Quote:
Originally Posted by Matt@Cosworth
thanks for the info Ade
also to answer weederr33 yes our unit is a R900 which displaces 0.9 ltrs every rev whereas a R1320 displaces 1.32 ltrs every rev
BUT
both have the same pressure ratio so the maximum boost that either can make is 1.4bar over atmospheric
the R1320 will reach maximum boost quicker than a R900 but you can compensate by spinning the R900 faster and the larger blower will also consume more power to produce the same level of boost
when we did our initial analysis we concluded the r900 is the right size for a 2 ltr engine
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Yes that's how I understood it. So the harrop car runs a pressure ratio of 2.2 to achieve about 320whp and with a 65mm pulley which is roughly 12k rpms - same as our stock pulley.
They cant spin it much faster as the max pressure ratio of the TVS units is 2.4 (1.4Bar boost).
With the R900 in the cosworth you just need to spin it at 17500 rpm to match that.
How fast can the R900 spin? Looks like much past 20k the efficiency starts falling off but that should be enough to get the max 2.4 pressure ratio?