Bucking car
11-26-2008, 12:09 AM
#1
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Bucking car Ok I am pretty much a newb to tuning my car so please dont give me to hard of a time.
I have worked on my tune to the point that it idles "ok" so I am not to worried about that for now. My main complaint is that the car bucks like crazy It seems to mainly do it in the 1000-1500 rpm range. It is at its worst at 1500ish rpms and about 25mph in third gear. The car is stock gearing in the tranny and 3.42s in the rear.
The only way I can combat the bucking is to overpower it by just giving the car some gas. It really sucks not being able to just "cruise" the car I am always giving gas having it buck slightly while it slows down and then bucks like crazy if I try just holding the gas steady. Please any ideas on what I should look at changing at least the areas that would be involved to help narrow it down.
Please help me with this I am at my wits end on this damn car. By the way it is full bolt ons, ASA cam and heads off of a 06 gto nothing done to them. If it helps the car smells like it is rich alot of the time, sooner or latter I will figure out how to change that. I also added 37lb racetronix injectors, the only thing I change in the tune was the injector lb size.
I have worked on my tune to the point that it idles "ok" so I am not to worried about that for now. My main complaint is that the car bucks like crazy It seems to mainly do it in the 1000-1500 rpm range. It is at its worst at 1500ish rpms and about 25mph in third gear. The car is stock gearing in the tranny and 3.42s in the rear.
The only way I can combat the bucking is to overpower it by just giving the car some gas. It really sucks not being able to just "cruise" the car I am always giving gas having it buck slightly while it slows down and then bucks like crazy if I try just holding the gas steady. Please any ideas on what I should look at changing at least the areas that would be involved to help narrow it down.
Please help me with this I am at my wits end on this damn car. By the way it is full bolt ons, ASA cam and heads off of a 06 gto nothing done to them. If it helps the car smells like it is rich alot of the time, sooner or latter I will figure out how to change that. I also added 37lb racetronix injectors, the only thing I change in the tune was the injector lb size.
11-26-2008, 09:58 AM
#2
Bucking is caused by the ECM asking for more RPMs then the vehicle is allowing it to have.
For example, if at 25mph, your car is asking for 1200 rpms, "You can test what it wants to be by putting it in neutral at that point", and your GEARING is making go lower than that point, say 900 rpms at 25mph, you will have a surge because the car is trying to make the rpms go to 1200rpms but it cant because doing that would make the car accellerate. So you get your surge.
For example, if at 25mph, your car is asking for 1200 rpms, "You can test what it wants to be by putting it in neutral at that point", and your GEARING is making go lower than that point, say 900 rpms at 25mph, you will have a surge because the car is trying to make the rpms go to 1200rpms but it cant because doing that would make the car accellerate. So you get your surge.
11-26-2008, 01:28 PM
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Bucking is caused by to little air, the wrong timeing or the A/F ratio. I bet u have all 3. If you do not have a wideband O2 sensor get one. Get ur VE table and maf right. Next look where u have bucking and add timing. In both the main timing table and the low octane one and the idle one. Next find the table that adds air. It is throttle cracker in HPT. Add air at the point where u have bucking. If you put to much air in it will want to make the car go with no pedal.
11-26-2008, 01:50 PM
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Bucking is caused by to little air, the wrong timeing or the A/F ratio. I bet u have all 3. If you do not have a wideband O2 sensor get one. Get ur VE table and maf right. Next look where u have bucking and add timing. In both the main timing table and the low octane one and the idle one. Next find the table that adds air. It is throttle cracker in HPT. Add air at the point where u have bucking. If you put to much air in it will want to make the car go with no pedal.
11-26-2008, 05:16 PM
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You might be chasing your tail without the wideband. My car was extremely lean with heads/cam before tuning, even though it smelled rich. I think this is because I have no cats. But AFR is one thing you can actually look at and get right if you have a wideband before spending countless hours tweaking airflow and timing.
