2016, 06:41 PM   #52
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no picture, wastegate boost pressure is 6-7 psi
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Old 12-18-2016, 02:24 PM   #53
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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.
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Last edited by kmo25; 12-18-2016 at 02:40 PM.
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Old 01-01-2017, 10:27 PM   #54
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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
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Old 01-04-2017, 08:21 AM   #55
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Quote:
Originally Posted by GAVBEY View Post
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.
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Old 02-11-2017, 09:31 AM   #56
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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 (Wastegate solution for sr20 turbo) 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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