pulleys and tuners

[stmitch]

Guys the parts themselves create a certain amount of resistance due to the design oand clearances of the parts. such as friction inside the alternator or power steering pump. The pulleys are design to reduce the 'feel of the friction. Its plain as the nose on your face. when rolling down a hill and "pushstarting" a truck 37's will turn it over easier than 31's. Same principal, the larger (underdrive) pulleys allow the accessories to turn slower than they would with smaller pulleys. But the amount of work the engine does to rotate that accessory is lessened. Anybody race Xmods? Swap the gears and little electric motors?

They dont free up all the drag from the accessories, but they lessen the load by a percentage. 10% underdrive pulleys require 10% less effort to turn the alt or steerign pump or a/c compressor. However that accessory will turn 10% slower as well.

I think you've got the idea, but it's a little backwards. This ^^ is basically correct, except the underdrive crank pulley is actually smaller than stock. They consider them underdrive, becasue they underdrive the accessories. The accessory pullies remain stock size (unless you get the alternator overdrive pulley which is smaller), and the engine crank pulley is reduced in size. The overall effect is the same as increasing the size of the accessory pullies though.

For example, if you put a smaller pulley on a supercharger, the supercharger spins faster (overdrive). If you put a smaller pulley on the supercharger's power source though, it has the opposite effect, and reduces the speed of the charger, or underdrive's it. Same priciple here, except instead of a supercharger, it's an alternator, and a water pump.

 

[feellnfroggy]

I think you've got the idea, but it's a little backwards. This ^^ is basically correct, except the underdrive crank pulley is actually smaller than stock. They consider them underdrive, becasue they underdrive the accessories. The accessory pullies remain stock size (unless you get the alternator overdrive pulley which is smaller), and the engine crank pulley is reduced in size. The overall effect is the same as increasing the size of the accessory pullies though.

For example, if you put a smaller pulley on a supercharger, the supercharger spins faster (overdrive). If you put a smaller pulley on the supercharger's power source though, it has the opposite effect, and reduces the speed of the charger, or underdrive's it. Same priciple here, except instead of a supercharger, it's an alternator, and a water pump.

Supercharger and underdrive are the same principal but different methods.

Supercharger pulleys go smaller to increase the rpm of the supercharger. It creates more power but more drag also, and the supercharger runs a hair hotter due to the increased workload.

on your ten speed the rear gears are larger to make it easier to pedal, these are the accessories. The pedal gear are smaller to make it easier to pedal these are the crankshaft gears. You are right about the crank being smaller I think, but the accessories are made the same or larger.


In your example the pulley is moving the supercharger, and in my example the engine is moving the pulley, two differnet types of workload.
Its harder for the engine to move large tires, however its easier for larger tires to move the engine.

 

[feellnfroggy]

I think you've got the idea, but it's a little backwards. This ^^ is basically correct, except the underdrive crank pulley is actually smaller than stock. They consider them underdrive, becasue they underdrive the accessories. The accessory pullies remain stock size (unless you get the alternator overdrive pulley which is smaller), and the engine crank pulley is reduced in size. The overall effect is the same as increasing the size of the accessory pullies though.

For example, if you put a smaller pulley on a supercharger, the supercharger spins faster (overdrive). If you put a smaller pulley on the supercharger's power source though, it has the opposite effect, and reduces the speed of the charger, or underdrive's it. Same priciple here, except instead of a supercharger, it's an alternator, and a water pump.

Supercharger and underdrive are the same principal but different methods.

Supercharger pulleys go smaller to increase the rpm of the supercharger. It creates more power but more drag also, and the supercharger runs a hair hotter due to the increased workload.

on your ten speed the rear gears are larger to make it easier to pedal, these are the accessories. The pedal gear are smaller to make it easier to pedal these are the crankshaft gears. You are right about the crank being smaller I think, but the accessories are made the same or larger.


In your example the pulley is moving the supercharger, and in my example the engine is moving the pulley, two differnet types of workload.
Its harder for the engine to move large tires, however its easier for larger tires to move the engine.

The intention was to argue with you but I think I just agreed, just not totally lol.

 

[stmitch]

Yeah lol. We're making the same point. Increasing the size of the accessory pullies, or decreasing the size of the crank pulley have the same net effect of changing the ratio of sizes between the pullies, and making it easier for the engine to turn them.
I just wanted it to be clear that the pullies for the 3.0 have a smaller than stock crank pulley, which provides most (if not all) of the gains. The water pump pulley is the same size as stock, just lighter, and the alternator pulley is smaller than stock to get it back up to stock speed so that charging isn't affected. It may be different for other engines, but that's what's available for the 3.0.

 

[Big Jim M]

Hmmmm

Yeah lol. We're making the same point. Increasing the size of the accessory pullies, or decreasing the size of the crank pulley have the same net effect of changing the ratio of sizes between the pullies, and making it easier for the engine to turn them.
I just wanted it to be clear that the pullies for the 3.0 have a smaller than stock crank pulley, which provides most (if not all) of the gains. The water pump pulley is the same size as stock, just lighter, and the alternator pulley is smaller than stock to get it back up to stock speed so that charging isn't affected. It may be different for other engines, but that's what's available for the 3.0.

