lets talk about exhast systems

[Mr Awsome]

so im looking at making a new exhaust for my car, been thinking about a few things in general.

question's i have:

whats the go with 2" 2.25" 2.5" and 3" exhausts?

why are they the best for e.g. NA, supercharged, turbo, 4cyl, srt6, v6 and v8, v12's. is it due to the back pressure needed and the flow of the motor?

what can act as flow stoppers e.g. cat converter, hot dogs, muflers and so on. how do they affect the flow of the system?

[biggo]

modern cat converters need alot of heat to work effectivly. The power loss of having one is so small its not worth the five figure fine you get if it fails emmisions.

Hotdogs are called resonators for a reason, the can quieten the exhaust noise to an extent.

You do not want back pressure under any circumstances, its not a fucking diesel with an exhuast brake.

So what you want is an exhaust that allows the exhaust gases the least amount of restriction, while allowing the catalyic convertor to heat up and work effectivly.

Cannons are gay, get a proper muffler if your getting a shop to do it.

[Frak]

They were ok back in the day when they were being put on Jap cars(GTR's etc) but as soon as they started gracing the rear ends of Falcadores they become gayer than Liberace....and that's gay!!!

[Jonny Rochester]

I was making my exhaust today. I have a 4A-GE (no turbo). The extractors are from Anthony, 4-1 with the collector a tad over 2". I have a short bit of 2" just at the collector flange, then I have 2-1/4" pipe all the way with cut and welded mandrel bends. I have a 2-1/4" hotdog in the middle of the car, and a oval muffler up the back. My muffler should be 2" or 2-1/4" in pipe size, but I got it for free and it's about 2-1/2" and may have a 3" tip.

For performance, the critical parts are the diameter and length of the extractors, and the diameter of the pipe at the collector or just after it. The diameter of the runners effect exhaust velocity. The length of the runners dictate the best RPM when all the pulses line up sweet and help each other along. The collector should not be too large because the velocity of the exhaust here help pull the next cylinders exhaust along.

After the collector, it can be any size as long as its not too loud.

A hotdog resinator or ultra-flow style muffler won't cause any restriction as you can see right thru them.

For a turbo car, the turbo quitens down the exhaust a lot. This is why you can have a 3" exhaust all the way after the turbo. The bigger the better for performance also (after the turbo).

[Mr Awsome]

interesting,

86 running 4agze. ill be making it my self, out of stainless steel and tig welded. coz i need some practice on my new tig machine i purchased. so i thought why not make a new exhaust. the car will be track only. but i might make a street exhaust for it, for some sneaky spirited driving. or put in an adjustable restrictor.

biggo----> cannons are gay.

[fantapants]

dont forget a true merge collector is to have entry and exits angles, gererally on a non even ratio.

so if you have a 2 1/4 exit to the collector the collecttor should be a like 2 inch or smaller?

but it must be shapped well to have a decent impact.

For the people have spoken to the collector can have the single biggest impact on the power delivery of your exhaust.

many poeple confuse back pressure with gas velocity. Gas velocity is what you want.

[Frak]

HOORAAAHHH, first time I've ever read anyone write this on a forum, about bloody time, I'm so sick to death of people(mainly old dudes or young dudes that get all their knowledge from HPI, ZOOM etc) saying you must have backpressure.....It's gas velocity you need.

Of course we could then go into my next fav topic exhaust sound energy tuning

[ke_70]

ok im thinking about a new exaust for my standed 4k
ive got some 1.5'' and 3'' stainless tube and what i want to do is.
come off the motor with the 1.5 inch. then go staight under the diff with a hotdog in there somewhere.
then put a flange there about 50mm after the diff and then hav 3'' shot gun tip that angles up and goes past the bumper about 200mm.
so itll basicly be a stright through under diff but with a hotdog.

id really rather a 1.75'' system but i cant get it free from work. only 1.5'' and 2'' and 3'' so will there be to much backpressure?

also should i go with with a hotdog or without one? what do hotdogs actually do? ive been told the crisp up the soung a take out the drone in the note?

[Jonny Rochester]

What is the RPM range of this 4K? 1000 - 2500? You can go with 2" if you want. But you may want a muffler.

[ke_70]

3500 i dont really want to run a muffler

i dont want any power increse because its a 4k
just dont want it to run crap