Re: Puzzling ignition issue
[Re: nitrousr]
#1901902
08/29/15 04:26 PM
08/29/15 04:26 PM
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Joined: Jan 2005
Posts: 2,540 Milwaukee WI
TRENDZ
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master
Joined: Jan 2005
Posts: 2,540
Milwaukee WI
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If you're sure it's ignition, I would check rotor phasing. I know I sound like a broken record on that point, but with small caps, boost referenced timing and high cylinder pressure, you have to get phasing correct. Phasing at peak cylinder fill when cylinder pressure is the highest(peak TQ) is a must.
"use it 'till it breaks, replace as needed"
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Re: Puzzling ignition issue
[Re: nitrousr]
#1901934
08/29/15 05:33 PM
08/29/15 05:33 PM
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Joined: Jan 2005
Posts: 2,540 Milwaukee WI
TRENDZ
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master
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Why the big step in the timing? Are you running a map, or pressure sensor? I would think you would get a much more even timing curve with load based timing. Maybe I'm not understanding what your set up is.
"use it 'till it breaks, replace as needed"
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Re: Puzzling ignition issue
[Re: nitrousr]
#1901940
08/29/15 05:44 PM
08/29/15 05:44 PM
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Joined: Jan 2005
Posts: 2,540 Milwaukee WI
TRENDZ
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master
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Milwaukee WI
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This is a generalization, but I would pull about .8 degrees pr lb of boost. That was with 93 ethanol pump gas. So, set up the timing curve like you would a N/A engine and remove timing in direct relation to boost pressure. If the timing at atmospheric pressure is 35, then at 3 lbs of boost the timing would be 32.6.
"use it 'till it breaks, replace as needed"
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Re: Puzzling ignition issue
[Re: TRENDZ]
#1901944
08/29/15 05:50 PM
08/29/15 05:50 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Romeo MI
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I'll ask ...if the timing drop is at the same rpm.. in other words.. is that rpm when you hit 3 psi and drops timing... that is a big drop
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Re: Puzzling ignition issue
[Re: nitrousr]
#1901993
08/29/15 07:05 PM
08/29/15 07:05 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Master
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Romeo MI
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Mr P i think i get where you are going here, right now its set up to go straight to 18* once the boost starts. But maybe a more gradual curve of timing versus boost? thats my thinking... have it follow the boost... is the point where it babbles at the timing drop
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Re: Puzzling ignition issue
[Re: nitrousr]
#1902010
08/29/15 07:28 PM
08/29/15 07:28 PM
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Joined: Jan 2005
Posts: 2,540 Milwaukee WI
TRENDZ
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You should have the 3 bar map on it. All your timing should be load/rpm based. Cruising around will want more than 35 degrees in certain situations, and less in others. Smooth transitions in the whole table. I believe msd allows for a 45 degree sweep.
"use it 'till it breaks, replace as needed"
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Re: Puzzling ignition issue
[Re: nitrousr]
#1902019
08/29/15 07:47 PM
08/29/15 07:47 PM
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Joined: Jan 2003
Posts: 245 regina sask
nitrousr
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regina sask
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Mr P I would think the timing drop is right before the babble starts. We do have the 45 sensor on. And double checked the box had the right sensor entered just in case.
Last edited by nitrousr; 08/29/15 07:49 PM.
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Re: Puzzling ignition issue
[Re: nitrousr]
#1902640
08/30/15 08:27 PM
08/30/15 08:27 PM
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Joined: Jan 2005
Posts: 2,540 Milwaukee WI
TRENDZ
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This is a sample of a decent timing curve for a 2 bar/ sbc. Get the timing curve corrected, then get after the fuel. It is only here to show the smoothness of the timing, and the range at different loads. Don't use these specific numbers as they are not intended for any motor but the one they were wrote for. If your engine rpm wont increase, it's because the engine load is higher than the engine power. You have a big blown hemi, you should have enough power, so your tune up has to be WAY off. Your timing curve is way out of wack, and most likely, the carb has a hard time transitioning from low boost to high boost. You are likely flooding, and retarding the engine at that part of the engines range. With tire spin, the engine can zing right through the bad section of the tune.
Last edited by TRENDZ; 08/30/15 08:41 PM.
"use it 'till it breaks, replace as needed"
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Re: Puzzling ignition issue
[Re: nitrousr]
#1905445
09/03/15 01:25 AM
09/03/15 01:25 AM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Master
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Romeo MI
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If the rich condition was caused by timing would it still produce the black smoke usually associated with too much fuel? Sure if its not burning it... with that fuel its slow burning and would like the timing... just get a good curve on it
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