Underdrive pulleys worth it??

[5.02GO]

Stock belt is 90.5" i believe. Belt for underdrives (a set) 90".

I am pretty sure 90.5 is the stock size. Whatever, doesnt matter. Underdrive set requires a belt that is .5" smaller than stock.

 

[THC420]

underdrive pulleys are great. they give a noticable increase. get a 130 amp alternator and be done with the charging issues. also they DO NOT require a shorter belt, your old belt will work fine.

my voltage never drops below 14 at night with my lights, stereo, electric fan and what ever other crap i have turned on. you wont find a cheaper mod that gives as good of gains as the pulleys.

 

[RsStanG1987]

I got pullies on my car and it runs fine. I bought mine from march performance. Never had a problem car picked up some pep too. Just buy the kit and use the whole kit its fine.

 

[Stump1000]

You can't beat the performance for the money. Most people end up taking the alt pulley off because the lights dim at idle. That doesnt mean anything though, you'd have to idle for a really long time for the battery to go dead enough for the car not to run. They charge fully at like 1100Rpm.. Just dont stare at the gauge

 

[fox_bodies_rule]

I agree with the HP for the bucks comments, I had a set of FRPP pulleys on mine when I bought the car, aluminum radiator and orginal alternater. My problem was the previous owner was a "hack" and had the cooling system all hosed up and I couldn't stand the alternater not charging at idle, especially with the a/c cranked up. In the process of trouble shooting the cooling system I pulled the pulleys, and it helped but definitely felt the difference in power. Now that I have found all of the problems with the cooling system I am tempted to at least put the crank pulley back on and give it another try. Yes the power is there, what are you willing to give up to get it? personal choice IMHO.

 

[93tealstang]

TTT

 

[Daggar]

This wasn't about a Mustang but I thought it was an interesting read:

The Horsepower Story

With various aftermarket manufacturers claiming up to 15 horsepower gains with their underdrive pulleys, we set out to the dyno to find out how much power WE could expect on our 1999 ITA-prepped Saturn twin-cam powerplant. The results might surprise you, but here they are.

Because there were no pulleys available at the time, we went to the extreme and actually REMOVED the accessory drive belt (only for one run, of course) to see what the impact would be to ZERO drag due to the accessory drive – sort of pulleys with infinitely small diameters. We figured that if we saw a big gain without a belt, that the pulley gains would be somewhere inbetween, right?

We fired up the dyno and low and behold, removing the belt netted a whopping 3 HP (and we’re rounding UP). That's it. The number was repeatable, and even correlated to data run earlier on the doomed BMW motors - they saw similar results in their application.

So, in light of the fact that 3 HP was completely without a belt, we estimated that the best we could do was to underdrive a few components by 20% - or a theoretical 0.6 HP gain (3 HP x 0.2). After that, it hardly seemed worth it to try to custom fabricate pulleys for less than a 1 HP gain.

I know, I know – stock pulleys, like stock suspension bushings, aren’t sexy, and you can’t brag about them in the pits…but in racing horsepower talks and marketing BS walks. We chalked up this exercise as yet another learning experience in the quest for REAL horsepower. Maybe someday we’ll find some.

 

[Lyncher]

This wasn't about a Mustang but I thought it was an interesting read The Horsepower Story

With various aftermarket manufacturers claiming up to 15 horsepower gains with their underdrive pulleys, we set out to the dyno to find out how much power WE could expect on our 1999 ITA-prepped Saturn twin-cam powerplant. The results might surprise you, but here they are.

Because there were no pulleys available at the time, we went to the extreme and actually REMOVED the accessory drive belt (only for one run, of course) to see what the impact would be to ZERO drag due to the accessory drive – sort of pulleys with infinitely small diameters. We figured that if we saw a big gain without a belt, that the pulley gains would be somewhere inbetween, right?

We fired up the dyno and low and behold, removing the belt netted a whopping 3 HP (and we’re rounding UP). That's it. The number was repeatable, and even correlated to data run earlier on the doomed BMW motors - they saw similar results in their application.

So, in light of the fact that 3 HP was completely without a belt, we estimated that the best we could do was to underdrive a few components by 20% - or a theoretical 0.6 HP gain (3 HP x 0.2). After that, it hardly seemed worth it to try to custom fabricate pulleys for less than a 1 HP gain.

I know, I know – stock pulleys, like stock suspension bushings, aren’t sexy, and you can’t brag about them in the pits…but in racing horsepower talks and marketing BS walks. We chalked up this exercise as yet another learning experience in the quest for REAL horsepower. Maybe someday we’ll find some.:

...that was very interesting. Could it be different on different cars? But 150$ for .6hp ... thats more insane than gas prices....well...not really

 

[Lyncher]

Daggar: Where did you find that article anyway? Do they have anymore like it? Thanks

 

[Daggar]

I got it here:

http://www.teamscr.com/pulleys.html

Sure it would be different for other cars. But let's assume for a moment, a car with twice as much HP and even twice as much parasitic loss. That's a whopping 6 HP (which is about as much as I've ever seen on a proven dyno).

 

[slow93]

i know this isnt classifieds but does anyone have any underdrives for sale?

