Yep - a closer look at the Garret GT30R and GT35 confirms they are both viable for high boost applications on the S2/RS2 engines.
Based on my calcs (from Corky Bell and other sources) I get a corrected airflow rate of ~48lbs/min at 7000rpm with VE=85% and Boost=1.8bar. That would need an uprated bottom end but the GT30R will *just* be happy with PR=3 without running into choke.
The GT35R has additional headroom and could sustain PR=3.2 at this engine speed.
Looking at the surge lines, assuming PR=3 from 4000rpm then the GT30R would be just OK - within surge limits, but the GT35R would definitely be unhappy with this condition - it is optimised for generating high PR values at high engine speeds only.
So my gut feel appears to be about right with the GT30R being a much better choice for road use. It would sustain PR=3.2 between 4500 and 6000rpm.
I'll write this analysis up properly sometime, but I'd like feedback from Marco, Mihnea and others on my brief summary here.
For reference I am assuming Delta P across a good intercooler of 2psi and Delta P across the air filter of 0.5psi as per Garretts guidelines for calculating PR.
I'd need a little more time on the spreadsheet to calculate a suitable boost profile on the GT30R so that it doesn't have surge problems at lower RPM.
Paul
PS - I'm lookng at the GT30R map for 700382-12 with the 56 Trim compressor wheel... I haven't got my head round the turbine wheel choices yet with regards A/R, but the 0.82 choice would appear to have less lag, so thats what I'd go for on a road car.
Oh and the GT35R would appear to be better in a 2.5L application at first sniff. Evidence to follow sometime next week when I get plotting some graphs
Based on my calcs (from Corky Bell and other sources) I get a corrected airflow rate of ~48lbs/min at 7000rpm with VE=85% and Boost=1.8bar. That would need an uprated bottom end but the GT30R will *just* be happy with PR=3 without running into choke.
The GT35R has additional headroom and could sustain PR=3.2 at this engine speed.
Looking at the surge lines, assuming PR=3 from 4000rpm then the GT30R would be just OK - within surge limits, but the GT35R would definitely be unhappy with this condition - it is optimised for generating high PR values at high engine speeds only.
So my gut feel appears to be about right with the GT30R being a much better choice for road use. It would sustain PR=3.2 between 4500 and 6000rpm.
I'll write this analysis up properly sometime, but I'd like feedback from Marco, Mihnea and others on my brief summary here.
For reference I am assuming Delta P across a good intercooler of 2psi and Delta P across the air filter of 0.5psi as per Garretts guidelines for calculating PR.
I'd need a little more time on the spreadsheet to calculate a suitable boost profile on the GT30R so that it doesn't have surge problems at lower RPM.
Paul
PS - I'm lookng at the GT30R map for 700382-12 with the 56 Trim compressor wheel... I haven't got my head round the turbine wheel choices yet with regards A/R, but the 0.82 choice would appear to have less lag, so thats what I'd go for on a road car.
Oh and the GT35R would appear to be better in a 2.5L application at first sniff. Evidence to follow sometime next week when I get plotting some graphs
bottom end, and hope that with some cleaver Mihnea mapping 
(which required a slight knock) and the only markings I can see are KKK?
, you are the man i hope to map my URQ with this combo when finished. Dont worry, it will be a while yet. It takes a Looooong time to save up the cash 
. I plan on using those big injectors you talk about etc. But i had read from some of your posts that with all the right bits added to say a RS2, eg, turbo, tube manifold, injectors, cams, intercooler, exhaust etc, BUT a sotck bottom end you could chip to 400BHP easy. Is this wrong? 
I will be running a Gt 30R, Rs tuning manifold, 7a cams, big intercooler, big exhaust, your injectors all in a aby in a URQ. I will run the car for fast road use and track days, not every day, but i will super unleaded 97 ron at least. It must last some time, not just a day, but not 100K miles though. What do you reckon is safe boost wise, torque and Bhp? Whats that bhp at the wheels on a 016 box? I could add a shim to the head to lower the Compression ratio, but am worried about stuffing up the squish and getting more ping. What do you think? This month i am geting the manifold, next moth some parts from you i hope. One part at a time. Thanks, des.
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