Underdrive pulleys...convince me that they work.

[Turkey Sammich]

One day, I'll conduct my own test. I run all stock pullies at present and would love to swap on a set from one of the better companies on a Mustang Dyno to get a final result.

Sounds like something to look forward to on the dyno thread.

 

[Dean85GT]

Well, do you guys think they are worth it in my current scenario? My car is running a 13.4 on a slick. My goal is to get down to 12s with the stock heads. The only mods I have yet to do (keeping the car NA and stock heads) are an E fan, U/D pulleys, 3g alternator and dumping my mufflers (current tailpipes are 2.25 crimp bent). Im relying on these mods to knock off 4 tenths. Am I being way too optimistic? My current 60' is a 1.80 but I think I may be able to improve it a little bit.

 

[Topdowncruise]

Well, do you guys think they are worth it in my current scenario? My car is running a 13.4 on a slick. My goal is to get down to 12s with the stock heads. The only mods I have yet to do (keeping the car NA and stock heads) are an E fan, U/D pulleys, 3g alternator and dumping my mufflers (current tailpipes are 2.25 crimp bent). Im relying on these mods to knock off 4 tenths. Am I being way too optimistic? My current 60' is a 1.80 but I think I may be able to improve it a little bit.

I think regardless of whether pullies contribute anywhere from 0 to 13 hp based on the test results noted above and the theories (which Daggar appears to be committing to prove someday),I think you are being optimistic.

 

[90mustangGT]

U/D pullies won't make a real difference, but it is one of those "little" mods that are cheap and add up. Sometimes it's the little things that separate the winners from the loosers.

Main thing it does is reduces the acceleration of the accesories, this won't show much on a dyno because it is spinning up so slow, while in first gear with 4.10's.... it will show up.

I ran a 3"UD pulley as well, you could read the belt size when the engine was idling. I also kept my regular pulley in the car in case of, well IDK... but I could swap pulleys and it made a difference.

One thing about the accesories, is they not only add drag to the engine, but add a lot of weight as well. I have a FR manual rack, no ac, no smog.... just an alternator, going with an electric W/P. It might not be that much actuall HP, but the weight reduction alone will make a sizable difference, when I get an engine.

 

[25thmustang]

Its funny, I read all the negetives with the U/D pulleys, but when I put mine on, it cured my battery dying issue (it would be fine day to day, dead after a weekend of no driving) and I actually felt a little SOTP difference. I have no proven numbers, but I rarely if ever "feel" a difference, and when the U/D pulleys where added, I did.

 

[f4fntm]

Regarding potential charging issues, you can always swap in an higher-output alternator. 'Course, that drives the cost of the project up...

 

[Foxfan88]

or u can just put the stock alt pulley back on, the majority of the underdrive is in the crank and wp pulley. the alt pulley doesnt do much so i just took it off and put the stocker back on and cured my charging issues.

 

[86bluecobra]

OK so do they give you more hp. A test was just done in the 5.0L mag with a 4.6L 3 valve mustang. I know its not a 5.0L but the underdrive pulleys netted 6 RWHP and 11RWTQ. so i guess one could say they work and are worth the time to install.

 

[Roland69]

did anyone get the DVD with the feb issue of MM&FF....they dyno'd a 05 after a each bolt on and the pully's gave it like 8 RWHP

 

[86bluecobra]

I didn't get it but that looks to be about or close to about what 5.0 MUSTANG got aswell.

 

[DMAN302]

I have it, I have not watched it...I will though.

 

[Roland69]

it cool if you have a 05....but I wish they would do the same with a 5.0....we were drinking one night and I thought I would play it cause nothing else was on

 

[bill302]

Maybe I am the lone person here but I think they are absolutely worthless junk. They are not worth the money. They gain what, 2hp on the wheels? At the cost of slowing you acc. Save your money. You will see more gain by eliminating the clutch fan like mentioned above.

http://en.wikipedia.org/wiki/Underdrive_pulleys

An Underdrive pulley refers to an aftermarket crankshaft or accessory pulley (such as an alternator pulley) that is designed to drive a vehicle's accessories at a slower rate than stock. Originally they were invented for race cars in the 1950s and 60s, whose engines had been modified and ran at higher RPMs for longer periods of time than the manufacturers had intended. It was therefore necessary to underdrive the belt-driven accessories (among other things like the water pump) to keep the accessories from burning out and the engines running reliably.

