Pulleys Question
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  1. #1
    Tadpole
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    Default Pulleys Question

    Are lightened pulleys really that effective in freeing up more power?
    Looking at changing altenator, air-con and power steering pulleys for light weight ones.



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  2. #2
    1000+ Posts CHRI'S16's Avatar
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    Quote Originally Posted by Seven
    Are lightened pulleys really that effective in freeing up more power?
    Looking at changing altenator, air-con and power steering pulleys for light weight ones.

    ...on what car? I know a few of the turbo owners dont put lighter pulleys, they use smaller pulleys to underdrive certain things such as A/C compressor and alternator. I can't see it much of a gain though, specialy lighter ones, the money would be better spent elsewere. - Chris
    ... ptui!

  3. #3
    Gone Fishin' Ray Bell's Avatar
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    Lighter rotating weights reduce inertia, so you might get some acceleration benefits. But not anything noticeable with the likes of alternator or water pump pulleys... even crankshaft pulleys. That sort of benefit comes from carving kilograms off flywheels, where it's a lot of weight right out at the periphery of the wheel, a real load to get moving.

    Of course, it's there (in the case of the flywheel) to smooth things out and principally to keep up the momentum.

    Reducing pulley sizes (on alternators and water pumps) will increase their speed and thereby increase the power they consume. But there is the question here of whether or not they will then function to a level that will get the job done.

    I wouldn't fiddle with the water pump, if you increase the size it may not pump to the capacity you want, if you reduce it you might get cavitation.

    The alternator... which is already pretty small... you might increase it, but watch out for running the battery down in night time driving.

    Basically, I think it's not much of a benefit to do anything, just leave it alone.

  4. #4
    1000+ Posts alan moore's Avatar
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    I reduced the crank pulley on my BMW 2002 to drive the water pump slower, as it was cavitating at 8000 rpm. At least I believe it was cavitating as it used to overheat on the track, and didn't after the pulley reduction. I reduced it from 140mm to 97mm. I made it on my lathe out of aluminium. It has lasted 8 years in another race car.

    It made a massive difference to the belt speed, you could amost read the belt at idle. The alternator light also flickered at idle, but wasn't a worry.
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  5. #5
    Tadpole
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    Cheers Guys!
    Hope you all had a Good New Year! Well I'm not really looking at underdriving the pulleys, cos I do a lot of city driving.
    So Alan you made your own pulley on a lathe? What kinda Alloy you use and was it much lighter than the original in the 2002? Them are one of my favourite Bimmers

    Cheers

  6. #6
    1000+ Posts alan moore's Avatar
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    I think T-6. Would not have been much lighter as the std one was only pressed sheet metal. Ray is one the right track, pull a few Kg out of the flywheel and feel the difference, particularly the outer part of the flywheel. Light pulleys would only be for the fanatical race car where there is nothing left to spend money on.
    '56 Renault 750 (16TS Power)
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  7. #7
    Budding Architect ???? pugrambo's Avatar
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    Quote Originally Posted by alan moore
    I think T-6. Would not have been much lighter as the std one was only pressed sheet metal. Ray is one the right track, pull a few Kg out of the flywheel and feel the difference, particularly the outer part of the flywheel. Light pulleys would only be for the fanatical race car where there is nothing left to spend money on.

    ah yes but machined up alloy pulleys look good

    i have made a few up for cars to go in the summernats

    nothing to do with power output for the cars but just foor looks, they were still servicable but they just looked the goods as well

    even better when they are polished up

    but as for power saving i think you will get the same effect by taking an A/C belt off during winter, have never been able to work that one out myself but many do it
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  8. #8
    Gone Fishin' Ray Bell's Avatar
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    It would certainly save wear on the belt and the idler bearing if there is one...

    But what about the advice to run the air con for a few moments once a week to keep the seals lubricated?

