which turbo spools faster?

[spankarooney]

which turbo spools faster? a pt4788 or a y2k88 on a 383 lt1 m6 car?

[Beerbelly]

That depends upon the A/R of the turbine, i.e., "hotside". It doesn't have anything to do with the compressor. However, if you undersize the turbine it will generally go out of the efficiency range of the compressor much more quickly, and the opposite is also true, if you oversize the turbine it will take forever "lag" before it gets into boost. Your question should really be, what tubine A/R should I use on X engine to have whatever amount of boost you want by Y RPM's based upon the turbo you are looking at.

[preston1980]

which turbo spools faster? a pt4788 or a y2k88 on a 383 lt1 m6 car?

Ive always heard, the bigger the turbo, the longer it takes to spool and build boost. the little turbos boost quiclkly, but with less boost. So find out which one is bigger and there is your answer. Either way, a turbo on an LT1 is going to make some serious horsepower, so good luck.

[Beerbelly]

That's a crude generalization and not entirely accurate. You could use a T-15 turbo with a 1.85 A/R Turbine and it would build boost very slowly and not exceed the turbo's maximum flow rating. Conversely, you could use a T-90 turbo with a 0.32 A/R turbine and it would be boosting at idle and you would exceed the turbo's rated flow at high rpm.

That's the whole trick with turbos - you have to look at the compression/flow map for both the compressor AND the turbine. With a supercharger it's much easier because you are only dealing with the compressor and a linear speed mechanical multiplier. The A/R of a turbine acts as the multiplier or driver of the compressor but it is variable, which is where "lag" can come into play if you undersize it too much.