Downpipe size - Tuner-Junction

88 rex · #1 (**permalink**) October 29th, 2006, 08:13 AM

Is it better to have a 2.5" dp to a full 2.5" exhaust OR a 3" dp to a 2.5" exhaust. I'm thinking that the transition from 3 to 2.5 will be too much of a disruption and that a straigt 2.5" from front to back might flow better. Anyone have any insight on which is better?

Thanks!!

triniskill · #2 (**permalink**) October 29th, 2006, 10:25 PM

having a full 3 inch will be alot better..the faster exhuast can get out is better for the turbo..
What my cuzin did was 3 inch straight threw to a 2.5 inch axle back.. Reason being to gain some extra torque..which did work.

88 rex · #3 (**permalink**) October 30th, 2006, 12:16 AM

Having a full 3" is not an option unfortunately. So a 3" dp would probably be a little more ideal as it would provide a little more space for exaust gas?

triniskill · #4 (**permalink**) October 30th, 2006, 08:44 PM

Quote:

Originally Posted by 88 rex

Having a full 3" is not an option unfortunately. So a 3" dp would probably be a little more ideal as it would provide a little more space for exaust gas?

Yea..also antoher thing..Depending on which turbo your are using..you wouldnt have to go 3 inch...like the disco potato..you can go with a 2.5.

Retroshark · #5 (**permalink**) October 30th, 2006, 09:11 PM

i have a 3 inch exhaust for my turbo, you can never be too careful even with a small turbo. i think you should stay 2.5, but run open dump, that way it wont be as bad

jadkar · #6 (**permalink**) October 30th, 2006, 09:24 PM

Quote:

Originally Posted by 88 rex

Having a full 3" is not an option unfortunately. So a 3" dp would probably be a little more ideal as it would provide a little more space for exaust gas?

Uh oh...... is someone going turbo???

triniskill · #7 (**permalink**) October 31st, 2006, 05:13 PM

Quote:

Originally Posted by Retroshark

i have a 3 inch exhaust for my turbo, you can never be too careful even with a small turbo. i think you should stay 2.5, but run open dump, that way it wont be as bad

very true..but knowing Will..he is going with a gt28rs(disco patato) they have internal wastegates..you can weld it shut and run a external..but that is pointless..its just ruining a good turbo..

Also..from what I have seen on some gen 3 supra's..is make a custom DP that has a external dump for the internal wastegate turbos..

this is one thats made by bic performance..

triniskill · #8 (**permalink**) October 31st, 2006, 05:15 PM

Quote:

Originally Posted by jadkar

Uh oh...... is someone going turbo???

It sounds like he wants to keep up with some other boosted crx

..

jadkar · #9 (**permalink**) October 31st, 2006, 07:22 PM

Quote:

Originally Posted by triniskill

It sounds like he wants to keep up with some other boosted crx

..

Please.......he already keeps up just fine. If he goes turbo it will be a massacre!!

triniskill · #10 (**permalink**) October 31st, 2006, 07:55 PM

Quote:

Originally Posted by jadkar

Please.......he already keeps up just fine. If he goes turbo it will be a massacre!!

lol..true....hey you never know...

88 rex · #11 (**permalink**) October 31st, 2006, 09:30 PM

^

You guys are getting carried away! There will be no turbo on my car anytime soon

I'm in in the middle of replacing my kitchen floor. Then we're buying a new fridge and a new range and then I'm refinishing the bedroom floors and remodeling a closet. All my $$$ is wrapped up at the moment. I've got a brand new wheel sitting in the garage with no time to go and have it put and have all my other wheels balanced.

Plus I fully intend on attending the ITR EXPO next June so I want my car to be in top notch shape for some track days.

HOPEFULLY, if all my good deads around the house earn me enough brownie points, I may be able to divert some funds into a turbo. BUT that is a big IF!!

Here's my goal, and maybe you guys can tell me what I want/need.

