SMP142

i was wondering if anyone here on the forum is running a single 4" or 5" exhaust, and how they ran it? which side they exit on and such. was planning on runnin 4" b/c most guys have a hard time with ground clearance on 5". its done alot in the supra world, just havent heard much single exhaust talk on the SC though.

thanks - Brian

LexusFTW

iTrader: (7)

Run Dual 4". You will love it!

SMP142

is that what your running? seems like overkill lol, what does it sound like?

LexusFTW

iTrader: (7)

Yes, check out th videos in my thread:

https://www.clublexus.com/forums/sho...d.php?t=360123

DryBlaze

The dual 4" that LexusFTW is sick! I myself have a dual 3" straight pipe.

SnShne1jz

I run the supra HKS carbon Ti which is 95mm on my car

100mgbluep

iTrader: (1)

Im going to do something like this with my build:

ppalamara

I run a 4" like pictured above, just without the zip ties and i have an actual muffler LOL!

SMP142

how hard was it to run the 4"? i havent actually been under the car and really layed it out. i am just trying to get ideas for when i do. doesnt look like it will go too bad. looks like going pass side exit will be easier.

SMP142

hey lexusftw, your exhaust sounds crazy! so you ran single 4" back to the axle, and then split to dual 4?

LexusFTW

iTrader: (7)

Basically. Its 4" off the turbo and split into a 4" Y right before the differential.

Blizzy

iTrader: (-1)

Standard exhaust convention is 115CFM per square inch of exhaust pipe cross section and 2.0-2.2CFM per horsepower required to prevent choke. These conventions are not based on turbo applications where certain amounts of back pressure must be overcome to provide the most efficient flow, but crunch the numbers:

3" pipe allows 812CFM of flow for 369-406hp without restriction.
4" pipe allows 1444CFM of flow for 656-722hp without restriction.

Those numbers are for a single pipe. If you have a dual 4" exhaust, you will flow enough air for over 1400hp without restriction. If you are not making near that number, your large exhaust pipe is adding to the restriction of your system as exhaust gases "get lost" on their way out, preventing efficient flow.

In general, the smallest exhaust pipe that does not provide restriction should be used in any given application. This way, there will neither be back pressure from choke nor will there be marked inefficiencies at low flow levels, supplying the best combination of low end and top end performance, quick spool and high speed flow, etc.

Again, turbo applications require slightly larger exhaust plumbing to compensate for the backpressure contributed by the turbocharger itself, but this does not need to be overdone. Eric, from TTC Performance, made 891whp on a 3" exhaust from the downpipe back on his 2JZ-GTE with a massive single turbo. While he was no doubt sacrificing top end flow with his small exhaust pipe and the power he was making was in the face of back pressure from choke, he likely had the fastest spooling ~900whp 3L car in the world at the time.

I am not suggesting any exhaust decisions to be made. I also understand that not everyone is exclusively interested in performance with their exhaust decisions. I am just sharing the science so that you may make your own decisions more informed ones.

SMP142

well the exit on my exhaust housing is over 4". i was planning on running 4" all the way back single. i know some guys have ran 5", but for a car thats gonna be on the street i think the pipe will hang down too low.