RB30DET and power nosing over after 5500rpm.

[Cubes]

Why does this occur?

Is it the small .63 exhaust a/r or is it a limitation of the RB25 cams?

If I were to use a .81 for example this should then open up the top end and allow peak power to be made higher in the rpm?

[meggala]

my thoughs are your right I owuld even consider going bigger than the .81 and yes joel I remember you want low down and midrange power.

nice to hear is running

cheers

[R31Nismoid]

.63 on an RB30DET?

fark, what a severly tight top end... get a .82 at least.

the VL boys with thier RB30det's run the 1.xx housing

[RIPS]

Is a bit small Joel, but we ran a 10 with a .63 housing and it made power hard to 7000

[Cubes]

This may be a good experimentation for a cheap $350 VG30DET BB turbo.

Long term plans are for a turbo similiar to Freebaggins that runs the GT30 600hp core with a cosworth .63 rear internal gate housing.

That turbo has made 280rwkw on 17psi.

A few other mods like exhaust cam gear etc but the point is it does make the power.

I hope the general flattening out of power over 5500rpm with the RB30DET's isn't due to the smaller exhaust a/r.

Well maybe I do as a larger exhaust a/r is cheaper than a set of cams.

VG30DET turbo should be able to tell me that fairly cheaply.

[RS500]

dude,

what turbo r u running now?

it could be that the turbine wheel itself is too small for the RB30DET.

also, given the extra flow of the twin cam head, you'd be much better off with an A/R .82 exhaust housing (with a decent wheel in there of course), otherwise you'll be choking the engine's air/gas flow which will also rob your engine of well earned power.

[Cubes]

There is a dyno floating around that was a GT30-11 475hp with a .82exhaust a/r.

That did the same flatten out over ~5500rpm.

I don't want this to happen.

Maybe it is the compressor wheel? Or possible the exhaust system fitted to that car?

[DoughBoy]

What cams do you have fitted to the engine? If there's a restriction you might as well trace the entire system looking for bottlenecks.

[Drifterdan]

HSVSUX on calaisturbo.com.au should be able to enlighten you. he has tried the .83 and the 1.06? on his 400+ hp rb30. I remember him saying that the .83 came on boost that hard that it broke traction with any more than 1/4 throttle. He said the 1.06? was his favorite on the track because it came on more progressivly(spelling?) and was still responsive/predictable. I like the idea of spinning the wheels when boost hits, though!

[Cubes]

Stock cams.

I'm with you Smooth.

I would like to see any dyno runs he has of the different exhaust a/r's.

[Wobbler]

Here is a thread which may be of interest to you.

[Cubes]

Thaaaaank you very much

[RS500]

There is a dyno floating around that was a GT30-11 475hp with a .82exhaust a/r.

 

That did the same flatten out over ~5500rpm.

 

I don't want this to happen.

 

Maybe it is the compressor wheel? Or possible the exhaust system fitted to that car?

like i said, an A/R .82 exhaust housing will work fine for top end flow (which was the discussion of this thread), but as mentioned, a decent exhaust wheel is required to flow that gas at the higher rpm.

fyi, the GT30 -11, has quite a small exhaust wheel, and is not suited to an RB30ET, let alone RB30DET.

plug in the numbers (3000cc, 7000rpm & 20psi) and you'll see that a GT30 (-14) core is recommended with an A/R .82 exhaust housing.

http://www.turbofast.com.au/TFmatch.html

[Cubes]

Thanks RS500..

538bhp at the flywheel isn't too shabby.

[RS500]

not at all ;-)