Aluminum pulley not a damper, thats ok with alotta folk?

[2gnt2wrx]

I ran a perrin pulley on my 04 wrx for 30k/mi with not a single issue. I ran the same pulley on my "loud" fully built 430whp sti for over 3 years without a single issue ever. You guys are over thinking this. Even the professional engine builders in the subaru world recommend them.

[Superhatch]

This is like the 50th thread on this topic, and in the end pointing back to the last 10 years of WRXs running lightened pulleys w/o any issue trumps any theory the naysayers might have imo.

[jdmitr]

There are many engines from many manufacturers that came without dampening built in (even with ac) without issues. Every engine has different characteristics and require different harmonic tuning. Many considerations change the needs for harmonic tuning too...(I.e. max rpms, load, sustained rpm's, heat, friction, etc). The longer the crank shaft the more this is needed and crucial.

Dampening the pulley not only can help harmonically but a lot of it is for AC as many oem pulleys dampen only the ac belt and not the other belts for PS etc. Think about it...when the compressor kicks on it "jars" the crank pulley. Some engineers build it in more as a "feature" to keep you from feeling it as much as many engineers and oem's are fighting to appease your average owner by making the car smoother and more quiet. Just like balance shafts in many engines. Their main purpose is to counter act the vibrations felt from the engine. The civic type r N1 crank pulley sold by honda is a solid pulley and is what they put on their race cars and are good for over 10k rpms and they ran 24 hour endurance races with them which is very extreme. The cranks in subarus are so short that a dampened balancer wont do much especially in a street car. Now a straight 6 over a 100k miles of hard use with the ac on "might" make the crank seal leak a little sooner then normal or if lubrication wasnt up to par might help in increased wear.

Run it...don't run it. I am sure that many engine builders and reputable aftermarket parts companies wouldn't run them or sell them if they were smart. I wouldn't make and sell anything that could end up in a lawsuit.

The very biggest concern with a crank pulley especially on a street car is how well it is balanced. MANY highly tuned race engines dont even have crank pulleys/harmonic balancers with phenomenal results!!!

http://9thcivic.com/forum/threads/ho...the-year.3784/

[gmookher]

right race motors get torn down and rebuilt alot too

Is it power or reliability this OE part ensure is the 1st question you need tro answer

[Lawnik]

Thankfully it is looking like the FA20 is significantly over engineered. I think the question for me is how to capitalize on this extra room.

I'm going to leave the pulley OEM since its performance gain is minimal and go FI for performance gains that sacrifice long term reliability.

[20valvewynn83]

Really come on now! The only way a crank pulley can be balanced is if they do it on the engine and I will tell you this "they don't". Also everyone is so concerned about vibration, what do you think the hydraulic belt tensioner is for. When we replace a crank pulley its not balance to every engine.

[VSGTS14]

none of subaru's motors have harmonic dampeners. it's confirmed the EJ isn't and therefore, it's fine to run a lightweight pulley.
the same applies to this motor.

[Style]

Sweet will be buying a light weight. Was going to buy it even before this showed up

Sent from my SAMSUNG-SGH-I717 using Tapatalk 2

[VSGTS14]

Originally Posted by Style

Sweet will be buying a light weight. Was going to buy it even before this showed up

Sent from my SAMSUNG-SGH-I717 using Tapatalk 2

this type of thread has been around forever. it figures someone would want to argue again about it, since it's a new car.

[jdmitr]

Originally Posted by 20valvewynn83

Really come on now! The only way a crank pulley can be balanced is if they do it on the engine and I will tell you this "they don't". Also everyone is so concerned about vibration, what do you think the hydraulic belt tensioner is for. When we replace a crank pulley its not balance to every engine.

I assure you I have a lot of experience in balanced crank pulleys and they need to be balance and checked to over the max rpm that the engine is expected to rotate. It does not need to be balanced on the actual crank assembled in the engine. How do you think cranks get balanced? In the engine with the rods and crank pulley on it? No. To balance a crank pulley is the same way. They mount it on a machine and spin it and balance as needed. Many oem crank pulleys have little round spots on the face that has been drilled into them. This is where they drill to remove material to balance the pulley. You see this more on pulleys that are dampened then a solid cast pulley from the factory. If the aftermarket companies that make the pulleys don't make sure they are balanced in quality control before it is finished then they aren't doing their job. I assume they do but you would have to ask whoever you are buying one from.

