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Underdrive pulleys, do they really help performance???

This is a discussion on Underdrive pulleys, do they really help performance??? within the Performance forums, part of the General Discussion category; Do underdrive pulleys really help performance? The smaller crank pulley drives the belt slower and larger alternator and etc. pulleys ...

  1. #1
    Registered User andrewgri's Avatar
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    Question Underdrive pulleys, do they really help performance???


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    Do underdrive pulleys really help performance? The smaller crank pulley drives the belt slower and larger alternator and etc. pulleys turn the belt driven things slower. Wouldn't this just help people running at higher RPM's to keep their stuff from wearing out faster and doing to much of whatever it's function is? Or does it also lessen the drag on the motor? If it does could someone please explain? I see people on here saying it gives em better gas mileage and a little more responsiveness, but I don't understand how that works.
    Last edited by andrewgri; 06-22-2007 at 01:05 PM.

  2. #2
    Get in sit down hang on. SolMan98's Avatar
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    Re: Underdrive pulleys, do they really help performance???

    You can gain a little, but don't expect huge numbers. Be wary of your voltage. You don't want that to drop too much.

    D/D-2006 HHR 1LT 5-Speed.
    1996 Silverado, 5.7, FIPKII, Elect Fans, S/S Headers, Duals, Wait4Me, 4/5 drop on 18" Weld Evo Velosity's. STOLEN ON 9/9/2006

  3. #3
    claviz13
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    Re: Underdrive pulleys, do they really help performance???

    Not worth the money and time.

  4. #4
    turning 10's
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    Re: Underdrive pulleys, do they really help performance???

    In the old days, Mopar claims that a V belt driven component requires 7 hp on average to turn when the engine is spinning at 7000 RPM. For that reason, a real drag car has electric water pump, no power steering and charging system. The idea is to reduce parasitic loss on the engine. Personally, I wouldn't waste my $$ on it for a street car.
    A bunch of 1st gen big block Camaro's

  5. #5
    Home of the Snooki punch! CKTA's Avatar
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    Re: Underdrive pulleys, do they really help performance???

    I think they are worth it.....I've had them on pretty much all my cars/trucks and felt a differance. However, I never use the alt. pulley.
    2015 Carlisle All Truck Nats info..
    http://www.fullsizechevy.com/forum/o...t-7th-9th.html


  6. #6
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    Re: Underdrive pulleys, do they really help performance???

    on other forums ive read people claim 11-13 rwhp on the dyno's. I bought a set and will be installing it probably next weekend
    06 Silverado/ext cab stnd bed/5.3L/4x4/3.42 rear
    Black ext /Charcoal Int/LT2

    -Blackbear Tune
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  7. #7
    claviz13
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    Re: Underdrive pulleys, do they really help performance???

    11-13 rwhp.
    Last edited by claviz13; 06-22-2007 at 09:47 PM.

  8. #8
    Fast and Cheap... MrLM7's Avatar
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    Re: Underdrive pulleys, do they really help performance???

    I just removed my AC belt and called it good when it comes to that department...
    2002 Silverado ECSB 2WD 5.3 4L60E with Raptor Blood, 3.73 G80, Headers, TBS, bypass, air gap, dumped exhuast, 160 thermostat, descreened MAF, Intake, wheatley tune, LS1 fans, Nelson harness, Nothing but Royal Purple, 2" drop shackles... 14's

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    Re: Underdrive pulleys, do they really help performance???

    Quote Originally Posted by claviz13
    11-13 rwhp.
    yea i don't know what'll happen but ill post up when i put em on. I won't be dyno'ing but i have a stretch of road that i open WOT from one sign to another and see what the mph is....we'll see if that changes
    06 Silverado/ext cab stnd bed/5.3L/4x4/3.42 rear
    Black ext /Charcoal Int/LT2

    -Blackbear Tune
    -Custom Moonroof

    Source: D3
    Power: JL 300/4 -- JBL 1200.1
    Sound: Pioneer 720's
    Boom: SS RL-p12 1.35 sealed

  10. #10
    NevR done 95nProgress's Avatar
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    Re: Underdrive pulleys, do they really help performance???

