Pulley kit have any downsides? Or stick to crank

[kuhlka]

Originally Posted by stugray

So I will ask this question again: When the engineers were trying to squeeze every last hp out of this engine to reach the rated "200hp" mark why didnt THEY just change the size of the pulleys?

Seems simple right?

If you want a drag car why not just bypass the alternator & AC entirely with a belt that only drives the water pump?
ON TOPIC enough?

Heavy stock bits = Smooth and reliable. Easier to balance.

Lightweight aftermarket bits = Fast revs, but easier to stall.

The stock parts are really just a matter of cost-savings and keeping daily driver reliability as a high priority. I'd be willing to bet even the next (rumored) Toyota Supra will have a fairly heavy pulley setup and flywheel because the vast majority of buyers won't spend a single minute on a track or autocross circuit.

I generally weigh my mods in terms of $/lb or $/whp. When you take that into account, a pulley set is pretty pricey in the grand scheme of things.

[Team STILLEN]

Just to make sure people don't get concerned about engine balance when talking about lightweight pulleys, here is what we have found at STILLEN and from my personal experiences. Most, if not all modern motors (especially Japanese Imports) are internally balanced. The crank pulley is rarely used for balancing purposes on most motors and is generally just used to drive the accessories and in some cases reduce NVH. We have found no issues with using lightweight pulleys on any of the cars we have developed them for and have even had customers say their engine runs a little smother.

Originally Posted by stugray

So I will ask this question again: When the engineers were trying to squeeze every last hp out of this engine to reach the rated "200hp" mark why didnt THEY just change the size of the pulleys?

Seems simple right?

Yes, engineers at Subaru and Toyota are always trying to squeeze every last HP out of the engine (with in reason). They have budgets, acceptable rate of failure, safety, and other regulations to consider that keep them from getting absolutely everything out of a motor. A CNC machined lightweight pulley will cost more for them to make and will generally not be an acceptable part to use. Also, if the crank pulley is being used as a dampener then they would not be able to mess with it much. Cost is always a huge factor that limits vehicles from the factory. Also I'm sure there are internal or external regulations on power allocated to accessories.

Originally Posted by stugray

If you want a drag car why not just bypass the alternator & AC entirely with a belt that only drives the water pump?
ON TOPIC enough?

Pure drag cars often bypass anything possible. Even running electric water pumps. Does not apply to anything you would drive more than a 1/4 mile at a time.

Originally Posted by kuhlka

The flywheel would make a big difference for revs, though.

I have always seen and felt great results from Lightweight Flywheels. Always a worth while upgrade IMO.

Originally Posted by kuhlka

The stock parts are really just a matter of cost-savings and keeping daily driver reliability as a high priority. I'd be willing to bet even the next (rumored) Toyota Supra will have a fairly heavy pulley setup and flywheel because the vast majority of buyers won't spend a single minute on a track or autocross circuit.

You're pretty much right now the money. Though in this case I'd say its more about cost as pulleys are flywheels generally don't affect reliability very much (on these types of cars at least), but who am I to question Toyota and Subaru.

[stugray]

Originally Posted by Team STILLEN

The crank pulley is rarely used for balancing purposes on most motors and is generally just used to drive the accessories and in some cases reduce NVH..

Mark,

excellent post! I agree almost 100%

There are definitely holes drilled in my stock pulley, so I assume that the rotating assembly is balanced at the factory.
I question "slightly" that these engines are 100% Internally balanced or that would call into question why most of the mass of the pulley is dead weight.

You can see by looking at the stock pulley that the internal part is cast while the "mass" is machined and attached to the pulley.
Why would they pay extra for the additional assembly cost of a two part pulley if they did not need to?
So I believe that the pulley is there for balancing purposes.

Would I replace the pulley if building a race engine from the ground up? Absolutely! Along with the rods, pistons, flywheel, clutch, etc.
Would I change the pulley from a previously balanced rotating assembly without rebalancing? - No.
You guys have been doing this long enough that I dont believe you would tell a customer that is having a custom engine built that they should change any rotating part without a rebalance either.

The arguement here comes down to "Can you replace the pulley to get a fraction of a hp difference?" or "Should you?"

I am on the side of "you shouldnt" UNLESS you do a few other things first.

[Team STILLEN]

Thanks Stugray.

