Hi,

I am looking for some advice on whether I should fit a light weight underspeed crankshaft pulley to slow down slightly my alternator, water pump and aircon. I am looking for a little less parasitic losses while driving that I hope will increase fuel economy.
This will be fitted in conjunction with a cat back exhaust from Cobra Motorsport and a Forge cold air intake. After all of this is fitted I will have the ecu edited for correct fuelling and ignition timing.
Just worried if a 7% or so underspeed pulley will affect cooling and charging too much, specially around town.
Hoping to gain around 40 hp and 40 lbs-ft.

Any feed back is welcome.

Cheers.
Andy.

 

I think the underspeed pulleys are overrated and unnecessary unless you are using it for racing applications where you aren't doing a lot of sitting in traffic. The exhaust and intake will do more to help gain HP than swapping out the crank pulley. The parasitic loss is not that much.

 

Thanks for the response.
I agree with you about the increase in power and that wasn't really the idea of the pulley. I know the other mod's will make the engine breathe and increase power, but my thoughts were along the lines of a long trip say more than 400 miles, would the pulley make any discernible difference to fuel consumption as you are on part throttle and at a constant medium range rpm so making is it easier enough for the engine to increase your mpg's? I would like to know if people have had problems in town running this kind of pulley?

 

I don't think you'd be much in the way of an increase gas mileage. You're driving habits make more of an impact on that than anything. On the interstate, you're going to get the best gas mileage your car will get anyway. My 03 A8L with a 4.2L gets a good 30-31mpg at 70-75mph cruise..