ajrothm

I'm curious as to if anyone has done any real A-B-A exhaust tests on our FI setups?

I come from a naturally aspirated back ground and have built a bunch of custom exhaust systems.. On our stuff, a truly non restrictive full exhaust system is paramount to get the most out of our 600-700 crank hp engines..

So looking at the amount of air flow forced induction C5/C6s put through the pipes, I am wondering how much power we are leaving on the table due to the C5 catback design with the transverse mufflers and 180*s bends or multi chambered muffs...

Now I know, I know.... Everyone here will say "I made XXX HP thru stock TIs" or "Brand X performs really well" blah blah blah... But have these groups actually tested anything else?

After looking at a cut away of a C5Z TI muffler, I can not believe that muffler flows well, even with a bypass mod with a little scrawny 2" jumper pipe. Same thing for some of the other large case mufflers like my XS Power 3" mufflers...The exhaust has to turn around 180* in there, that can not be good for flow...

Does flow improvement translate into anything we can see on the slip?

Thoughts?

Ti muff cut away:


How the exhaust changes flow direction:




This can't be good...

Anyone tried dynoing without mufflers to see if there is significant restriction in flow or hp?

This is something I would like to look into.... We could all be leaving power on the table for the sake of a nice quiet ride (which I want).... But I think a different design in the catback system could still yield a quiet ride with an improvement in flow.....Just not sure how to rework it.... That's IF its even worth any significant power..

Just the fact that most of us run 2.5" catbacks blows my mind....(although mine is 3")...

We run 3.5" straight flow systems on 650 CRANK hp cars for zero loss....Just seems dumb to me to run either a 2.5" system with a free flow muffler or a 3" system with a restrictive style muffler (XS or LG Big3) with 900+ rwhp....

A 900 rwhp car with TIs COULD be a 950-975hp car with no exhaust restriction....who knows?

Thoughts from you race veterans...?

ajrothm

Here is a true 3" system from XS Power:


However on the outlet side of the muffler, its still only 2.5".. and I can not find any cut away pics to see how the exhaust is redirected.... Albeit a 180* U bend pipe inside, or just an open ended chamber with and inlet and outlet pipe.... Either way, changing directions in air flow is never good for flow..

I contacted Jon at Huron last year about pics from inside the mufflers and he didn't have any, only info he had was that it is a "straight flow" muffler...interpret that as you will.... I will say this exhaust system sounds killer and is drone free inside which I love.... windows up its quiet inside.... But is there a restriction? You bet there....to some degree...

Chevy changed the exhaust design on C6s for a reason...straight in/straight out...(on the NPP anyway)


LG BIG 3 muffler...



Looks like a perforated core...but is it straight thru? It looks like it may utilize a chamber after the inlet to change direction...atleast its 3" tho...

95wht6spd

This is a good read.

http://www.popularhotrodding.com/eng...re/0505em_exh/

a/c man

I would like to know also! good thread Allen

neutron82

how about the corsa xtreme?... it's still 2.5" but it doesn't wrap around like most of the other mufflers and is straight through, it doesn't even flow directly through the muffler... and doesn't borla make a straight pipe that goes straight to the center of the bumper?

Chris Stewart

I notice a big difference going from Ti to Borla Stingers. They are straight thru and I needed a re-tune afterwards.



For grins I pulled em off and added turn downs. A cool $20 exhaust mod. Too loud for the street tho...

GenerationX1

I run Borla straight pipes on my C5 Z06 however they're 2.5".

slow ride

The LG big 3 has one perforated 3" pipe that enters the muffler, on the endcap about 1 or 2 inches of open area for the flow to openly transfer to the outlet which is 3" perforated pipe also. Not sure if any flow transfers through the perforations, it's large, but not quite stright through.

PEETYZ

Very curious on this subject as well. I am running a smaller aftermarket system than most. 1 3/4 Tri-Y headers with factory H pipe (catless) and XSP 2.5 system. I have an X pipe I just havent got it installed yet. Love the sound but wonder how much is on the table? For my combo and local dyno numbers I made pretty good power tho and its a pretty safe tune still on stock bottom end.

Everyone tells me how loud my car is under WOT even more so than my friends similar A&A set up with a 1 3/4 TSP Headers, X pipe, and quad tip borla stingers. They are both loud in my opinion.

An independent test with a FI car over say 600hp across various systems would be awesome

ajrothm

Good info!

That's kind of what it looks like in the pic above.... I wish it just had a U bend inside of it instead of the open chamber to change direction....looks like a pretty good system tho..and its a true 3" in and out..

Maybe a good option...

ajrothm

Chris, I saw that system when researching this.. I bet it has great flow (for a 2.5" system) but I bet it would be hellaciously loud on my car... Atleast yours has a turbos to quiet down the exhaust some...

I bet that system drones terribly.. I like the design, If only it was a 3" pipe and had a slightly bigger muffler, it may be liveable.....


