changing the pulleys to increase hp?
06-09-2003, 11:00 AM
#1
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changing the pulleys to increase hp?
Has anyone here changed their crankshaft and alternator pulleys to increase horse power. If done where can I get a pair of them.
1982 US 928 manual tranny.
1982 US 928 manual tranny.
06-09-2003, 11:11 AM
#2
Burning Brakes
I'm not sure I understand how changing the crank and alternator pulleys would increase HP. The only thing I can imagine is that some other pulley size or arrangement may decrease the load on the engine, and thus have a slight increase in the amount of HP available to the drive-train. Is that it? YMMV.
06-09-2003, 11:21 AM
#3
Burning Brakes
Yes, pulleys are a common mod(Mustangs and Chevys). But I would not do it on a 928. Because the alternator is to weak and you would have a dead battery in no time. Mustangs have a crazy 130-amp alternator, so they can spare to loose some charging(your car only has 75-amp).
About the same thing as installing pulleys would be to bypass you airpump(with a short belt) and bypass the engine driven fan with an electric unit. These modes will give you real power that you can feel. It has the same effect as pulleys by reducing the engines drag.
About the same thing as installing pulleys would be to bypass you airpump(with a short belt) and bypass the engine driven fan with an electric unit. These modes will give you real power that you can feel. It has the same effect as pulleys by reducing the engines drag.
06-09-2003, 11:36 AM
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Interesting thought that maybe running the accessories a little slower might extend their life? I don't know if I would want to run the A/C compressor any slower, though!
06-09-2003, 12:10 PM
#5
lacast,
A few years ago, I remember seeing a pulley kit specifically made for the 928. If I remember correctly, a link was posted on Phil's site. I believe it was made out of black anodized aluminum.
I later tried finding the site but had no luck. Not sure how compatible 944 parts are, but you may want to try asking the question on the 944 forum as well.
Regards,
Roger 87s4
A few years ago, I remember seeing a pulley kit specifically made for the 928. If I remember correctly, a link was posted on Phil's site. I believe it was made out of black anodized aluminum.
I later tried finding the site but had no luck. Not sure how compatible 944 parts are, but you may want to try asking the question on the 944 forum as well.
Regards,
Roger 87s4
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06-09-2003, 09:41 PM
#8
Nordschleife Master
<a href="http://www.alamomotorsports.com/products.html?http://www.alamomotorsports.com/ur/ultras.html" target="_blank">http://www.alamomotorsports.com/products.html?http://www.alamomotorsports.com/ur/ultras.html</a>
As stated earlier, you can achieve the same results, as underdrive pulleys, if you bypass the air pump and install an electric fan in place of the belt driven fan.
An average of 2.7 HP is gained from every pound lost off the crank shaft. 85% of Unorthodox gains are from weight loss. The rest of the gains are from underdriving.
As quoted fron the Alamo MotorSports Website.
I ran ASP underdrive pulleys on my 92 GT 5.0 - The biggest problem I ran into was overheating - but it did give my pony a good boost - I remember running a WS-6 on the freeway. I was literally on his bumper and he couldn't pull - (It was a Few Years Back and I can't tell you what year WS-6 [FireBird] it was)
I think the main concern is what application the pulleys are for - Some cars won't see the gains as others may.
As stated earlier, you can achieve the same results, as underdrive pulleys, if you bypass the air pump and install an electric fan in place of the belt driven fan.
An average of 2.7 HP is gained from every pound lost off the crank shaft. 85% of Unorthodox gains are from weight loss. The rest of the gains are from underdriving.
As quoted fron the Alamo MotorSports Website.
I ran ASP underdrive pulleys on my 92 GT 5.0 - The biggest problem I ran into was overheating - but it did give my pony a good boost - I remember running a WS-6 on the freeway. I was literally on his bumper and he couldn't pull - (It was a Few Years Back and I can't tell you what year WS-6 [FireBird] it was)
I think the main concern is what application the pulleys are for - Some cars won't see the gains as others may.
06-10-2003, 08:32 AM
#9
Burning Brakes
Well, I will not bypass the airpump for at least two reasons. One - I like to pass emission inspections, and two - if the pump is left sitting for awhile, the blades can rust and the pump becomes uncurable frozen (and they are not cheap). YMMV.
06-10-2003, 02:01 PM
#11
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I had the pulleys on my 951 track car. The pulleys are best suited to underdrive the accesories so that they do not burn out so quickly when run on the track at higher RPM's. Other than that the power benefits are insignificant (IMHO). I would spend the money on suspension, brakes, or tires.
03-20-2013, 06:28 PM
#12
Electron Wrangler
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I suspect you already have one power boost button (turn the AC off), maybe use the same type of clutch on the alternator and airpump - set it to turn them off only for a little while at a time (20 sec maybe).
Has all kind of practical difficulties.... but would probably have a noticeable effect for power bursts (very low duty cycle of usage).
For other reasons:
How easy is it to change the crank pulleys on a 928? - are there any modular pulleys or is stock always a single bell type unit? like to use a larger Alternator pulley and a different air pump pulley (for an alternate vac pump)
Alan
Has all kind of practical difficulties.... but would probably have a noticeable effect for power bursts (very low duty cycle of usage).
For other reasons:
How easy is it to change the crank pulleys on a 928? - are there any modular pulleys or is stock always a single bell type unit? like to use a larger Alternator pulley and a different air pump pulley (for an alternate vac pump)
Alan
03-20-2013, 07:52 PM
#13
Team Owner
almost 10 YO thread
03-20-2013, 08:18 PM
#15
Team Owner
Alan might you try asking what your looking for a different way,
the post you made really is very scattered JMHO
the post you made really is very scattered JMHO