tune with cam question.
05-07-2003, 01:19 AM
#1
tune with cam question. Ok.....this is kind of a mute point for me (already done) but a number of people have asked me this question. I know that even stock cars can show gains from a performance tuning, but for questining sake, lets assume that the factory tune was perfect.
If a person installs a new cam or heads in a car and does not change ANYTHING else (EGR, AIR system, MAF), do they need tuning.
My answer was always "no...I don't think so..."
Reason being:The computer does not know what "cam" is in the car, all it knows is how much air comes through the MAF and what the O2 readings are (rich/lean). If the MAF is stock, wouldn't the new cam just cause the engine to pull more air? The MAF would read this increased air flow and just add more fuel.
Adding headers would also not cause a problem with tuning right? You still have the factory MAF and it’s still calibrated with the computer.
Chris
If a person installs a new cam or heads in a car and does not change ANYTHING else (EGR, AIR system, MAF), do they need tuning.
My answer was always "no...I don't think so..."
Reason being:The computer does not know what "cam" is in the car, all it knows is how much air comes through the MAF and what the O2 readings are (rich/lean). If the MAF is stock, wouldn't the new cam just cause the engine to pull more air? The MAF would read this increased air flow and just add more fuel.
Adding headers would also not cause a problem with tuning right? You still have the factory MAF and it’s still calibrated with the computer.
Chris
05-07-2003, 01:36 AM
#2
Re: tune with cam question. I think your theory works on headers, but not on cams of a decent size. Somehow cams over a certain size fake the PCM into running extra rich. Another thing the PCM doesn't seem to adjust for is idle speed with big cams. I'm not sure what the explaination behind it is, but maybe it's related to valve overlap or missfire. Even if you didn't tune, you still have to program the PCM to ignore idle missfire.
05-07-2003, 04:07 PM
#3
Re: tune with cam question. hmmmm....I didn't think about the idle speed or the missfire problem.
I don't understand why the car would run any richer/leaner than it would otherwise (off idle and WOT). Again, the computer gets all its info from the MAF and O2s.
I'm sure there is someone on here who can explain this to me.
Chris
I don't understand why the car would run any richer/leaner than it would otherwise (off idle and WOT). Again, the computer gets all its info from the MAF and O2s.
I'm sure there is someone on here who can explain this to me.
Chris
05-07-2003, 06:42 PM
#4
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Re: tune with cam question. I would think that the car would run lean from all the extra unburned fuel and air getting pulled into the exhaust pipe causing the O2 sensor to think the car is too rich. Regardless I would think that either cam or headers would cause the problem.
05-07-2003, 11:14 PM
#5
Re: tune with cam question. The question I'm trying to get answered is WHY.......at 3000 RPM (for example) you are not getting missfires anymore (if you are, you have problem). You don't have any leaks anywhere (air comes in the TB and exhaust goes out the tail pipe) so the MAF is still reading the air comming in.
This is why I posted this question. Everyone seems to "think" that it needs tuning to work, but it seems no body can give a definitive answer.
Someone out there (someone from TR or LG....anyone....) who has really worked with these cars should be able to answer the question.
Chris
This is why I posted this question. Everyone seems to "think" that it needs tuning to work, but it seems no body can give a definitive answer.
Someone out there (someone from TR or LG....anyone....) who has really worked with these cars should be able to answer the question.
Chris