Backpressure: The myth and why it's wrong

[BV1]

Sorry , I didnt clarify, and no I don't think your being jerk (whoever said that)

Just saying when calculating what kind of exhaust you want, and what kind of powerband your tuning for, you need to now how many CFM your flowing, and in what kind of pulses, twin eng, inline 4, etc.

In that sense, all 2.0L 4 Cyl's draw in ROUGHLY (+- 5-7% depending on volumetric efficiency, DOHC, SOHC etc) the same amount of air at 3000 RPM... which means they will all expend roughly the same amount of exhaust gases (were not talking about AFR... just CFM). This means making the calculation in pipe diameter and length for peak torque for that RPM is roughly the same on each engine. 500cc (expanded by combustion) pulsed pairs exiting in an even fashion. (And no this isnt going into firing order, I dont want to go into that, but trust the calculations will be close and the pulses spread out.)

Thats all I was saying.

I am not disputing any powergains reported, at all. Just explaining why you will lose power if you go too big. I'm not calling brand X exhaust too big for your setup, with proper transitions any exit size will work. I'm talking in general, and the theory behind it. If you gained both top and bottom end power, then sweet, you got a great setup. Every now and then I stumble across a setup like that like I mentioned a few posts back. (I was exiting with 2.5" twin mufflers on my Suzuki X90 and picked up low and high as well). You didn't go TOO big, TOO soon, thats what Im trying to say.

By too soon, I mean, you have enough 2" or 2.25" piping (for this engine) to still produce great bottom end torque, and you still retained the flow for more top end.

If you went straight to 3" at the header (or ran open header for that matter) then you will have less bottom end power then stock. Thats all I am saying.

No worries mates,

-Steve