If the above is true, and I spect it is, then where would there be a gain? All that is done in the above post is the 8 inch 1 to 1 pulleys are replaced with 6 inch 1 to 1 pulleys.. So the result is zackly what was started with, 1 to 1!

What we are supposed to be doing is THINKING! The ENGINE doesn't care what the size of the accessory pulleys is.. The engine is only using the HP it takes to pump the coolant, charge the battery, turn the steering wheel and make the inside cool.. NO MATTER what size the pulleys are.. the engine MUST expell the same amount of energy (HP) to make all this happen.

The CONSTANT in all this bicycle/pulley debate would be the amount of energy NEEDED to do the all the accessory thingys. Granted if there was ONLY a crank pulley changed to underdrive, the needed HP would be at a higher rpm in the engine... but never the less it STILL would take the same amount of HP..

The reason for uderdrive pulleys in a racing vehicle is simply because of the 7/9,000 rpm the engine is running at all day long. The larger pulley would OVERDRIVE any needed accessories. So RACERS have good reason to use smaller pulleys than streeted vehicles.

One more example of racing parts improperly used by guys THINKING they really have something.

Big Jim

 

[stmitch]

If the above is true, and I spect it is, then where would there be a gain? All that is done in the above post is the 8 inch 1 to 1 pulleys are replaced with 6 inch 1 to 1 pulleys.. So the result is zackly what was started with, 1 to 1!

You are correct, but the reason we install the underdrive pullies is to change that ratio so that it's no longer 1:1. By reducing the size of the crank pulley (or increasing the size of the accesory pullies), the ratio changes so that the accessories are slowed down, and need less hp from the engine to turn. It's easier for your crank to turn large pullies than small ones (or in this case, stock sized pullies if the crank pulley is smaller than stock), and therefore requires less of the engine's power.

If you then add the overdrive pulley to the alternator to avoid charging issues, the ratio between the crank pulley and alternator pulley is still 1:1 (or close to it I'm not exactly sure), BUT the water pump pulley is still underdriven, and you still see some gains, although perhaps not as much as if you had only used the crank pulley. Some of the gains that would be lost with the overdrive alternator pulley can be regained however, with the lower rotating mass of the lighter water pump pulley.

 

[Big Jim M]

If... If..

You are correct, but the reason we install the underdrive pullies is to change that ratio so that it's no longer 1:1. By reducing the size of the crank pulley (or increasing the size of the accesory pullies), the ratio changes so that the accessories are slowed down, and need less hp from the engine to turn. It's easier for your crank to turn large pullies than small ones (or in this case, stock sized pullies if the crank pulley is smaller than stock), and therefore requires less of the engine's power.

If you then add the overdrive pulley to the alternator to avoid charging issues, the ratio between the crank pulley and alternator pulley is still 1:1 (or close to it I'm not exactly sure), BUT the water pump pulley is still underdriven, and you still see some gains, although perhaps not as much as if you had only used the crank pulley. Some of the gains that would be lost with the overdrive alternator pulley can be regained however, with the lower rotating mass of the lighter water pump pulley.

If you were to weigh the entire rotating mass, both with and without them few onces of pulley you would prolly decide the possible gain to be so slight that it wouldn't be worth the effort to unbolt the original one..
Big JIm

 

[stmitch]

The difference between the weight of the 3 pullies (smaller crank, smaller alternator, and stock sized water pump) is more than a few ounces. The crank pulley alone is a couple pounds lighter than it's stock counterpart. As I've already said, the majority of the gains come from the pulley's underdrive abilities, and not the lighter weight. BUT, weight is constant with the pullies. So they're the same (much lighter than stock)weight if the engine is turning @ 0 rpm or if it's turning 5500rpm. And when you're spinning thousands of rpm, every little bit of weight saved on the rotating mass makes a difference.

 

[Rearanger]

I concede that a lighter crank pulley will enable faster acceleration just as a lighter flywheel will. You do loose the cruising smoothness though that a heavier in motion rotating mass gives you. I don't think there is much weight gain to go to lighter alt/waterpump/A/C pulleys, so I'd have to see the weight difference. But I think the crank pulley was engineered with extra weight for a reason and that would be harmonic balance and crank bearing life. Nothing in engineering is free and the Ford engineers figured out what compromises would work best for a long life road vehicle. I too doubt any "measurable" or significant wheel HP with the smaller diameter pulley. Unbiased dyno would help.

P.S. Why do you guys even need an extra 1/2 second between traffic lights anyway?

 

[Beef52751]

I had one on my 99 and i'm not sure that it gained any power but consistantly got me better fuel mileage. I still have the pulley if your interested in a used one.
PM me.

 

[2wdmuddin]

i guess ill keep looking at other options, because i wont trukey noticable gains. thanks for all the help