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I have a 1995 mx3 with the KLDE how big should my eshaust be, I wanna go turbo next year, I was think 2.5" should be jus right

I think 2.25 should be ok. 2.5 may be a bit to big for n/a . I may have lost a bit of torque but gained hp from going 1.8 inch tgo 2.5

if turbo 3''

I kind of thought the general rule for N/A was something like 1" per liter... So a 2.5L would be 2.5". Of course, I don't know much of anything, so... But that Exhaust Pressure faq that I rewrote has loads of info in it to read over!

That's an awesome rule . I'm gonna tell my friend with his 5.7L Mustang. lol, but I guess that's what dual exhaust is for.

I'd kinda like to try dual exhaust from the headers back; no y-pipe.

It's just a rule of thumb, but a good guideline none the less, but there are other factors as well like mendrel and crush bent. As well, some like going 2.25 for better low end, and like fieromx3 mentioned, if your going forced induction, you want larger since you are forcing more air in, you need to efficiently get that air out (which would help the turbo spool as well).

so go 2.25 this year and when goto Turbo change it to 2.5?

I agree, 2.25 is better. But if your going F/A you might aswell get 2.5

I like 2.25 because there are alot of mufflers, cats, ect that support that

tehbrookzorz wrote:That's an awesome rule . I'm gonna tell my friend with his 5.7L Mustang. lol, but I guess that's what dual exhaust is for.

I'd kinda like to try dual exhaust from the headers back; no y-pipe.

You have to keep in mind that the change in area is not linear with respect to the change in diameter. The change in area has a r^2 dependence. In other words, the area increases exponentially with respect to the radius increase. For example, dual 2.5" exhaust has approximately the same area as a single 3.5" exhaust pipe; not a 5" exhaust pipe. In fact, a 5" exhaust pipe has exactly double the area of dual 2.5" exhaust. So, one 5" pipe is equivalent to quad 2.5" exhaust.

either way 2.25 or 2.5 will be better but i think its personal prefrence. I have 2.25 and its just fine. 2.5" you will loose a bit of torque but will have more in the high end, compared to 2.25 will retain torque but of course not in the high end. Either way its going to barely noticeable. I think if its a daily driver think about what you do the most city of highway driving. if city than go 2.25 for the torque, if highway go for high end!

Just have a exhaust valve that varies with rpm Sort of VRIS for the exhaust.