Alternator short belt clearance

[exlxdx]

So I installed a short belt to bypass my A/C compressor and it kind of touches by like a nanometer, it's all flush with the compressor pulley it just touches under load but BARELY.

Probably okay, right?

[johnl]

Possibly OK, possibly not. Personally I wouldn't want the belt to ever touch something it shouldn't be.

But why are you trying to bypass the compressor? The compressor won't drag on the motor unless the AC is switched on, and the drag caused by the bearing in the clutch when 'idling' won't be any more than a tiny %age of a miniscule %age of the engine power...

[exlxdx]

Possibly OK, possibly not. Personally I wouldn't want the belt to ever touch something it shouldn't be.

But why are you trying to bypass the compressor? The compressor won't drag on the motor unless the AC is switched on, and the drag caused by the bearing in the clutch when 'idling' won't be any more than a tiny %age of a miniscule %age of the engine power...

i had to get a new belt since one of the pulleys is wobbly and the mechanic had to do a hack job to fit my new alternator. i use the mechanic for alternator because sometimes you get bad ones and then you're up sh** creek when you're poor like me.

anyway some idiot broke the tension bolt/bracket and bolt so i went to the junkyard to get the bolts and bracket to do it right

the pulley for a/c looks kind of wobbly when i spin it without the belt but it only BARELY touches and it still sits flush (just touching upside-down since the bottom of the belt is touching the top part of the pulley).

they had to tighten the old belt to all hell to get the alternator to even function due to the wobblypulley and it squealed like hell until it warmed and i figure with winter coming and my system needing to be evacuated and charged since it doesn't work very well to begin with, a/c isn't very important.

[wildBill83]

Try and get washers between the block and compressor to space it out further. Those belts are meant to be used without a compressor.

[marneus901]

Possibly OK, possibly not. Personally I wouldn't want the belt to ever touch something it shouldn't be.

But why are you trying to bypass the compressor? The compressor won't drag on the motor unless the AC is switched on, and the drag caused by the bearing in the clutch when 'idling' won't be any more than a tiny %age of a miniscule %age of the engine power...

You do know the properties of physics and know that when you shorten the belt, you're shortening the circumference distance that the engine torque has to travel (figure running 2/3 pulleys is 33% less distance). You're not necessarily gaining horsepower on paper, but your throttle and acceleration response is much faster. This has also been a somewhat of a known method for making cars track ready. But yes, you should remove the A/C compressor when shortening the belt; under high torque, the belt is under high tension again the pulley, as well as it will be turning the compressor the wrong way.

[wagon-r]

You do know the properties of physics and know that when you shorten the belt, you're shortening the circumference distance that the engine torque has to travel (figure running 2/3 pulleys is 33% less distance). You're not necessarily gaining horsepower on paper, but your throttle and acceleration response is much faster. This has also been a somewhat of a known method for making cars track ready. But yes, you should remove the A/C compressor when shortening the belt; under high torque, the belt is under high tension again the pulley, as well as it will be turning the compressor the wrong way.

Engine torque is what occurs at the crankshaft. Belt length has no effect on this.

[marneus901]

Maybe the case if we are in a perfect frictionless world; however we are not. Having the compponent there regardless if its running or not robs power. Plain and simple.

[wagon-r]

I agree that components rob power. But the length of the belt has virtually no impact on this.

[marneus901]

Yea I should've worded differently or used a diff example.

[johnl]

You do know the properties of physics and know that when you shorten the belt, you're shortening the circumference distance that the engine torque has to travel (figure running 2/3 pulleys is 33% less distance). You're not necessarily gaining horsepower on paper,

The only power loss that can be associated with a longer belt running around an 'extra' pulley (that isn't driving anything, i.e. AC switched off) is the miniscule friction in the pulley bearing, and the power it takes to 'bend' the belt as it wraps around the pulley. With thin 'flat' belts this is pretty much immeasurable, it certainly wouldn't be enough parasitic loss to show up on a dynamometer. 'V' style belts do take a bit more power (than 'flat' belts) to 'bend' around a pulley, but it's still not enough to even think about.

If we want to get really anal about power loss associated with belts, then the longer the belt is the more mass it has so the more inertia it has, so the more energy is required to speed it up as rpm rise, so greater parasitic loss (but only when accelerating, no effect at steady rpm). The pulley itself will also have mass and inertia, so similar deal if there is an 'unnecessary' pulley. But really, if we were to put a number on power loss caused by the belt and an idling pulley there would be a zero at the front, a decimal point, then a line of more zeros, then a digit...

but your throttle and acceleration response is much faster.

Placebo...

This has also been a somewhat of a known method for making cars track ready.

For racing it's just good practice to remove anything unnecessary, because of weight and deleting something that might fail and cause other problems. You'd remove the AC because it's heavy. You'd then use a shorter belt because you'd have to.

But yes, you should remove the A/C compressor when shortening the belt; under high torque, the belt is under high tension again the pulley,

The torque at the crank has no affect on the belt tension. This is only a product of the drag caused by the component being driven by the belt. If the AC is switched off then it's a non issue.

as well as it will be turning the compressor the wrong way.

?

Regards,
John.

[marneus901]

Touch'e
A/C turns the wrong way with the shorter belt; I noticed it too when doing this and I felt that having something like that going reverse isn't good.

[johnl]

Touch'e
A/C turns the wrong way with the shorter belt; I noticed it too when doing this and I felt that having something like that going reverse isn't good.

?? You'd only fit a shorter belt to delete the AC compressor, in which case if still fitted the compressor wouldn't turn in any direction, only the alternator would turn.

The only way the compressor pulley could rotate (with a shorter belt by-passing the compressor pulley) would be if the back of the belt were rubbing on the AC pulley, in which case the belt is definitely contacting the pulley too hard (even if only lightly). It's to do with potentially damaging the belt, it won't affect the pulley or the compressor.