Cost effective CO2 reduction in the Valve train

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https://www.dsm.com/content/dam/dsm/stan...TI_Dec_2010.pdf

Don't let the CAFE like title put you off, this paper looks at the power losses associated with simply running the cam chain on a Ford Duratorque 4 cylinder diesel, including change of direction friction, and the rubbing on the chain tensioners and guides.

2,000 RPM, the heat generation of the timing chain is of the order of 700W...at 4,000 RPM 1,400W...imagine how quickly a chain would heat up sitting on a 1KW glowing element radiator.

Mentions the heating effect (note no raging fires in the timing chain case), and what carries the heat away.

Plus the frictional and temperature stability differences between some common guide materials.

Conclusion...2.1g CO2/km is available by changing to the better material, for a cost of 1 Euro per vehicle on average....saving the car Company about 200Euro in carbon fines/taxes on a new vehicle sale.
 
It was a good read. I'm not a plastic chain guide fan. Plastic chain guides fail and the damage can be catastrophic. Would running a timing belt create less heat? If replaced before they break, a belt becomes an engine wear item with a defined use interval. Do you still have the 325i?
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Originally Posted By: andyd
It was a good read. I'm not a plastic chain guide fan. Plastic chain guides fail and the damage can be catastrophic. Would running a timing belt create less heat? If replaced before they break, a belt becomes an engine wear item with a defined use interval. Do you still have the 325i?
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Yet well designed ones can be in service 30+ years and hundreds of thousands of miles.

My issue with chains is that as they wear, getting timing back via an offset key is NOT a common practice. MB diesel design has a means of measuring and a set of offset keys, as they're built to last. Will others?

Doing a chain wear and offset fix, plus new plastic guides every 100k would be prudent if longevity is still key. But that's work and at that point, why not have a belt?
 
Originally Posted By: JHZR2
why not have a belt?


Why not have gears? Think some Volvo's had, and presumably they're not alone. The obvious comparison is motorcycle chain/belt/shaft final drive.

I'd guess there is a weight penalty. Dunno how the frictional losses would compare.
 
While interesting, it kinda read like an advertorial which makes sense since the paper was written by DSM who market Stanyl.

I also wonder how much more efficient timing belts are, andI believe they are as they are also insulators and the adiabatic heatingwould be enormousat those power levels.
 
Is there a reason they don't use a hydraulic tensioner with an idler gear in a chain application ? That seems like it would give the best of both worlds.

My Dad's old Willys with the Kaiser engine had gears. If I remember correctly, one was phenolic.
 
My old Alfa with a cam chain uses a tensioner with an idler, but it's not hydraulic. You're supposed to tighten them once in a while (undo the locking nut, push the car backwards while in gear, tighten nut).

This was a twin cam design originating in the mid fifties though.
 
Originally Posted By: Wheel
Is there a reason they don't use a hydraulic tensioner with an idler gear in a chain application ?


The over designed Yamaha XS650 engine used an idler spocket on the tensioner. Inside the timing chest of the problematic GM 3.6 V6, it is always very dry, not much oil in there, and looks like they run hot there. I prefer chain drive, but modern engines using a chain seemed to have missed the point, they need replacement almost as often as a belt.
 
Gears are heavy and have more inertia to spin-up. They are also difficult to manage when they wear - there is no easy way of removing the lash - in a transmission this is less critical than in a valve timing system.

Chains are robust and rarely slip, but do stretch and wear which, even with a tensioner, makes the timing sloppy. They can also be noisy (same for gears). However they are the go-to choice for many motorcycle engines, so must be worth the pay-off.

Belts are quiet and cheap and light and tend not to stretch but need to be installed as a continuous loop and can slip and snap, with both miles and age causing them to deteriorate. Ford's EcoBoost engine brought belt-in-oil to the masses, helping with packaging but making oil/belt compatibility a requirement.
 
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