Thread: Custom Exahust problem

Well I admit I did look for exahust advice/previous post but I doubt reading any of them will really help me out, if I missed something that I shouldn't have please post the link so I can find it.

The situation:
I am installing an SR20DET redtop into a Nissan pickup. Everything about this is pretty much custom but I need some advice. I do not have room for a top mount turbo or anything bigger than a GT28RS. I believe my motor is currently in stock form so I am pretty sure it has the T25 factory turbo. My goals are good streetable HP and I would like around 350WHP. I think my goal is reasonable but I see 300WHP being more like the final result.

This is a custom show truck and it might see a track but my main goal is to keep up with newer stock camaros and mustangs today (a few years ago I would said to beat them but lets get real here). I am looking at the GT2871 for a turbo and admit besides a basic fact of: the bigger the turbo, the more power you can make but the more lag you will have, I wouldn't know whats better for me the .64 or .84 exhaust housing. I do understand about the T2 or T3 flange but thats about the extent of it.

My problem comes down to the exhaust size I can run. This truck is laying frame with a body drop so I do not have alot of room underneath for the exhaust to run. I will try to add a picture below so you can see what I am working with but I know if I screw this up to change it later will be a nightmare or my performance will suffer. The picture shows 3" exahust running in the holes in the frame (cross members). If I run 3" exahust I would pretty much be welding the exahust pipe directly to the holes in the frame. I am not sure how long stainless exahust pipe last but if I ever had to change it I think I am screwed. If I can run 2.5" exhaust and it wouldn't be a factor for my 350WHP goal I am fine with it. I might be able to get 2.75" through the frame and not have to weld to the frame directly. I hope my picture shows up so you can see what I am working with, thanks.

If I were you, I would do the 3" for sure, and simply wrap the pipe with something like header wrap or whatever can take the heat and provide some cushion to take up the space between the pipe and the frame rail so the pipe doesn't bang around in there. I would not weld the exhaust pipe to the frame no matter what.

I've always loved seeing exhaust done through the frames like that. Your other option is to simply weld v-band flanges to each side of the frame rail and not run a pipe through it at all. I'm not sure how crazy the sound will be in the cabin doing that though.

Good choice on the GT2871R for your goals. With the RWD setup you could even make upwards of 400WHP or more if you wanted and still be fine when it comes to the transmission. That turbo is up to it.

Yeah, the issue with that is the sound and volume in the cab and the rattles. I would say to get the 300whp you are after, you would want 3" exhaust. You could however run the 2.75" and be ok and wrap the pipes like Ben said.

Brent

Planning on running a GT2871R on my SR20det too and previously researched the .64 vs the .86 question. Here's some quotes, I had saved, from a couple people on this forum who's advice is worth taking.

Originally Posted by Andreas Miko
"I found that the .86 GT2871R makes 25-30 more WHP than the .64 unit. If an extra 200-300 RPMs is a lot of lag then I don’t know what to say. This turbo is like having a supercharger on your car, spools fast with a lot of torque. Serban’s friend Robert has the .86 AR on his Sentra making 380 WHP at 17 PSI, not bad and spools fast to."


Originally Posted by snickers
"The .64 does spool faster than the .86, but you can have boost creep issues.
The .64 CAN make 400whp but you need the right parts and a bit more effort but I don’t feel it’s worth it because of the higher back pressure.
The .86 housing does make 30whp peak bolt on over the .64 housing on a typical DET, S4 setup.
The .86 housing with S4 cams will make more power AND SPOOL FASTER than stock cams with a .64 housing (in my testing at least).
A .64 housing 2871 is a bit more of a comp flow/turbine flow miss match and a .64 28RS does perform better than the .64 2871."


I vote with Ben on the 3". The turbo exhaust research I've done outside the forum has convinced me not to go less than a 3" exhaust on a 2.0 liter engine and makes me wish I could run 3 1/2" exhaust on my DET.