I have built many cars that require modifications to the crank pulley to fit in an engine bay like removing an un-needed section like for A/C. We send the crank pulley to the machine shop and they mill off the section that is not needed and we make sure they balance it as well just like balancing a crank.

[20valvewynn83]

Originally Posted by jdmitr

I assure you I have a lot of experience in balanced crank pulleys and they need to be balance and checked to over the max rpm that the engine is expected to rotate. It does not need to be balanced on the actual crank assembled in the engine. How do you think cranks get balanced? In the engine with the rods and crank pulley on it? No. To balance a crank pulley is the same way. They mount it on a machine and spin it and balance as needed. Many oem crank pulleys have little round spots on the face that has been drilled into them. This is where they drill to remove material to balance the pulley. You see this more on pulleys that are dampened then a solid cast pulley from the factory. If the aftermarket companies that make the pulleys don't make sure they are balanced in quality control before it is finished then they aren't doing their job. I assume they do but you would have to ask whoever you are buying one from.

I have built many cars that require modifications to the crank pulley to fit in an engine bay like removing an un-needed section like for A/C. We send the crank pulley to the machine shop and they mill off the section that is not needed and we make sure they balance it as well just like balancing a crank.

Yeah I know how it works iv been in the industry for a long time rebuilding engines and maintaining them. You can always balance the crank pulley like you mentioned but it will never be truly balanced to the engine meaning you will always have slight vibration but will never harm your engine. It's just funny how people always talk about pulleys killing engines but very few if any have actually seen it cause damage. Plus normally the ones that go out have many mods. Really I'm not worried about a pulley causing damage especially after seeing a turbo kit slapped on this motor boosting at 20psi with out throwing a rod out of the block.

I do feel people do need to know the risk of running pullies but in the real world they don't cause issue's and that's why they are able to sell so many.

[wlfpck]

This point is argued multiple times on the various Scion forums....


I think this can also help to sum things up. A lot of the guys on ystc are a lot older and have the engineering experience.


http://www.yoursciontc.com/forums/12...lley-info.html

[Crawford]

The actual benefits of a lightweight pulley are so slim that it is not even worth arguing about.

Now if its a smaller diameter pulley to slow down the accessories then there is a gain to be had.

Team Crawford

[RossGA]

Since this motor is internally balanced, the pulley only needs to be balanced 'to itself', I.E, it does not have a counterweight to offset the crank like is common on VW/Audis. The forged crank will be spun up and balanced using drill points before it is installed during the manufacturing process. They are not spinning this motor up and balancing it as a monolithic assembly; that I promise you.

That being said, the only other use of the pulley besides spinning the belt would be as a dampener. After looking at the design of the "dampener" on the stock pulley, it would appear to me that it is there only to isolate devices on the accessory belt from cylinder pulses from the motor and doesn't provide any kind of resonance dampening to the motor itself. The construction is a bit suspect to suggest it has that kind of capability. The dampening surface/zone of the pulley is far too thin to achieve any kind of harmonic dampening, unless the damn thing was spinning 10-15K RPM. I would have to bandsaw a stock pulley in half though to be sure.

What I would like to see however, would be a lightweight pulley that is also reduced in diameter by 5-10%. Then there is a real gain. Most automotive manufacturers "overengineer" the belt system to be able to achieve full alternator output and full AC capacity even below idle. The water pump is irrelevant as it's primary flow determinate is going to be the thermostat.

But dropping the belt speed 5-10% would save accessory life, wear, and get a HP or two back from parasitic accessory drag.

Yes, if you are sitting is traffic with the AC on max, the seat heaters on max, the stereo on max, all lights on, and are rolling the windows up and down, you are not going to get a full charge to your battery..........but I think most if not all situations would be just fine with a 5-10% underdrive. 20% is pushing it, that is when people start having issues.....