RB20 with RB25 turbo - need info

[VLRB20DET]

Im looking at getting a RB25DET turbo and bolting it onto m RB20DET, what sort of mods would i require to bolt it up or is it a direct swap, also what sort of power could I achieve with one of these turbo's?

[R31 POWER]

I have done this convo so it's not stuff I have heard.

- It does bolt straight up

- Get the RB25 elbow,or drill out the holes in the Rb20 one.Just beware the RB25 one is larger inside

- Use RB20det actuator coz it makes more boost

- One mod to do is tee into a hose from the plenum coz the RB25 compressor housing does'nt have a hole for it unlike the RB20 turbs.

Any more Q's just ask.

[warpz0r]

hows the new diff going?

any times?

still looking for a cheap wrecked 5L 28 spline diff to put some pintara gears in

[VLRB20DET]

I did a 10.134 @63.38mph down the 1/8th mile (200m)

[B0oStEr]

Maybe you should changeyour signature to

I LIVE A 1/8 MILE AT A TIME

[discopotato03]

RB31 power , my opinion only , I would drill and tap the RB 25 comp cover and use the compressor discharge pressure as the wastgate actuator signal source . Using inlet manifold pressure signal can make the wastegate do strange things like opening and closing very quickly . Those Hitachi turbos have enough problems with ceramic turbine failure (particularly with increased boost meaning higher shaft rpm's) so throwing extra transient loads on them only agravates the probs .

My opinion only , not interested in turbo mods that could lead to failures , the cost and inconvienence is not worth it .

Cheers A .

P.S My prefference is the early RB25 turbo with the aluminium compressor wheel , seen too many shattered plastic ones .

[Cubes]

Discopotato03,

Thats an interesting theory regarding the wastegate actuators signal source.

It could also explain why the rb20t turbo's appear to be much tougher than the rb25 turbo's. I.e able to run more boost and in my case 16psi for 2years or so.

[VLRB20DET]

16psi, im running my stock rb20 turbo at 14psi, from what i have heard the exhaust wheels dont like been overspeed.

Jst out of curiousity are the rb25 turbo's a ceramic design or steel wheeled?

I agree with what Discopotato03 said, you get a more acurate boost response when the actuator gets its vacume pressure from the comp cover..

For what its worth will i get much more power using a rb25 turbo or will I still be restricted at running 15psi??

[discopotato03]

I did try that once with eratic results . I'm not sure if the waste gate actuator is designed to run at lower that atmospheric pressure which you get in the inlet manifold at part throttle off boost . The danger is that the turbo could be running at higher boost than the manifold pressure indicates ie flow losses through intercoolers , leaks etc . Plenty of production cars can boost against a partly closed throttle so if the manifold pressure is below the actuators spring rate the turbo can be worked harder than intended . However if you take the signal from the turbos outlet you can be sure the pressure your regulating is what the compressor is putting out .

Would I be right in assuming R32GTST's don't have electronic boost control and R33 GTS25T's do ?

Cheers A .

[R31 POWER]

Yer thats right.I said to VLRB20DET in a PM that I reckon drill and tap a thread in the comp housing,there's even a flat bit where it looks like is was made for it.