which exh. mani/o2 housing is bigger: JDM GVR4 or 1G USDM

[tsi_turboawd]

Im wondering if anyone actually took apart the exhaust manifold and o2 housing of the JDM 4G63T(89-91) motor and compared it to the US 1G exhaust manifold/o2 housing. which one do you think flows better? same?

 

[L2RTSiAWD]

I believe they are the same.

 

[tsi_turboawd]

i dont want boost creep again. no, no, no.

I have ported my 14b along with 1g manifold and o2 housing from my old motor and STILL the boost creeps, tho it helped a tiny bit.

FFWD>>Right now i got a mechanic swapping a JDM motor for my dead one w/ ported everything. I dont know if i should keep the JDM manifold/14b turbo/o2 housing the way they are and see if it will creep OR swap in my ported ones from my old motor to the JDM one.
boost creep kills the fun racing

 

[L2RTSiAWD]

Boost creep occurs when you have to much open exhaust. A more restricitve exhaust will lessen boost creep.

 

[tsi_turboawd]

correct.

so wat now, i should keep the jdm manifold/14b/o2 housing on unported and slap in my 2.5" DP/TP/back exhaust? ..im thinking about just swapping in only the ported turbine housing and o2 housing leaving the manifold unported on the jdm motor.

 

[L2RTSiAWD]

Well if you don't want boost creep I wouln't put any ported parts on except for the turbine housing.

 

[ChicagoGSX]

So confused now. Why does porting the O2 housing and wastegate flapper area lessen boost creep? Is it the fact that you have differences in flow if you have a stock O2 and a 3" exhaust?

 

[nine5raptor]

it allows more flow through the wastegate (which is bypassing the turbine). If you don't have enough flow through the wastegate and an open exhaust after the turbine, then the gasses will take the path of least resistance and voila! Boost Creep.

 

[DrZiplok]

Yes. Put on the ported parts, but first hog out the wastegate hole to give yourself better boost control.

 

[zac83]

JDM manifold owns the US manifold

o2 housing should be better also since its off of a 16g...

USDM manifold flange to turbo is 1.75 inches, the JDM one is 2 inches. this makes for a large difference in spooling and volumetric efficiency.

ive got pictures around here somewhere, cant find them at the moment tho.

 

[tsi_turboawd]

is the JDM exhaust manifold really bigger(and o2 housing)?!

well my JDM motor came with blue top injectors(450cc) and a TDOH5 turbo which looks like a 14b and its hard to believe the JDM ones are bigger than USDM.

please post the pics tho to prove. remember mines a jdm 14b

 

[tsi_turboawd]

how about JDM 14B and USDM 14B motor? prolly same right? ..hmm i guess so