so i've been reading how ppl who have changed their exhaust, header, plenum, etc. are running less than ideal AFR (rich or lean)...tell me what you guys think about this train of thought:
if a person only changes up components that help flow air out of the engine (i.e. exhaust, header) they may run rich because there is less air in the engine.
if a person only changes up components that flow more air into the engine (i.e. plenum, intake, throttle body, etc), he may run lean becasue there is now more air in the engine.
so if i follow this thought, a person theoretically can have a close to ideal AFR if he cahnges up the right intake components and exhaust components.

this is only one of my random thoughts. i am by no means saying that this is right. i just wanted some opinons on the subject. who knows, maybe i can save a few hundred bucks on not reflashing my ECU after i get these parts.

 

I think that regardless of your mods, what will determine your A/F ratio will be how the ECU reacts and compensates for those mods. That is how a reflash works -by taking into account the mods you have and correcting the A/F ratio. A stock ECU has the capacity to compensate up to a certain point. So, regardless of mod combinations, it will be the ECU's reaction that matters...

 

yeah that's what i thought...thanks ZBoater

 

Putting on exhaust mods increases power because first of all there is less resistance on exhaust stroke allowing the piston to move quicker thus creating more torque(angular acceleration). At the same time the rapidly exiting exhaust helps to actually pull in more air from the intake side, causing a leaner condition, but in most cases more power (something known as scavenging). So both intake and exhaust mods can cause a lean condition. Most people have been ok with every NA mod in regards to running to lean, except when they put on test pipes or high flow cats. The more exhaust going out, the more air going in!