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Discussion Starter #1 (Edited)
After the fan belt disintegrating during the track day yesterday we thought about a serpentine belt conversion for the S38

It will mean having to reposition a few engine accessories so they all line up.

We can use some existing pulleys and tensioners from other BMW engines such as the M60.

Hopefully some of these BMW pulleys will be bolt on to the S38 accessories.

I have an M60B40 sitting in the workshop at the moment so we can experiment.

The conversion can be reversible if future generations want to restore the M5 , we put all the bits removed in a box.

What do you think ?

Advantages
It is more efficient than the older multiple belt system and may consume less space in the engine compartment. By using a single, wider belt instead of multiple, thinner belts, the belt may be put under increased tension without stretching. Higher tension reduces slip, which increases belt life and mechanical efficiency. Reduced slip can allow the use of lower-ratio pulleys; this reduces the load on the engine, increasing fuel economy and available power. The tendency for V-belts to "flip over" in the pulley groove (at high RPM and/or when the belt stretches) is eliminated, and a serpentine belt is also much easier to maintain and replace, since there is no need to remove multiple belts in order to replace one of them, although newer adjustable-length V-belts ("link belts") can be put on without having to remove other belts, and their link design also allows a self-tensioning characterisc to reduce the risk of flipping over. Also since only one movable belt tensioner is required all of the peripheral components (alternator, A/C compressor, etc.) can simply be mounted to the engine without the need to swivel.

Disadvantages
The drawback of this single belt is that if the belt breaks or is knocked loose, the vehicle instantly loses multiple critical functions such as the water pump, the power steering pump, and battery charging and becomes instantly unusable due to loss of engine cooling; however, the belt typically gives ample visual warning of impending failure, sometimes even totally shedding several grooves (ribs) while continuing to function normally, though the issue of belt displacement remains.

Serpentine belt - Wikipedia, the free encyclopedia
 

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This sounds like a brilliant plan, I will be following this with great interest! Sod originality, let's have the things as efficient and simple as possible! :D
 

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Discussion Starter #5
I've collected a stack of drive parts and we have a machine shop now but no further progress at the moment

I'm reluctant to do this to GA25324 as it's a 57k km original M5 , it's being saved for GA25388 track car (half share with Taffy) but Taffy and I are not in a position to do this atm.
 

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I have been looking into this off and on, I found someone who had done it on an M30 so it should translate over fairly well.
 

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Discussion Starter #8
I think the belt drives are a weak point and the only thing (to me) that makes the S38 look dated.

There's been a few water pump belt failures on the board.

The serpentine belts give you a lot more warning , you can hear something isn't right at idle
 
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Discussion Starter #9
This quick sketch needs some more idlers for proper belt tension BUT it looks like something can be fabricated using existing bolts on the standard brackets which means the conversion could be reversible if desired.
 

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As you go through this, are you looking at it with an eye towards making a run of unique parts coupled with a list of part numbers for any other items which can be sourced off another car? Sounds like there is decent interest in this (include me on the list).

Thanks,

Eric
 

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Discussion Starter #11 (Edited)
As you go through this, are you looking at it with an eye towards making a run of unique parts coupled with a list of part numbers for any other items which can be sourced off another car? Sounds like there is decent interest in this (include me on the list).

Thanks,

Eric

Other than the adaptors / mounts we want to use parts out of the BMW parts bin , for example the tensioners could come from the M60

Also try and use standard M60 or other BMW belts

It might also be possible to set up the air cond / air pump to take 2 different sized belts , one for daily driving / competition and a longer belt which can be installed for smog / roadworthy tests

,
 
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