[grza]

Hey everyone, I was just checking out the following lightweight aluminum crank pulley:
http://www.fastscions.com/Scion-Lightweight-Aluminum-Crank-Pulley-2AZFE-tC-xB.aspx


“These pullies are actually the same size as stock; however they weigh over 3.5lbs lighter than the OEM. By reducing rotating mass, this lightweight aluminum crank pulley gives the 2AZFE engines a gain of 5-6 horsepower and an increase in torque by 6-8+ ft/lbs.”



So it’s not actually an underdrive pulley, just a different lighter material to reduce the amount rotating mass driven by the crank. Even though 5-6hp is not a lot, I’m actually surprised it’s that much considering the pulley ratio is the same as stock. If that’s the case, I bet a lightweight flywheel/clutch assembly would also free up a few extra horses. Anyone talking about replacing their flywheel/clutch on manuals under this same principle?

 

[gr8scape]

Quite a few people on this site already have the lightweight pulley's on their xB's. It does make a difference.

 

[grza]

yeah, it sounds like getting the lightweight pulley is a must, but I was checking out lightweight flywheels for my transmission too, but couldn't find anything for a 2008 xb, just the older model and Tc's.

 

[TrevorS]

yeah, it sounds like getting the lightweight pulley is a must, but I was checking out lightweight flywheels for my transmission too, but couldn't find anything for a 2008 xb, just the older model and Tc's.

If you want to lighten the flywheel, the tC replacement should be fine (same engine), but ask the manufacturer first.

 

[TartanJack]

If I had the manual (wife won't drive stick except VERY reluctantly- just doesn't like it- and my Miata is a stick), I'd get a performance clutch and lightened flywheel before I'd worry about a lightened crank. The clutch would make much more difference to the driving experience.

 

[TrevorS]

If I had the manual (wife won't drive stick except VERY reluctantly- just doesn't like it- and my Miata is a stick), I'd get a performance clutch and lightened flywheel before I'd worry about a lightened crank. The clutch would make much more difference to the driving experience.

Downside to a lightened flywheel is that it's easier to stall the engine and engine vibration would increase. I consider those aspects to be a loss in the driving experience. The only gain would be an improvement in acceleration, however, if that's all you care about, then that's indeed an improvement !

 

[TartanJack]

The lighter flywheel increases spool up and spool down.
If too light, then stalling is a real issue (spools down at idle too fast for the driver's clutching). Engine vibration would come from either one that isn't finely balanced to begin with or from the less momentum muffling a small vibration coming from the crankshaft (a spinning flywheel that is well balanced works similar to a bicycle wheel stabilizing a bike when spinning).

 

[TrevorS]

The lighter flywheel increases spool up and spool down.
If too light, then stalling is a real issue (spools down at idle too fast for the driver's clutching). Engine vibration would come from either one that isn't finely balanced to begin with or from the less momentum muffling a small vibration coming from the crankshaft (a spinning flywheel that is well balanced works similar to a bicycle wheel stabilizing a bike when spinning).

The engine vibration I'm talking about has nothing to do with crank balance, and everything to do with cylinder firing pulses. Regarding engine stall, many feel the stock engine is very close to stalling when releasing the clutch from a stop in first gear (even the infrastructure reviewers commented on this), a lightened flywheel will make that more of an issue.

 

[TartanJack]

I meant any vibration coming through the crankshaft, which includes all the normal engine stuff (inc. pulses from the cylinders, which are what turns the crankshaft by the pistons moving in sequence).
The spinning pulleys act as mitigators for that movement.
One is on the belt side of the engine, while the flywheel is on the "other" end of the engine. Both are tied to the crankshaft.

Engines are complex things . . .

 

[TrevorS]

yeah, it sounds like getting the lightweight pulley is a must, but I was checking out lightweight flywheels for my transmission too, but couldn't find anything for a 2008 xb, just the older model and Tc's.

Just one last comment . If you get a lightweight crank pulley, make sure it has a reputation for quality you can hang your hat on. Just because it's light doesn't mean it's designed or manufactured correctly for your engine. A less than correct design (as in balance, concentricity, and raw fit) can result in expensive shop repair, so take this purchase very seriously.

PS. I use a lightweight pulley myself, so I'm not arguing against getting one, just be cautious in your selection.