Under Drive Pulleys and Old Fashioned HP's

[dsm_mike]

I saw a magazine article that included a dyno test of these wires on a 1992 eagle talon. They added something like 10 hp and 25 ft lbs. Of course this was an older car and the original ground connections were not optimal at the time. IMO these wires dont add any power, they allow the engine to make better use of the power it does have. I dont think it would make as much of a difference on newer cars, as your comments indicate Ian. But still, 25 ft lbs out of ground wires, damn[?]

[Mike Radowski]

An underdrive pulley doesn't add anything. It just gives back some of what the older pulley took away.

Mike

[Ant]

quote:Originally posted by Mike Radowski

An underdrive pulley doesn't add anything. It just gives back some of what the older pulley took away.

Mike

Not sure what you are talking about. Please explain, in detail your knowledge and experience with UDP's.
Ant

[don668]

You would have to be on crack to pay $135.00 for 8gau. ground wire and crimp on connectors. You are looking at about $30.00 cnd. $15.00us in parts. I work for a high end home theater store in Calgary and we star-ground things all the time to get rid of issues. Just good solid core, a few twisted strands are ok, and replace what chrysler installed.

Don

[Cal Cruzer]

Ant...Mike is correct, they do not "make" power, they free up power that is being lost though parasitic devices that are being driven by the power of the engine. It takes HP to turn the Alternator and water pump (I am using the case of my mustang). Car companies used to rate HP in engines higher because they would dyno them without accesories attached. This is the same effect that UD pullies provide. They turn the alt and water pump slower thus using less power. Some mustangers experienced diminished cooling because the pump was moving slower so we had to put in a bigger alum radiator and your lights would dim just a bit at a 750 rpm idle but they would always dyno out at about 10HP so it was just a trade off.

[Ant]

quote:Originally posted by Mike Radowski

An underdrive pulley doesn't add anything. It just gives back some of what the older pulley took away.

Mike

Cal, it is interesting that you got that understanding from this post. I still don't understand it.
You are correct, the UDP frees up power. However don't overlook the fact that a majority of the power is gained from less rotational mass (the UDP being lighter than the OEM)not the actual under driving.

[Cal Cruzer]

There is very little rotional mass in pullies. You will reduce rotational mass with a lighter flywheel that can be measured in pounds, but with pullies were are talking ounces. No, parasitic loss is what the smaller pullies address. The engine just does not have to work as hard turning these items.

This is just a snippet from a very simple search on the subject.

quote:Underdrive Pulleys
For nearly 15 years, underdrive pullies have been one of the most popular performance upgrades for 5.0-liter Mustangs, and as soon as the modular 4.6 engines appeared on the scene in 1996, underdrive pullies were again one of the first readily available modifications. It’s a known fact that underdrive pullies reduce the parasitic drag on engines, which frees up horsepower that can be delivered to the rear wheels. Certified tests have shown that underdrive pullies can free up as much as 8 to 10 horsepower on 4.6 modular engines

You can read the entire text here: http://www.modularpower.com/tech.html
or another article here: http://www.sportruck.com/howto/highw...rive%20Pullies

I will be willing to read any research on the subject that specifies gain from reduced rotational mass of underdrive pullies.

[tallypt]

ok, so the concensus is that the UDP may very well help without reducing coolant flow. The big question is then does anyone have a part suggestion?

[COP TZER]

i believe that either www.modernperformance.com or www.howellautomotive.com have some in stock

[Ant]

quote:Originally posted by Cal Cruzer

There is very little rotional mass in pullies. You will reduce rotational mass with a lighter flywheel that can be measured in pounds, but with pullies were are talking ounces. No, parasitic loss is what the smaller pullies address. The engine just does not have to work as hard turning these items.

This is just a snippet from a very simple search on the subject.

You can read the entire text here: http://www.modularpower.com/tech.html
or another article here: http://www.sportruck.com/howto/highw...rive%20Pullies

I will be willing to read any research on the subject that specifies gain from reduced rotational mass of underdrive pullies.

quote:
Unorthodox Racing Ultra Street (Ultra S) lightened under drive crank pulley. Made of lightweight Premium U.S. made 6061-T6 billet aluminum to ensure consistency of the material's strength and balance. Every pulley is inspected multiple times from machining to anodizing to stocking and finally at shipping time. If at any point a pulley does not pass inspection it is pulled from production. An average of 5 to 12 HP and 4 to 8 lbs.-ft. on normally aspirated engines and 8 to 16 HP and 8 to 18 lbs.-ft. on forced induction engines. Higher gains are possible. For example, a Nissan 300ZX twin-turbo saw gains as high as 37 HP and 45 lbs.-ft. on the dyno just buy replacing the stock crank pulley with the Ultra S lighted underdrive crank pulley. Power gains are obtained in two ways. First, and most important, is the weight loss. An average of 2.7 HP is gained from every pound lost off the crank shaft. 85% of our gains are from weight loss. The rest of the gains are from underdriving, which accounts for about 15% of the total gains. Underdriving is not pushed for two main reasons. The main reason is to keep charging systems, air conditioning, power steering, and water pumps moving fast enough for every day driving. Second, not much horsepower is gained from extreme underdriving. In most applications all of the underdriving is done with the crank pulley, not the accessory pulleys. This is done so maximize weight loss can be achieved at the crank where most of the horsepower gains are found.