Dropped valve?

[Engineer]

Air-cooled is ok up to a point, but beyond that you really do have to go water-cooled if you want more power, and meet emissions requirements, this is why BMW made the LC. It is interesting to note that the LC has 'precision cooling' i.e. the cooling system is concentrated around the exhaust valves in in the cylinder head.

I think that the twin-cam was pushing the boundaries of what was practical, perhaps it is sailing just that bit close to the wind and that's why we get the occasional failure - I was always a little concerned when I was in the queue at French motorway tolls with an ambient temp of more than 30C - I am not so worried with the LC.

 

[MattW]

Air-cooled is ok up to a point, but beyond that you really do have to go water-cooled if you want more power, and meet emissions requirements, this is why BMW made the LC. It is interesting to note that the LC has 'precision cooling' i.e. the cooling system is concentrated around the exhaust valves in in the cylinder head.

I think that the twin-cam was pushing the boundaries of what was practical, perhaps it is sailing just that bit close to the wind and that's why we get the occasional failure - I was always a little concerned when I was in the queue at French motorway tolls with an ambient temp of more than 30C - I am not so worried with the LC.

The oilhead motors are actually partially oil cooled (hence the name) and employ the same sort of 'precision cooling' that BMW seem to think they've invented in the LC. The cylinder heads have large oil ways around the exhaust valve and port area - they employ a twin rotor oil pump that has a separate low pressure, high volume feed for the cylinder head cooling.

 

[cookie]

Air-cooled is ok up to a point, but beyond that you really do have to go water-cooled if you want more power, and meet emissions requirements, this is why BMW made the LC. It is interesting to note that the LC has 'precision cooling' i.e. the cooling system is concentrated around the exhaust valves in in the cylinder head.

I think that the twin-cam was pushing the boundaries of what was practical, perhaps it is sailing just that bit close to the wind and that's why we get the occasional failure - I was always a little concerned when I was in the queue at French motorway tolls with an ambient temp of more than 30C - I am not so worried with the LC.

The Bear's bike being an 09 is unlikely to have been a twin cam. all the valve issues i've heard of are on the earlier models.

 

[MattW]

The Bear's bike being an 09 is unlikely to have been a twin cam. all the valve issues i've heard of are on the earlier models.

Good to hear as I've just bought a twincam

 

[Engineer]

The oilhead motors are actually partially oil cooled (hence the name) and employ the same sort of 'precision cooling' that BMW seem to think they've invented in the LC. The cylinder heads have large oil ways around the exhaust valve and port area - they employ a twin rotor oil pump that has a separate low pressure, high volume feed for the cylinder head cooling.

Without getting too technical oil is nowhere near as effective at carrying away heat as water.

 

[MattW]

Without getting too technical oil is nowhere near as effective at carrying away heat as water.

Get as technical as you want, my MSc focused on computational thermodynamics and I spent ten years in research modelling heat transfer in composite materials.

I was just pointing out that a major component of the cooling on oilhead motors is achieved through oil cooling not just 'air' as stated earlier.

 

[Delboy777]

Get as technical as you want, my MSc focused on computational thermodynamics and a spent ten years in research modelling heat transfer in composite materials.

I was just pointing out that a major component of the cooling on oilhead motors is achieved through oil cooling not just 'air' as stated earlier.

Touche !!

 

[Engineer]

Get as technical as you want, my MSc focused on computational thermodynamics and a spent ten years in research modelling heat transfer in composite materials.

I was just pointing out that a major component of the cooling on oilhead motors is achieved through oil cooling not just 'air' as stated earlier.

Then you will know that specific heat capacity of water is much higher than that of oil, so it is much more effective at cooling the exhaust valves than oil (for a given flow-rate and radiator size). My premise is that the air/oil cooled bikes are easier to overheat than the LC, particularly in hot weather or if operated with little air-flow over the exhaust ports - BMW know this and water cooling has allowed the exhaust to now exit downwards instead of forwards making for a better overall engine design.

 

[Ex-Call Centre Chimp]

Don't get too technical, I failed 'O' level physics.

 

[Beemerman59]

BMW know this and water cooling has allowed the exhaust to now exit downwards instead of forwards making for a better overall engine design.

Purely out of curiosity as I only went to Art College and spent most of that time hallucinating, why does having the exhaust exit downwards rather than forwards make for a better engine design?

 

[JohnnyBoxer]

Purely out of curiosity as I only went to Art College and spent most of that time hallucinating, why does having the exhaust exit downwards rather than forwards make for a better engine design?

