ELIMINATOR
Registered user
Just copied this of "ADVENTURE RIDER" thought it might be of interest.
The new R-series engine was envisioned to be just as powerful as the first K series bikes. In other words, approx. 90 horsepower and even a bit more torque…Wow! This was accomplished using 4 valve heads, meaning 2 intake valves and 2 exhaust valves. This arrangement allows much better engine breathing at higher rpm. The air/gas mixture flows into and out of the cylinder head more effectively since there is a larger overall combined valve area. This can be enhanced with a properly tuned intake and exhaust system, which can boost low end power, as well. But there was a problem… a classic 4 valve head makes more power and runs hotter. The valves are close together and there is less cylinder head area to dissipate the heat from the valve seat area into the cylinder head fast enough. Also, in order to help the catalytic converter come up to operating temperature quicker the Motronic control module retards the ignition spark, thus causing a large exhaust flame within the exhaust port and out into the header pipe. This along with the extra horsepower required the use of oil as a medium to transfer the extra heat and keep the engine from overheating. Part of the remedy included using exhaust valves filled with sodium salts (as used in turbo-charged engines) which become liquid when the exhaust valves are at operating temperatures. These valves can transfer heat more effectively into the valve guides. A 5-valve cylinder head runs even hotter. Thus late model cars circulate the liquid coolant for a period of time after the ignition is turned off, to prevent overheating of the cylinder head.
Tidbit: Exhaust valves actually glow cherry red while the engine is running. The color of the exhaust valve (when cold) is actually a much better indicator of fuel mixture than the color of the spark plug.
So, now we've got more power and torque… but how do we get rid of the extra heat?? In a liquid cooled engine it is done by routing more coolant via extra passages around the exhaust port area of the cylinder head. But how do we get rid of the extra heat without the use of a water/ethyl coolant and without adding more cooling fins?? It is the classic problem as seen before, remember??
Using Something Hot to get Rid of That Extra Heat
Since there was oil in the engine anyway, it was decided to use this as a medium to transfer the heat away from the very hot area around the two exhaust valves in each cylinder head. This extra heat could also be used to warm the engine oil after a cold start, and yet the extra heat could be dissipated via oil coolers, which were thermostatically controlled. Additionally, if you inspect the front of the oilhead cylinder, you can see an extra air passage to allow cool air to flow to the hot area between the 2 exhaust valves. More importantly, oil which has just come out of the oil cooler (and is therefore at its coolest temperature) is directed through the oil passages around the exhaust valves. To further enhance the naturally good engine cooling of the boxer design (remember the cylinder heads and cylinders hang out there in the cool air stream), the cylinder head was rotated by 15 degrees forward. This was done to better direct airflow to the exhaust port/exhaust valve area. Of course, with all the need to do this for the above reasons, additional items to make it work were required: 2 oil pump rotors, oil pump drive via an auxiliary shaft, 2 oil pump pick-ups, more oil passages in both the engine crankcase, cylinder heads, oil coolers, etc. But as you can imagine, it was worth the extra effort, for the boxer continued to live on…great!
As indicated before, when in heavy traffic for a long period of time, shut off the engine while waiting for the jam to clear. One indication that an engine is near overheating is that it will get mechanically very noisy…clatter (valves etc).
This concludes our discussion of using air, liquids and a combination of air and liquids to help engines maintain optimum operating temperatures, normally by cooling. Now if we can only cool ourselves off as well. It looks like Jim has been covering this in the Parts section of the newsletter!
The new R-series engine was envisioned to be just as powerful as the first K series bikes. In other words, approx. 90 horsepower and even a bit more torque…Wow! This was accomplished using 4 valve heads, meaning 2 intake valves and 2 exhaust valves. This arrangement allows much better engine breathing at higher rpm. The air/gas mixture flows into and out of the cylinder head more effectively since there is a larger overall combined valve area. This can be enhanced with a properly tuned intake and exhaust system, which can boost low end power, as well. But there was a problem… a classic 4 valve head makes more power and runs hotter. The valves are close together and there is less cylinder head area to dissipate the heat from the valve seat area into the cylinder head fast enough. Also, in order to help the catalytic converter come up to operating temperature quicker the Motronic control module retards the ignition spark, thus causing a large exhaust flame within the exhaust port and out into the header pipe. This along with the extra horsepower required the use of oil as a medium to transfer the extra heat and keep the engine from overheating. Part of the remedy included using exhaust valves filled with sodium salts (as used in turbo-charged engines) which become liquid when the exhaust valves are at operating temperatures. These valves can transfer heat more effectively into the valve guides. A 5-valve cylinder head runs even hotter. Thus late model cars circulate the liquid coolant for a period of time after the ignition is turned off, to prevent overheating of the cylinder head.
Tidbit: Exhaust valves actually glow cherry red while the engine is running. The color of the exhaust valve (when cold) is actually a much better indicator of fuel mixture than the color of the spark plug.
So, now we've got more power and torque… but how do we get rid of the extra heat?? In a liquid cooled engine it is done by routing more coolant via extra passages around the exhaust port area of the cylinder head. But how do we get rid of the extra heat without the use of a water/ethyl coolant and without adding more cooling fins?? It is the classic problem as seen before, remember??
Using Something Hot to get Rid of That Extra Heat
Since there was oil in the engine anyway, it was decided to use this as a medium to transfer the heat away from the very hot area around the two exhaust valves in each cylinder head. This extra heat could also be used to warm the engine oil after a cold start, and yet the extra heat could be dissipated via oil coolers, which were thermostatically controlled. Additionally, if you inspect the front of the oilhead cylinder, you can see an extra air passage to allow cool air to flow to the hot area between the 2 exhaust valves. More importantly, oil which has just come out of the oil cooler (and is therefore at its coolest temperature) is directed through the oil passages around the exhaust valves. To further enhance the naturally good engine cooling of the boxer design (remember the cylinder heads and cylinders hang out there in the cool air stream), the cylinder head was rotated by 15 degrees forward. This was done to better direct airflow to the exhaust port/exhaust valve area. Of course, with all the need to do this for the above reasons, additional items to make it work were required: 2 oil pump rotors, oil pump drive via an auxiliary shaft, 2 oil pump pick-ups, more oil passages in both the engine crankcase, cylinder heads, oil coolers, etc. But as you can imagine, it was worth the extra effort, for the boxer continued to live on…great!
As indicated before, when in heavy traffic for a long period of time, shut off the engine while waiting for the jam to clear. One indication that an engine is near overheating is that it will get mechanically very noisy…clatter (valves etc).
This concludes our discussion of using air, liquids and a combination of air and liquids to help engines maintain optimum operating temperatures, normally by cooling. Now if we can only cool ourselves off as well. It looks like Jim has been covering this in the Parts section of the newsletter!
