Exactly

And even the 4inch intakes.

one of the guys at HPF should hook me up with a deal on there 3.5 in exhaust, and let me test it out vs a few other exhausts, on a GT35R

 

i made my own 3.5" exhaust (but then again, my fabricator is the sh*t and hes put a lot of R&D into it).....you dont want any backpressure in your turbo exhaust. yes, a 3 " is sufficient, but wouldnt a 3.5" be more sufficient? what my question would be is, although the 3" is used by everyone to make X amount of horsepower or run a XX.XX in the quarter, wouldnt having a 3.5" help in both those examples? but i dont think anyone has done this to show any findings. having a bigger exhaust can also help the turbo spool.

like one person said in here, having a 3.5" would be good if you were recirculating the wastegate into the exhaust because of the fact that you dont want any backpressure whatsoever and the bigger diameter would compensate for it. to me, having the wastegate dump to atmosphere WITH a 3.5" exhaust would help even more because of that fact. then people want to talk about price.....i made mine for about the same price that someone would have to go and buy a full 3" turboback, and I am ready for whatever wheel horsepower that I want.

 

Contact Hoover at Turbohoses.com. He did several dyno tests with the Supra trying to understand at what point is going bigger necessary. I can tell you that from his results it does make a difference.

 

yea but a supra and an evo are 2 completly different cars

i would love to see tests on an evo, like i said if HPF Tom or someone was interested in sending me a discounted or free 3.5" exhaust, id be glad to do dyno testing and full compairson between the two, and a huge write up

 

Sorry I didn't have time to read the whole thread so I hope I am not covering anything that has already been discussed

Please check out this page
http://www.airpowersystems.com.au/us...wrx-hoe-r2.htm

about 2 pages down there is a chart with backpressure readings at certain horsepowers with certain exhausts.

for those that do not know

R2 = 3" downpipe tapering to 2.5"
R1 = full 3" turboback single tip outlet
R8 = full 3" turboback twin tip outlet
R5 = full 3.5" turboback

Keep in mind that Evos normally flow better then subarus so the psi would be a little higher.

 

The best exhaust in a turbo car is no exhaust, So the biggest realistic exhaust is always the best option when looking for maximum performance. Theres no way around it.

 

RallySport, great job posting that up.....i didnt even know what was on APS's site.

Yes, the best exhaust is no exhaust for turbo cars, but idiots on here say 3" i perfect since person/vendor X ran 10 seconds or less.....they dont think that having a larger diameter will help anymore. (people just being ignorant). But hey, most people just listen to what everyone has or wants and never does anything for themself on here.

Look at AMS's black Evo that made 903whp. It had a 4" exhaust......why? I would like to ask everyone on here that says 3" is fine......Im glad they used that on that car.

 

I hear the same comments on 300ZX TT. Basically on any turbo car, bigger is better.

Bigger downpipe, mid pipe, and cat back ... not resonators, no cats, minimum bends, and bigger diameter piping in the muffler ..

 

i have minimal bends in mine, but i have one resonator. resonators, like i said before, only lose about 2-4whp MAX. people think resonators kill HP by a lot, but they just hear that from others. they dont people. study this stuff and then you will understand.

 

thanks for the post! very interesting and informative

 

it IS very interesting......but hey, since so and so is running whatever time at the track with 3" then this must be wrong right everyone?

i am glad APS has this on their site.

 

yea exactly, thats why id like to see some 3.0 vs 3.5 inch exhaust tests

id like to see an ams or buschur 3.0 vs a hpf or someone else 3.5 turbo back!

 

I doubt any test will show a 3.5 inch will produce less horse power than a 3 inch or would make a high horsepower EVO slower in the 1/4 mile.

 

yes of course lol.

but i wanna see how much of an actual GAIN there is, especially with a bigger turbo, cuz it might make some of those big turbo guys go 3.5 instead of 3.0

 

Bigger is ALWAYS better, but not always cost cost efficient. Whether you would realize any appriciable gains with a 3.5" over a 3" is questionable unless you have the supporting mods to take advantage of the higher flow rate. A 3.5" will definately look & sound better though.
My 3.5 exhaust will be fabricated tomorrow or Saturday. It will be pretty much a straight shot with 2 slight bends and a straight thru bullet type muffler at the tip. The reason I'm having one made is because I wanted something that would sound different, and look good, plus I can take advantage of it with my mods & a bigger turbo while road racing, and it's costing just a little over $500 installed!