Word. Lighter/underdrive Alt, H2O, P/S would be sweet. Even if I do go with manual steering. It looks like a good mass market price is about $200 for a set of 3. Naturally a small run of CA pulleys would be more $$$.Jezz_s13 wrote:I would definately be interested in some ancil pulleys though.
Under drive crank pulley, any one interested?
Re: (Jezz_s13)
Re: (WeldingHank)
you won't feel the vibration, how do you know if you did or didn't have any?WeldingHank wrote:i had an undrive/lightweight solid Al pulley on my previous car. it was an I-4 and i had no problems with vibration at all. if the price is right, i will order one for my CA as well.
That aside I accept that people run these things without problems, I'm just presenting the theory as to why they are viewed by some to be evil.
I won't fit one though, my engine is worth too much time and money to risk.If it was a stocker or a semi fettled lump then maybe, but the line is I can't afford to have any more variables that might rock the already unstable cart.
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redamnavit
- Posts: 445
- Joined: Tue Feb 10, 2004 6:34 pm
First, I'd definitely be more interested in a set of accessory pullies. I can't think of a fair price for the crank pulley that would make it feasible to produce.
The harmonics issue is a wierd one; I've never seen the issue be apparent all across the rev band, just in a few special rev ranges. Its not consistent between engine configurations or size either. This behavior is really obvious on a lot of motorcycle v-twins. For instance, my BMW oilhead is dead smooth all through the rev range, -except- for right around 4000-4500, where it shakes enough to blur the mirrors. I'd imagine the engines that experience problems with solid pulleys are those whose harmonic resonance comes into play in an rpm range where the engine spends a lot of time.
Whatever. If someone is capable of doing an analysis of engine vibration vs. RPM then we can see where it spikes and determine if that spiked area is one of concern.
The harmonics issue is a wierd one; I've never seen the issue be apparent all across the rev band, just in a few special rev ranges. Its not consistent between engine configurations or size either. This behavior is really obvious on a lot of motorcycle v-twins. For instance, my BMW oilhead is dead smooth all through the rev range, -except- for right around 4000-4500, where it shakes enough to blur the mirrors. I'd imagine the engines that experience problems with solid pulleys are those whose harmonic resonance comes into play in an rpm range where the engine spends a lot of time.
Whatever. If someone is capable of doing an analysis of engine vibration vs. RPM then we can see where it spikes and determine if that spiked area is one of concern.
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WeldingHank
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- Car: 1989 240sx CA18DET
Re: (redamnavit)
i also know of someone whos had a pulley on their I-4 car for the last 50K without problems.
Re: (WeldingHank)
Rafi, can you see about the set of 3 pulleys? I think the idea is drawing interest.
WeldingHank, it may not be detrimental at all even in the 100,000 miles of driving range, but it's still costly for a proportionally modest gain. If you were to attach a rod to the stock crank pulley and twist it with your hand and note how much effort it took, then do the same with an object the same total mass as the pulley but the same size and shape as a flywheel, the flywheel would take much more effort. Flywheels have greater leverage against the motor and more weight can be saved by moving to a lighter one. I realize you probably new that, but I pretty much just wanted to say it for those who haven't considered such things.
WeldingHank, it may not be detrimental at all even in the 100,000 miles of driving range, but it's still costly for a proportionally modest gain. If you were to attach a rod to the stock crank pulley and twist it with your hand and note how much effort it took, then do the same with an object the same total mass as the pulley but the same size and shape as a flywheel, the flywheel would take much more effort. Flywheels have greater leverage against the motor and more weight can be saved by moving to a lighter one. I realize you probably new that, but I pretty much just wanted to say it for those who haven't considered such things.
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pulsar gtr
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WeldingHank
- Posts: 559
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- Car: 1989 240sx CA18DET
Re: (pulsar gtr)
i've realized that the flywheel is the best place to save rotating mass weight. but considering the effects of a lightweight flywheel, using both would seem to make things even better.
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Turbogixxer
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Re: (pulsar gtr)
Very correct. The piston/rod wants to go everywhere but where the crank (and rod for piston movement) let it go. Like the link said, the piston actually twists causing the rod to do the same.pulsar gtr wrote:Torsional vibration is a twisting vibration caused by the pulses of each combustion event. The force of the piston causes the crank to deflect ever so slightly in the direction of the force, and when that force goes away the crank ever-so-slightly springs back. At certain frequencies the crank can resonate, making the vibration much worse. This is where the harmonic dampener comes into play
RPM does have a effect on vibration (or the amount of it). As the RPMs increase, so does the vibration. The basic nature of increase RPM will show this.
We will take a one-cyl. engine into example. For one complete cycle (4-cycles for most cars), combustion happens once. As more cycles are added into the same time frame (increase of RPM), the period of time between each combustion cycle decreases. As you can see, this creates more vibration at the same time frame as lower RPM.
All set-ups are different. This is just a general rule.