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.

[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. :thumbup:

[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]

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


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 ;)

[Frak]

Cannons are gay

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!!!

[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.

[bigm]

I had a 2 Inch with a resonator from extractors on my 4k, noticed a huge gain over stock. cant compare it to a 1.75 tho sorry.

[timbo]

i also have a set of 4-1 extractors off anthony with a 2 1/4 inch system under diff, mild steel, cut and welded mandrel bent. the first thing i noticed was a huge improvement in low to mid torque, which improved daily driving due to the fact that the car has a more responsive powerband. i would think that any more than 2 1/2 inch on a 4age would be overkill let alone 3 inch... the system on the car before was a cat back with a cannon, an absolute piece of shit compared to the current setup.

[spiderman]

What would you guys recommend for an NA 2.6l four that'll spend it's life in the 1500-7k rev range?

[timbo]

What would you guys recommend for an NA 2.6l four that'll spend it's life in the 1500-7k rev range?

please tell me its not a magna! but 2 1/2 would be fine.

[ke_70]

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

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

[Mr Awsome]

so what would be best for a 4agze: currenty has 4-1 headers. but im thinking a 2.5straight pipe to muffler?

when you say exhaust velocity, your referring to it having a low as possible "back pressure." but high as possible exhaust stream velocity. to create a negative pressure behind the exhaust valve, to scavenge the cylinder of exhaust gas?

[Jonny Rochester]

For supercharged, I guess there would be no difference in exhaust to N/A.

Any performance gains of losses are probably in your header design. You already have your headers and are not going to make them, so don't worry about any other theory. You just need pipes to the back of the car.

For a 4A-G(Z)E 2.25" seams common for a sports setup. But this can be loud. Even 2" was loud on my old car. A single muffler up the back may sound harsh. That is why we have a resinator up the front also.

[corknose]

i thought extractors u have 4-2 for a wider power range and 4-1 for a short range for f1 cars etc.

[Golberg]

I had a 2 1/4 system on my 4AGE streeter and I ended up swapping it out for a full 2 inch system.

It really didn't need to be any bigger than 2 inch, all having it a big bigger did was to contribute to more noise.

So now I currently have a 2 inch high flow cat and a single 2 inch glasspack rear muffler. Its quiet enough that I can cruise past the police at 2.5 - 3k RPM and they wont turn their heads. But it opens right up loud when you're up at 8500.

[Mr Awsome]

side pipes. haha!

[driftke70]

on my 4age i ran a 2 1/4 straight through, was loud....

before that i ran a 2 1/4 kaizen headers high flow cat and a hot dog, was louder than above.

before that i ran the same but with a sports style muffler just after the diff.

all of it was under diff. last setup was pretty awesome.

new setup behind 3s is a 2.5 mandrel with high flow cat and 2.5 straight through muffler.

[marvis]

Can I run a resi and no muffler in an 1985 car?

Or will I get bent over?

[sundee]

heres a few links

http://www.pacemaker.com.au/faq.html

http://www.cobbtuning.com/info/?ID=3222

:)

[spiderman]

please tell me its not a magna! but 2 1/2 would be fine.
No, it's a Scorpion. I had a Magna though:embarassed: They're only good for EFI parts lol
Cool, thanks :thumbup:

[ke_70]

so 1.5'' straight through on a 4k
yay or na?

[skidindish]

Dont know if anyone will see this or not considering the age of this thread but Im thinking about running a side pipe (just behind the L/H/F wheel, track worrior styles) 2.1/4 from my jasma 4-1 headers, off my bigport 4age...

I dont care about legality as this baby is off the road (defected for exhaust and too low, etc...:yeah:) but I am concerned about the burning of exhaust valves (apparently this is some what of a myth?). I know back pressure will be very little (more like nil) but will this be to much gas velocity for the headers to keep up with? the collector is rather far from the beggining of the runners, although they are also rather thin... Just wondering if it would be a wise thing to do, really...

[Sam-Q]

can you measure the specs of your headers in length and diameter?

burnt exhaust valves would be more likely with a restrictive exhuast, as for back-pressure dynos everywhere say it's a myth

[skidindish]

Ahaah... yeh sure, will measure them up tomorow. cheers for that Sam

[sundee]

Just a note, put the same exhaust system on a GE a GZE and the GZE is an easy 1/4 louder .

It's the same as opening a fresh bottle of coke to a semi flat bottle. Higher pressure = higher SPL output.

The sections on the system in relation to size and shape also play a good part.

Unless your doing time attack or something similar.

Here are a few nice basic rules...
Hi velocity comes from smooth flowing bends.
Hi flowing cat and mufflers.
A dagless inner sidewall and flush butt joins.
So do some test welds and get it right before you start .

To work out pipe size you will need to figure out how many CFM the head flows with intake etc.
And at what speed , but if it's standard and stock cams, 2" and 2.5 " rear pipe to get a deeper note out the back .

There's my backyard DIY tips for a home built speed racer

[tuned86]

Dont know if anyone will see this or not considering the age of this thread but Im thinking about running a side pipe (just behind the L/H/F wheel, track worrior styles) 2.1/4 from my jasma 4-1 headers, off my bigport 4age...

I dont care about legality as this baby is off the road (defected for exhaust and too low, etc...:yeah:) but I am concerned about the burning of exhaust valves (apparently this is some what of a myth?). I know back pressure will be very little (more like nil) but will this be to much gas velocity for the headers to keep up with? the collector is rather far from the beggining of the runners, although they are also rather thin... Just wondering if it would be a wise thing to do, really...

its pretty deafening.

[skidindish]

its pretty deafening, aye?

Awesome.


Still haven't got'n a chance to measure them headers yet but will do as soon as I get the time to take them back off agian

[tuned86]

does sound sic though but yeah, scary to even turn on.

[slowKeto]

Anyone have vids of their exhaust on a 4K?

[skidindish]

Still haven't had the time to remove my headers to measure them up but today I took the thing for a quick test drive to see how it goes with the side pipe. Unfortunatly, it didn't even rev over three and half grand and then it would go all sputery and not rev any more! Could this be caused by the lack of back pressure or gas volacity (being such a short pipe, only 1 and 1/2 foot of pipe after the collector). After a short drive, it just completely died. Felt like it ran outta petty but the guage said its got a 1/4 tank and I have no recollection of the guage not working...

I have a fealing this side pipe isn't going to workout... Was it wishfull thinking to think that a bigport 4age would run a side pipe?

[NIZLAH]

car should rev out regardless, me thinks you have other issues......

[skidindish]

I thought would be the case. thanks man... thats the answer I was looking for. I'll have another look in the morning.