 

[95silverstang]

Had them on my 95 GT and could not really tell any difference. Never had a problem with overheating or charging but then again I was never in a hot environment. No complaints from me.

 

[Lyncher]

I got it here:

http://www.teamscr.com/pulleys.html

Sure it would be different for other cars. But let's assume for a moment, a car with twice as much HP and even twice as much parasitic loss. That's a whopping 6 HP (which is about as much as I've ever seen on a proven dyno).

true ture

 

[Daggar]

It also comes to mind that regardless of the power output of the motor that the parasitic loss from the accessory drive it going to be the same. In other words: The drag from the accessories isn't a percentage of the total output of the motor but the measure of the drag through the RPM range. So if you've got a 190 HP Mustang or 390 HP Mustang, similar accessories are going to drag the same HP right off the top. Seems like it would make more sense to put money into motor enhancements as opposed to trying to free up parasitic loss by turning the accessories just 20% slower.

Just a thought.

 

[ALMOST STOCK]

Daggar Thanks for the info...

Quote:With various aftermarket manufacturers claiming up to 15 horsepower gains with their underdrive pulleys, we set out to the dyno to find out how much power WE could expect on our 1999 ITA-prepped Saturn twin-cam powerplant. The results might surprise you, but here they are.

Because there were no pulleys available at the time, we went to the extreme and actually REMOVED the accessory drive belt (only for one run, of course) to see what the impact would be to ZERO drag due to the accessory drive – sort of pulleys with infinitely small diameters. We figured that if we saw a big gain without a belt, that the pulley gains would be somewhere inbetween, right?

We fired up the dyno and low and behold, removing the belt netted a whopping 3 HP (and we’re rounding UP). That's it. The number was repeatable, and even correlated to data run earlier on the doomed BMW motors - they saw similar results in their application.

So, in light of the fact that 3 HP was completely without a belt, we estimated that the best we could do was to underdrive a few components by 20% - or a theoretical 0.6 HP gain (3 HP x 0.2). After that, it hardly seemed worth it to try to custom fabricate pulleys for less than a 1 HP gain.

I know, I know – stock pulleys, like stock suspension bushings, aren’t sexy, and you can’t brag about them in the pits…but in racing horsepower talks and marketing BS walks. We chalked up this exercise as yet another learning experience in the quest for REAL horsepower. Maybe someday we’ll find some.

After all these yrs my underdrive pulleys were my only hope to regain possibly .5 hp and now even that is in doubt. Oh well :

 

[5.0tbirdguy]

Maybe if a mustang ran a saturn ps pump and water pump it would be the same.

What does it take to spin a FORD ps and water pump to 6000 rpm engine speed + the multiplication of the pulley ratio?

It must be worth 5 hp but then the decreased inertia would let it spin up faster like an aluminum flywheel and lighter reciprocating assembly. Max hp doesnt win races, max acceleration does.

With an electric fan it obviously wouldn't make as big a difference.
I will get some u/d pullies for my car, but with an electric fan it can wait.

 

[DTT92LX]

$150 for 6hp, that's about $25 per HP. Isn't that pretty much the going rate for the 5.0s these days? I know it's "freed up", not gained, but you gotta pay for it either way. Also it's only 6hp but its also only $150... Just a thought.

 

[fox_bodies_rule]

WOW! real dyno data. Thanks for shedding some light on the subject Daggar I wnet to the site and those guys are serious! I have to also go back to my original comment re. dollar/hp and sign up with DTT92LX's comment about the $25/HP ratio. A set of 185 AFR heads filled with the parts, AFR catolog price $1,375. Assume all is there to support the heads and figure about a 60 hp gain, guess what? $23/hp and some change, not including gaskets and other assorted crap, so round up to $25 dollars! Science and math, what a concept.

 

[9mm]

I got U/D's on my '87 GT and they do work, but I didn't change the Alt. pulley. I just used the crank, and water pump pulley and got a shorter belt. No probs with charging.

 

[Daggar]

WOW! real dyno data. Thanks for shedding some light on the subject Daggar I wnet to the site and those guys are serious! I have to also go back to my original comment re. dollar/hp and sign up with DTT92LX's comment about the $25/HP ratio. A set of 185 AFR heads filled with the parts, AFR catolog price $1,375. Assume all is there to support the heads and figure about a 60 hp gain, guess what? $23/hp and some change, not including gaskets and other assorted crap, so round up to $25 dollars! Science and math, what a concept.

True enough! I guess the thing that makes me most wary is the sheer lack of dyno information out there for these under drive pulleys. We all know that while many of the magazines provide some great information, that they are all commercially driven. What magazine is going to show actual dyno results for a company claiming a 15+ HP gain from their pullies that's also in direct conflict the folks that pay their bills? I agree that 6 usable HP might be worth the expense of the pullies so long as there were no detrimental side effect in cooling or charging. I've also noted that many folks endup installing underdrive pullies then end up with and overdrive on either the alternator or water pump. If we end up with a solid 20% reduction with a good set of pullies then we're dipping into that figure if it's necessary to cpmpensate for the side effect. Sooner or later, I'm going to get my hands on a set of these things and get the dyno done on my Mustang so that we can compare apples to apples. I'm willing to pay for the Dyno time to get a final answer on the whole thing and maybe lay this issue to rest.