Tuning Help
Thread Starter
Drifting
Joined: Mar 2000
Posts: 1,956
Likes: 135
From: Maryland
Tuning Help
Last year my car started to feel weak at high RPM's. I ran it on a dyno:
http://www.geocities.com/rx7rob/Vettepics/AFR.jpg
and found it to be running rich and weaker than I expected. Car has Vortex, removed MAF screen, catless, and hollowed out mufflers. No the power didn't disappear when the cats were removed.
I got autotap and an AFR1. Front O2's look good at .87-.88 and go to .91 at higher RPM's with just occasional knock retard at the higher RPM's. I install the AFR1 and dialed back some of the fuel at WOT. O2 is now .88 right up to redline. Doesn't feel like the power has come back, and I seem to be getting more knock retard. I run 94 octane fuel.
Anybody have any ideas? Could this be indicitive of something like a weak/broken valve spring or bent push rod?? I have a few weeks of warranty left, .....
Thanks
Rob
[edit, WTF happened to my sig ?]
[Modified by Rx7Rob, 7:10 AM 4/21/2003]
http://www.geocities.com/rx7rob/Vettepics/AFR.jpg
and found it to be running rich and weaker than I expected. Car has Vortex, removed MAF screen, catless, and hollowed out mufflers. No the power didn't disappear when the cats were removed.
I got autotap and an AFR1. Front O2's look good at .87-.88 and go to .91 at higher RPM's with just occasional knock retard at the higher RPM's. I install the AFR1 and dialed back some of the fuel at WOT. O2 is now .88 right up to redline. Doesn't feel like the power has come back, and I seem to be getting more knock retard. I run 94 octane fuel.
Anybody have any ideas? Could this be indicitive of something like a weak/broken valve spring or bent push rod?? I have a few weeks of warranty left, .....
Thanks
Rob
[edit, WTF happened to my sig ?]
[Modified by Rx7Rob, 7:10 AM 4/21/2003]
Instructor
Joined: Sep 1999
Posts: 163
Likes: 0
From: Orlando FL
Re: Tuning Help (Rx7Rob)
Rob,
The A/F ratio is definitely too rich at the top end. You really need a wideband O2 sensor to determine the actual A/F ratio rather than utilizing the front O2s. They just are not accurate enough outside if 14.7:1 to makes changes against. Looking at your graph I suspect that COTs is kicking in. If that is happening you will have a very difficult time leaning the car out past 5K.
Tim
http://www.cs-performance.net
The A/F ratio is definitely too rich at the top end. You really need a wideband O2 sensor to determine the actual A/F ratio rather than utilizing the front O2s. They just are not accurate enough outside if 14.7:1 to makes changes against. Looking at your graph I suspect that COTs is kicking in. If that is happening you will have a very difficult time leaning the car out past 5K.
Tim
http://www.cs-performance.net
Thread Starter
Drifting
Joined: Mar 2000
Posts: 1,956
Likes: 135
From: Maryland
Re: Tuning Help (TimZ28)
What the hell are COT's?
Looking at your graph I suspect that COTs is kicking in. If that is happening you will have a very difficult time leaning the car out past 5K.
Tim
Looking at your graph I suspect that COTs is kicking in. If that is happening you will have a very difficult time leaning the car out past 5K.
Tim
Instructor
Joined: Sep 1999
Posts: 163
Likes: 0
From: Orlando FL
Re: Tuning Help (Rx7Rob)
COT = Catalytic Over-temp
COTs will kick in if the PCM calculates that the cats are at too high of a temperature (this is not a measured value). The PCM will richen the mixture to cool the cats but it can do so to the degree that power is reduced. Correcting the PE tables generally will do little to compensate. The only option is to turn of COTs (can be done via LS1Edit).
Tim http://www.cs-performance.net
COTs will kick in if the PCM calculates that the cats are at too high of a temperature (this is not a measured value). The PCM will richen the mixture to cool the cats but it can do so to the degree that power is reduced. Correcting the PE tables generally will do little to compensate. The only option is to turn of COTs (can be done via LS1Edit).
Tim http://www.cs-performance.net
Thread Starter
Drifting
Joined: Mar 2000
Posts: 1,956
Likes: 135
From: Maryland
Re: Tuning Help (TimZ28)
Is that something AutoTap can monitor?
Seems like the AFR1 would help if thats the cause. The AFR1 is telling the PCM there's less air flowing into the motor. If the PCM is calculating Cat Temp based on A/F, it should be calculating that the motor is rich (since the MAF signal through the AFR1 is indicating less air flow).
Seems like the AFR1 would help if thats the cause. The AFR1 is telling the PCM there's less air flowing into the motor. If the PCM is calculating Cat Temp based on A/F, it should be calculating that the motor is rich (since the MAF signal through the AFR1 is indicating less air flow).
COT = Catalytic Over-temp
COTs will kick in if the PCM calculates that the cats are at too high of a temperature (this is not a measured value). The PCM will richen the mixture to cool the cats but it can do so to the degree that power is reduced. Correcting the PE tables generally will do little to compensate. The only option is to turn of COTs (can be done via LS1Edit).
Tim
COTs will kick in if the PCM calculates that the cats are at too high of a temperature (this is not a measured value). The PCM will richen the mixture to cool the cats but it can do so to the degree that power is reduced. Correcting the PE tables generally will do little to compensate. The only option is to turn of COTs (can be done via LS1Edit).
Tim
Drifting
Joined: Nov 2000
Posts: 1,456
Likes: 1
From: Allen TX
Re: Tuning Help (Rx7Rob)
no i don't believe autotap but but with ease you can. their scanner has it as a parameter. also you don't to turn off the cot but you can raise it.
[Modified by thefly, 2:03 PM 4/23/2003]
[Modified by thefly, 2:03 PM 4/23/2003]
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Thread Starter
Drifting
Joined: Mar 2000
Posts: 1,956
Likes: 135
From: Maryland
Re: Tuning Help
Finally got a chance to do some more WOT runs. Knock retard seems to have slightly diminshed. One thing I've noticed is that its MUCH less in 2nd gear than in 1st.
I wonder if its some kind of false triggering of the knock sensor due to exhaust noise? Maybe I need to edit the car and decrease the knock sensor sensitivity.
I wonder if its some kind of false triggering of the knock sensor due to exhaust noise? Maybe I need to edit the car and decrease the knock sensor sensitivity.