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Quick Turbo Upgrade/downgrade Question

Incurafy

By Incurafy,
in Engines & Forced Induction

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Incurafy Apprentice

Incurafy

Posted
Posted (edited)

Hi,

My R32 has a VG30-something turbo on it that came with the car when I bought it. It's had several problems with boost creep and the like, but I've managed to fix that. The problem I have now is that it just doesn't hit boost (only 10 psi) until 4500-5000rpm which makes it unresponsive and shitty lower in the rev range. Obviously this is because it's an RB20 and it's a mismatched turbo for a 2.0L engine, and that's fine. However, I've got the chance to buy a stock RB20 turbo with literally no shaft play for $50. I don't care about the high end power loss, I just want more early-mid responsive while I save for something better.

My question is, should I be able to just remove the VG30-something turbo and replace it with the stock one, or would the conversion to the VG30 turbo have required modifying something which would stop me from doing a straight swap back to the stock turbo?

Sorry for the nooby question, but I'm still learning as I go. Don't want to buy the stock turbo, pull everything apart, then find out that I can't put it on for some reason. ;)

Cheers,

Tom

Edited by Incurafy
GTSBoy Grand Master

GTSBoy

Posted
Posted

A couple of points....

1) The VG30DET turbo is very very similar to the stock RB20 turbo. The turbine is actually the same turbine. The turbine housing is a little bit larger (hence why it can make a bit more power and hence why it can slow down the boost response). The compressor wheel is a little bit bigger, hence the extra power capacity.

2) A VG30DET turbo when installed on an RB20 will barely add any extra delay in bringing on the boost. Maybe up to 500 rpm. I've personally driven them that felt like they came on at least as well as the stock turbo.

3) If you have yours not coming on until over 4500rpm, then something is wrong. Either turbo is crook, or something else is crook. The most likely candidate is that the wastegate is not tight shut.

But the answer to your question is.....yes. Straight swaps. About as easy as it is possible to get.

Incurafy Apprentice

Incurafy

Posted
  • Author
Posted (edited)

What ECU do you have? You won't know what you have till you get the turbo off.

I have the stock R32 ECU. I know what the turbo is because I was told that buy the guy I bought it off. I also checked the stamp on compressor housing when changing the dump pipe. :)

A couple of points....

1) The VG30DET turbo is very very similar to the stock RB20 turbo. The turbine is actually the same turbine. The turbine housing is a little bit larger (hence why it can make a bit more power and hence why it can slow down the boost response). The compressor wheel is a little bit bigger, hence the extra power capacity.

2) A VG30DET turbo when installed on an RB20 will barely add any extra delay in bringing on the boost. Maybe up to 500 rpm. I've personally driven them that felt like they came on at least as well as the stock turbo.

3) If you have yours not coming on until over 4500rpm, then something is wrong. Either turbo is crook, or something else is crook. The most likely candidate is that the wastegate is not tight shut.

But the answer to your question is.....yes. Straight swaps. About as easy as it is possible to get.

That's interesting. I was under the impression that the RB25DET turbo was slightly larger than the RB20DET and added around 500rpm to the spool time, while the VG30DET turbo was even bigger again and took a lot longer to spool? At least, that's what I got from reading the threads around here.

While I've got your attention, my turbo has 45V1 stamped on the compressor housing, and from what I've found on these forums, that is a VG30 turbo. Sound right to you?

Regardless, I think I'll swap it over and see what difference it makes. It will be easier for me to wrap my head around a diagnosis of any problems if I can see the difference between the stock turbo and the VG30DET turbo (never driven a stock one).

Cheers mate!

Edited by Incurafy
GTSBoy Grand Master

GTSBoy

Posted
Posted

I have the stock R32 ECU. I know what the turbo is because I was told that buy the guy I bought it off. I also checked the stamp on compressor housing when changing the dump pipe. :)

That's interesting. I was under the impression that the RB25DET turbo was slightly larger than the RB20DET and added around 500rpm to the spool time, while the VG30DET turbo was even bigger again and took a lot longer to spool? At least, that's what I got from reading the threads around here.

While I've got your attention, my turbo has 45V1 stamped on the compressor housing, and from what I've found on these forums, that is a VG30 turbo. Sound right to you?

Regardless, I think I'll swap it over and see what difference it makes. It will be easier for me to wrap my head around a diagnosis of any problems if I can see the difference between the stock turbo and the VG30DET turbo (never driven a stock one).

Cheers mate!

The VG30DET turbo is actually the same turbine housing as the RB25DET Neo (this is the OP6 housing). This is slightly bigger than the 21U housing on the R33s, which is slightly bigger again than the RB20 turbo.

But let's be very clear......they're all basically the same turbo. The RB20 compressor housing is noticeably thinner than the others though.

The 45V1 is actually the marking on the R33 turbo. So it may not be the VG30 turbo you've been told it is. If you get it off and the turbine housing says 21U, then that's your answer.

tridentt150v Grand Master

tridentt150v

Posted
Posted

And without a Nistune or am ECU [or a bender like a SAFC} gains are minimal for any turbo swap. Also you have an RB20, so low down torque is not going to improve probably as much as you would be looking for.

discopotato03 Grand Master

discopotato03

Posted
Posted

Same ceramic turbine , three different compressor wheel sizes . Late RB20DET smallest comp , BB VG30DET then RB25DET . From memory early BB RB20DET was same approx same as RB25DET but with smaller compressor housing casting .

VG30 and R33 RB25s use same compressor housing machined for native wheel , RB25 with anti reversion groove in snout .

The throat size in RB20 and 25 turbine housings isn't great but the 25 to VG30 is a bit more significant .

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