rear turbo cls6

My cl wil be turbo in a couple of weeks and I want to upgrade to 2.5in piping. But I want to keep either my mufflers which is 2.25" or the aftermarket mufflers i picked also have a 2.25" fitting. So if I run the 2.5 all the way to the back until it reaches the split between the two mufflers and use a reducer, would it be pointless because I am still keeping the smaller piping for the mufflers???? I dont want to waste the 350 on the custom exhaust and its worthless!

Nersh7

shouldn't be pointless, as soon as it splits your increasing the volume for the exhaust to flow through so the quarter of an inch smaller means you still have a larger volume after the split

civicdrivr

iTrader: (9)

^

As long as the surface area stays the same (or greater) it will be fine.

Turbos like to breath though, a 3" exhaust would be better.

rear turbo cls6

i dont think 3 in will fit properly and I would imagine that at 3inches its going to be insanely loud. I still want to keep this as my daily driver and I dont plan on making more than 400 whp at the absolute most. When I decide to sell the car, I will leave it up to whoever to decide to blow the motor up or not. lol

gfrg88

iTrader: (2)

don't forget that turbo cars aren't as loud as NA cars.. I would do 3" with a nice resonator, and nice mufflers.. shouldn't be too loud

Italiano

Plus 3 on the 3inch exhaust

rear turbo cls6

so even 2.5 would be too small??? My downpipe isnt even 3in. Its only 2/12 so I was going to keep it all the same. Am i wrong?

rear turbo cls6

and also Im only running a t3/t4 turbo because I am just testing the waters. I still want to keep it as a dd. So I dont even think the turbo is big enough to push enough exhaust through a 3in pipe.

Italiano

what kinda horsepower are we talking? I mean it makes sense to run same piping all the way through if possible

Italiano

If u think about it people run 2.5 on a N/A engines so a 3inch is the way to go on a turbo. t3/t4 is a decent set up. also what size injectors u running?

rear turbo cls6

lol. I dont want to go any higher than 400hp to the wheel. I am looking to get 350 to the wheel from the current setup though.

Italiano

I jusy saw where u said 400hp,my bad. u probaly are running at least 740mm injectors. 3 inch for sure

rear turbo cls6

so my downpipe from the turbo is 2.5, I do an exducer to 3.0 and run 3in to the back. When I reach the duals, would I still be able to keep the 2.25 stock piping for the duals? I just see this custom exhaust job getting really expensive really quick with 3in piping also considering I want it all to be mandrel bent. I know they will charge me more to do the dual split. And by me being able to keep the stock piping where the duals start, I can run my exhaust pipes that I want.

rear turbo cls6

as far as injectors go, they are still stock. I want to upgrade, but I dont know what to. Ive been searching and cannot find any aftermarket ones. I was thinking about paying someone on here to do the rdx injectors for me so i dont jack them up

rear turbo cls6

I posted a separate thread on my turbo setup and am looking for some people to help me fill in the holes.

rear turbo cls6

I say 400 because I was reading on a separate site where a guy turboed his cl and he ran 417whp i believe on all stock internals, including the injectors. So I figure I would stay around these numbers. But I think even 400 may be to high for all stock. So I want to stay around 350 till I can reinforce.

rear turbo cls6

and one last thing. I was told by a mechanic that I need the back pressure from the smaller exhaust so that I dont burn out my motor. Is this not true for turbo applications?

Italiano

Gotcha,i was just wondering about injectors because i had a 240sx with an rb swap with 400hp to rear wheel. i had tomei 740mm injectors that worked great.
i had a three inch exhaust but of coarse it wasnt dual. my down pipe was 3 inchs custom. You got to pay to play

Italiano

Never heard of that. the more ur car can breathe the better

rear turbo cls6

Do you think that the 3in to 2.25in duals would be sufficient enough

gfrg88

iTrader: (2)

2.5" duals.. or else you'll be bottlenecking it

rear turbo cls6

whats the largest I could run while still keeping the 2.25 duals?? I really really want to either keep my stock exhaust or run the aftermarket ones I found.

Italiano

+1

rear turbo cls6

ok Im going to suck it up and get the 3in to 2.5 duals

Italiano

PAY 2 PLAY lol

rear turbo cls6

yea i think its starting to sink in!!! lol

gfrg88

iTrader: (2)

turbo aint cheap!! you gotta pay to do it right

civicdrivr

iTrader: (9)

Fuck the duals. If you want to make the exhaust routing efficient, have one pipe all the way back. You can put a fake tip on the other side so people wont notice.

civicdrivr

iTrader: (9)

rush

iTrader: (1)

i did that before and had to get a new motor . google exhuast starvation

gnuts

iTrader: (1)

^ please expand

Nersh7

The split at the mufflers wouldn't affect it at all because overall volume is increased due to the split.

If he were to decrease the size of piping then that may be applicable but other wise your post makes no sense.

rear turbo cls6

googled it and nothing...???

gnuts

iTrader: (1)

^ ya same. i think what nersh said is right. at the split the pipe is still increasing to 4.5" so we should be fine. i have a 2.5 inch all the way to the split.

friesm2000

iTrader: (4)

i don't think your math is quite right, remember you have two smaller circles/diameters, when it splits not just one

friesm2000

iTrader: (4)

anyhow...

(A = πr2 ; formula for the area of a circle) (π = pi = 3.14159)

2.25 (diameter after the split) / 2 for the radius = 1.125
so 1.125 x pi = 3.9760782021996 in2 X 2 ( for the duals) = 7.9521564043992 for the total surface area of the dual setup

so now we need to find a single pipe diameter that is roughly equal to that (or maybe a little less, cause a single pipe can flow more because there is less wall area to cause drag, so it flows a little bit better)
r = √(A / π), since we already know the area, we just need the radius

√(7.9521564043992 / pi 3.14159) = 1.5909902576697 radius x 2 for diameter = 3.1819805153394 is the size of the pipe you need in order to match those dual 2.25 mufflers in surface area


so really about a 3" pipe (and alot easier to find then like a 3.25 pipe)(and it is compensateing a little for the better flow out of the single pipe by going with the smaller diameter) will do it, and not having those mufflers being the choking point of the exhaust system

civicdrivr

iTrader: (9)

I still say if you want to keep it cheap, simple and free flowing run 3" exhaust all the way back and have one single dump, ditch the dual setup entirely.

friesm2000

iTrader: (4)

let alone less weight, especially weight that is outside of the wheelbase (acts as leverage for that weight)


but yes 3" at least needed especially if going turbo (a stock Subaru WRX has a 2.5" exhaust factory, and that is with only a 2.5 liter motor and a SMALL turbo too (it dies up at the top of the power band)

gfrg88

iTrader: (2)

Nerd.

civicdrivr

iTrader: (9)

Fixed