Backpressure
 

Hello all. I need some info. Im in the process of adding a stright pipe to my FC. I have an 88 gxl and lookin to add a bonez striaght pipe, and exaust but my car is pretty much a daily driver. Ive been reading about how having virtually no restrictions in the exaust causes almost no backpressure, I need to know why this is bad/ if at all and what you guys would recomend. Keep in my mind my intentions are MAX POWER while keeping this car a daily driver- WHAT WOULD YOU RECOMEND>?:confused:

oh yeah and its a non turbo

Well, a turbo car needs as less backpressure as possible, in order for the exhaust gases to spin the exhaust wheel of the turbo as fast as possible.

This principal does not apply to NA piston engines, because these engines need the backpressure in order to "keep" the A/F mixture in the chambers while in overlap.

However, a rotary engine, unless ported, does not have any overlap (or rather a very small percentage of the overlap of piston engines), so an NA will benefit from the lowest backpressure as well...;)

You need a slight bit of backpressure to open the auxilary ports.

umm ok this sorta help me

would a 2.25" from the engine to a 2.5" tip provid just enough back presure to open the extra 2 ports

cool thanks guys so one last thing then, My upgrades are; a 2.5" stright pipe with pre-silencer, the Apex gt exaust which is 3.75" diameter pipe, so does all this shit have any backpressure?

well yes and no most na cars tha trequir back presure would have a set up similar to what i suggested

You mean a header, straight pipe and nothing else? NO.
You will need a presilencer and/or a muffler at least.

nah man like afull exhaust system

2.25" mandrel bent front engine up towards the rear of the car then a nice droopy 2.5" tip

yes, you can do this with a presilecer and muffler. but I would run 2.5 from the collector back

ok

S5 = 5th and 6th ports open by the air pump so backpressure not required there.

ahh i was thinking s4

I only know it in milimeters, but according to HKS, the cat back dual 50mm exhaust will yeild more low end torque than a 60mm that a T2 would use.

just wire them open.. i have seen no loss in the bottom end... and the same up top..

yer spose

i have 2.5 inch exhaust w/a rb header and a dynomax straight through high flow.......backpressure a plenty.....even spits fire!..:)