Presently, these pulleys are marketed as performance enhancers that actually produce additional torque and horsepower by reducing parasitic drag caused by belt-driven accessories, or by being lighter and reducing rotational mass, or both. However, the gain is usually minimal, on the order of 1-6 wheel horsepower depending on the engine. There are trade-offs for this "free power," however.

Changing the original crankshaft pulley can have negative effects on the harmonics of the crankshaft: a pulley that is too light or not properly weighted cannot reliably balance natural frequencies that occur along the length of the crankshaft at certain RPMs. The original pulley may have been carefully designed, balanced and weighted to counteract (harmonically dampen) this naturally occurring harmonic frequency, and without it, eventual engine damage may result. See: Engine Balancing

A less severe side effect is somewhat intended by the design of these pulleys. Since the alternator, power steering, and/or air conditioning units are not spinning as fast, corresponding dips in alternator voltage, power assist, and A/C effectiveness may be noticeable, especially at idle. The headlights may dim when coming to a stop, or the stereo may lower in volume, for instance. For a race car, this is not of concern, but for a daily driven vehicle it can be an annoyance.

could not say it better myself........"but for a daily driven vehicle it can be an annoyance", last sentance id the wikipedia link....

 

[MikeC]

I look at it this way, each little increase adds up to a lot. Pulleys 3-5 hp, K&N air with silencer removal 3-5 hp, increase timing to 14 degrees 3-5 hp, shorty headers 5-10 hp, synthetic oil in engine, trans and diff 3-5 hp. Pretty soon you have an increase of 17 to 30 more hp. each one alone is unnoticable, add them up it's noticable. IMHO

 

[seijirou]

I look at it this way, each little increase adds up to a lot. Pulleys 3-5 hp, K&N air with silencer removal 3-5 hp, increase timing to 14 degrees 3-5 hp, shorty headers 5-10 hp, synthetic oil in engine, trans and diff 3-5 hp. Pretty soon you have an increase of 17 to 30 more hp. each one alone is unnoticable, add them up it's noticable. IMHO

No no no, this is not how power is made. They don't add up in a linear fashion like this. This is the kinda thinking you get from the ricer kids who after adding up all their +hp mods they've got 350 horse from a 1.5L with ebay boltons.

These "mods" only free, or release horsepower, they do not make horsepower. The first 5 horses are easy to free, the next 5 are harder, and the next 5 harder still.

Any one of these mods standing alone might free up 5 horses. But two mods will free up maybe 7. Three mods maybe 8 or 9. It does not add up linearly.

So real world, do the rest of them, don't bother with the pulleys because after it's said and done you're not getting anything but less coolant flow, less charging, less power steering flow resulting in shorter power steering pump life, and less air pump function making emissions harder to pass.

 

[DucatiRdr]

Is it not true that the 93 Cobra came with a set of reduction pulleys (not true underdrive) compared to the OEM 5.0 set?

 

[25thmustang]

I think the $85 that pulleys cost is worth it. I have under drives, no charging issues, and love them!

 

[Strype]

Dear god don't put those on your car. If you do only put the one on the crank unless you have a 3g alternator. Just from 10 years experience with underdrives.

 

[JBeezy53]

When I installed mine they seem to give the car a little more torque, or it could have been the fact that the engine reved faster. JMO.

 

[MikeC]

No no no, this is not how power is made. They don't add up in a linear fashion like this. This is the kinda thinking you get from the ricer kids who after adding up all their +hp mods they've got 350 horse from a 1.5L with ebay boltons.

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