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GCG hiflow on rb20?

B0oStEr

By B0oStEr,
in Engines & Forced Induction

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B0oStEr Mentor

B0oStEr

Posted
Posted

I spoke to someone from GCG at the Mingara s&s about a turbo for my rb20

He said they could hiflow my stock rb20 turbo but it would be better to use one from an rb25 preferably with a vg30 turbine housing.

I asked him how these would compare to an HKS GT2530.

He said they were much bigger more like a GT30.

I asked him how these options would affect the boost threshold.

He wasn't sure for rb20 but estimates

rb20 hiflow = stock + approx. 400rpm

rb25 hiflow = stock + approx. 800rpm

rb25 hiflow vg30 housing = stock +1100rpm maybe a little less.

I drive two r32 gtsts. One is manual with a exhaust and hybrid fmic and boost starts about 2400rpm.

The other is auto with just exhaust and pod and boost starts at 1800rpm.

Which one should I compare the hiflow to?

I'd appreciate feedback from anyone with experience of the GCG hiflows on the rb20.

Thanks.

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BHDave Grand Master

BHDave

Posted
Posted

If the current highflow with vg30 exhaust wheel is anything like the old stage 2 highflow expect full boost around 4100rpm with stock manifold, pod, front mount and full exhaust.

I found mine would start building boost from about 3000 make about 5psi by 3700 and then just shoot up to 14psi by 4100.

Cubes Grand Master

Cubes

Posted
Posted

Bl4ck32.

The reason your bush highflow is spooling like a stock turbo now is due to the rb30. :rofl:

On the RB20 I remember it used to hit hard around 4000rpm.

When Mark owned it that is :rofl:

The RB30 has ample exhaust gas to spool the turbo.

My stock rb20det turbo on the rb20det use to be on 1.1bar by 3000rpm in 3rd gear and over. Second accelerating out of a corner at say 2000rpm would have it kicking me in the arse as well as a stock turbo can by 3500rpm.

--------------

The GCG Highflow using the VG30 exhaust housing hits hard around 3700-3800rpm as stated previously. On the RB20DET slap another 500rpm + a softer hit, in other words it will spool up to what ever by ~4300rpm, it won't simply hit hard but more so be more progressive this is 'gay'.

I personally think its a bad combo on the rb20. Stick with the stock exhaust housing a keep the nice turbo kick in the arse feel.

I am going to buy a SB8006A GT30 600hp CHRA and a .7 comp cover, then get my vg30 turbine housing machined up to suit the VG30 turbine housing.

On that note have you considered doing some thing similiar?

On the RB20 I would consider a GT28 CHRA .6 or .7 comp cover and machine up the stock rb20 turbine housing to suit.

GT28 vs the GT30 you would really have to think about it and talk to a turbo person who knows their stuff. I personally would use the GT28 CHRA if I had an RB20. Which I don't so :lock:

The larger comp cover will no doubt be more efficient at high boost levels compared to machining up the small high boost restricting stock comp cover.

Bl4cK32 Grand Master

Bl4cK32

Posted
Posted
Bl4ck32.

The reason your bush highflow is spooling like a stock turbo now is due to the rb30. :)

On the RB20 I remember it used to hit hard around 4000rpm.

When Mark owned it that is :D

The RB30 has ample exhaust gas to spool the turbo.

Sorry...lol I had a line of thought, then managed to type something different :( Long day at work me thinks...

What i was trying to explain was that the rb20 highflow is making about the same max power it would on the rb20. Just its got a bigger motor to help it get there...faster obviously :)

Cubes Grand Master

Cubes

Posted
Posted
Sorry...lol I had a line of thought, then managed to type something different :( Long day at work me thinks...

What i was trying to explain was that the rb20 highflow is making about the same max power it would on the rb20. Just its got a bigger motor to help it get there...faster obviously :)

:)

ALSO.. :) The RB20DET would need around another 6-7psi of boost as the head doesn't flow anywhere near as good.

So.... your highflow turbo would have to be efficient at around 22-23psi and have an intercooler good enough to drop the inlet temps to the same as if it were running 16psi, thats to make 218rwkw with it on the RB20DET.

I would be curious if the theory held true. :D

22-23psi is a lot to hold right to redline, I suspect it will drop boost as it will run in to choke.

B0oStEr Mentor

B0oStEr

Posted
  • Author
Posted
i have the exact same but my boost starts at 2,5-2,800rpm.

how do you get it to start so early?

The auto makes boost from 1800rpm when I nail it up a hill and a bit later when the load is less.

The manual now makes boost a bit later since fitting the fmic but I can feel assistance from the turbo a few hundred rpm before the needle rises above the zero.

As others have said boost is just a measure of the restriction to airflow.

B0oStEr Mentor

B0oStEr

Posted
  • Author
Posted

quote Cubes

The GCG Highflow using the VG30 exhaust housing hits hard around 3700-3800rpm as stated previously. On the RB20DET slap another 500rpm + a softer hit, in other words it will spool up to what ever by ~4300rpm, it won't simply hit hard but more so be more progressive this is 'gay'.

OK so the vg30 housing will make it too laggy on the rb20.

GCG seemed to recommend the rb25 turbine as base for highflow over rb20 turbine.

What would the GT28 option cost?

Who would do it?

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