what are under drive pullies?
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Wildstringer
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- Feb 20, 2011
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Think of under drive pulleys like the gears on a bike. The larger the front sprocket is compared to the rear sprocket the harder it is to pedal.The smaller the front sprocket is, the easier it is to pedal. The under driver pulleys reduce the size of your crank pulley(front sprocket) and it increases the size of your accessories like water pump and alternator( these are like the rear sprocket of the bike.) The pulleys make it easier for your engine to turn your accessories, freeing up a little horsepower.
That's an excellent description.
They are a great, lo-buck, easy to install way to get a noticeable seat of the pants increase in performance.
A smaller diameter crank pulley spins the accessories like power steering, alternator, and water pump slower. NASCAR drivers usually run a 50% larger pulley on their power steering pumps to slow it down because of the high rpm's their engines operate at....idle speed on their engines is 2000 rpm.
I have these: March Performance 1015 March Ford Pulleys The Power & Amp series keeps your charging system up to power, while giving you a performance increase you can feel. I have the steel ones here that I just installed on one of my cars and I've had the aluminum version on my other for several years.
CVF Racing has a store on Ebay. Their prices beat all the big companies prices. You may want to pay extra $$$ for the clear powder coating. I made a purchase with them and will be painting mine with clear coat engine paint before they get installed. They were about 2/3's the price of the bigger companies.
Wildstringer
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Most of them all advertise a 15 HP gain. Its kinda hard to screw up a pulley, but I also like the March brand
In reality... You might get 7.
Food for thought: A couple of years ago I came across an article about underdrive pullies. The wheel output of the car was roughly 200 with the stock pullies and sperpantine belt installed.
Later, the removed the serpantine belt completely and powered the electrical system through a shop source to the battery. The total wheel HP gain on this particular vehicle was 5 whole HP. I wish I'd scanned and saved the damned article. Driving normal accessories took 5 rear wheel HP from the car.
Figure in underdrive pullies that are say.... 20% underdrive. On THIS particular vehicle, and you'd net a RWHP gain of 4. Ummm.... yay? The downside is that your electrical system is putting out less, your water pump is putting out less, the fan (if not electric), and every other thing you've just underdriven.
I'd LOVE to see a back to back dyno of a stock-ish Fox with OEM and then underdrive pullies.
Seat of the Pants feel to me means some 30ish HP at the wheels. Gonna get that from UD pullies? Not likely. I attribute most advertised gains from UD pullies mostly to ricer math.
Hey guys,I know this is my first post on here.I was an advid member years ago!!Anyways,I have to agree 100% that you will NOT feel a "seat of the pants" increase in installing underdrive pullies.In The 15 years that I have been fooling with thse Fox body cars,I have never said,WOW those pullies really made a difference.I don't want to discourage anyone from putting them on there car (all 4 of my cars have them).I just think (KNOW)that the manufacturers HYPE up the HP ratings drastically.If you can get a chance to go to a swap meet,That is the best place to pick up a set, of underdrive pulleys for as cheap as $15-$20 or less!!Hope I didn't step on any feet here!!!
When I did them on my LX, I did them with a bunch of other stuff, so I couldn't tell any specific gain. HOWEVER, I just installed them on my otherwise stock Saleen a couple of weekends ago. There was a very noticeable SOTP difference. Not huge, but noticeable. At some point this summer, I'm going to attempt to get it on the dyno and see what's what.
YOu and me both. I've wanted to do that very thing for years! strap a car to the dyno, run it, shut it down, swap pullies (never removing car from dyno), then run again.
haha ok thanks guys. so with all that being said should i even put some on? im thinking about getting some but they they just seem like they might not be worth it? so to all of you that do have them what do you honestly think? should i get tome or is it not worth it? and thanks again for all your input
haha ok thanks guys. so with all that being said should i even put some on? im thinking about getting some but they they just seem like they might not be worth it? so to all of you that do have them what do you honestly think? should i get tome or is it not worth it? and thanks again for all your input
If it were me...
I would buy a set of March pullies just for the looks. If there's any HP advantage at all... BONUS!
not sure what kind of car you running but i got some from summit long time ago. and they look great. I have a 89 5.0 and i have to say i noticed that the lights get dim and the stock alt. can not power even a stock sound system cranked up with bass.
its also known as parasitic drag. Try running your car up a hill with the A/C on and then turn the AC off half way up. If you feel a bit of HP increase thats what the pulley supposedly free up.
Read this. They got an increase of 10 dyno proven horsepower with nothing but a pulley change, as well as better power across the powerband.
Nice read! I've quoted the portion pertinent to this conversation for simplicity. This is certainly a plus for the, "Pros" side of the convo.
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