944 Kevlar™ Timing belts
04-16-2005, 05:12 PM
#48
Burning Brakes
Originally Posted by Bill
Moon hit the nail on the head.
There are several reasons the Porsche engineers used a belt over say gear drive or chain drive. Belts are quieter. Belts are cheaper. But I believe the main reason is, aluminum expands at twice the rate of cast iron. As the 944 engine heat up, it grows and the belt needs to grow or stretch with it. Especially since there is no automatic belt tensioner on these engines. I have taken readings on a hot engine belt with the 9201 gauge, and the belts are over double the cold tension. If a kevlar belt does not stretch, will the tension become way too tight as the engine grows? Or lower the tension and will it be too loose when cold?
Prove to me that kevlar will perform with the engine's expansion rate, and I would be interested.
There are several reasons the Porsche engineers used a belt over say gear drive or chain drive. Belts are quieter. Belts are cheaper. But I believe the main reason is, aluminum expands at twice the rate of cast iron. As the 944 engine heat up, it grows and the belt needs to grow or stretch with it. Especially since there is no automatic belt tensioner on these engines. I have taken readings on a hot engine belt with the 9201 gauge, and the belts are over double the cold tension. If a kevlar belt does not stretch, will the tension become way too tight as the engine grows? Or lower the tension and will it be too loose when cold?
Prove to me that kevlar will perform with the engine's expansion rate, and I would be interested.
Even if belts were substantially quieter, I don't understand the rationale behind that argument. The 944 engine is a relatively loud engine as is, not to mention it is in a sports car, so I can't see a small amount of noise from a chain posing a problem.
I was recently involved in a headgasket project on a 1994 Sundance....the timing belt was twice the width of the 944s--it is a 2.0 liter and it wasn't even an interference engine.
I stand by the idea that the timing belt arrangement in the 944 has inherent flaws that either weren't intially seen or shrugged off as a regular interval item to cut costs by engineers designing the car.
04-16-2005, 07:34 PM
#49
Rennlist Member
Originally Posted by fast924S
The trick is not to find the best T-belt, The trick is making some kinda auto tensioner for the 944/951. This way the belt will always be in spec. Now if some one where to make a auto tensioner kit that had a better belt, Even if it only doubled the maintenance periods on the belt then I would go for it
Rollers that last at least 100k would be nice. Belts usually get sheared because the bearings freeze up. A 60-100k mile belt change would be awesome.
04-16-2005, 07:58 PM
#50
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Originally Posted by Swagger93
Belts are quieter? Explain the loud whine coming from the front of about half of 944s despite good rollers and proper tension. My saab exhibits almost NO noise from the timing chain, the head is aluminum, and the chain is still the OEM at 194,000 miles. The fact that there is no oil-fed tensioner in the 944 is beyond me.
Even if belts were substantially quieter, I don't understand the rationale behind that argument. The 944 engine is a relatively loud engine as is, not to mention it is in a sports car, so I can't see a small amount of noise from a chain posing a problem.
I was recently involved in a headgasket project on a 1994 Sundance....the timing belt was twice the width of the 944s--it is a 2.0 liter and it wasn't even an interference engine.
I stand by the idea that the timing belt arrangement in the 944 has inherent flaws that either weren't intially seen or shrugged off as a regular interval item to cut costs by engineers designing the car.
Even if belts were substantially quieter, I don't understand the rationale behind that argument. The 944 engine is a relatively loud engine as is, not to mention it is in a sports car, so I can't see a small amount of noise from a chain posing a problem.
I was recently involved in a headgasket project on a 1994 Sundance....the timing belt was twice the width of the 944s--it is a 2.0 liter and it wasn't even an interference engine.
I stand by the idea that the timing belt arrangement in the 944 has inherent flaws that either weren't intially seen or shrugged off as a regular interval item to cut costs by engineers designing the car.
04-16-2005, 09:27 PM
#51
Official Bay Area Patriot
Fuse 24 Assassin
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hey guys looking at the tensions I was thinking about something. A kevlar timing belt would never expand when exposed to the heat conditions the common rubber timing belt goes through. I personally would love to have a Kevlar belt too! Just still afraid of even pushing it past 60,000. 
04-16-2005, 09:27 PM
#52
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I seem to remember my mechanic telling me that 994S engines have a self adjusting tensioner...I am not a wrencher so I can't speak from experience or much of anything...
04-17-2005, 04:15 AM
#56
Rennlist Member
Originally Posted by Serge944
All 944 87 and after had a spring tensioner, except the 968, which had a hydraulic unit. They are all less reliable than the original eccentric.
