My 3in exhaust, from down pipe too magnaflow

[2010 Rallihead Sportback]

http://i151.photobucket.com/albums/s121/chrisrefaei/23692_1417481474469_1155591867_1243.jpg

http://i151.photobucket.com/albums/s121/chrisrefaei/23692_1417482034483_1155591867_1243.jpg

http://i151.photobucket.com/albums/s121/chrisrefaei/23692_1417482394492_1155591867_1243.jpg

http://i151.photobucket.com/albums/s121/chrisrefaei/23692_1417491674724_1155591867_1243.jpg

[2010 Rallihead Sportback]

http://i151.photobucket.com/albums/s121/chrisrefaei/23692_1417489874679_1155591867_1243.jpg

http://i151.photobucket.com/albums/s121/chrisrefaei/23692_1417491194712_1155591867_1243.jpg

http://i151.photobucket.com/albums/s121/chrisrefaei/23692_1417489634673_1155591867_1243.jpg

http://i151.photobucket.com/albums/s121/chrisrefaei/23692_1417489154661_1155591867_1243.jpg

[TheBlackBeast]

Pretty 3" pipe. So, in the second to last pic does it go from 3" to 2.5"? Looks like a bit of a bottle neck to me...

[2010 Rallihead Sportback]

yep it does drop from 3in to 2.5, I was informed by him that from that distance there isn't any loss, being that from that far back its pretty much a exit and wouldn't interfere with the flow whats, you opinion on this? should i do something before i get the Evo turbo and intercooler and intake and accessport, or will this setup on the exhaust ruin my tune?

[TheBlackBeast]

If it were me, putting in a 3" exhaust pipe, I would make the effort to have my exhaust 3" all the way. This should actually start on the intake side of things - trying to keep the same diameter. I am not basing this on technical proof, rather personal preference. Your exhaust guy might be correct, but without dynoing a before/after run with your current exhaust vs a 3" exhaust, its hard to say for sure. Still, the purest in me says that if I'm going to the trouble to running a 3" all the way from the turbo to the exhaust, it better be a 3" dia. all the way.

[jRox]

No matter how you look at it, from 3" to 2.5" is a bottle neck.

[Jdmboi]

whats the stock size of the the exhaust??? 2.5??

[Blaze]

It's like running a baffle or a resonator. It will negate most of the power gains from the larger diameter exhaust.

To say there's no affect on power in that short distance is fraudulent to say the least. My exhaust is 80mm all the way through. But would you suppose placing a 2" silencer at the tip would have no affect?

You're losing about 10WHP. I'd ask him to finish the job or take it to a more performance oriented shop.

[2010 Rallihead Sportback]

"It's like running a baffle or a resonator. It will negate most of the power gains from the larger diameter exhaust."

wait a sec how does a resonator negate power.. its just to quiet down the sound, like a mini, only without the negative impact...

[2010 Rallihead Sportback]

I just came back from the shop, he said there's no problems because its a free flow system, there's no chambers and no baffles to restrict the flow, but he did understand what are discussion was about and said the only problem if any would be from the inlet of the muffler,(what we've talked about being the bottleneck) but the problem would be the room to turn the piping to the muffler since were talking about 3in's here and also magnaflow doesn't make it in the same setup as i have it (sad face) :( but there's no out let issues obviously cause i have (2)2.5 outlets

[2010 Rallihead Sportback]

whats the stock size of the the exhaust??? 2.5??

yes stock is 2.5 but, thats why I bought the magnaflow the same size, then I changed all the plumbing too 3" and now im stuck with the aftermarket 2.5 Magnaflow @ the end... shouldn't hurt the tune, hopefully.

[Blaze]

"It's like running a baffle or a resonator. It will negate most of the power gains from the larger diameter exhaust."

wait a sec how does a resonator negate power.. its just to quiet down the sound, like a mini, only without the negative impact...


Check out an Apexi Noir system. They use a resonator inside the piping which reduces the ID of the system. But generally speaking, anything that isn't smooth on the inside of the piping is going to reduce the exit speed of the exhaust. I'm being nit-picky with resonators, but reducing the diameter of the exhaust would be my main concern here.

[2010 Rallihead Sportback]

true when reducing the diameter of the exhaust there will be impact.. im just hoping it'll be minimal to none, when I tune it:confused:.. maybe when i tune it'll throw that impact out of the window, like it doesn't matter:eek::)

[TheBlackBeast]

I guess one way to find out would be to do a dyno run with the exhaust attached and without it attached...

[Blaze]

I guess one way to find out would be to do a dyno run with the exhaust attached and without it attached...


Good call. That's what Mike at RRE did: http://www.clubralliart.com/showpost.php?p=3608&postcount=11

[2010 Rallihead Sportback]

went to secret services, (the ppl who are gonna tune it), they said its not gonna cause any problems since the outlets are dual 2.5in so it would be similar to having a 5in single muffler, if it were a single 2.5 output muffler then there would be issues of not getter the air out through the back fast enough, guess im safe