Debate on Supercharger and Stall???????

[Chappy]

I have been debating with a mate on the subject of stalls and superchargers.

So out of curiosity I decided to ask the question on here as there is some very switch on people on this forum.

Ok the question is: If you have a positive feed supercharger (Harrop) on your 5.7L motor and its auto is there a advantage or disadvantage in fitting a stall converter (3600rpm) for example, given that the supercharger give you torque from idle.

I await replies with interest.

Ken.


I have been debating with a mate on the subject of stalls and superchargers.

So out of curiosity I decided to ask the question on here as there is some very switch on people on this forum.

Ok the question is: If you have a positive feed supercharger (Harrop) on your 5.7L motor and its auto is there a advantage or disadvantage in fitting a stall converter (3600rpm) for example, given that the supercharger give you torque from idle.

I await replies with interest.

Ken.
What no one else got any idea ?????????????

[Ellistwo]

You are no doubt thinking that because it's a torque convertor the numerical value input value is the determinant. So one argument is that if the torque comes on early, as with a S/C you can bring stall on early too. The flip side is that the engine mechanicals don't come on cam until mutch later.

I think there is still merit in ballparking around peak VE. My main reasoning is that at the end of the day the engine is a power production plant, the car moves in a linear direction and torque is just a cross product vector of power and displacement in between energy release at the pots and the car moving from point A to point B.

The argument could be made that the addition of the S/C moves the peak VE downward and thus the stall point should follow, however that is a bootstrap situation.

Torque of 1000N-m @ 1000 rpm does not require the same power production as 1000N-m @ 3500 rpm ( a factor of 3.5 times more power). So if you have an engine hooked up to a low rpm stally you will soak a lot of the power early, without the benefit of torque multipication. On any engine this can result in slow engine acceleration and combined with WOT a drop in overall VE and thus BMEP. This will be particularly evident on a turbo setup where the exhaust mass flow remains low thus boost due to low engine power production, but an S/C will also have a low pumping duty due to restrained engine RPM and poor engine VE.