Anyone have Underdrive pulleys? CLICK HERE Ive heard about them making your alt spin faster, can burn it up, but are they smaller pulleys than stock. And simply are they worth it at all? I wont have my fan on the water pump much longer but i dont wanna waist money. .02 cents welcome! Also, im not looking for much more hp, im looking for gas mileage... Well shoot a little extra hp would be great to.

from Summit's product description:

...but you'll also get better gas mileage

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seems like an awful bold quote. yea, you SHOULD, but to say YOU WILL get better gas mileage seems like quite a statement

yea but all in all do you think this would be better for my truck? I mean ive been told for YEARS to get as much weight as you can off the front of that thing.. I Do know those crank pulleys are HEAVY! not so sure bout the alt and water pump, those are pretty light. But i also like the looks. I wish they had a size...

from the little i know about underdrive pulley's...
they're supposed to make everything but the engine spin slower (including the AC, alternator, water pump, etc). it looks like this kit has extra replacement pulley's to keep your alternator and water pump going at the stock speed/output.

having said that i also think i've heard people talk about how they got virtually no gain out of them.

someone please correct me if i'm wrong

95bronk said:

Anyone have Underdrive pulleys?

Ive heard about them making your alt spin faster, can burn it up, but are they smaller pulleys than stock. And simply are they worth it at all? I wont have my fan on the water pump much longer but i dont wanna waist money. .02 cents welcome! Also, im not looking for much more hp, im looking for gas mileage... Well shoot a little extra hp would be great to.

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They are bigger pullies that make the accessory spin SLOWER by comparison at any given RPM. This is good for a motor that spends all it's time at 8000RPM so that the accessories don't spin too fast. Using the underdrive pullies will reduce parasitic load, but it MAY also cause problems by not spinning a given accessory fast enough. Using smaller pullies will increase parasitic load at a given RPM and spin the pully faster.

The best way to increase your MPG is by changing your driving habits, not by any mods! So, don't throw your money away on mods that are totally useless!
With the CAFE standards today, vehicle manufacturers design and build their vehicles to be as efficient as possible! This includes optimizing the RPM that the accessories run by the crankshaft pulley will turn at.

Just a point of interest, if you decrease the RPM of the alternator, depending on the current load on it, can actually cause more load on the engine! The voltage regulator will increase the field current to try and keep the battery at
~14V, so decreasing the RPMs on the alternator will cause more mechanical load on the engine.

yea the alt wont put out enough amps, it already is crappy. Driving habbits lol, im not bad. On my way to school today i did 40 MPH tops on the roads and on the highway i was probably 60 MPH, bad snow storm. But its the best gas mileage ive gotten in a long time, bad things is... I cant drive 40 mph in a 55 or il either A. Get a ticket B. get my ass ran over lol, same with the high way. The roads where clear by the time i got out and i did the exact speed limit, 70 MPH at about 1900 RPMS, and 55 at 1600 RPMS. I was back to my normal crappy mileage. Its winter time tho so im sure in the spring it will jump back up..

95bronk said:

yea the alt wont put out enough amps, it already is crappy. Driving habbits lol, im not bad. On my way to school today i did 40 MPH tops on the roads and on the highway i was probably 60 MPH, bad snow storm. But its the best gas mileage ive gotten in a long time, bad things is... I cant drive 40 mph in a 55 or il either A. Get a ticket B. get my ass ran over lol, same with the high way. The roads where clear by the time i got out and i did the exact speed limit, 70 MPH at about 1900 RPMS, and 55 at 1600 RPMS. I was back to my normal crappy mileage. Its winter time tho so im sure in the spring it will jump back up..

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It sounds like you have proved my driving habits theory! One other thing to consider in the winter, the oil companies normally add more ethanol to the gasoline mix in the winter time, which will reduce MPG.

Underdrive pulleys are useful if you increase the RPM range of your engine by building it for such.

Other than that, you're spending money needlessly.

Running the alternator slower results in less output.
Running the PS pump slower results in less pressure and in turn more work to parallel park.
Running the AC compressor slower results in warmer AC air.

So, what's the point?

yep it was just an idea, not gonna do it lol.

95bronk said:

I wont have my fan on the water pump much longer but i dont wanna waist money. .02 cents welcome!.

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Please don't tell me your considering an e-fan?????

Yea why not? Alot of people do it.

Bob Ayers said:

Please don't tell me your considering an e-fan?????

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Please don't tell me you think the e-fan mod is of no value.

95bronk said:

Yea why not? Alot of people do it.

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"Alot of people do it" is not a good reason to install an e-fan!
Alot of people install Tornados, and we all know they are useless!

This one is easy:

1) There are no advantages to an e-fan, if the mechanical fan/clutch are working properly!

2) E-fans are far less reliable than mechanical fans

3) E-fans don't have the cooling capacity mechanical fans have


These points are brought out in this article on "Efan Myths":

http://www.aaroncake.net/rx-7/efanmyth.htm

RX-7's dont have electric fans????

eco said:

Please don't tell me you think the e-fan mod is of no value.

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Not only are they no value, they can cause major problems if they stop working, which is possible due to their reliability. And they have far less
cooling capacity than a mechanical fan!

They will, however, lighten your wallet!!

So Bob, you're saying that when the mechanical fan is engaged it doesn't create drag? There's no power left sitting on the table by a clutch driven fan.. attached to the the waterpump and in turn the engine itself?

I don't see where you're drawing your conclusions from. It's also fairly widespread fact (that I've come across) that an engine rev's more freely without that drag.

Bob I'm not sure I've ever disagreed with anything you've said but I've got to step in and call you out here...

I did the Taurus fan swap on my truck and I'll never look back. The improvement in throttle response over the clutch fan is incredible. No it didn't go and add 40 horsepower but, like I said, there was a noticeable improvement in throttle response and a very small improvement in gas mileage. And rightfully so. The clutch fan adds an incredible amount of weight, and thus load, onto the water pump pulley, and thus adds parasitic draw. And yes the fan is often times disengaged but due to friction in the clutch mechanism it is always going to be spinning SOME, not to mention there is the weight of the clutch mechanism and the arm creating a leaver on the pulley.

I'm not expert but it seems to me that completely removing that fan would offer benefits. I haven't needed to turn on my efan for MONTHS... That's a lot of power/gas that I was wasting spinning that big heavy fan for no reason before. Not to mention that I've also heard the engine warms up faster without the fan spinning.

As for not having a cooling capacity? That depends ENTIRELY on the type of engine, radiator, and fan being used. I know that if I let my truck idle for too long at a stop light and my temp gauge starts to ramp up, I can flip the switch on to LOW speed and watch my gauge drop to normal operating temp in a matter of 20-30 seconds.

Reliability? Okay you got me there... I guess an electrical fan motor would be more prone to going out than a clutch fan... But I do know many guys that have had to replace their clutch fans so this one could be a tossup...

Yeah I don't have facts and numbers to back these things but, but I've done the mod to my truck and I'm willing to put MY reputation on the line and SO BOLDLY declare: the efan conversion is worth EVERY PENNY.

Just my .02

Thank you, kind sir. My thoughts exactly. I'm just too lazy to put it into that big of a reply.

people talk about the quicker startups, but i don't get y

mine takes forever to warm up and yes, the fan is blowing on it the whole time. but...even with an efan wouldn't it warm up at the same speed? the thermostat won't open until the engine is warm, so y does it matter either way.

it'd make sense if the thermostat was open during warm-up and the fan wasn't blowing. am i missing something?