scott4.6

Has anyone run one before? Just wanting to know if you can still run your stock belt or if you have to modify anything for it to work. Also does it cool, meaning will a street car run hot in trraffic ? And most important how much hp and tq will you gain? Thanks

school boy

ive never ran one but know there is a pulley on them just for a belt to run on. the pulley doesnt power anything though

cliffyk

You will gain no horsepower, however over a short term you will free up horsepower that will be then be available to accelerate the car.

Over the long term you will actually lose HP to the wheels, and increase fuel consumption, as the electricity used to drive the electric pump comes from the generator. The generator is an inherently inefficient device (50-60% efficiency) so the mechanical power used to drive it will me more than if used to drive the water pump directly.

And as that power will in large part be stored to and retrieved from the battery there further efficiency losses.

So, the short story is that on a drag car, or when street racing (a thoroughly stupid thing to do), the electric pump can free up some ponies to send to the rear wheels.

However on DD, over time, it is a net loss...

school boy

cliffy, you always seem to surprise me with how much knowledge you have obtained over the years!

cliffyk

It is easy to fall into the trap of believing that a car's electricity comes from someplace other then the engine/generator...

school boy

exactly, its one of those things that slips the mind on "where" and "how" its generated

Schmalgar

Possibly the best summation on this topic I have seen. Simply put, but well explained, so that even us noobs can get it.

The thing that I admit not fully understanding, and perhaps others are in the same boat, is regarding the alternator. Isn't it always being turned, regardless of how much power is actually being used? Or does it engage and disengage on demand? So when engaged there is more resistance on the pulley? And when disengaged there would be less? So more power used means more time being engaged? Or am I just way off and showing my ignorance in an amusing manner?

cliffyk

With no power applied to the field coils the generator spins more or less freely, however in practice this situation never happens and the generator's field coils are always powered so that it rather then the battery is supplying the vehicle's electrical needs (and recharging the battery just after start-up).

As the electrical needs increase (headlights, heater blower, etc.) the voltage regulator senses the increased load (via the drop in system voltage caused by the added load) and increases the current to the generator's field coils, increasing the strength to their magnetic field and causing the generator to output more power--and consume more power from the engine.

The GT generator has a maximum output of 110A @ 14.8V at 6000 pulley rpm, which is about 2000 engine rpm. 110A @ 14.8V = 1628W or 2.2HP. But as the generator's efficiency is at best 60% it requires 3.6HP from the engine to produce that full output.

The good new is that only very rarely is the generator expected to make that much power, more typical loads would be less than 400W, taking less than 1.0HP from the engine...

Schmalgar

Thank you for that further explanation CliffyK. I *think* I get it now. As the magnetic field is increased, the resistance is increased on the generator, as it requires more effort to spin through the stronger field?

cliffyk

Yup, the generator's making more power requires more power from the engine...