3inch vs 3.5inch

[Ray_GZ20]

hey guys just after peoples oppion putting 1jz vvti into my gz 20 been told different things money not such a big issue but if it is worth the while ill invest, plus in a year might be going bigger turbo. So ill be changing from turbo outlet right through to the back with seperate pipe off the wastegate which will join back into exhaust bout 70cm down. So should i go full 3inch, full 3.5inch or combination off the two either 3.5 turbo to cat then 3inch back or other way round? also have been looking at metal cat so i can get 3inch or 3.5 outlets or is magic cat better? Also stainless or mild? Cheers guys

[styler]

mandrel bent or not? personally i think its more expense than its worth compared to the pressed exhaust system

and apparently but having a 1/2 inch bigger in press bent system it will flow the much the same as the a mandrel bent system.

also most people forget that while pipe diameter increases, the exhaust velocity decreases, which is an important aspect. and you do need some backpressure
down low too.

turbo exhaust systems have their own characteristics vs a naturally aspirated exhaust systems, maybe someone knows more about turbo exhaust tech...

sorry dont know much about the 1jz particually!

[Draven]

what arse.
on a turbo you want SFA backpressure, all it does is screw things up.

Personally I'd probably go a 3.5" back to the cat, then down to a 3" - by the time the gas hits the cat it will have cooled a bit, thus decreased in volume, thus needing a smaller area to pass through.

edit: also ,the stock wastegate may not be up to holding boost if you free up the exhaust this much, so be prepared to install either a restrictor ring or real wastegate (common problem with the 2j, I have nfi on the vvti 1j).

[Ray_GZ20]

yeah thanks draven sounds good any one can back this up or offer differant advise experiences regaurding wastegate pipe? Plus advice on cats cheers

[Ray_GZ20]

also any advice on stainless vs mild is it just for show? or benits

[styler]

what arse.
on a turbo you want SFA backpressure, all it does is screw things up.

.......................

turbo exhaust systems have their own characteristics vs a naturally aspirated exhaust systems, maybe someone knows more about turbo exhaust tech...

[Draven]

ok, so I was a little harsh.. sorry

stainless is purely for the bling factor, and it lasts forever and ever

[JP]

I've got a 3" mandrel bent system on my VVTI 1J with a metalcat and a "Lukey Race Welded" offset in/straight out rear 3" muffler.

It makes full boost and torque around 2600rpm, great to drive and best of all no drone in my wagon!

I made it myself with bends purchased from Midway metals so it didn't cost too much.

[IN 05 NT]

finding a shop that will PRESS BEND 3.5....GOOD LUCK,

it will have to be mandrel bent if you go for 3.5, all the bend will be a seaparate weld in job, not one solid pipe,

plus with 3.5" you start to have serious ground clearance pobs with going unda the diff,

just recently had to modify a 1jz20 3.5 zorst as it was scrapping badly, and probaly had the flow rate of a 3" where it had been scraping and crushed.....

if your expecting power levels unda 300rwkw, just stick with 3",

blake

[IN 05 NT]

magic cat or metal cat...both the same, both high flo, so the articles in zoom say, lol probably give each reatiler a call and see what they can give you to compare,

stainless is overated and overpriced, just go for alloy coated mild steel, will still most likely out live the car anyway, and save you a few $$$'s

blake.

[Ray_GZ20]

yeah cheers man i know bout if i go to 3.5 will have to get all welded in but all good budget around 1500 or bit more if required. plus both systems either 3 or 3.5 will be mandrel. anyone had any other experiences will seperate waste gate pipes? Jp what setup do you have on ur car turbo back wastegate pipe, 3inch full system, what cat and what car you got this in? also any probs with motor turbo any info advice you can offer would be great cheers

[mic*]

I am confused how you have a separate pipe for an integral wastegate? That is in reference to the "separate pipe 70cm down" bit together with Draven saying be prepared to get a real wastegate... Or is that for the bigger turbo - ie ext wastegate... In a year ???

[Ray_GZ20]

nah on the back of the turbo there are two outlets and you can split the exhaust in two then join it back in down the exhaust i was talking bout doing this while i had the standed turbo

[mic*]

nah on the back of the turbo there are two outlets and you can split the exhaust in two then join it back in down the exhaust i was talking bout doing this while i had the standed turbo

Oh k. Thanx for the info i didn know. Have to take a closer look next time im up close with a 1J...

[Ray_GZ20]

yeah 1jzvvti is different from normal cause single turbo instead of twin so it is easier to have the split exhaust system with seperate pipe for wastegate