Exhaust sizing help

[Cya]

While im waiting for my 1jz to get wired up i've been tossing around a few thoughts about he exhaust. I will be running a Master Power T70 with a 3" Dp, i've tossing around the ideas of:

1. 3" turbo back
2. 4" DP back
3. True dual 2.5" DP back

Any Ideas?

P.S. I also remeber a thread a while back that disscussed this but i've had no luck finding it. Any help is appreciated. Thanks.

ED

 

[86_sports_1jz]

depends on what you want and how much power you want to make. i have a 4" dp n exhaust n sometimes my exhaust scraps the ground. my friends tell me that when i scrap sparks come out like crazy, thats what i don't like about the 4" the ground clearance and my car is not lowered yet

 

[jdub]

Besides that, the amount of air pushed through a 2.5L engine makes using a 4" DP hardly worthwhile. A 3" DP should be plenty

 

[Syris]

another vote for the 3'' turbo back

 

[Jostar]

Well i have a MP T70 on my 1jzgte, It's a lil bit laggy, I still need to be tuned though, I have 3" from turbo to the back, I'll post my results with the turbo, I did floor it once & full boost was around 4200 rpms & when full boost kicked in!! it roasted the tires & i bouncing off the rev limiter before i knew it, I know tuning might help alot, I do run a AEM ems...

 

[Cya]

Well i have a MP T70 on my 1jzgte, It's a lil bit laggy, I still need to be tuned though, I have 3" from turbo to the back, I'll post my results with the turbo, I did floor it once & full boost was around 4200 rpms & when full boost kicked in!! it roasted the tires & i bouncing off the rev limiter before i knew it, I know tuning might help alot, I do run a AEM ems...

wow! at what psi was this (ill be running 440's for now)?

 

[jdub]

Might want to think about bigger injectors before you install that turbo

 

[foreverpsycotic]

Might want to think about bigger injectors before you install that turbo

Def look into that, I am starting to worry about 440cc injectors with a 58mm turbo and a 400whp goal (pump gas). If you are that worried about power with a t70, put an electric dump in the downpipe.

 

[Jostar]

I run 550cc MKIV injectors..

 

[Cya]

Might want to think about bigger injectors before you install that turbo

Yeah, that was next on this list after I got it to crank. Im thinking either 800cc or 1000cc.

 

[86_sports_1jz]

yea i'd run bigger injectors with that setup and maybe just stick to the 3" because my 4" kinda sucks n i kinda wished from time to time i was only 3"

 

[group a supra]

a 4" dp back would be good on a 3"dp if it being the dp the turbo and the manifold are fully wrapped.
this would allow for the expansion after the downpipe when it is not wrapped and cools down.
Due to the faster dispersment rate of the exhaust gases when it runs so much hotter with the wrap this would also aid spool up by up to 5oo rpm lower depending on the setup and the mapping of course as timing also plays a big part in this side.