FAQ: The Exhaust Thread

3inch tubing.then sizing down to 2.5......

video

rockin the slippers. but its sound ok, kinda raspy but nice do you have a resonator

palermocorey90 wrote:

do you have a resonator

nope. no cat, no resonator, nothin but pipe and a decent pair mufflers. Think a 3in resonator would make it better somehow?

sounds nice at idle. but i dont know if it's the sounds recording or your exhaut pop, but its a little too raspy on throttle.
zzp has a high flo resonator out that may take care of some of the pops.

Mr.Riviera wrote:

sounds nice at idle. but i dont know if it's the sounds recording or your exhaut pop, but its a little too raspy on throttle.
zzp has a high flo resonator out that may take care of some of the pops.

yea it only does it when reving like such - not when driving, but i may get the 3in resonator from zzp at some point. It's an easy ad in at this point so I figured i'd try without first. It's not going to be the first thing on my coming agenda though. For the $200 it will cost to buy, ship, and install the resonator, i could put towards getting the blower ported - which is next on the list.

sounds pretty good. How is the highway drone?

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3inch tubing.then sizing down to 2.5...... lmfao

What is so funny?

Jason wrote:

sounds pretty good. How is the highway drone?

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3inch tubing.then sizing down to 2.5...... lmfao

What is so funny?

i was sorta wondering that myself.
3in mufflers was not a possibility as the mufflers were an impromptu addition and only 2.5 were available. I kind of think 3in duals would look if not be overkill

Jason wrote:

sounds pretty good. How is the highway drone?

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3inch tubing.then sizing down to 2.5...... lmfao

What is so funny?

well i thought it was done on purpose...but he said it want an option...

anyways...whats the point? if your trying to increase flow,you dont go from large to small that would be recockulous..

I still don't get it.
The area of TWO 2.5" diameter pipes is a lot greater than that of a single 3" pipe.
2*[pi*1.25^2] = 9.82 in^2
pi*1.5^2 = 7.07 in^2

A pair of the mufflers he chose have just the right flow for our engine output. There is no need to have dual 3" mufflers on a car with a 1 into 2 configuration (not-true-dual).

You could get away with a good single 3", a great flowing single 2.5 (hooker maxflow or dynomax ultraflo) a pair of good dual 2.25" or even a pair of great 2" mufflers.

I thought the point was to gradually decrease pipe diameter towards the rear of the car in an effort to keep exhaust gases warm and moving at higher velocity.

Bernoulli's Principle states that as you decrease tube diameter, pressure inside decreases, increasing velocity of the exhaust gas. In short, smaller diameters flow faster than large ones.

Why is this important? Exhaust gases cool off more quickly the longer they stay in the exhaust pipe. If you use too big a diameter, the gas moves more slowly, so becomes cold (and dense) before it leaves the system. This is bad, because the gas itself is forming a blockade. This is why why we wrap header tubes - to keep the gases hot and moving fast. Smaller diameter pipes do the same thing.

Obviously, a diameter that's too small isn't good either. It's worse. But once you've achieved sufficient diameter to flow the needed exhaust, going bigger isn't good, imo. And since we know the exhaust is cooling off as it travels down our very l-o-o-o-ng pipes, I think gradually tapering the pipes is a good idea.

Im not saying 3inch was the way to go....im saying drecreasing the size is dumb...

you can give me all the purposes.and mathematical equations an principles.....but actually doing it is where the real data comes,and ive been in this business for almost 10 years,ive seen my share of things..an have not seen anyone ever decrease the exhaust size..

especially on a FI application...your forcing air in....there for you want it out,choosing the right size diameter is where its critical...2.5 would be ideal for this particular HP level..whats on there now is wayy too big...Im not saying your wrong as far as what decreasing the size does...but on a FI app its creating backpressure...and is not needed.

I've heard when you're using a turbo, you throw all the theoretical stuff out the window... there is no scavenging effect because the turbo blocks the exhaust pulses from the engine. The idea is to just open up the system. I'll buy that

You could be right (probably are), but I can't help but think about these theories before I make cuts and welds. With a blower the idea is similar to turbo, so opening things up as much as possible could be best. I can see how boost would force the exhaust gas out, so maybe you needn't be concerned with scavenging. But unlike turbo, the blower is on the intake side, so exhaust plumbing is connected directly to the engine. Perhaps its design (tuning) still has some effect?

