Tuner and Dyno gurus - please read
Thread Starter
Race Director
Joined: Aug 2003
Posts: 11,043
Likes: 3
From: San Jose Pat Tillman - American Hero
Tuner and Dyno gurus - please read
Yesterday I put my car on a dyno for the first time. I was overall very pleased with my numbers, but the tech running the dyno thought I might have something wrong with my car. I'll post the dyno sheet and let you guys have at it, but basically I'm just wondering where to begin diagnosing and then solving this problem. Essentially, there are two things I want you to look at:
1) What do you think caused the little "blip" in power in the upper RPM range?
2) My car seems to be running on the lean side (dangerously lean, some said in C4 Tech/Perf). The guy at the dyno suggested replacing O2 sensors? Someone in C4 T/P suggested that maybe it was the *dyno's* sensor that was off, as my A/F is straight as a board all the way across. I personally watched the guy hook up a new sensor just prior to my run, though, as the other was acting up.
Any and all ideas/suggestions are greatly appreciated! I'd much rather let the "doctors" diagnose this than just taking it to a different shop and throwing money into parts and dyno runs until I "see" a difference on the printout. Thx.
1) What do you think caused the little "blip" in power in the upper RPM range?
2) My car seems to be running on the lean side (dangerously lean, some said in C4 Tech/Perf). The guy at the dyno suggested replacing O2 sensors? Someone in C4 T/P suggested that maybe it was the *dyno's* sensor that was off, as my A/F is straight as a board all the way across. I personally watched the guy hook up a new sensor just prior to my run, though, as the other was acting up.
Any and all ideas/suggestions are greatly appreciated! I'd much rather let the "doctors" diagnose this than just taking it to a different shop and throwing money into parts and dyno runs until I "see" a difference on the printout. Thx.
Melting Slicks
Joined: Aug 2000
Posts: 2,925
Likes: 3
From: Dover NH
Originally Posted by Perfusion
2) My car seems to be running on the lean side (dangerously lean, some said in C4 Tech/Perf). The guy at the dyno suggested replacing O2 sensors? Someone in C4 T/P suggested that maybe it was the *dyno's* sensor that was off, as my A/F is straight as a board all the way across.
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
Originally Posted by Perfusion
Yesterday I put my car on a dyno for the first time. I was overall very pleased with my numbers, but the tech running the dyno thought I might have something wrong with my car. I'll post the dyno sheet and let you guys have at it, but basically I'm just wondering where to begin diagnosing and then solving this problem. Essentially, there are two things I want you to look at:
1) What do you think caused the little "blip" in power in the upper RPM range?
2) My car seems to be running on the lean side (dangerously lean, some said in C4 Tech/Perf). The guy at the dyno suggested replacing O2 sensors? Someone in C4 T/P suggested that maybe it was the *dyno's* sensor that was off, as my A/F is straight as a board all the way across. I personally watched the guy hook up a new sensor just prior to my run, though, as the other was acting up.
Any and all ideas/suggestions are greatly appreciated! I'd much rather let the "doctors" diagnose this than just taking it to a different shop and throwing money into parts and dyno runs until I "see" a difference on the printout. Thx.
1) What do you think caused the little "blip" in power in the upper RPM range?
2) My car seems to be running on the lean side (dangerously lean, some said in C4 Tech/Perf). The guy at the dyno suggested replacing O2 sensors? Someone in C4 T/P suggested that maybe it was the *dyno's* sensor that was off, as my A/F is straight as a board all the way across. I personally watched the guy hook up a new sensor just prior to my run, though, as the other was acting up.
Any and all ideas/suggestions are greatly appreciated! I'd much rather let the "doctors" diagnose this than just taking it to a different shop and throwing money into parts and dyno runs until I "see" a difference on the printout. Thx.
From what I see in the AFR trace, my money is on the fact that perhaps the dyno operators wide band wasn't working. Unless someone has modified your PE tables in your PCM, I doubt that its that lean. I could be wrong but its a virtually flat line like there was no activity. I dynoed a car today and I had a problem with my wide band, and it too indicated 14.5 nearly straight across the board. Your blip could be from knock retard, but without more data its hard to say what caused it but thats where my money is.
Also replacing your O2 sensors won't do anything but throw your cash away. In PE (power enrichment) mode the PCM ignores O2 feedback, and all fueling is based on the PE tables and incoming measured air flow from the MAF. Some will disagree but there are alogorithms in the code that account for incoming air flow as part of the fuel strategy in PE Mode.
Last edited by tjwong; Oct 24, 2004 at 08:24 PM.
Thread Starter
Race Director
Joined: Aug 2003
Posts: 11,043
Likes: 3
From: San Jose Pat Tillman - American Hero
Originally Posted by tjwong
From what I see in the AFR trace, my money is on the fact that perhaps the dyno operators wide band wasn't working. Unless someone has modified your PE tables in your PCM, I doubt that its that lean. I could be wrong but its a virtually flat line like there was no activity. I dynoed a car today and I had a problem with my wide band, and it too indicated 14.5 nearly straight across the board. Your blip could be from knock retard, but without more data its hard to say what caused it but thats where my money is.
Also replacing your O2 sensors won't do anything but throw your cash away. In PE (power enrichment) mode the PCM ignores O2 feedback, and all fueling is based on the PE tables and incoming measured air flow from the MAF. Some will disagree but there are alogorithms in the code that account for incoming air flow as part of the fuel strategy in PE Mode.
Also replacing your O2 sensors won't do anything but throw your cash away. In PE (power enrichment) mode the PCM ignores O2 feedback, and all fueling is based on the PE tables and incoming measured air flow from the MAF. Some will disagree but there are alogorithms in the code that account for incoming air flow as part of the fuel strategy in PE Mode.
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
Originally Posted by Perfusion
Thanks for the info and suggestions, Tom (it is Tom, right?!)... Glad to know that new O2s would be throwing money away. As for the blip - you'll have to forgive me, but what's knock retard? Something internally derived? And as for my PCM, I *highly* doubt it's been reprogrammed. I bought the car from a Vette dealer in AZ that took it in on trade from an elderly couple from WA. The CARFAX showed less than 5000mi. in their years of ownership...
Yes, its Tom
As for KR (knock retard) when the PCM "Hears" or :"senses" detonation via its knock sensors on the engine block. There is code in the PCM that retards timing to eliminate or minimize detonation. Hence the term knock retard. Of course when the PCM retards timing you get a little blip in the power curve. Sometimes on blown applications when one retards timing Hp actually increases, so it can go either way depending on the circumstances.