Some theories are that 2.5" pipes that far back down the system are of no restriction due to the loss of velocity that far down....however on a 900+rwhp car (1050-1100 crank hp), I can definitely see 2.5" restricting it..

On our big power NA cars (900 crank hp), we run 4" collectors, 4" pipes straight off the headers into a 4" straight thru race muffler (oval or bullet) and 4" out dumping about a foot passed the muffler.. We have cars running 8.90s@147-148 mph like this... NA at 3500lbs.. That is a zero loss system..

Obviously 3" is the best we can do on a C5, but minimizing the bends/chambers and muffler restriction could net some gains..

algZO6

I was thinking of trying a Corsa Extreme and welding some Magnaflow 14419's in the X-pipe to quiet it down.

ajrothm

Interesting design on the Corsa extreme.. Pretty much straight pipe with just a small "draw off" into a dead headed muffler to knock the edge off the drone.. If this was a 3" system, they may be on to something..

I'm gonna contact PYPEs about possibly building a system for a C5, setup the way I want it... Or I may build my own using the 3" cat back I have and just revamping it before the muffs... Gonna research this for a while...

Ideally, I'd like to Dyno mine as it sits with the XSP exhaust, then pull the mufflers off and see if it picks up power...if it does, then I know I need to do something.. If not, I'll let it ride.. The problem is I have my mufflers welded on so its not gonna be an easy task to yank em off and throw em back on.... Not to mention the pipes falling down over the axles when the muffs are off.

JDS99

Good topic for sure. I can't imagine 3" isn't a restriction, let along 2.5" at the end, on a car putting down 900+whp.

FWIW, on my twin turbo setup I made my own custom 3" exhaust all the way back including over axle pipes. I have 2 of the Kooks race bullets (straight through perf. tube, no bends) about where the cats sit mid car. Even with the 2 .85a/r T3-3" vband turbine housings restricting flow on my 8.75CR 403ci at idle... it still huffs out exhaust with some force before the race bullets if a clamp is loose. Since the bullets slip over the downpipes, the exhaust pressure literally has to turn 180deg and come back through a tiny gap. No way in hell even a 3" exhaust on a supercharged car isn't a restriction if it even is post turbo with no bends...

slow ride

I plan to mod the mufflers if I feel they are a restriction in the future. I could add a u bend and perforate it/add more stuffing to the muffler. The U bend is terrible, but it's hard to do much muffing without a decent amount of surface area. I already had to chop the heck out of the exhaust to make it fit around the c6z drivetrain and coolers. What a pain.

In the import world we would always have larger exhaust than downpipes so it's weird to see the reduction in vettes.

slow ride

The B&B PRT is like this system also. It used a side chamber "tuned" type resonator to kill certian freq problems. it will be loud for most tones except the one it is tuned to.

philadd

Over the years, I've seen quite a few people report their dyno results, in which they had numbers with cutouts open and closed. I know it's not quite what you're looking for, but it may be the best answer you're going to see.

algZO6

from what ive read the prt's drone while the extremes do not. i would still add some type of muffler in the x-pipe to quiet it down.

ajrothm

That is similar to the exhaust I have on my wife's G8. I have a Solo Perf axle back exhaust on her car, it's basically a muffler delete that has a J bend that comes off the muffler delete pipe and dead heads into a cap..

Believe it or not, this is the best sounding exhaust I have heard on a G8. No drone, no rasp, no glass packish sound..... Just a good, clean tone..... Apparently the J bend is the magic behind it... I couldn't believe it when I saw it and heard it...

I guess drawing off a small amount off of the main exhaust flow just just enough to kill the rasp/drone..

I looked into the Pypes exhaust thing... They make a system for a C5.. It's only 2.5" and only uses their Violator mufflers (which sound TERRIBLE)... Their RACEPRO mufflers sound and flow great, but they won't modify them for C5 applications.. So that's out. Also they are not interested in building a 3" system for a C5..

Turbo-Geist

Here is some testing that I did back in 2009. I went from a C5 Z06 Ti to a custom 3" exhaust that I designed and had fabricated at an exhaust shop.

Thread link complete with pictures, video links, and links to thread discussions concerning C5 Z exhaust restriction. http://forums.corvetteforum.com/c5-f...ck-for-fi.html

Picture:


I am now running the Corsa Z Street Titanium exhaust. It has straight through perforated resonators in the h-pipe and rear section mufflers at the end before the tips. The difference is that the rear mufflers aren't flow through. They are attached to the main 2.5" pipe via 2 small tubes and the muffler is more like a sound chamber. Here is a link for pictures since I don't have any of mine available. http://www.superchevy.com/how-to/73978/
They operate off the helmholtz resonance principle which is the "phenomenon of air resonance in a cavity". Think of the sound you hear when you blow across the top of an empty bottle.

Corsa called it RSC (Reflective Sound Cancellation) technology and it works. I would like to duplicate it on my next build when I go with a 3" system. I just need to figure out what size chamber is needed.