Here's my thoughts so far:

Stock block and head. 11.1 compression

- GT28rs (should I used the T25 housing w/internal waste gate or drop it into a T3 housing and go external wastegate....although ATPTURBO makes a nice internal gate adapter)

-Log manifold....I want to run stock full radiator and it can be done with a log manifold. Already know which one I want.

- Any semi-decent intercooler that fits nicely and obviously paint it black

- 2.5 dp.....should i get the custom external dump tube? Would that help with potential boost creep problems?

- 440 injectors (or would 370's work....John

)

- Hondata S200 w/boost unless I find something else. My ecu is Hondata ready so it would just be a simple plug in. S300 my be out of my budget, but who knows.

-Tuner....????

---Goal is to make enough power to be on par with my buddies Mustang. Roush stage 2 with lots of goodies and very healthy for what it is. Just found out he sourced a nice new supercharger and we're going to be throwing it own when he gets it.

I want a conservative tune on 7-8 psi making whatever power I can make.

300 whp would a nice touch

njn63 · #12 (**permalink**) October 31st, 2006, 09:52 PM

tuner should be jeff evans, no doubt. Especially considering your location.

This build should be of interest. Very similar to what you're talking about. 10.5:1 comp b18c1 with a GT2871R. Leung's Car Home Page He has ITB's though. I wish i could find the video of that car, it's pretty impressive.

edit: Couple videos: TunerTrader.com

triniskill · #13 (**permalink**) October 31st, 2006, 10:55 PM

everything sounds real good..
For the turbo..I say stay witht he t25 housing and internal wastegate..
440 injectors will be perfect.

tuner- Jeff evans should be your number one choice..
You can also check out E-shift for tuning..

jadkar · #14 (**permalink**) October 31st, 2006, 11:13 PM

hahaha......and you can be just another ricer girl with a turbo Honda

Yeah, I have a thing about "the same thing everyone else does". I say, since your car is super light you build a sick all motor beast. That's just my own .02

Anyway, if you go with 440s you can buy mine. I think I'm gonna have to upgrade....again

88 rex · #15 (**permalink**) November 1st, 2006, 08:52 AM

Quote:

Originally Posted by jadkar

hahaha......and you can be just another ricer girl with a turbo Honda

Yeah, I have a thing about "the same thing everyone else does". I say, since your car is super light you build a sick all motor beast. That's just my own .02

Anyway, if you go with 440s you can buy mine. I think I'm gonna have to upgrade....again

You're geting bigger injectors!!!

Building an all motor set-up with decent power will cost almost the same as going turbo. I will have more power and little if any noticable lag. Also, seeing the tight fit of your supercharger and the difficulties with removing stuff has swayed me from JRSC. The Vortech might fit a little better, BUT that would have the lag of a turbo with less power. The turbo will fit better for me and my budget.....although the GT28rs isn't exactly a cheap fanboi turbo

88 rex · #16 (**permalink**) November 1st, 2006, 01:07 PM

Hey John, looking at RC's webpage it looks like they recommend an injector in the 750 cc range for your power output. Were you maxed out on your 440's?

jadkar · #17 (**permalink**) November 1st, 2006, 03:48 PM

Quote:

Originally Posted by 88 rex

Hey John, looking at RC's webpage it looks like they recommend an injector in the 750 cc range for your power output. Were you maxed out on your 440's?

No I wasn't maxed out although I was coming up on the limits. That's why I think I'll have to go with larger ones now

triniskill · #18 (**permalink**) November 2nd, 2006, 12:15 AM

very true...gt28rs is not a cheap turbo..

I think 750cc's will be to big for Johns setup..I say either 550's or lil over 600cc...my cuzin is going with 750cc next..but he is looking to crank out over 500whp out of this ek..he also got 2 fuel pumps.

M.A.R.C. · #19 (**permalink**) November 2nd, 2006, 12:26 AM

go 2.5" to 3" on the downpipe and then 3" downpipe back. fuck a cat.

Retroshark · #20 (**permalink**) November 2nd, 2006, 12:28 AM

i agree, but still, i think 3 inch all the way is best

oh and marc, i heard your car is scary fast, i always thought it was a hatchie til i saw the picture in your sig, looks nice.