KR when I get off the gas. Any ideas???
02-27-2004, 11:36 AM
#1
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KR when I get off the gas. Any ideas??? Really weird. Blown 98 Formula. Doing some boost testing and I only get KR when I am letting off the gas. It's really wacky. I know 98's have tempermental knock sensors but I find it weird I consistantly register KR when lifting off the gas. If I don't get into boost no KR, but if I do I only see it when I lift.
any theorys out there?
TIA.
any theorys out there?
TIA.
02-27-2004, 01:37 PM
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The transitions between boost and vacuum are pretty large compared to N/A engines. When you go from boost to vac, the fuel curve has a sharp drop and the timing probably goes up. The hard part to figure out is which way you want to move the curves.
One thing you might try is to change your MAP Hysteresis value. This should give you a little control over when the AFR comes back up. This would cause it to stay in PE mode shorter (for smaller values) or longer (for higher values) amounts of time after you let off the throttle. I'd say don't go higher than about 15-20 for this parameter...
One thing you might try is to change your MAP Hysteresis value. This should give you a little control over when the AFR comes back up. This would cause it to stay in PE mode shorter (for smaller values) or longer (for higher values) amounts of time after you let off the throttle. I'd say don't go higher than about 15-20 for this parameter...
11-01-2004, 06:56 PM
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Blackbird,
I was wondering if you have solved your KR problem with your car? Interestingly, I am seeing the very same thing. My car is a blown 98 formula, and I am seeing approximately 4 degrees of KR when I begin to back off the gas. It typically happens around the .24 g/cyl range. I am wondering if you tried playing with the MAP hysteresis and if it worked? Any help would be greatly appreciated.
Best regards,
98redformula
I was wondering if you have solved your KR problem with your car? Interestingly, I am seeing the very same thing. My car is a blown 98 formula, and I am seeing approximately 4 degrees of KR when I begin to back off the gas. It typically happens around the .24 g/cyl range. I am wondering if you tried playing with the MAP hysteresis and if it worked? Any help would be greatly appreciated.
Best regards,
98redformula
11-01-2004, 09:19 PM
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Guys check out your DFCO settings. That might be a good place to start. It sounds like you guys are entering DFCO, and it is pulling the fuel but not the timing. Do a search on the HPT site on DFCO, there is a lot of reading regarding it's function.
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11-05-2004, 09:37 PM
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Blackbird and WS6snake-eater,
I wanted to thank you both for your replies. I looked on the HP tuners website and found a lot of interesting stuff, but it didn't seem to match the problem I was experiencing. Interestingly enough, if it were the problem, I may not have been able to correct it as I have not found the settings discussed in the forums in LS-1 Edit.
In addition to the thanks, I wanted to post a solution that I have come up with that may help Blackbird and others. Now here comes the disclaimer...I am not sure if my solution is technically correct, so I would caution you to use it at your own risk. I am new to this whole tuning thing. If there is something wrong with the solution, hopefully somebody will point it out to me before my car has a problem. The solution does however seem to be working for me.
I found that the additional fuel added by PE was causing the KR. I was experiencing it because I was allowing my car to enter PE too early (at 23% TPS and 15 kpa MAP). The early entrance into PE caused a late exit, and hence the KR. After looking at my data, it consistently showed that the KR was happing at MAPs of ~57kpa at around 2000 RPM. To prevent this, I changed the MAP to enable PE to 70 kpa. The KR has been almost totally eliminated. This will obviously only solve your problem if you have similar criteria for your PE TPS and MAP enable parameters. I hope this helps.
I wanted to thank you both for your replies. I looked on the HP tuners website and found a lot of interesting stuff, but it didn't seem to match the problem I was experiencing. Interestingly enough, if it were the problem, I may not have been able to correct it as I have not found the settings discussed in the forums in LS-1 Edit.
In addition to the thanks, I wanted to post a solution that I have come up with that may help Blackbird and others. Now here comes the disclaimer...I am not sure if my solution is technically correct, so I would caution you to use it at your own risk. I am new to this whole tuning thing. If there is something wrong with the solution, hopefully somebody will point it out to me before my car has a problem. The solution does however seem to be working for me.
I found that the additional fuel added by PE was causing the KR. I was experiencing it because I was allowing my car to enter PE too early (at 23% TPS and 15 kpa MAP). The early entrance into PE caused a late exit, and hence the KR. After looking at my data, it consistently showed that the KR was happing at MAPs of ~57kpa at around 2000 RPM. To prevent this, I changed the MAP to enable PE to 70 kpa. The KR has been almost totally eliminated. This will obviously only solve your problem if you have similar criteria for your PE TPS and MAP enable parameters. I hope this helps.
