Any HP gain from free-flowing muffler?
 

Well I'm sure in theory there is, but I was just wondering if a free-flowing muffler will give the same effect as an aftermarket cat-back. I know the stock pipes themselves are already in good shape, decent size, good bends, so going with a less restrictive muffler should do good over stock right? I was just curious if the muffler swap I did a while back (primarily for change in sound) has benefited at all. Dyno #s and whatnot are in the sig, and that's with all the mods listed.

Nate

the muffler really isnt the restriction.. the size of the tubing is..

0-3 seems to be the theory.. no dyno can proove this..

What about cat-backs then? They worth it? I was thinking of just keeping the muffler for the nice sound, but get an elec. cutout when I do headers this year. What do you think? Is it just more preference?

Nate

For exhaust to really do anything you'll need pipes. The stock 2.75" press bent pipes aren't exactly the best. Getting mandrel 3" pipes will make it sound better as well as perform better. Then get headers and a new y-pipe and it'll be even better.

The factory pipes are 2.75" and they are mandrel bends not compression. The most restriction is in the muffler. Lots of people gaining 8-10 ponys with just adding a muffler. Even people getting 6h.p. with just the so called bad flowing flowmaster muffler.


Jason

what about with muffler removed and replaced with a pipe?

take a look at my dyno:

http://www.planetcpp.com/~adrian/ls1/dynocompare.jpg

thats with just having my "dynomouth" exhaust, which is just a bullet muffler #24222 ($35). I gained 15RWHP on the dyno(you can see the comparison...and thats dynoing after a few WOT runs)...and its one of the cleanest sounding exhausts on an LS1 (no rasp or much drone). Here is the diagram on how its setup

http://www.planetcpp.com/~adrian/ls1/bullet.jpg

and btw, flowmaster has the crappiest flows. im also using my stock tips :D

I personally don't know how much of an increase I gained from the Dynomouth Exhaust but I do know that you can feel it as well as hear it.. My 02 Z is an A4 w/ 2.73, w/ stock muffler you could get the rear wheels to burn by putting the tranny in 1st gear and floor it otherwise it would spin a little and then when tranny shifted, the wheels would stop spinning... Now w/ DM, leave it in O/D or even D and Floor it, damn wheels will spin untill it shifts into Overdrive.... But that is proof enough to me, that w/ 2.73 gear ratio and spins like crazy, shows that I have more rwhp...

Plus how can 2 and 3/4 " flow that much less then 3".. I can see 2" not flowing as well as 3"... This is my opinion... Now on the otherhand upgrading the Y-pipe will flow since the stock one is Flat in one area....

But I have read somewhere that LM versus DM (where DM is on stock I-pipe) flows the same and even when converting LM to DM (replacing resonator w/ Dynomax Bullet Muffler), flows the same as well... So I just cannot see how there is much of a difference for flow... Sound might be better on 3" but not too much to tell the difference...

charlie

2.75" does flow less but not that much as you think.I figure 3" flows a little less then 10% more exhaust volume than 2.75". 10% is more though,I imagine velocity and intake air play major roles in the benifit of 3" over 2.75".
The stock pipes are mandrel bent that has been the case on both my Camaros.But still I cut them out to put larger tubing in.Thats when I SAW the Mandrel bends.

where are you RS Drag going to find free flowing muffler with dual outlets thats other then ones used in catbacks? If your thinking of just one tail pipe and Dyno. or Magna. replacing the stock dual outlet on your 2.75". Yeah it would be better then stock.And can compare to an aftermarket catback flow in which most of them right at the end of the line take flow and split it to duals(somewhat slow it/restrict).So in theory if you get the free flow single in/out straight thru design it'll evacuate exhaust gases quicker moving ABOUT the same volume by velocity verses a 3" catback.IMO

I think most of the gain you would have gotten from a catback would have come from the muffler. If the Dynomax muffler you have is the straight through design one, I wouldn't get a new catback until you're making a lot of horsepower. If you really want to upgrade your i-pipe and tailpipes, Dynomax sells those pieces alone for pretty cheap.

3 IN.?
 

290 rwhp is not enough to make 3 inches work for you. 2.75" is fine. the muffler is what you needed. if you just take off the muffler, your car will sound like a truck. some people like that, but i don't think you will get the sound you want.

i recommend a dynomax muff for greatest increase in hp and flowmaster for best sound. magna flow has some of both.

-J-

Re: 3 IN.?
 

Definitely,let just say if you hold the catback Magnaflow muffler up(like I have) and look thru "There's light at the end of the tunnel" true to the straight thru design they claim. And good sound to boot and lifetime warranty.
The flowmasters WELL may have good sound I'm more performance minded.As far as the flow I dont really know...But I have seen the cross section views of them and its pretty cluttered even have dead end spots.These walls and chambers harmonically make the good sound at the same time destroy the flow.

I was actually stating that 2.75 does flow less but not much then 3"... Actually if your car is making something like 500 HP, then 3" would actually help out but 2.5 or 2.75 would actually be too much restriction.. Trust me you are not going to tell too much difference between 2.75 and 3" on a single exhaust like most F-bodys... Plus when people actually jump over to Dual Exhaust, 2.5 is the better size since 3" will make it lose power... Now going from 2" single to 3" single exhaust, you will notice an increase but only a 1/4 " is not that much of a difference to tell.. I know there are going to be people that are ignorant to think that larger the diameter the more power, but that is not always the case... I am not trying to start a flame war but 3" pipe is not going to outflow maybe like you said about 10% more then 2.75 ".. The biggest set back in the exhaust systems are the mufflers themselves.. I have read about tests where people have dynoed car stock, then put on a cat back system and gained like max of 25 HP, but then saw a very similar gain by just swapping out the muffler.. So in actuality, if you are running more then 400 HP @ the flywheel, then I would say 3" or larger would be a better choice.. I will defintely change the I-pipe to 3" and even my custom Y-pipe out back to 3" when I add headers and a Cam upgrade later on.. but right now on Stock Manifolds, CAM, Heads and Intake, then I just don't see how changing to 3" Pipe will be that beneficial for power... That is why if you can add a straight through design muffler to your car, then the exhaust gasses and escape faster then going through a stock restrictive muffler...