I see a lot of offers for tuners selling pulley changes on the LT4, and I'm just curious if when changing the upper pulley size, do you change the constant in the tune? It defaults to a 2.990 ratio.
Anyone know what the tune uses the pulley size for? I don't see a blower displacement constant so why it cares about the drive ratio I'm at a bit of a loss to explain.
I do... I always figured it used it for transients and boost figures during torque calculations?
Better question is what is it in reference too, the stock upper is a 2.5 and lower is a 8.0 so it should be 3.2 not 2.990. I adjust it as a percentage of increase.Quote:
Originally Posted by davepl
I would be interested in knowing what it references too. The 3.2 is correct for the actual ratio.
Description says Compressor Speed to Engine Speed even though the name of the field is Pulley Ratio.
GM rated the max blower speed on the LT4 at 20,150 which would be 6,740 at the engine.
Not too surprising the stock Rev Limiter is 6600-6700 RPMs....