Help On RB20DET Downpipe N Exhaust Size

[Moses Lai]

To All RB20DET Sifu
Currently i'm doing my project on my RB20DET manual, i'm upgrading to Garret T3/T4 turbine with 42mm external wastegate.

My question is, wat size of downpipe n exhaust pipe should i b running n i prefer my car to have more torque on low end, i guess is more suitable for town drive.

Currently i'm running 2.5 inche downpipe n exhaust pipe, can i still maintain this size coz my foreman advice me stick to tis size so that i can cut down on my turbo lag.

BTW, any idea wat's d pro n cons if i install d AFM after d intercooler?

Thanks.:stupid:

 

[Nats autoparts]

put in 3" or even bigger since you are running t3/t4 - bigger a bit compare your stock rb20 turbo
as boost building in, it need to be release asap
with 2.5 yeah you can have response immediately and through out the middle rev but getting to higher rev - is like poking donkey ass with da carrot
change to 3" as advisable as you already using 42mm waste gate ,try to plumb back your waste gate back to the exhaust system to make it more back pressure built up in the chamber pipe ( release on atmosphere really give good sound,fast response but - noisy and bad to air too )
been there ,done it, proven but no theory
sounds logic but do it at your own risk - no promise what sot ever result will be
cause this is modification

 

[kaminari]

stick wth 2.5inch... as wht ur foreman say...reduce lag and it`s sufficient for RB20DET if ur talking abt 350hp below.Reduce the intercooler size will also help u gain response on low rev...rather than u use big I/C frm GTR.

AFM after I/C is bad idea. Hot air comes from the turbine even after I/C still will damaging ur fragile AFM sensor compare air before turbine suction.RB AFM is knwn for it`s fragile to HOT air/engine bay.Plus wth air pressure ON/OFF from turbine and throttle will make it more WORSE.

 

[olskool]

i think 3inch would be the way to go....instal exhaust temp first if you're not sure..that way you will know if you're hurting the engine or not..use wastegate for further tuning...i used a sr20 ARC intercooler which worked out fine..it's almost as thick as the RB26 but way much smaller..all based on what you want to achive in HP..remember, the shorter pipings the better..

having 2 exact same engines with same mods can still perform differently....

as for AFM, i agree with kaminari.

 

[Turn1]

Your AFM is on the intake side of the turbo so temp and pressure won't affect it. It won't matter when you upgrade your AFM, you will only want to upgrade your AFM if you have an aftermarket ECU (power FC or EPROM) otherwise you are wasting your time and money.
The only thing the Z32 AFM gives you is more voltage resolution so the ECU can cope with the extra intake airflow.
My advice would be to upgrade AFM when you upgrade turbo, injectors and ECU. Front mount I/C won't make any difference to your stock AFM!

Hope this help.
Turn1