07-15-2009, 10:05 PM
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Registered User
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Join Date: Aug 2007
Location: South Australia
Posts: 512
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 Quote:
Originally Posted by space
For BB turbos I would recommend garrett gt2871r for a dual set-up you would not have much lag.
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If you could get the full potential out of a pair of GT2871r's, youd be pumping over 400RWKW. Unless you have a need for more KW, there is no need for turbo's bigger than that.
Having said that, your intended quite high static compression ratio has me wondering what sort of fuel be using and the cars intended purpose...... 
If it is planned to be a track car running any of the 'heavey' high octane race fuel or (better still  ) methanol, then possibly a move to the Garrett GT30 range would be better interms of turbo durabillity.
External wastegates aren't really necessary. Unless you require the system to run at very low boost pressure, the flow capacity of the newer Garrett turbo's should be plenty. Of course the GT30 type are only available withe wastegated housings from certain groups and they are typically based on the turbine housings from the Nissan R33 Skyline GTSt housings (.64 A/R ratio only). So GT30 type turbo's will require external gates.
Blow off valves are without a doupt the most over rated devices in the world! OK, maybe second to turbo timers. They serve a purpose but most of that purpose is more to do with emissions (reversion back thru a hotwire airflow meter) and to a degree durabillity (reversion thru a vane/trap door style AFM). Factory Bosch types (like what Greg use's on his SC kit) should suffice unless you simply must have some machined and anodised aluminium thing bolted to your intercooler pipes.
Aftermarket BOV manufacurers will tell you how important they are, but then that's marketing for you.
The F1 turbo cars didn't use them. Only the factory 1s were used on the Skyline GTRs and Cosworth Siera's during the Group A touring car era here in Oz.
Actual compressor damage from not running a blow off valve is highly unlikely. The only time it could possibly happen is if the turbo is pumping HUGE boost pressure and the additional pressure spike when the throttle is shut excedes the physical strength of the compressor wheel and it forces it to change shape and contact the compressor housing.
Lag master huge turbo's suck!
High static compression ratio with really high octane fuel (and good tuning) would help improve drivabillity a whole lot! Anti-lag will also help at the expence of turbo, manifold and probably exhaust valve life.
But ultimately you are going to be traction capacity limited, especially on any sort of road tyre, so if you start making in the 350+RWKW, then it would be a hugely fun ride with lots of tyre smoke .
A 3.45l twin turbo engine in a rear wheel drive car not much bigger than my go-kart  :c ool:
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Last edited by Duk; 07-15-2009 at 10:26 PM.
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