Why is it that you can move up one cam size if you have a performance chip? is it just for idle quality, or for power throughout the entire RPM band?
thanks

 

Anyone?

 

huh? i reckon noone answered cuz we have no idea what you are asking. An 'off the shelf' chip does not allow you to run a bigger cam any more than the stock chip would. If you buy a 'custom' chip from a tuner like ed wright or formatto, it is tailored to whatever specs you give them, and again, if it is writtten for a stock car, does not allow you to change cams any more so than the stock chip would.

In short, a cam 'is' how the engine runs, if you chane it, then so does practically everything about that engines fuel and timing requirements. The chip provides the fuel and timing to the engine. So if you're shotting for more performace and driveability, you run a chip matched to the cam/engine.

 

Hi, sorry I wasn't more specific. When I was shopping for a cam, the parts guy looking in his catalogue asks me " do you have a chip?" . No I don't, why? " because if you did you can move up one size of cam. Just curious why this is, even the people at compcams on their tech help line say that for certain cams you "require" a chip. I had never really considered a chip after reading posts and books that say they are generally useless unless they are custom burned for your setup. But if it can help Idle quality or part- throttle acceleration then I'll think about it.
Thanks, Jeff

 

Ed's correct, that you need a custom prom if you want to change the cam (and often heads).

This is because of the factors Ed mentioned (idle and part-throttle), but also because the VE dynamics of the engine has changed.

Most of the stock eproms tend to be "overly rich" by GM design. This is why you can move up a "little extra duration/lift" and not really need a new prom. In fact, the engine may perform better because you are closer to the proper mixture now.

With SD, the VE tables MUST be changed to ensure the engine knows where to add fuel (and where to not). MAF is a little more forgiving (but not much), but MAF has a problem in the "idle department" and if you exceed the 255 gm/sec flow limitation.

For EFI cars, eproms are critical for optimum performance. Even a basically stock engine can benefit from a GOOD custom prom as it will have a better mixture and optimum spark advance.