As a simple solution to the typical supercharged L98 reversed alternator problem, I intend to use a smooth pulley on the alternator. With the smooth pulley, the rotation direction will be reversed again, so the alternator and fan will be spinning the proper direction.

If I can't find a smooth pulley, I'll just cut the ribs down on a standard pulley.

What makes this possible is that I already have added a grooved idler on the inner alt mount between the alt and the water pump to improve belt routing.

This change should also improve the belt wrap around both the blower pulley and alt pulley and restore the in-out-in belt pattern, killing 2 birds with one stone so to speak.

If anybody has a source for a smooth alt pulley, please let me know.

Here's the existing pulley that I intend to cut down, its a fairly large alt pulley about 2 3/4 - 3" in diameter:

http://store.summitracing.com/partde...p?part=MCH-120

 

I think I can just reroute the belt as-is under the existing pulley.

With the car running and a file, it shouldn't take long to knock down the grooves. No need for a lathe to machine the pulley.

 

I'm not sure how you would get the file in to file down the pulley with the car running. I also don't think you'd want metal shavings getting into your alternator and everywhere else under the hood. You could just take the pulley to a machine shop and they'd to it correctly for pretty cheap.

 

at first I thought brillant.........then ........I'm thinking there will be too much resistance when the alternator is loaded.....it might just slip with a smooth pulley and no tention..........worth a try though.

 

There could be some belt slip.

A 2 sided belt would be the ideal solution, but they aren't available in too many sizes.

The larger alt. pulley diameter will tend to help in this regard. If there is an issue, I'd expect it to be at lower rpm where the alternator torque load could be high. This will tend to decrease as the revs rise.

The alt could draw up to 3 hp at max output, say 1700 Watts (120 Amps * 14 volts), so the low rpm torque loading could be significant maybe as much as 15 lb. ft. at 1000 rpm.

Its unlikey that it will draw this much load very often.

The flat side of the belt will reduce the belt friction by about a factor of 2 or 3, so it will be more likely to slip than the ribbed side.

If it does slip at low rpm, I guess I can drive faster or turn the lights off.

I should be able to get an idea of the limit torque for the flat side of the belt and pulley with a torque wrench easily enough.

If a similarly sized blower pulley can handle a 40-50 lb. ft. and a similar HP draw on the ribbed side at high rpm, I think the flat side should be able to support approx. 3 hp and up to 15 lb. ft at low rpm.

Of course, belt wrap angle is also a factor since it influences the tight and slack side tension ratio. The difference between the tight side and slack side tension times the pulley radius determines the limit torque.

 

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Of course, belt wrap angle is also a factor since it influences the tight and slack side tension ratio. The difference between the tight side and slack side tension times the pulley radius determines the limit torque.[/QUOTE]

ahhh what ........it's a great idea if it works.........I keep a spare with me all the times..........I've burned up two.......the one I have now was rebuilt with heavy duty parts and the biggest rear fan the rebuilder had......but of coruse it's backwards with alittle fan blade tweeking.....the front fan is made by procharger and is better than stock but just bearly...........keep us posted on it.........I'm in the middle of a bracket design and could incorporate the alternator alingment change.

 

lead foot: How long of a belt do you think you need?

I found a few double sided 6 rib belts up to 73 11/32 long, and some even longer double sided 7 rib belts.
Unfortunately not long enough for my application. Maybe you will get lucky.

I need something between and 835 and 845. I have an 845 (85 1/4" outside length belt) on the car currently. I may look into having some custom length belts made up.

I ran it tonight with the belt running under the pulley spinning the alt clockwise.

I decided to keep the grooves for now to let the pulley cut some grooves into the belt. The belt now has some fine lines where the grooves have begun to cut themselves in.

At idle it seemed to be charging ok and didn't appear to be slipping.

However after a few minutes, I noticed that the voltage began to drop into the mid 11 volt range. The pulley also seemed to be pretty hot after I shut it down.

I marked the fan with chalk and restarted. It appeared to be spinning without slip and the voltage improved. I couldn't really see the chalk mark, just a white blur.

Hard for me to tell if its really slipping or if the alt is already on its way out. I need some more time with it to determine what is going on.

In any event, its an easy job to reverse by simply rerouting the belt back over the pulley, so I can compare both routings easily.

 

I'm in the same boat as you........I run a 92 inch

 

I know you guys like AC, and it's taboo to remove AC from a perfectly good working Corvette but I figured if it's hot enough out to need AC, i'll probably be out on the seadoo rather than the vette anyhow. My solution was to move the ALT over to the right side.

http://members.cisdi.com/~anesthes/p...ngine-4808.jpg

I wish I had some suggestions for what you are trying to do, but that was the first thing I did when I started my install. I got the 'supernatural kit' which is the temp kit, and I was like "no i'm not mounting the alt like that!!!".. No way.

Hopefully your plan will work. I'd avoid the double-sided-belt solution though, because then your married to expensive belts every time you break one.

-- Joe

 

Not really related to the issue at hand, but here's a pic of the new impeller from 928Motorsports that I just installed yesterday:

 

Here's a couple pics of the proposed belt routing:





I think its going to slip, but I'll give it a try. I may also try a shorter belt, since I've lost a little tension with this routing. It would be nice if I can get an 835 belt to work since the local stores seem stock it. My current 845 belt is a little harder to find. The 835 is a no-go, so I'm going to try an 840 next, but at least I found a local source for the 845 (AdvanceAuto).

 

I went for a drive tonight with the revised belt routing as shown above. It is working well. No issues with charging or any obvious alternator slip even while running the headlights and fans.

Blower belt slip is also improved. Boost is now steady and hitting 7 psi, it was oscillating somewhat yesterday with the conventional routing and sometimes slipping.

My Ford MAF voltage is now also up to 4.9 volts at the ecm (after the voltage divider) or 5.88 volts at the sensor. Its getting pretty close the 6 volt cap for the Ford sensor.

With the present calibration 4.9 volts is equal to roughly 500 gm/sec. O2 voltage showing 919 mv with a 10 ms injector pulse on 42# injectors at 6,000 rpm, 11.5 Target AFR. Its likely a little on the rich side, but should be safe for now.

After a week, the reverse routing seems to be working well. No issues with alternator slip. The pulley has cut itself into the belt, but this is probably good for grip. We'll see how long it lasts. If it tears up the belt too quickly, I'll cut down the grooves.

I've since backed off on the MAF calibration so that 4.9 volts is now around 420 gm/sec. O2 still looks reasonable over 900 mv in 2nd and 3rd. BPW is down to around 9 ms at 6,000 rpm, roughly 90% duty cycle on the 42s.