Made me chuckle

 

[RedRick Esq.]

Then you will know that specific heat capacity of water is much higher than that of oil, so it is much more effective at cooling the exhaust valves than oil (for a given flow-rate and radiator size). My premise is that the air/oil cooled bikes are easier to overheat than the LC, particularly in hot weather or if operated with little air-flow over the exhaust ports - BMW know this and water cooling has allowed the exhaust to now exit downwards instead of forwards making for a better overall engine design.

I seem to recall something about specific latent heat ! What is the difference?

Purely out of curiosity as I only went to Art College and spent most of that time hallucinating, why does having the exhaust exit downwards rather than forwards make for a better engine design?

Same question from me

 

[MattW]

Then you will know that specific heat capacity of water is much higher than that of oil, so it is much more effective at cooling the exhaust valves than oil (for a given flow-rate and radiator size).

Yep, I'm fine with all that and don't dispute that comparing like for like, watercooling is generally more effective than oil.

My premise is that the air/oil cooled bikes are easier to overheat than the LC, particularly in hot weather or if operated with little air-flow over the exhaust ports - BMW know this and water cooling has allowed the exhaust to now exit downwards instead of forwards making for a better overall engine design.

This, I'd dispute.
Surely facing the exhaust port directly into the airflow will improve air cooling of the exhaust port area (which even on an LC is still a component of the overall cooling regime)?

I thought the redesign of the induction and exhaust paths was to do with rationalising the overly complicated valve actuation design in the TC (skew ground cams, inlet and exhaust shared on cams etc) and improving gas flows?

Water cooling also makes for much quieter engines which helps meet noise regulations.

 

[MattW]

I seem to recall something about specific latent heat ! What is the difference?

The specific latent heat of a substance is the amount of heat energy required to phase change (ie melt / boil it etc). It's different for different substances and for different phase changes in the same substance. Not usually a factor in automotive engine cooling unless you're specifically extracting energy by boiling the coolant.

 

[RedRick Esq.]

The specific latent heat of a substance is the amount of heat energy required to phase change (ie melt / boil it etc). It's different for different substances and for different phase changes in the same substance. Not usually a factor in automotive engine cooling unless you're specifically extracting energy by boiling the coolant.

I am now much the wiser !

 

[MattW]

I am now much the wiser !

Happy to help

Now you know how fridges work

 

[RedRick Esq.]

Now you know how fridges work

Trust me on this

No i dont !!

 

[Engineer]

Yep, I'm fine with all that and don't dispute that comparing like for like, watercooling is generally more effective than oil.



This, I'd dispute.
Surely facing the exhaust port directly into the airflow will improve air cooling of the exhaust port area (which even on an LC is still a component of the overall cooling regime)?

I thought the redesign of the induction and exhaust paths was to do with rationalising the overly complicated valve actuation design in the TC (skew ground cams, inlet and exhaust shared on cams etc) and improving gas flows?

Water cooling also makes for much quieter engines which helps meet noise regulations.

Water-cooling of the hottest part of the engine has allowed them to improve the gas flow - this is what BMW said in their original press release for the LC (I downloaded a copy when I bought my LC back in March 2013) - the air-flow around the engine will be complex but they indicated that the exhaust was better cooled by air when forward facing - I guess that did their analysis.

P.S. the lC certainly isn't quiter than my twin cam, it clatters quite a bit more! but the water jackets is only around the valves not the rest of the engine.

 

[Engineer]

Please excuse the grammar and spelling - I am trying to post on here while at the same time do some heat sink tests and calculations on an enclosure design for a new product and it is currently getting too hot! - so I am thinking of changing the design from stainless steel to aluminium - alumininium has a far higher thermal conductivity than steel or iron, perhaps that's one reason why engines are made from aluminium alloy (apart from being lighter)

 

[Deleted account 211025001]

Water-cooling of the hottest part of the engine has allowed them to improve the gas flow - this is what BMW said in their original press release for the LC (I downloaded a copy when I bought my LC back in March 2013) - the air-flow around the engine will be complex but they indicated that the exhaust was better cooled by air when forward facing - I guess that did their analysis.

......................

In those same press releases they also claimed the following:

The 6-speed gearbox of the new R 1200 GS was also redefined to meet the demand for light, precise shifting and optimum gearshift connections so as to achieve excellent riding dynamics

Do you believe everything you read?

Andres