Exhaust pipe sizing for maximum HP/TRQ

[prostreeter600]

Has anyone played around with exhaust sizing when Dyno testing their combinations . Of special interests with large compound turbos say like a 76 mm with a 106 mm atmospheric . Assuming all other variables are ideal , such as injector size etc. With turbos of that size will a person get better #s with running an exhaust the same size as the exit of the atmospheric (5") or will better results be achieved choking it down to a 4" exhaust . Keep in mind we are talking about a fully built motor ported factory heads with all the supporting mods . Thanks in advance for any info .

 

[prostreeter600]

Seems others may have the same question . Hard to believe nobody has experimented along these lines . Anybody ?

 

[CaptPhil]

I just don't think that a 4 vs. 5 inch would really make much difference considering both sizes should flow considerably more than the exhaust housing. Just my thoughts on it.

 

[prostreeter600]

I just wondered if the 4" would create a bit of back pressure thus helping create more torque . Question would then be would it lower HP . I know on the stock turbo I had early on the 5" actually hurt the torque

 

[Dirtymaxx03]

I just wondered if the 4" would create a bit of back pressure thus helping create more torque . Question would then be would it lower HP . I know on the stock turbo I had early on the 5" actually hurt the torque

No. The only back pressure a turbo motor needs it the pressure feeding the turbine.

 

[ty_LBZ]

No backpressure needed on a turbocharged engine

 

[lts1ow]

With gas stuff its usually 25% bigger than turbine exit.

Bigger is almost always better.

 

[prostreeter600]

Has anybody made over 1000 RWHP on a compound setup and 4" exhaust ?

 

[delong_1]

Has anybody made over 1000 RWHP on a compound setup and 4" exhaust ?

yes but there is no reason to downsize the exhaust, dont you suppose there is a reason the turbine housing has the size that it does?

 

[prostreeter600]

True

 

[Harbin_22]

I made 987hp. My down pipe is 4" out of the exhaust housing. Straight 4" the rest of the way out

 

[Hot COCOAL]

I made 987hp. My down pipe is 4" out of the exhaust housing. Straight 4" the rest of the way out

He was asking if anyone made 1000hp with a 4" exhaust Kyle, not close to 1000... :bootyshake: :ban-hump: :fluffy: :baby:

Maybe you should slap a 5" exhaust on there with a 5"-12" tip, then Im sure you'd make way over 1000hp
:thumb:

:roflmao:

Pretty sure Pat (McRat) has some info floating around on this subject when he was dyno testing parts on Casper???
Think it was called the LLY upgrade thread or somethin like that...

I remember reading the gains being non existent on a single turbo street truck, going 5" vs 4", but there were some gains to be had on twin turbo trucks shooting for 1000whp

 

[prostreeter600]

Interesting though . I made 923hp/1480 TQ with DP 72mm and an S483 and 85% over sticks but I had a 4" down pipe into a 5" exhaust . I'm sure tuning and dynos have something to do with it or does the 4" exhaust help make more torque ? He made 100+ more torque than me with less fuel to boot .

 

[dmax_ty]

Dynos are a crap shoot at best when it comes to numbers. They are great tuning tools, but I wouldn't get too caught up in the numbers.

 

[prostreeter600]

For sure .

 

[blue09dmaxx]

Pretty sure he had 100s in for 987

 

[Harbin_22]

Yeah 100's went 987/1627 around 2750 pulse. 60's went 907 with 2800ish pulse. 60's did 960 on 3000 pulse though lol

 

[Harbin_22]

That was with a billet 68mm 4094avnt in the valley at the time.

 

[prostreeter600]

Cool. Nice to see the changes with the different nozzles and pulse widths .

 

[schulte]

I made 982 wheel horsepower on my compounds; 4" downpipe and 4" exhaust. 5" isn't worth it, there really isn't much if any backpressure difference...