i was thinking of getting this underdrive pulley from lgmotorsports.com, but i was wondering how much it would affect driveability since it changes the power steering, air compressor, water pump, and alternator? i wouldn't mind if it took a tiny bit more strength to turn the wheel but nothing huge, and i almost never use the a/c. it's the water pump and alternator i'm really worried about. it says it will increase the life of the water pump. does anyone know how the underdrive pulley would affect these accessories?

lg also claims gains of12-15 hp and even 13 rwhp on a stock ls1 vette. is this really reasonable or how much power gain should i expect? i've got a CAI and magnaflow catback and will eventually add more.

here's the site(s): http://www.lgmotorsports.com/catalog...oducts_id=1529
http://www.lgmotorsports.com/catalog...roducts_id=105
are there any differences between the pulleys you can find(no part # on one of them)?

 

My experience including actual dyno tests is that an underdrive pulley gives you about 3-5 more HP. It does turn the various accessories slower (that is where the power comes from, they aren't getting as much power). I imagine there are some sort of conditions where it might reduce accessory load by 12-15 HP, but under normal performance circumstances (AC is off so its not an issue, car is pointed straight so the power steering pump is not loaded) about 3-5 is all I have ever seen.

You will get that much, and a bit more, but simply installing an electric water pump. Admittedly it is more work and money but it gets rid entirely of the one big accerssory drain on HP. (The alternator does have to work harder but that load is evened out over all the time the car is idling -- net effect is a gain of 8-10 HP).

My thoughts are:
- I would not install an underdrive pulley on a daily driver with mostly stock equipment - the accessories were designed to turn at certain rates, etc.
- I would install one on: a) a car which had had a higher axle ratio installed (say 3.73 instead of 3.42), or b) a car with a heavy cam. In the former case the car will be reving a bit higher all the time on the street. In the latter case the engine will be tuned to a higher idle speed because of the cam. In both cases the underdrive pulley tends to correct the situation for the accesories back to closer to stock, as intended.
- Don't install an underdrive pulley on a superchargedcar: you'll end up underdriving the supercharger -- noticeably cutting into power.

 

thanks that was a big help. i didn't realize how little effect it would have since i don't use the a/c and i won't really need that extra hp while i'm turning on the streets.

 

actually you mentioned you would install it on a higher gear ratio like a 3.73, so would you still not recommend it for my 4.10 gear ratio? thanks for letting me tap your expertise like this, speaking of which do you own a shop or are you just a genius