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Old 09-15-2011, 01:56 PM   #74
CosentinoEngineering OP
Gnarly Adventurer
 
Joined: Oct 2010
Location: NYC
Oddometer: 183
what to do next...

At the end of the last post we were making a lot of power and scrap parts. There's an old expression that the best engine builders stand head and shoulders above the rest because of the size of the pile of broken parts they are standing on! If that is true I must be standing pretty high!

Anyway, Todd was riding well but the engine refused to give him a long streak of trouble free running to allow us to really dial the chassis in. Lap times were impressive but race performance was lacking due to repeated mechanical DNFs. And still Todd never crashed. Damn.

I knew the engine was an experiment, partially successful, but partially flawed. It drove home yet again that the more existing parts you use the more compromises need to be made. And in an engine a bad compromise is not a good thing. Since this engine was never meant to be the be-all and end-all I was not completely depressed. The engine's purpose was to see if a new water cooled performance head would increase power levels significantly. It did. The fact that I had to make cylinder spacers, dual belt drive systems and a host of other small adapter parts meant the engine was not the most stable assembly. Spinning a 104mm piston at 11000 rpm can cause a lot of movement on the taller than stock cylinder/head assembly. Also, not having a 1:2 gear reduction to reduce the cambelt speeds meant that I needed to operate the belt drive system way outside its intended range. Ducati has an internal jackshaft that reduces the crank speed by 50% to drive the cams. The belt is then only spinning at 1/2 crankshaft speed. Due to my compromised design there was no jackshaft so the belt was subject directly to full crank speed which was about double the max recommended use! While this worked, it lost power both in increased frictional losses and the magnified timing inaccuracies due to the higher belt speeds. Then add in the compromised airbox size and intake restrictions. I clearly had a list of items to redesign.

One area where my adaptation lead to am improvement was in the water cooling system. Being an air cooled engine the Rotax bottom end had no allowances for a water pump. I ended up using a 12V DC booster pump sold by a company in Australia, Davies Craig. The pump was run in a closed loop system controlled by the ECU and a motor driver circuit in the relay board that an electrical engineer friend (thanks, Leo) had designed. This let the pump act as a thermostat to keep the engine at a specific temperature and worked great. The pump has a low current draw and no seals to go bad and in my experience is nearly indestructible. Compared to the dual multi-stage seals in a standard engine driven water pump this was much lower friction. Normal water pumps are designed to provide adequate flow to cool at idle with no airflow to radiators so at higher speeds the water pump is very over-designed. Having the electric water pump be independent of engine speed made it easy to supply the engine with as much cooling as it needed in every situation with no wasted pumping. In the new engine design I have the option of running both cylinder banks in serial, parallel, or completely independent circuits. I'll try completely independent first with the idea that variable independent cooling will allow both banks to run at the same temperature and therefore the same thermal efficiencies, something nearly impossible to do with a traditional cooling system and a V configuration engine.

So, we had run the bike for a couple of years and learned a whole lot on what was breaking and why. What to do next you ask? Easy, I needed to design an engine that would take the Ducati head and provide a rigid and compact mounting and timing structure. It was at this point that Ducati came out with their new 1098 that had an engine that was vastly more production oriented than their previous 999 family. I decided to use the 1098 head instead of the expensive WSB 999F02 stuff I was using and to design a bottom end to suit. Of course I couldn't put a gem like this in the existing chassis that had been extensively modified. I would need to come up with another complete revision, the MK3 which I hoped would be something good and refined enough that I could sell to people.

I made good progress on this front for a while with a nearly complete 3D CAD model of the needed engine parts and a completely updated chassis and suspension that was much more visually pleasing. Then it happened.

Oops, out of time for now, will reveal details in the next post......
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