throttle body, cat back?

basically, what is the throttle bodies purpose, and how does changing this help performance?

and a catback exhaust? how does a aftermarket catalytic converter help performance?

thanks

the throttle body does half the job of the carburator, it controls how much air enters the engine. buying an aftermarket throttle body will allow more air into the engine and therefor more fuel because it is less restrictive and it's larger. if you only buy a throttle body you may not notice much of a difference in power(if at all, maybe a couple of horsepower) but if that is what is restricting the airflow you will. i'd say first install a cold air intake and new filter, then install a throttle body, then get your heads ported and polished or get new ones.

A catalitic converter is very restrictive on the exhaust, it's full of tiny platinum (or another catalist) beads that help reduce harmful emmissions. installing an aftermarket one might help if it is less restrictive, but you might fail your emmissions test. of course you can have the stocker installed when you go for drive clean and then change it (i am not condoning illegal activity i am just saying what could happen). also you might notice more performance gains from other mods (headers, cat back exhaust, etc) then you would if you didn't install the less restrictive cat (or just run a test pipe and not have a catalytic converter at all but that's bad for the environment and i dont suggest you do it)

hope this helped

yep, thanks man

also curious though, what does heads ported or polished mean?

sometimes upgrading throttles bodies can hurt performance. Think of an engine as a big vacuum. It pulls air in, and it pushes it out. The faster it can draw and push air out, the more hp it makes. Air velocity, consequently is key. Sometimes upgrading to a bigger throttle body or larger exhaust piping can slow intake and exhaust velocity down and decrease hp because its too large. However, thats not to say there isnt a throttle body that could increase performance. If all else fails, you could at least "optimize" the current one you have by countersinking the bolts, knife-edging the butterfly plate, etc.

Porting and polishing is a process thats done to the head ports. Porting meaning, removing metal material from the ports to enlarge them, and polishing is just smoothing. Again, if not done properly, it can lose hp. A lot depends on the engine application, whether its naturally aspirated or forced induction. If its turbocharged for example, your going to want to open up the exhaust ports quite a bit more than if its a naturally aspirated motor, because exhuast energy is what drives the turbo. Usually youll hear the terms, "3 angle valve job" or something like that. Thats just how much material was removed. Its best to actually create the ports to look like funnels so to speak so the air velocity speeds up as it moves down the ports.