Underdrive pulleys...convince me that they work.

[fast4cheap]

I have owned several mustangs,the very first mod do under the hood is under drive pulleys they are worth there weight in gold, you may only show a peak horse power gain of 3 to 5 but thats peak, i have read about gains as much as 15 hp at other rpms, remember we dont always keep our cars at peak power rpm, i can notice the power,especially when i put a set on my 94,it was clear i had gained power in the entire rpm range. plus using aluminum pulleys lighten the load.

 

[jwcma]

Nobody else cought this BS?? Come on! (WHAT IS THE JOB OF THE HARMONIC BALANCER?)
Seriusly guys...

That's a generic description, and is not specific to our cars. Some motors are internally balanced and have dampers integrated with the crank pulley.

I've had my UD pullies on since 1989 with no regrets. Sure the voltage drops at idle, but the car never overheated, so it was a worthwhile tradeoff for me. I'm a big fan of increased efficiency. If I had to replace my steel UD pullies, I would go with aluminum UD for less rotational mass and less corrosion. My crank pulley is covered with surface rust and looks like crap.

 

[joncash]

After debating about it for quite a while I finally threw the set of ASP UD's that I bought a while back. Cobra radiator, new stock fan and clutch, new Ford water pump....car overheats at idle. Pretty sure it's actually an airflow problem for me (on the highway the temp drops back down very quickly), so it sounds like they can have a different effect on each car. Now I have to buy a flex fan or go back to stock.....

I guess I wouldn't have bought them if I knew that would happen. My vote is stay stock and keep your $75 for something more useful.

 

[seijirou]

So your saying if full synthetics alone give 5 hp. And bumping timing to 14-15 degrees alone gives 5 hp. But together you will only get 7 hp?

That is exactly what I'm saying, and there's a reason why.

Again, these mods don't make horsepower. They free or release horsepower. But you need to ask yourself how they're doing this.

The way this is done, is by increasing the efficiency of the motor. Making the timing optimal increases efficiency, reducing friction increases efficiency. Underdrive pullies is just another way to reduce friction/drag.

So the timing somehow effects the physical properties of the oil so there is less friction reduction?

No, the static (measured) amount of friction loss does not change. How much closer that brings the motor to 100% efficiency, after that starting efficiency has already been bumped up some does change. The fact of the matter is, going from 50% efficient to 60% efficient is easier than going from 60% to 70% and so on. 90% is pretty much unheard of nomatter what you do, 100% simply cannot happen.

The closer you get to 100%, the less and less effective modifications to increase efficiency become, and so detecting the change (horsepower) becomes harder and harder to do (less and less hp gained).

I quoting real world hp gains, not the crap quoted from manufactures the ricers go by. Besides thats why I gave a range of hp values, it's easy to get 17 hp from the mods I listed and not impossible to get 30.

These rated numbers are produced on an otherwise unmodified, stock engine. The farther away you are from 100% efficient, the easier it is to pick up some efficiency and make some gains. These companies are not marketing fools, and they know the way to make their product look the best without falsifying information is to use an unmodified test motor. You gotta take it in context. The truth is always in the context.

 

[Dean85GT]

I thought it was always the higher powered cars that gained the most. Like 30hp for a set of long tubes on a car with a big blower (this is just a random example).