quick question on exhaust and intake

[Gday360]

lancer sportback ralliart 04

Im a welder by trade and am going to be piecing together a new bigger exhaust and i was wondering what diameter i should go. and if there was anything i needed to know before i start putting it together i.e. distances between the cat and the resonator or muffler, and so forth. Also, im in the process of putting a cold air intake on. which one should i do first exhaust or intake or does it matter?

Any help would be great

Cheers all!

Garrett

 

[old-git]

A properly designed and fabricated exhaust system will give you better results than a cold intake, IMO.

I don't want to sound negative, but you could be the best welder in the world but the exhaust could make matters worse unless it is properly thought out and designed.

The design and size of the primaries and secondaries isn't something that can be recommeded with confidence as each engine setup is different. I suggest talking to a specialist for your engine to see what they recommend with regard to pipe sizes and lengths (the length and shape of the primary can have as much affect on performance as its diameter).

Are you looking for torque or BHP, as this will determe whether you build a 4-2-1 or 4-1 system.

How much space do you have, as this may mean compromises have to be made in order for the system to fit.

 

[Gday360]

Thanks for replying! i really appreciate it.

You didn't sound negative at all. i had no clue size and shape mattered so much. And i only specified i was a welder, as to lead questions away from my ability to fabricate, and more towards what i want to do. Now what do you mean by primary and secondary? im looking for more bhp. i don't think im too concerned with increasing torque at this stage. Im looking for a nice sound and a little more bhp. And one more clarification what do you mean by 4-2-1 or 4-1. i really am a complete novice at all this stuff so if you feel like youre sounding too dumb, you probably aren't.

Thanks again!

Garrett

 

[old-git]

If you treat the gases as if they are a fluid, you will get a better appreciation as to what is required to get the gases away.

4-2-1 means (on a 4 cylinder car or cylinder bank) the pipes from the head join in pairs then join again a little further on. 4 pipes into 2 pipes into 1. This gives good torque compared to 4 pipes into 1 which will maximise BHP at the top end at the expense of low RPM torque.

Primaries are the pipes from the head to the first junction. Secondaries run from here to the main exhaust pipe (assuming a 4-2-1 system).

To get a feel for exhaust design have a read of this

http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm

 

[T9 man]

That's some very handy information to know, thanks for the heads up OG

 

[Gday360]

Ah, ok. Welli had a look under my car, and the exhaust pipe is already about 2in dia with a couple 45s. Its a pretty straight shot and it seems like there is quite a bit of room to work with. Maybe i just want to start with a new header and exhaust and see what that does? And if i were to do an cold-air intake, do i need to do anything with the exhaust since there should be more air going through?

 

[old-git]

Ah, ok. Welli had a look under my car, and the exhaust pipe is already about 2in dia with a couple 45s. Its a pretty straight shot and it seems like there is quite a bit of room to work with. Maybe i just want to start with a new header and exhaust and see what that does? And if i were to do an cold-air intake, do i need to do anything with the exhaust since there should be more air going through?

If looking for gains I recommend buying a decent header from a reputable tuning house. I have made a lot of parts for my car, but left the exhaust to the professionals.

Any increase in intake volume from a cold-air intake will be minimal so won't affect exhaust design, IMO.