When I research exhaust design, it's usually divided between N/A and turbo and applications. There is very little conclusive info specifically for blown engines that I've found. The only thing so far is Thrasher's tests, which didn't show much improvement from increasing exhaust tube diameter.

yes with a turbo that is correct...the other thing to think about is a good tune is important to make the best use of an exhaust..especially with a turbo.i used to think a little bit of back pressure on a turbo app was absolutely needed,to keep spool up,and low end..but i was proven wrong,all an any back pressure is bad,playing with the tune can gain you this lowend,and spool up back...and it should be no different with an SC except you dont need the spool up,you just need the engine to breath..i dont have any concrete prrof yet behind my opinion except the pioneers in this business that have been there done that.. there are however soo many other factors that play into all this,1 big one being the cam.proper cam tuning will ensure that whatever is lost with the new exhaust is gained back,with the added flow .

if your looking for a scavenging affect there are mufflers designed to do this,but there only for N/A apps..

It is my understanding that a fully engineered exhaust system can greatly improve the performance and efficiency of the engine. As already stated, bigger is not always better and the principles of scavaging are important for n/a cars and beneficial to supercharged also.

two problems I and probably most of us have:
1 - not even exhaust shops have the ability to or the no-how in physics to make a perfectly tuned and engineered exhaust for any car. It's a very rare capability that I have yet to personally witness. Perfectly tuned exhaust is out reach for most of us especially since there is no aftermarket for the riv.

2 - I know I don't know what i'm going to end up doing to my car so there's no way I could tune it anyway. Even if I could engineer a tuned exhaust system, it would be compromised as soon as I get a cam, heads, higher boost, etc

I figure the best I can do is what seems to work for everyone else. Most of the moderately high-powered gtp's and such do best with a 2.5 to 3 in straight design with decent flowing mufflers and I know its plenty of flow for anything i'll ever do with the turtle

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Im not saying 3inch was the way to go....im saying drecreasing the size is dumb...

you can give me all the purposes.and mathematical equations an principles.....

He's not tapering down though. He is doing the opposite. After his 3" section of pipe, the Y is in effect a larger pipe.

3" single pipe from the engine into a Y, out of the Y to two 2.5" pipes, there's no reduction in flow there. ? Are you saying that 1 3" pipe flows more than 2 2.5" pipes?

no i agree with you.. i was under the asumption it was being reduced down.. before the 2.5 pipes.my apologies for being rash. but the other thing i was getting at also was 3.0 is overkill... but im gonna quit hijacking Turtlemans thread...the best of luck to you an your setup!

This is good discussion, guys. Not a hi-jack.

To what Rob was saying, I was thinking the same at first. 3" tapering to 2.5", but it didn't seem that bad because 2.5" is big enough anyway, so although tapered, not restrictive.

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I don't know if it makes any sizable difference but they had put the glasspacks on backwards and those ones had a directional design. Don't think it would have made much difference at all though.

yes, louvered glasspacks flow slightly more when put on backwards. You can check out one of the exhaust posts I have on here for specs. Depending on how long your glasspacks originally were, you could put them after your Y split in series with your mufflers. A resonator is very similar to a glasspack.

Jason wrote:

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I don't know if it makes any sizable difference but they had put the glasspacks on backwards and those ones had a directional design. Don't think it would have made much difference at all though.

yes, louvered glasspacks flow less when put on backwards. You can check out one of the exhaust posts I have on here for specs. Depending on how long your glasspacks originally were, you could put them after your Y split in series with your mufflers. A resonator is very similar to a glasspack.

I had hookers and instead of just having round holes in the metal, they had what i could best describe as little scoops like hood scoops - i suppose, to direct the gas into the fiberglass area. I would think it would flow more backwards if anything however be louder because the sound deadening is being bypassed. Either way, you're looking at a muffler that you can see straight through and should have potentially the same flow as a piece of pipe that size, with the aerodynamics aside. Long story short, they sounded, worked, and arguably looked great with stock piping, cat, res, etc. but with uninterrupted straight 3in all the way, they were too damn loud.




Jason, what is actually the difference between the two really? it seems like a typical resonator is just larger thus having more sound absorption than a high flow glasspack muffler. And some resonators aren't even that. Aren't some pretty much just blown out pipe for tuned sound deadening..?

i agree, but use one of the glasspacks as a resonator before the y pipe, wont hurt flow and will quiet down your exhaust. Well the louvered types may add backpressure.

true helmholtz resonators use the reflective principle, not absorption like a glasspack

no do NOT use one of your 2.5" glasspacks upstream of your Y pipe. You don't want to be choking down from 3" to 2.5" then back into 2x 2.5".

I don't think exhaust resonators use solely Helmholtz resonance. Intake pipes, on the other hand, do. The riviera has a small one. Most exhaust resonators use the glasspack design. They are just a perforated tube with sound deadener around it.

my apologies, I mistyped about the position before the y-pipe..forgot they were smaller diameter, any case they are cheap enough i would through one before the y pipe anyway, cleaner installation.

Jason, most actual exhaust resonators are open pipe with perforated steel, and use reflection to deaden sound. Hence their name. Not here to argue of course, just thought I'd give input.

Good luck with the exhaust turtle, hope you are able to calm the sound down.