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I used my lathe to reduce the mass of the crank pulley. I was very reserved when shaving the material off. Consider this beta or stage 0. The idea here to reduce the moment of inertia, or inertial force/resistance. I reduced the mass by 0.46lbs. This changed the inertial force by 0.0821-newton meters (0.726 lb-in). I know half a pound is not going to change a lot but this is beta. My end goal would be to reduce the diameter of the dampener mass. Diameter plays a much larger role in inertial force. For round two, I plan to reduce the diameter by only 5mm. This small change will change the inertial force by another .0502-newton meters (0.444 lb-in). That's not even accounting for weight change, just diameter. That is the equivalent of taking off another 1/4lb. But I care about nm of inertia, not lbs.
For the members who are not so much into engines and engineering, lightening a pulley reduces the resistance of that pulley to rotate. This resistance is called inertia. Inertia is also the mass' resistance to stop rotating as well. Think of a flywheel. Hard to get moving, hard to stop moving. So by reducing the inertia of a rotating part on an engine, you can 'free' energy in the system.
Shows where I'm taking the material from. Again, helps show where the material is being shaved from. OEM lightened
So help me understand your goal. Less turbo lag, quicker throttle response, better gas mileage? I’m impressed that anyone would go to this degree to reengineer part of their engine, but I’m not enough of a gearhead to understand the benefits of a lighter crank pulley.
I did this on my B18C Acura.
Only thing that was lightened was my wallet.
But when i replaced my flywheel to a lightened one, that made more of a noticeable difference.
18lb stock fly to an 8lb Fidanza.
.2 shaved of my 1/4 times and revved much quicker.
So help me understand your goal. Less turbo lag, quicker throttle response, better gas mileage? I’m impressed that anyone would go to this degree to reengineer part of their engine, but I’m not enough of a gearhead to understand the benefits of a lighter crank pulley.
Thanks.
Yes, Yes and Yes.. That is exactly what this would do. Everything can spin up or spin down faster. In lamens, this is revving up or revving down.
But when i replaced my flywheel to a lightened one, that made more of a noticeable difference.
18lb stock fly to an 8lb Fidanza.
.2 shaved of my 1/4 times and revved much quicker.
Well yeah, 10lbs off a flywheel with a radius of probably 12in. That would be an insane change in moment of inertia.
Why didn't Lexus do it? Serious question. I'm sure they purchase metal by the pound, and fight to save weight for CAFE.
So why did they NOT lighten the crank pulley? What downside are they avoiding?
Many (most) mass production engines have heavy flywheels, pullies, etc. The idea in doing this is to help smoothen rpm, gear, etc transitions. Smoothen it for the operator, not the internal assembly. People want to feel like their engine is smooth and linear. Jerks and jarring are not desired. This is why Toyota also controls your true throttle. So when you hammer it, you get a lesser % of your throttle that slowly grows the longer you hold it and falls during shift points. Performance is put to the side for a smooth feeling car.
As for CAFE, this would not affect that much. Once the assembly is spun up, the engine works the same (uses the same energy). This is changing how quickly it can spin up. A good analogy would be flicking a light spinning top compared to a heavy spinning top. Consider they both have the same coefficient of drag. In the end, the same energy is put in and taken out. You can not create or destroy energy. Just transfer it. Energy can be stored though, and that's what flywheels are doing. This is why automakers sacrifice a small amount of efficiency (the time during RPM transition upward) for a smoother running car.
If I worried about warranties every night when I went to bed, I would not have anything fun in my garage. I would hope my degree and knowledge would keep me from doing something that would cause a catastrophic failure. BUT, let's say it did. I would just put my stock pulley back on. Who would know the difference? You're not going to snitch on me, are you?
Many (most) mass production engines have heavy flywheels, pullies, etc. The idea in doing this is to help smoothen rpm, gear, etc transitions. Smoothen it for the operator, not the internal assembly. People want to feel like their engine is smooth and linear. Jerks and jarring are not desired. This is why Toyota also controls your true throttle. So when you hammer it, you get a lesser % of your throttle that slowly grows the longer you hold it and falls during shift points. Performance is put to the side for a smooth feeling car.
As for CAFE, this would not affect that much. Once the assembly is spun up, the engine works the same (uses the same energy). This is changing how quickly it can spin up. A good analogy would be flicking a light spinning top compared to a heavy spinning top. Consider they both have the same coefficient of drag. In the end, the same energy is put in and taken out. You can not create or destroy energy. Just transfer it. Energy can be stored though, and that's what flywheels are doing. This is why automakers sacrifice a small amount of efficiency (the time during RPM transition upward) for a smoother running car.
That makes sense... and probably a "Brand Consistent" decision for the near totality of drivers. And not rocket science for those who prioritize differently. THANKS
If I worried about warranties every night when I went to bed, I would not have anything fun in my garage. I would hope my degree and knowledge would keep me from doing something that would cause a catastrophic failure. BUT, let's say it did. I would just put my stock pulley back on. Who would know the difference? You're not going to snitch on me, are you?
Would have been so un American... not to. But, I am from another world. It's simply when vehicle happens to be at dealership and someone happens to see shaved pulley (for no apparent benefit, actually) - THEY will definitely notice it. Don't you have other circular things around your place to practice your turning skills on?
I'm going to go on a limb and say that a dealer would honestly not even notice that the pulley was milled. In fact if you coated the milled part black it would look stock.
Completely agree with you. I have taken and modified everything I own. If I was concerned with warranty none of my stuff would be personalized or fun.
I have a lightened crank pulley on my STi and it was a nice little noticeable difference. I know you do have to be careful if it's a harmonic balancer built in but I'd be down to try anything to free up any rotational mass that would possibly increase pick up in this vehicle.
If you get it down to a "exact" ratio let us know if this is something that you would provide via a service... I wouldn't mind sending you my crank pulley to have the same thing done.
Clearly, I and Nigel are the same type of person.
I did re-coat it black. Matte black as well so it looks completely stock.
No way in hell a dealership tech will notice it. 1) unless they are working over there, they wouldn't even look. 2) unless they are VERY familiar with the 8AR engine and are carrying around calipers, they could not tell.
Nigel, That's not a bad idea. I would probably wait till I reduce diameter for much higher inertia reduction though.
02-17-19, 06:13 PM
Lightened crank pulley
