Bucking/Surging
Thread Starter
Burning Brakes
Joined: Oct 2009
Posts: 1,231
Likes: 1
From: Paramus NJ
Bucking/Surging
Maybe someone can help me, I have a SC'd Z06, ever since my SC install I am getting a slight bucking/surging issue while accelerating at low RPM. It will buck slightly as I try to accel and then will smooth out as the RPM rises over 3k. Has this happened to anyone else? Does anyone know what it can be? I am running an A&A kit, V-3si head unit, 3.8 pulley and full meth kit. Any help is appreciated.
Le Mans Master
Joined: Oct 2007
Posts: 6,149
Likes: 11
From: Greater Detroit Metro MI, when I'm not travelling.
Maybe someone can help me, I have a SC'd Z06, ever since my SC install I am getting a slight bucking/surging issue while accelerating at low RPM. It will buck slightly as I try to accel and then will smooth out as the RPM rises over 3k. Has this happened to anyone else? Does anyone know what it can be? I am running an A&A kit, V-3si head unit, 3.8 pulley and full meth kit. Any help is appreciated.
1- You are right at the boost level where your meth comes on, and the meth kit is cutting in and out, adding fuel in a large step which causes a momentary rich condition, making the engine lose power, then it goes back to normal, and repeats.
2- Your MAF signal is fluctuating (datalog it) due to turbulence over the sensor.
3- Your airflow is fluctuating because your blow off valve is opening and closing (this would only happen at part throttle. Datalog your MAP signal to verify.
The gist of the matter is that you will need to datalog the event to understand what is happening. Without that log all the forum can offer you are guesses. With the log you will know what is causing the issue and be able to fix it.
I'd love to log it for you but I won't be in NJ for a while now
Thread Starter
Burning Brakes
Joined: Oct 2009
Posts: 1,231
Likes: 1
From: Paramus NJ
That is a tuning issue. You need to datalog the air/fuel ratio while that happens to see what is happening; my first guess is that the AFR is fluctuating, and the cause could be one of the following:
1- You are right at the boost level where your meth comes on, and the meth kit is cutting in and out, adding fuel in a large step which causes a momentary rich condition, making the engine lose power, then it goes back to normal, and repeats.
2- Your MAF signal is fluctuating (datalog it) due to turbulence over the sensor.
3- Your airflow is fluctuating because your blow off valve is opening and closing (this would only happen at part throttle. Datalog your MAP signal to verify.
The gist of the matter is that you will need to datalog the event to understand what is happening. Without that log all the forum can offer you are guesses. With the log you will know what is causing the issue and be able to fix it.
I'd love to log it for you but I won't be in NJ for a while now
1- You are right at the boost level where your meth comes on, and the meth kit is cutting in and out, adding fuel in a large step which causes a momentary rich condition, making the engine lose power, then it goes back to normal, and repeats.
2- Your MAF signal is fluctuating (datalog it) due to turbulence over the sensor.
3- Your airflow is fluctuating because your blow off valve is opening and closing (this would only happen at part throttle. Datalog your MAP signal to verify.
The gist of the matter is that you will need to datalog the event to understand what is happening. Without that log all the forum can offer you are guesses. With the log you will know what is causing the issue and be able to fix it.
I'd love to log it for you but I won't be in NJ for a while now
By the way Sam, are you doing the Toys for Tots run this year?
Le Mans Master
Joined: Oct 2007
Posts: 6,149
Likes: 11
From: Greater Detroit Metro MI, when I'm not travelling.
Thanks Sam, I was thinking option number 1 might be the culprit because it seems to be just a single buck around the 3k rpm range and then accel is smooth. I don't have the equipment to datalog it all myself so I guess I will have to wait until I can get it back to my tuner and have him do it. With the weather changing and him being a good distance from me...... Add that to my daily changing work schedule and it may be next spring before I can get it there. Incidentally, I don't feel the surging when accelerating in 1st or 2nd gear. I just feel it at low rpm in 3rd gear and above. Im thinking the surging may still be there but im not feeling it because of the much stronger hp/tq in 1st and 2nd.
By the way Sam, are you doing the Toys for Tots run this year?
By the way Sam, are you doing the Toys for Tots run this year?
I'll PM you if I do; I'd love to see your car since a boosted Z is one of my number 1 considerations for a next vehicle.
Melting Slicks
Joined: Apr 2005
Posts: 3,418
Likes: 1
From: Chicagoland Area IL
Maybe someone can help me, I have a SC'd Z06, ever since my SC install I am getting a slight bucking/surging issue while accelerating at low RPM. It will buck slightly as I try to accel and then will smooth out as the RPM rises over 3k. Has this happened to anyone else? Does anyone know what it can be? I am running an A&A kit, V-3si head unit, 3.8 pulley and full meth kit. Any help is appreciated.
Dumb question is bucking/surging under light throttle?
Mike
Last edited by Skunkworks; Oct 2, 2010 at 01:45 PM. Reason: typo
Thread Starter
Burning Brakes
Joined: Oct 2009
Posts: 1,231
Likes: 1
From: Paramus NJ
The bucking/surging happens at low rpm acceleration, typically 3rd/4th gear at around 2,500-3,000rpm with the accelerator pedal depressed 2/3rds of the way or more.
Last edited by NJLS708; Oct 2, 2010 at 07:37 PM.
Melting Slicks
Joined: Apr 2005
Posts: 3,418
Likes: 1
From: Chicagoland Area IL
If MAF or other table(s) are off your trims can swing drastically. Ideally you want trims -10% or better. A negative number means ECM/PCM is pulling a bit of fuel.
Now before saying your tune is off...
* Have you cleaned and oiled air filter? Oil can deposit on MAF can throw it off.
* If you can't clear trims (software needed) then disconnect battery which will clear trims (yes windows will need to be reset). But if car runs better for a while, then gets worse, tune likely issue. EDIT but don't get on it too hard.
I can list a few more things but suspect driving and logging is best solution.
Mike
Last edited by Skunkworks; Oct 2, 2010 at 08:23 PM. Reason: Typo
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Instructor
Joined: Feb 2010
Posts: 244
Likes: 0
Maybe someone can help me, I have a SC'd Z06, ever since my SC install I am getting a slight bucking/surging issue while accelerating at low RPM. It will buck slightly as I try to accel and then will smooth out as the RPM rises over 3k. Has this happened to anyone else? Does anyone know what it can be? I am running an A&A kit, V-3si head unit, 3.8 pulley and full meth kit. Any help is appreciated.
i had the same exact issue as you.... i described it to my tuner and brought back and he fixed it in the tune... bring it back to your tuner
Instructor
Joined: Feb 2010
Posts: 244
Likes: 0
o hell ya u better go to a new tuner... lean will POP ur engine... as a matter of fact its good to run it a tad fat to be on the safer side... ur not gonna feel the 15 hp loss at the wheel... better to be safe than sorry
