Pulley change?

Hi,

I'm with Ed...

Or, as they say in the sporting good stores, fishing lures catch more fishermen than fish!

Lightweight alloy pulleys were all the rage back in my air-cooled VW days and I'm sure still are with the afficianados. They looked nicer than the stock stamped pulleys, but nobody could put many real numbers (other than the usual "100% increase in horsepower, gas mileage and sex appeal" advertising hype) on their performance beyond sales figures showing how much the buyers' wallets had been lightened!

Rick

Agreed - I have 2 air cooled Bugs (or Beetles if you will) and they're all about the light weight pulleys but I've never seen anyone get hyped up about them elsewhere.

There's aspects to the construction of the OEM crank pulley that allow it to function "like" a harmonic balancer. There's some fine points to it, so I'm phrasing it *that way*. I looked into it and concluded a lightweight pulley wasn't an advantageous mod for a WRX, and promptly dismissed the details. ;-)

If you spend some time looking thru the mod commentary over on Mike Shield's site,

I believe you'll find the info there...along with a lot of other well thought-thru philosopy and information on modding WRXs.

And I've seen a Subaru Tech memo that says the pulley was not designed and does not act *as* or *like* a harmonic balancer.

I'll try to find it and then post the link.

I've read his site and generally agree with most of his points. However, some of his stuff is at direct odds with other tuners who also know their stuff.

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Found the link to the pulley stuff on NASIOC.

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Stick around on NASIOC, and you will be AMAZED at what people report SOA as saying.

You can eyeball the *construction* of the OEM pulley and see there's more to it than a pulley; like I said, I've already "discarded the data", but when it comes to saving money & simplifying design, all auto makers are there...have fun, get a CAI and a BOV too.

Whatever. I guess some people just won't believe data published by the carmaker.

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Yes, I saw the link...someone posted that he asked SOA, and SOA replied that it was not...no "Subaru Tech memo".

Actually, I couldn't find the original memo so I linked to the conversation that referenced it.

In any event, the little piece of rubber between the two halves of the crank pulley isn't a harmonic balancer.

I had a af/x underdrive pully on my NT Eclipse. The stock pully on an eclipse does work as a harmonic balancer. I never had an issue having it on there, i put it on at 70k with a timing belt change and the car ran fine. I traded it in on the WRX at 135k. I noticed a little improvment in power.

i switched out my "03 wrx wagon pulley for a vishnu alloy crank pulley myself-----relatively easy job.

yes it's much lighter, however the main advantage is diameter (underdrive means easier to drive compressor, alt, p/steering, --less effort but they do not spin as fast either. first question, will this affect p/steering, a/c, & alt operation??? answer---no noticeable change, except more power. after 2 years, i have had plenty of juice even at idle, to operate all i need, however i've never been the type to run stuff at idle that i do not need to be on. the beauty of this is that power gain is at ALL rpms, so driveabilty is better especially at lower rpms where turbo is lagging. vishnu claims 5-10HP which sounds about right.

jellymax

What do y'all think of this in comparison?

I note that he doesn't address the issue that Subaru itself says the crank pulley is not a harmonic balancer.

There are light weight pulleys and underdrive pulleys.

The light weight pulley is used to reduce the rotating mass or inertia of the motor so there is less resistance to rapid speed changes. That can help race motors to respond faster. How much benefit there might be on the street is questionable IMO.

The underdrive pulley reduces the speed that belt driven accessories run. Alternators, AC compressors, etc use engine power and the slower they run, the less power is lost driving them. The power increases are smal;l but measurable, but there is a direct price to be paid. Your accessories will not run as designed, eg: your alternator will put out less amps and batteries will charge slower or you will have to turn down your 3000watt stereo.

Philip