Austarion

how much boost can i run on a stock bottomend 4g63?

Depends on whether you have forged pistons - if so then up to 21-23 "should" be Ok if everything else can support it. If not, then maybe 14psi tops.

VR4 bottom end or Evo ??? bottom end... or other

cant they like take 16-18PSI stock?

obviously depends on turbo but a stock vr4 eninge in good condition with a big16g can take anywhere from 18-23 psi (turbo becomes useless above around 23)

guys in nz run them all day everyday on 20 psi

from my research, stock vr4 motors will take up to 22 psi, and then will give you the finger.. remember that they have a ratio of 7.8:1 to begin with..

however, my research has largely been based on internet hearsay :P going from forum to forum to see what the most common answer is, and trying to ensure it's not the same guy or his mates saying it on every forum lol

I'm with Wantson and would reccomend caution particularly when upping boost on an unknown bottom end

to the people who have rebuilt their sohc motors with vr4 pistons, what sort of boost have you run successfully?

TOMSUN wrote:VR4 bottom end or Evo ??? bottom end... or other

vr4 motor.

thrash wrote:to the people who have rebuilt their sohc motors with vr4 pistons, what sort of boost have you run successfully?

More than 10 or 11psi and I hit the fuel cut! Should do something about that one of these days...

Boost will not kill a eng , detonation kills engs .

Lean fuel mixtures combined with detonation , will hurt even a forged motors.

If you have good control over your engine and supporting parts , with a aftermarket ecu and a good dyno tuner that wont let the engine knock . You can as a high in boost as your turbos efficiency will let you .

I ran my vr4 with stock internals at 18psi with no probs, mind you, I was running a GM AFM and translator to control fueling.

well the last time i got my car tuned it ran 18 psi but now it has bigger turbo, different inlet, bigger intercooler piping, different fuel reg/ rail.
now i was going to run 20psi or even more this time.
For my motor to live it will need a good tune/fuel/timing etc. I dont know how long it will last but as long as i treat it right it should put up a good fight.

MR Bender wrote:well the last time i got my car tuned it ran 18 psi but now it has bigger turbo, different inlet, bigger intercooler piping, different fuel reg/ rail.
now i was going to run 20psi or even more this time.
For my motor to live it will need a good tune/fuel/timing etc. I dont know how long it will last but as long as i treat it right it should put up a good fight.

well if it doesnt it means you can goto forgie town :)

well i think why fix something that isnt broken yet!
See how much power i can get out of it till it pops!