Lightweight pulleys?

[finney]

Just a quick query into the gains that could be made by replacing the standard pulleys on engines? I have noticed that they are available and was wondering whether they would be worth the financial outlay for the gains.

Personally i'd be looking at putting them on a silvertop 20V 4AGE, but thought it would be intersting to hear of any personal opinions on them and also what people have heard about them.

Any info on the topic would be appreciated.
Cheers.

[RA23]

Gain is marginal compared to flywheel, because the diameter is much smaller. Only worth the money if it is for serious race work (or wank value).

[oldcorollas]

you will almost certainly not notice on the street.

they are usually done to underdrive the alt and water pump at high rpm.. to save alt, and reduce losses/cavitation of water pump..

until you have done everything else possible to lighten your car, and you, and driveline weight, then light pulleys will do buggerall

[BigWorm]

I agree with Stew & RA23, unless you can get some cheap or free, don't bother. Plus unless it's for a dedicated high RPM track car, water pump & alt. speeds will be compromised in my opinion.
I had an under sized crank pulley made for mine (good old Q-mart, 7075 T7 alloy on the CNC lathe, price= 6 pack of crownies ) purely because the standard pulleys I had were slightly damaged & it gave the boys at work something to do (and yes, because of the wank factor) but now whenever I'm cruising for moderate distances at low revs & speeds and the temp works its way up I can't help wondering if the water pump is spinning a tad too slow.
Someone once told me (I think it was IRALLY) that the 4AGE water pump isn't in its efficiency until 2500rpm and is fine up & over 7 grand, so unless you're keeping it over 7 grand for extended periods (or can get one/them made up for free but kept standard size), don't bother.

However if you know someone handy with a lathe I have a spare "blank" made up, just needs the grooved OD machined into & the keyway cut, which were the hardest parts of getting it done. The grooves required a custom tool to be made up & it took a little searching to find someone to cut the keyway. Plus it's the alt/water pump pulley only, no provision for A/C or P/S.

[mullett]

Best way to cut keyways is someone with a wirecut machine. Ultra accurate and neat. But there isn't much gain. Cheaper (and much better) to get an electric water pump.

RM.

[BigWorm]

Best way to cut keyways is to know someone with a wirecut machine.

Fixed.....

[mullett]

Oh, it's all in the subtle differences. Like knowing someone who anodises, being able to walk into a shop full of CNC machines, knowing wirecutters and springmakers and engine rebuilders and and and.

RM.

[oldcorollas]

(good old Q-mart,

i heard it's a bit tighter now than it used to be?

[BigWorm]

Mullet, yeah, it's a bit like that!

Stew, you could say that, but more accurate would be "it's a bit more non-existant than it used to be."
The fitting shop in Mascot is virtually no more, & the new (I use that term very loosely) shop in Bankstown leaves alot to be desired. Plus the fact that I now live a few thousand kms away. Adelaide is highly lacking when it comes to machinery of any description.
Although we do have a pedestal drill!

[limbo]

There are some minor gains, maybe 1-5kws somewhere in that area, but i heard that as the normal engine pullies, especially the crank pully are weighted to balance the crank and to ensure less vibration to the engine. Thus putting a lighter crank pully will allow for more vibrations in the engine causing the engine to wearout faster. That's why generally people go for a different way to make power. Running Higher octane fuel will give you somewhere near that mark.

[RA23]

There are some minor gains, maybe 1-5kws.

There are 3 separate things:
1) lighter pulley, less inertia, engine revs (accellerates) easier
2) lighter pulley, less mass, car accellerates better
3) different pulley ratios, e.g. spin your alternator/waterpump slower/faster

1) only makes sense in serious racecar, and then still marginal compared to lightened flywheel
2) only after you have done everything else to save weight (including diet)
3) makes a lot of sense for racecars, as the engine rev range will be much different to a street car, therefore you might save a few kW by changing the ratio.

What would make more sense from a kW point of view would be to get a separate (electric) water pump and to disable the crank driven one completely. This will cost 50-100W of electric power, but it may save you several kW at redline.

[adamaw11]

This will cost 50-100W of electric power, but it may save you several kW at redline.

So can we assume that to make an extra 100W of electric power, that the alternator will take about an extra 100W to turn harder to make that extra electrical power? or will it actually drain even more than that due to friction etc.

[Billzilla]

FWIW my 4AGE ran cooler with the water pump running at about 50% normal speed - but only after the engine was fully run-in.
I tried it when running-in and it ran hotter!

I also tried running the alternator at 1:1 with the engine speed and it was juuuust okay, but I wouldn't run it that slow again. I'd have to give it about a 30% over-drive to be sure.

[RA23]

So can we assume that to make an extra 100W of electric power, that the alternator will take about an extra 100W to turn harder to make that extra electrical power? or will it actually drain even more than that due to friction etc.

If we assume that a mechanical waterpump takes 1kW at 8000 revs (this is very conservative) and that an the electric waterpump takes 100W at any speed (suppose it is not controlled by water temperature, but simply on all the time), If all efficiencies added up (alternator belt, alternator, wiring) are 50% (very conservative) then you would still only sacrifice 0.2 kW of Alternator power to gain 1kW by not having the waterpump. So: .... profit (0.8 kW)
Of course a scenario with a controlled waterpump based on water temperature would be more efficient and you can also get rid of the thermostat & bypass.

[RWDboy]

There are 3 separate things:
1) lighter pulley, less inertia, engine revs (accellerates) easier
2) lighter pulley, less mass, car accellerates better
3) different pulley ratios, e.g. spin your alternator/waterpump slower/faster

1) only makes sense in serious racecar, and then still marginal compared to lightened flywheel
2) only after you have done everything else to save weight (including diet)
3) makes a lot of sense for racecars, as the engine rev range will be much different to a street car, therefore you might save a few kW by changing the ratio.

What would make more sense from a kW point of view would be to get a separate (electric) water pump and to disable the crank driven one completely. This will cost 50-100W of electric power, but it may save you several kW at redline.

The first point doesn't technically change the engine's 'power figure' at all (unless measured by an inertial dynanometer, in which case you will see some difference, but technically there's no difference in 'power' at all).

It's like a flywheel in a sense, you can't ignore the fact that some energy is stored (as inertia) and some of that energy may go towards accelerating the car when you change up a gear. So lighter isn't necessarily better - but then again, inertia can cause stress on the gearbox (ala porsche 924)

Other two points is ok