  9. #9
    Budding Architect ???? pugrambo's Avatar
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    Quote Originally Posted by Ray Bell
    It would certainly save wear on the belt and the idler bearing if there is one...

    phooey

    the wear is negligible

    how often have you ever replaced an A/C belt due to it wearing out or breaking ?

    i know i never have

    the only 'V' belts i have ever needed to change have been alternator/waterpump belts

    as for idler pulleys well they last a fairly long time as a rule

    i have always wondered why in the hell when winter arrives all these dimwits get out there and remove the A/C belts and then come summer they put them back on and then remove thermostats

    yes they do pay for it in the end as they are the ones gassing up their A/C every year while they haven't saved a thing by taking the belt off in the first place

    mind you the majority of these people drive holdens and fords so i think that accounts for the thinking involved

    i think if Mr holden and Mr ford could save the $5 per thermostat in the assembly they would so the thermostat is there for a reason but try telling some people that

    anyway i can't see alloy pulleys having any gains and if they do it would be very minute and it would be the same amount as taking off the A/C belt during winter
    3 x '78 604 SL

    1 x '98 306 GTi6

    1 x secret project

    1 x '98 406 STDT troop carrier and i don't care if it stinks, i don't sniff it's arse Death by wank tank

    1 x '99 406SV 5spd wagon, time to burn more fuel

    1 x 1994 605 SV3.0


    WTD long range fuel tank for 605

  10. #10
    Tadpole
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    So most say there isn't any gain so I guess I'll leave it well alone, I'd like to get the flywheel lightened but there just isn't any decent engineering workshop here that can do a real kosher job!
    I've heard of some real nightmare stories of flywheels exploding at full revs.


  11. #11
    Gone Fishin' Ray Bell's Avatar
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    That's why you take the weight out of the periphery of the flywheel... you don't thin it down in the middle...

    Has more effect in the inertia department out there at the edge as well.

  12. #12
    Fellow Frogger! pips's Avatar
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    Removing the thermostat.

    Reminds me of when I was trying to explain to someone why his fuel economy was higher after removing his.

    A simple man with old (circa 1960's) cars all his life. Which probably benefited from the removal of the thermostat.

    Some people just don't get it.

    pips
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  13. #13
    Gone Fishin' Ray Bell's Avatar
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    Please explain to us all...

  14. #14
    Fellow Frogger! pips's Avatar
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    Well, by removing the thermostat on an EFI car, it will run cooler.

    The engine is not meant to though, and because it is running cooler, will most likely be injecting more fuel into the inlet, possibly idling higher, running rich, using more fuel.

    I have seen the results of an engine running rich for extended periods. The cylinders can get glazed, eventually resulting in higher running temps.

    This is just from my experience with bikes, and engines are engines so I can't see why it would be too different. Correct me (enlighten me) if I am wrong.

    This guy was saying that its better for the engine to run cooler cause the heat will kill it. Which is fair enough. But he wasn't looking at other factors.

    pips
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  15. #15
    Budding Architect ???? pugrambo's Avatar
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    the thing that people never understand is that engines run at their most efficient when they are running as close to boiling point as they can

    i only ever change thermostats in cars when they kark it not for seasons

    i have never changed an A/C belt and yet i have one here for a 604 that i bought new in '88 and it has lived in the boot of every 604 i have ever owned

    i have only ever changed the bearings in 1 idler pulley
    3 x '78 604 SL

    1 x '98 306 GTi6

    1 x secret project

    1 x '98 406 STDT troop carrier and i don't care if it stinks, i don't sniff it's arse Death by wank tank

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    1 x 1994 605 SV3.0


    WTD long range fuel tank for 605

  16. #16
    Gone Fishin' Ray Bell's Avatar
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    Originally posted by pips
    Well, by removing the thermostat on an EFI car, it will run cooler.

    The engine is not meant to though, and because it is running cooler, will most likely be injecting more fuel into the inlet, possibly idling higher, running rich, using more fuel.....
    All I would like to add was that you misled me with your earlier post... that's why I asked you to explain...

    Earlier post from pips
    .....Reminds me of when I was trying to explain to someone why his fuel economy was higher after removing his.....
    His 'fuel economy' wasn't higher, his 'fuel consumption' was.

    Think about it...

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