Hi guys, i was just wondering, my 90 leg fwd 5speed car has the loose crank pully/messed up crank key, i was going to replace my pulley (since the keyslot is worn on it) and i found a really good deal on an underdrive pulley for the ej22. Im just trying to decide if there are any bad points to using an underdrive pulley on these cars.

 

Im going to try and repair the keyslot in the crank itself with some jbweld and the key, and hope it holds long enough for me to arrange the cash and source an EJ22t from a 91-94 turbo. Mainly im just asking if there are any negatives to going with an aftermarket underdrive pulley, as i can get a new one for ~ 20.00 more than a junkyard pulley. Thanks everybody.

Other than the need to be aware of potential electrical system voltage/discharge at low RPM, and/or during times of high accessory usage, you've also got issue of the non-standard accessory drive-belt size to contend with, so you'll need to document the belt part# and keep it with your manual for future reference.

 

The last issue is that of crank harmonics. The best info I've been able to glean on this subject is that the ultra-short Subaru crank suffers little from inherent harmonics with the exception of one sharp resonant peak which occurs in the upper RPM range. Exactly what that RPM is, is unknown to me and there appears to be zero conscensus on this issue. My opinion is that if Subaru didn't think it was important to have a three-piece harmonic damper, they wouldn't have included it.

Ah well, ill give it a shot for a while, im not really concerned with the longetivity of this motor since if i can ever find one i can afford ill be swapping an EJ22T in, the underdrive pully is just a much cheaper option for me to get the car running again.

4 years, 140,000 miles 300+ HP turboed EJ25 with unorthadox lightened pulley and a 9.5Lb flywheel, no problems.

Josh (Legacy777) had one on his 90 Legacy forever. He did report a dimming of lights and such at idle coz the alt. simply wasn't spinning fast enough, but I don't think anything else happened. He now has stock-sized, but lightened, pulleys...

Please clue me in:

 

Why use an "underdrive" pulley? What's the advantage?

Please clue me in:

 

Why use an "underdrive" pulley? What's the advantage?

"Underdrive Pulleys" place somewhat larger diameter drive pulleys on components such as the alternator, the power steering pump, and sometimes the water pump. These oversized drive pulleys effectively reduce the drive speed of these auxillary items, and lower the peak Horsepower loads they place on the engine. It makes the engine able to rev up faster in response to the throttle, and so undrive pulleys are favored by rally and street race performance tuners. The downside is, as has been posted here, that the undrive pulley on the alternator sometimes makes it spin too slowly at idle to keep the electrical system charged, so folks who use underdrives have to watch out for that.

 

James

"Underdrive Pulleys" place somewhat larger diameter drive pulleys on components such as the alternator, the power steering pump, and sometimes the water pump. These oversized drive pulleys effectively reduce the drive speed of these auxillary items, and lower the peak Horsepower loads they place on the engine. It makes the engine able to rev up faster in response to the throttle, and so undrive pulleys are favored by rally and street race performance tuners. The downside is, as has been posted here, that the undrive pulley on the alternator sometimes makes it spin too slowly at idle to keep the electrical system charged, so folks who use underdrives have to watch out for that.

 

James

 

It's actually a _smaller_ crank pulley. Why replace multiple driven pulleys when you can replace one drive pulley?

I must note that I had an underdrive pulley on my EJ18 before, but switched to a stock sized lightweight pulley. I noticed a significant loss in engine revs between 2000 and 4000 rpms (IE the underdrive is faster than a stock sized, lightweight pulley)