High Cr, Small Turbo Combination?

[works 510]

Guys,

Im still accumilating info and parts for my conversion and had a interesting thought at work today.

If I remember correctly, the GMS Bathurst GTR's ran a 9. something to 1 Comp ratio on mild boost.

Now,

From what I read, the 30det isnt a fan of smaller turbo's that choke them down restricting power at decent rpm.

The Bathurst cars, being twin turbo, in theory, there would be no/minimal restriction?

While trying to keep costs down, I would like to keep my current turbo setup (kkk k26 2770 with 42mm ext wastgate)

Turbo is rated at 330ps.

Would the larger size of the ext gate help with back pressure and restrictions?

How would it go with using the 9.1:1 CR pistons?

I can imagine it would be reasonably smooth power curve if it could still make power up top?

Thanks for your time again

Edited July 16, 2009 by works 510

[N1GTR]

Ok, this brings one guy to mind: "Al"

I drove his on a skidpan and quickly on the street, it was crazy quick, sure it doesnt have dyno winning figures but the way it makes usable power and torque it doesnt need huge power.

I can honestly say its the most fun GTST ive ever driven.

Hopefully he'll see this thread, if not, send him a pm - he's a really nice bloke

[R31Nismoid]

Al's turbo isnt a 330hp/ps turbo steve lol... Its a fair whack larger than that

The problem you'll have Dan is the turbine housing. It'll choke up very easily.

You could have a small turbo, no problem there - but the key is to have a larger rear housing - obviously not too large

Gate size is largely dependant on boost levels... id imagine to make any power on that little huffer your going to be running a fair bit of boost.

This will mean you want a smaller gate rather than a larger one for optimal boost control as most of the exhaust will go via the turbine housing to get turbo spinning up to speeds for the boost you need.

[Sydneykid]

I don't think that compressor will have enough airflow to make meaningful boost at any decent rpm, after all 30 lbs per minute isn't whole lot. You can't just up the shaft speed as it physically won't handle it, plus it's just going to churn out hot air. Really it's too small a turbo for a decent 2 litre engine let alone a 3 litre.

Cheers

Gary

[N1GTR]

Oh yeah sorry i know Als is more than that, didnt see the 330hp bit

[CEF11E]

I had a 3071 based hiflow on my RB30det. it was built by sliding performance and made a shade over 250rwkw with boost tapering off after 4000. full boost was about 2400rpm and it hauled... no top and but for street use it was FANTASTIC!

never raced it but it was very fun to drive. it now has a dirty big holset hx35 strapped to the side of it and they are worlds apart. The hiflow I had used the stock rb25 housings and was really to small.

[rob82]

I'm running 9:1 comp on my rb30/26 with std cams and twins-5's and seeing about 14deg timing at peak torque at 12Psi of boost on pump. So by the time I get 20 psi of boost into the thing I think my peak torque timing numbers will be around 8degrees which will be close to the edge on pump. However the gains in using higher octane fuel will be huge!

I think with bigish cams (270 and 10.5mm lift) you could get 10:1 comp in fairly safely. Remeber the bore/stroke ratio of the 30 doens't lend it self to high compression in comparison to the 26 and 25.

[psi]

Dan..

empty your inbox mate. I cant send you a detailed reply to your question if I cant send it to you!

Go and delete some old PM's out of ya box mate.. then send me another PM to let me know that I can send you the info your after!

cheers mate

Aaron

[unique1]

i run a gt3076r on a stock internal 30 (refreshed) and its making boost at ~2000rpm and makes 1 bar (current boost setting) at 2800rpm, dont choke it too much it will just be a slug at anything over 4000rpm or so.

I put stock 26 twins back on the same motor and it was absolutely shocking and would struggle to rev out over 4500rpm, it was very very very bad to drive and was pretty much on boost just cruisin at 80kmh.

The 3076r is the smallest turbo i would personally use, there is no way anyone could say its too laggy.

[works 510]

Aaron,

Will do, cheers man

Cheers for the advice unique1

Currently looking at kkk k27's