I got to thinking about the previous posters water pump pully change...

So, IF we used a larger pully (eg, slower/less turns from the water pump), in theory we would have more HP... so, the question is, how much bigger can we safely make it (without rubbing to the next pully, and still providing enough juice to keep the engine cool).

Seem like a reasonable mod, or am I on crack again?

-- Aaron

 

'Underdriving' the accessories is a known performance tweak. There are companies that make different pulley sizes to do this for different cars, so you are not on crack again . Consider that the ac condenser, alternator, etc., run off the belt from the engine.

 

More Power = More Heat = More cooling needed

 

Or better yet, what UL was talking about; no pulley, and run an electric water pump (if someone would fabricate one for the s2k).

 

The way I figure, electric water pump would be good for short bursts, like drag rather than say, a road race.

The energy has to come from somewhere, it'll put a load on the alternator. Just like my electric SC, any benefit is negated by the drag on the alt. The power source has to be isolated, but the water pump has to run all the time . . .

 

The drag from the alternator is, for all intents and purposes, static regardless of the electrical load (I'm not going to get into back-EMF current arguments here), so if you have juice left over once everything else is powered, use the extra to run an electric water pump and save on the drag of a mechanical pump.

 

electric pumping systems tend to be more efficient than mechanical. They just don't do well under very high load situations (mechanical vs. electric fuel pump for full bore drag cars for example). In a road car, short bursts can take excess current needed from the battery and short of a top speed run, you're always going to have times when you're off the throttle when the alternator can recharge the system.

You're going to be taking energy in either case, but going electric is more efficient both in power required, as well as in overall power usage and cooling because you can maintain more consistent flow at just the level required. Mechanical pumps don't have that ability.

UL

 

I agree with the basics.

I have watched the alternator put a significant drag on the acc. belt when a high load is drawn from the system. There are so many arguments pertaining to parasitic losses, just like you're losing energy just in converting mech-elec-mech . . .

When all is weighed, including cost and reliability, a lighter pulley is more than likely the way to go.

 

I noticed SPA does have an electric water pump available for purchase.

 

[QUOTE]Originally posted by ultimate lurker
[B]electric pumping systems tend to be more efficient than mechanical.