    I have the 2pc set on my TBI and it was a noticeable modification. If your looking for every little bit then do it. Some say if you can feel any difference from a mod with the butt-o-meter then its anywhere between 5-10HP, +/- 2 cheeks. 1996Silverado is right even my 2pc set is pretty worthless for charging the battery at idle when accessories are on (i.e. A/C, headlights, stereo etc.) Even with a 150amp alt. If its a daily driver I would not even consider the 3pc set. Kinda sucks though, when I was looking the aluminum pullies were only available in the 3pc set.

    Brian
    Last edited by 95nProgress; 06-23-2007 at 01:00 PM.
    95 Chevy ecsb 2WD 5.7L far from stock

    Never done!

  11. #11
    AKA Slim Picks whitesilvy2000's Avatar
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    Re: Underdrive pulleys, do they really help performance???

    i think this all depends on what you're expectation is out of your truck too. if you keep it low for the mod, you'll be surprised. then there's people like me who are never satisfied. anyway, it's probably not going to be a huge difference, but it could be sinificant(sp?)

  12. #12
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    Re: Underdrive pulleys, do they really help performance???

    I have just the crank pulley from asp and it made a bigger difference than my wheatley tune. It spins up much faster. my voltage gauge dropped a 1/16th of an inch. the only downside ive seen was that if i sit idling for more than 30 minutes and my ac cranked it will start to get warm. then again whitesilvy2000 is right about the expectations of your mods.

    Clint
    Silverado 1500 RCLB 2WD 5.3/60E H/C boltons

  13. #13
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    Re: Underdrive pulleys, do they really help performance???

    All I know about the serp. system on my 1997 Vortec 350, is that I dropped 1- 1-1/2 of a tenth and gain about 1 mph in the 1/4 mile when I install a shorter serp. belt that bypasses the power steering pump.

    In 3500 lb F-bodies, every 1 mph increase in mph indicates about a 10 hp gain in power. Since our trucks are heavier and less areodynamic, gaining 1 mph in the 1/4 mile equates to more of a power gain tahn the F-bodies. I would say that 1 mph gain in a truyck would equal about 12-14 hp gain depending on teh weight of teh truck.(which vaies greatly, a stripper no options rcsb can weight 3800 lbs, my loaded rcsb weighs 4050 lbs, some 4 door Tahoes with 14 bolts and 4l80e's can weigh almost 6000lbs).

    When I bypassed the power steering, it sure was difficult steering in the pits and making the 180 at the end of the strip.

    Drag induced by the front accessories, trans, driveshaft u-joints, pinion/side and axle bearings is called a parasitic loss.

    I have heard of teh high revving 302 Mustangs having good results with underdrive pulleys.

    peace
    PAuly
    97 GMC 2wd RCSB 5.7, s10 2700 footstall, Hooker 24621hkr LT's , 2.5" cats dual 4"pipes exit B4 pass. side tire, custom driveshaft 3.42 G80 FIPK MAF descreen GM/Mercruiser Marine intake manifold 29lb LS2(EV6) injectors Ed Wright PCM(best mod), LT4 KM 14.8@94mph 2.007 4000lbs 122mph

  14. #14
    Registered User andrewgri's Avatar
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    Re: Underdrive pulleys, do they really help performance???

    I just put on my underdrive crank, electric fan, and overdrive alternator pulley (to makeup for lost power) and it made a noticable difference. I don't know how much of it is do to the underdrive pulley but there was a definite improvement.
    '07 Chevy NNBS 5.3L Crew Cab, LT2 Texas Edition, 2wd
    '97 Chevy K1500 5.7L Z71 ECSB Flowmasters, K&N FIPK, Accel coil, Mark VIII efan, underdrive crank pulley, overdrive alternator pulley, "big 3", 1000W rms Audiobahn amp & sub

 

 

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