I think it might be in the tune but i'm really not sure - Miata Turbo Forum - Boost cars, acquire cats.

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Old 11-15-2015, 09:39 PM   #1
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Default I think it might be in the tune but i'm really not sure

I just rebuilt my motor I have 8.5:1 compression ratio and a lightweight flywheel. well basically now that I have the engine back in its very difficult to start it backfires on the exhaust side and sometimes it seems like it fires and tries to turn the motor backwards..i've checked my timing belt and checks spark timing and everything seems to be good. once it starts in runs perfectly but it seems the easiest way to start is by push starting it...any ideas on what might be causing this problem? I have about 10 miles on the motor.
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Old 11-15-2015, 10:24 PM   #2
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Can you post a copy of your tune so we can see if it is the issue, can't do much with out it.
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Old 11-15-2015, 10:26 PM   #3
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Did it run fine on ms before the rebuild?
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Old 11-15-2015, 10:38 PM   #4
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it worked perfectly with the MS before. It really baffles me.
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File Type: msq 91Miata1.6.msq (107.9 KB, 64 views)
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Old 11-16-2015, 01:35 AM   #5
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Coils are backwards or timing belt is installed wrong
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Old 11-16-2015, 08:37 AM   #6
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Quote:
Originally Posted by Savington View Post
Coils are backwards or timing belt is installed wrong
I'm pretty sure the coils are correct. Considering the engine runs very smooth. I will check the timing belt tonight.
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Old 11-19-2015, 08:10 PM   #7
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If you put in new injectors, you may have cranking PW too high.
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Old 11-19-2015, 08:18 PM   #8
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Looking through the tune; Your cranking PW @ 105*F is funky, there is a dramatic drop at that point. It could be causing the MS to interpolate around that wrong, leading to a hard start.
Did you scale the Req Fuel?

Also your AFR table looks weird along with the IGN table; though those will not cause the issue you're having. The tune looks like it could use some work.
Other than the tune being the issue, can you check to see if you are infact getting spark on turn over, ever time?

Do you smell gas when you try to turn it on and it fails?

What is the ambient temp?

Is everything grounded properly and/or plugged in completely?

Can you check your plugs for fouling or any other issues?

Last edited by HexRX; 11-19-2015 at 08:47 PM.
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Old 11-20-2015, 02:15 PM   #9
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Quote:
Originally Posted by HexRX View Post
Looking through the tune; Your cranking PW @ 105*F is funky, there is a dramatic drop at that point. It could be causing the MS to interpolate around that wrong, leading to a hard start.
Did you scale the Req Fuel?

Also your AFR table looks weird along with the IGN table; though those will not cause the issue you're having. The tune looks like it could use some work.
Other than the tune being the issue, can you check to see if you are infact getting spark on turn over, ever time?

Do you smell gas when you try to turn it on and it fails?

What is the ambient temp?

Is everything grounded properly and/or plugged in completely?

Can you check your plugs for fouling or any other issues?
I found a huge part of the issue. I had the starter housing powder coated and did not realize there is a needle bearing in there. And although I cleaned all the parts that bearing was full of sand..it turns over much faster now and starts alot more reliably. Although it seems sometimes the starter doesn't engage with the flywheel....I'm really not sure what I'm doing with the tune. I grabbed a base tune and ran auto tune on it. I'm not currently running boost and I'm keeping it under 4k. I wanna get a few miles on it before I take it to the dyno. But if you have suggestions for the tune or maybe there is a better base tune to start with. I would very much appreciate the help. So far I have about 50 miles on the engine and it seems fine although not much power.
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Old 11-20-2015, 04:33 PM   #10
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Start with the base tune and tune idle by hand. Then use the settings within VEAL to prevent it from adjusting your idle cells when autotuning.
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