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Popping and backfing under boost

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Old 04-14-2009 | 10:28 AM
  #41  
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Originally Posted by SuperC1
It had it up to 15 at one point, then I backed it down, I may give it a try at 18 and see what happens. 20 seems like it could be dangerous with my compression.

OK, did not see that you are running the 10.8, Yea you are right, 20 might be a little high, but if you had it up to 15 and it was still doing the same then I would think that it is probably something else, 15 degrees should be enough for 7lbs but if it is only hitting 4lbs then that still is too little, try the 18 and see if any changes occur. On high compression applications as yours, I usually take 1 degree per pound, but of course this multiplies as the boost goes up, meaning if you are running say 10lbs I just do not take out 10 degrees I will add another 1-2 degrees, add in the compression and take out another 1-2 to be safe. so at lets say 7 lbs with your compression I would take out a total of 10-11 degrees. so if you are running at a total of 28 degrees then 17-18 should be OK, Of course you are running premium fuel yes? I know this is a dumb question but you would not believe how many forced inducted cars I have tuned that were running 87 octane...
Old 04-14-2009 | 11:45 AM
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Originally Posted by moehorsepower
OK, did not see that you are running the 10.8, Yea you are right, 20 might be a little high, but if you had it up to 15 and it was still doing the same then I would think that it is probably something else, 15 degrees should be enough for 7lbs but if it is only hitting 4lbs then that still is too little, try the 18 and see if any changes occur. On high compression applications as yours, I usually take 1 degree per pound, but of course this multiplies as the boost goes up, meaning if you are running say 10lbs I just do not take out 10 degrees I will add another 1-2 degrees, add in the compression and take out another 1-2 to be safe. so at lets say 7 lbs with your compression I would take out a total of 10-11 degrees. so if you are running at a total of 28 degrees then 17-18 should be OK, Of course you are running premium fuel yes? I know this is a dumb question but you would not believe how many forced inducted cars I have tuned that were running 87 octane...
Yea, 93 octane is the lowest I can go. 18 degrees should be optimal but 15 should let it run safely, I'll give 18 a try and recheck the map sensor and see what happens.
Old 04-14-2009 | 02:51 PM
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My car acts the exact same way when the plugs go. I run the NGK 8s gapped at .035 and one set lasts all year. Boost off the 1 bar spring and a 50 shot of spray. When the nitrous kit was hooked up wet it fouled the plugs so I just disconnected the fuel line and fine. If your doubting its your tune/plugs make sure your charging system is 100%. My alternator started to die last year, car still started, ran fine but only charged at like 11 volts. I was fouling out plugs left and right.
Old 04-22-2009 | 07:57 PM
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Originally Posted by SincalT/A
What is your voltage reading through all this?
Made another test run, voltage was at 13.2-13.5
Old 04-22-2009 | 10:30 PM
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i had the same issue ones. it would sputter and i cant remember if it was popping but im almost sure it was. i took some fuel out of it and it was perfect. try also smoothing out the VE. i was tuning and it got a little spiky, that also cause some issues. i now make sure my timing curve is smoothed and fuel is smoothed. i also run tr8s, your should be able to run these all day, lean out your off boost and idle and they are perfect. i use to run tr10s yes 10s, in a 383 wieand supercharged truck as a daily driver and never fouled one of those. i also dont run as rich as some, 12.0-12.2 under boost. drowning it with fuel wont fix a bad timing curve.
Old 06-05-2009 | 04:02 PM
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Problem solved, it was fuel, the single walbro wasn't cutting it, changed over to a double pumper setup, now she pulls all the way to 7500 rpm easily. Thanks for all the input guys, I really appreciate it.



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