I agree that the motors aren't necessarily 100% balanced from the factory (as 4 cylinders are inherently imbalanced), but I doubt the pulley contributes much to that but I can't say for sure (safe bet would be not to touch it). The two piece design is generally used as a dampener for NVH (which we have found in the past to make very little difference). We have not tested this particular car's pulleys so I'm not sure. I agree that on this engine there is less gains to be seen with a pulley but I haven't seen any solid dyno sheet indicating either way (though the math indicates very little gain).

We have seen up to 8 whp on the VQ motors with underdrive and lightweight pulleys, but those are bigger motors with almost 5 lb crank pulleys. Also the 350's and 370's have PS pumps to underdrive so there is a little more power to be saved.

I also agree that there are much better upgrades that one should spend money on before looking at pulleys.

[Jaylyons1]

Originally Posted by stugray

When I hear about how people can "feel" that the engine is more responsive with a lightened pully, I want to call BS.

If you think about it, it supposedly "reduces" the rotating mass.
However if you consider the alternator, air conditioner, belt, crank, pistons, flywheel, cams, and timing chain, the pulley is a tiny fraction of all of that inertia. (I would bet that the timing chain contributes 10X more than the pulley in rotating inertia).
I seriously doubt it makes any difference at all, much less a difference that you can feel.

Also, when the engineers were trying to shave every single ounce off of this car & engine, WHY would they put a heavy pulley on it? I am guessing it has to do with vibration & dynamic balance.

I would not mess with it UNLESS you are doing a dozen other things that would make a bigger difference.

I noticed a change when I had one on my WRX 4 or 5 years ago. I didn't really notice a power gain though. It was noticeable in winter when I would lose traction. The revs would shoot up way faster than it did with the factory pulley.

[Mathewgzlz]

Originally Posted by JDKane527

I have GFB lw crank, alternator, and waterpump pulleys, as well as Raceseng idlers. I didn't notice a difference when I installed idlers on, except for rpms dropping faster. Blips are quicker. Regarding acceleration, I didn't notice as big of an improvement as when I got header and tune. I still have stock flywheel and steel drive shaft, so it will be more noticeable after lightening those.

My butt dyno was recently calibrated to Mil Spec.

Edit: seems like some people's sarcasm detectors need recalibration.

i have a question for you, i went with the gfb 3 pulley kit as well when i went turbo but now occasionally itll bog out while fluttering the clutch or slowing down is there a chance tht the reduced mass of the pulleys is causing to rev down to quickly or do you all think i might have a shitty tune/maybe internal damage? besides the occasionally bogging the engine runs great air/fuel is right around where its supposed to be and i never have any hesitation in acceleration.

[JDKane527]

I get occasional bogging if there's high ambient temps (80F) and there's some heatsoak from sitting in traffic. On FA20 tune, the idle was lower rpm than V-Tune, and would bog more frequently with the lower idle. The V-Tune bogs less.

You can try changing back to the stock crank pulley and see if it's more stable. I was considering trying the stock crank myself as well.

[Mathewgzlz]

Originally Posted by JDKane527

I get occasional bogging if there's high ambient temps (80F) and there's some heatsoak from sitting in traffic. On FA20 tune, the idle was lower rpm than V-Tune, and would bog more frequently with the lower idle. The V-Tune bogs less.

You can try changing back to the stock crank pulley and see if it's more stable. I was considering trying the stock crank myself as well.

I'm probably going to swap them all back to stock the gfb pulleys are under a 1lb and I've heard thts a no go for pulleys and see if it helps


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[jamesm]

I don't know if they present any issues on this car (no one does yet), but for what you gain it definitely isn't worth any amount of risk.

[Victor Draken]

Originally Posted by jamesm

I don't know if they present any issues on this car (no one does yet), but for what you gain it definitely isn't worth any amount of risk.

for the price you have to pay for a full pulley kit is not whort it as well

[dj petey]

Lighten your drive train if you want increased throttle response. Be prepared to adjust your shift habits to keep everything smooth. When i went to a lightweight flywheel the difference was very apparent in first and 2nd gear acceleration. Throttle lag is greatly diminished. Pulleys won't have as much of an affect as a FW but will help in the grand scheme. Pulleys also don't usually cost as much as a flywheel and the install doesn't require a clutch and tranny re/re. So if you're short on cash and install time pulleys will get you started in the right direction.