Single fan pulley - yes or no?
11-01-2001, 01:59 AM
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Single fan pulley - yes or no?
What are the advantages or disadvantages to switching to a single pulley system for the fan on my 964 engine? Remember, it's in a '77, and I don't have the little rider thingy for the belt. I was checking the belts this weekend, and one looks a bit long in the tooth (new one already on the way) but if I lost the fan-side belt, I wouldn't know until it was too late!
By the same token, is there any advantage or disadvantage to going whole hog and going to the single-drive crank pulley at the same time?
Since the engine will be out next week, this would be the perfect time to do this...
http://www.patrickmotorsports.com/93...ml#lowerpulley
http://www.patrickmotorsports.com/93...html#beltdrive
By the same token, is there any advantage or disadvantage to going whole hog and going to the single-drive crank pulley at the same time?
Since the engine will be out next week, this would be the perfect time to do this...
http://www.patrickmotorsports.com/93...ml#lowerpulley
http://www.patrickmotorsports.com/93...html#beltdrive
11-01-2001, 08:38 AM
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Thom,
The factory went to one pulley/one belt on the 964 cup cars. As I recall, they did something to, in effect, allow the alternator light to be the belt warning light (maybe this is as simple as disabling the wheel thingy). This is something I've thought about too....it's a simpler system like the earlier engines, and one less pulley/belt for the engine to turn. I'd have to go back to the 964 specs, but maybe someone else knows, when converting to one pulley, does that speed up or reduce the alternator speed (as compared to the dual belt setup where the alternator and fan turn at different speeds)?
The factory went to one pulley/one belt on the 964 cup cars. As I recall, they did something to, in effect, allow the alternator light to be the belt warning light (maybe this is as simple as disabling the wheel thingy). This is something I've thought about too....it's a simpler system like the earlier engines, and one less pulley/belt for the engine to turn. I'd have to go back to the 964 specs, but maybe someone else knows, when converting to one pulley, does that speed up or reduce the alternator speed (as compared to the dual belt setup where the alternator and fan turn at different speeds)?
11-01-2001, 03:34 PM
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Thom,
The theory behind the single fan drive for the Euro RS and American "Carrera Cup Edition" cars is that since these cars have no A/C, radio,cruise control, power seats etc. there is less requirement for electrical output from the alternator. The engine fan on a C2 turns at 1.6 times engine speed and the alternator turns at something faster than this, I can't find a factory number but it looks like maybe 2 times engine speed. When you convert to single belt everything turns at 1.6 times engine speed, i.e. the alternator turns slower. So, if you go to the single belt system less average output from the alternator will be available and you may run into a weak battery situation if you usually drive the car with A/C, etc. running all the time. A nice side benefit of going to single belt is the elimination of the fan belt monitor since the alternator light can now perform this function. There may also be a very minor power increase from the engine. Conversion to single belt a no brainer for a track car, somewhat dicy in an electrically "loaded" street car IMHO
The theory behind the single fan drive for the Euro RS and American "Carrera Cup Edition" cars is that since these cars have no A/C, radio,cruise control, power seats etc. there is less requirement for electrical output from the alternator. The engine fan on a C2 turns at 1.6 times engine speed and the alternator turns at something faster than this, I can't find a factory number but it looks like maybe 2 times engine speed. When you convert to single belt everything turns at 1.6 times engine speed, i.e. the alternator turns slower. So, if you go to the single belt system less average output from the alternator will be available and you may run into a weak battery situation if you usually drive the car with A/C, etc. running all the time. A nice side benefit of going to single belt is the elimination of the fan belt monitor since the alternator light can now perform this function. There may also be a very minor power increase from the engine. Conversion to single belt a no brainer for a track car, somewhat dicy in an electrically "loaded" street car IMHO
11-01-2001, 04:08 PM
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What's the ratio for a pre-3.6L car?
I'd heard somewhere the twin-pulley system was designed to reduce noise by slowing the fan.
I don't have A/C, power seats or a big stereo.
It could be an issue when I install my e-Ram
I'd heard somewhere the twin-pulley system was designed to reduce noise by slowing the fan.
I don't have A/C, power seats or a big stereo.
It could be an issue when I install my e-Ram
Originally posted by Cupcar:
<STRONG>
The theory behind the single fan drive for the Euro RS and American "Carrera Cup Edition" cars is that since these cars have no A/C, radio,cruise control, power seats etc. there is less requirement for electrical output from the alternator. The engine fan on a C2 turns at 1.6 times engine speed and the alternator turns at something faster than this, I can't find a factory number but it looks like maybe 2 times engine speed. When you convert to single belt everything turns at 1.6 times engine speed, i.e. the alternator turns slower. So, if you go to the single belt system less average output from the alternator will be available and you may run into a weak battery situation if you usually drive the car with A/C, etc. running all the time. A nice side benefit of going to single belt is the elimination of the fan belt monitor since the alternator light can now perform this function. There may also be a very minor power increase from the engine. Conversion to single belt a no brainer for a track car, somewhat dicy in an electrically "loaded" street car IMHO</STRONG>
<STRONG>
The theory behind the single fan drive for the Euro RS and American "Carrera Cup Edition" cars is that since these cars have no A/C, radio,cruise control, power seats etc. there is less requirement for electrical output from the alternator. The engine fan on a C2 turns at 1.6 times engine speed and the alternator turns at something faster than this, I can't find a factory number but it looks like maybe 2 times engine speed. When you convert to single belt everything turns at 1.6 times engine speed, i.e. the alternator turns slower. So, if you go to the single belt system less average output from the alternator will be available and you may run into a weak battery situation if you usually drive the car with A/C, etc. running all the time. A nice side benefit of going to single belt is the elimination of the fan belt monitor since the alternator light can now perform this function. There may also be a very minor power increase from the engine. Conversion to single belt a no brainer for a track car, somewhat dicy in an electrically "loaded" street car IMHO</STRONG>
11-01-2001, 06:25 PM
#5
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Thom-
The early 2.0,2.2,2.4 and pre 5 blade fan 2.7 911's all had a ratio of 1.3 times engine speed. The 5 bladed fan 2.7 liter 911 was at 1.8 times engine speed. The 3 liter Turbo was at 1.67 times engine speed and I think all 3.0 and 3.2 liter are also at 1.67 times engine speed, but not totally sure. Sounds like you could go to single drive no problem with your car.
The early 2.0,2.2,2.4 and pre 5 blade fan 2.7 911's all had a ratio of 1.3 times engine speed. The 5 bladed fan 2.7 liter 911 was at 1.8 times engine speed. The 3 liter Turbo was at 1.67 times engine speed and I think all 3.0 and 3.2 liter are also at 1.67 times engine speed, but not totally sure. Sounds like you could go to single drive no problem with your car.