RB20-DET turbo replacement issues

[aeverton]

I recently had the blown out turbo, and had it replaced with a RB25 turbo. I've noticed since that the engine does not have a smooth idle, and tends to stall once or twice a day when stopped at a red light. The boost gauge barely registers an increase in boost when at full throttle, although there is a lot of pull.

I plan on replacing the timing belt later this summer, which may fix the idle issue.

What do I need to be concerned about, or paying more attention to now that I have a bigger turbo installed in the car?

[amnash]

rb25 turbo is only a hair bigger then the 20. side by side theyre almost identicle so the bigger turno thing wouldnt be the issue. check all the clamping you messed with when you changed the turbo.
The timing belt change isnt going to fix anything unless your out a tooth and correct that when installing the new one, you should just check it as it is and if timing is off a tooth reset the original belt if your on a budget as long as it isnt cracked or signs of wear.

stalling at a red light is normally from tps. check the voltage. dont have to have the car running for that. just turn key to on without starting check voltage at tps with mulimeter hooked up adjust to spec if you need to, then still watching multimeter open throttle all the way slowly and watch the voltage change, make sure its nice and smooth through full travel.

download FSM for r32 and start reading through it. there's so many easy things to check thats free and shows you how to do it.. these cars are pretty simple to keep running as long as you can follow the fsm

ps im bored at work hence the long ass reply

[mptjimmy]

with the lack of boost built up or gauge reading also check all the vacuum lines maybe something is miswired or not plugged in/ could also relate to the bad idle and stall at low rpm

[Skym]

Check intake hoseclamps, TPS as mentioned above. Especially the intake pipe infront of turbo. Also check BOV for leaking, as can get oil deposits around valve seat. Rough idle can be due to engine running leaner (run on dyno with wideband to see what I mean) and combine with stock narrowband 02 sensor making engine run leaner (sometimes is due to intake airleak, so check that first). You'll need a ECU retune to suit a bigger turbo.

After blown turbo (if failed on compressor side) you should replace intercooler, as sometimes there can be metal shavings from compressor wheel touching compressor housing that have made their way into intercooler core. Also can be coated with oil that drops the cooling ability of the intercooler. Then clean out AACV (need new gasket from Nissan), IACV, as they can get oil inside them if turbo oil seal has failed on compressor side or due to too much oil via blowby.

[supersayianjim]

or try another rb25 turbo(buy mine)!!

[aeverton]

I turned up the idle by a couple hundred rpm and that solved the stalling problem, and replaced the hose leading to the boost meter, had a hairline crack in it that was causing the gauge not to register boost. been running like a top since!

[Skym]

Might have a TPS problem (not on idle contact) if have to raise idle rpm to stop engine from stalling.