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Old 08-11-2013, 05:35 AM   #320
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Originally Posted by ktmmitch View Post
Hey John, great to see some pictures of the progress, engineering from home at it's best, I love to see this!

A few questions I would have coming from a background of tuning supermono, single cylinder road racing engines would be: (and I'm sure you have considered them all but it'd be nice to know the thought process you have been through on them)

1) What are your thoughts on flame propagation and cylinder efficiency with such a complicated piston top? Obviously a flat top piston and well shaped combustion chamber helps with turbulence and combustion rate, but here you certainly don't have that. What did cosworth have to say about this, I mean they have the experience in this field so I'd be interested to hear what their thoughts were?

2) Reducing the valve shrouding on a piston helps to get gasses in and out faster which is particularly important when you have an over square engine, obviously you are fully shrouded during cross over points so you must have your cam design pretty mature? Interested to see your cam profiling and overlaps chosen for the 450 project and will this be different for the different options of engine?

3) Finally, how did you avoid piston distortion during welding and do you intend to heat treat the piston again before using it? Appreciate it's only for demonstration and measurement purposes but still, thought I'd ask.

4) Valve and port sizing is pretty important too, do you have a plan to reduce the port volumes or valve sizes in the future to try and get the gas speed up a little?

5) Balancing? Extra piston weight really does screw with the balancing, will the Cosworth piston weight the same as stock or are you going to get everything balanced?

My intention was not to overload you with questions, just genuinely interested as I'm sure the other engineers amongst us will be.

On the down-drafted CRF450 motors that I used to build, even with a raised piston, we still had to achieve a relatively flat top and put a load of work into the combustion chamber to make this possible. Granted, we were always looking for around 70rwhp from a 450 and I know that's not the goal here.

I for one am really interested to see this project unfold and succeed, probably less for the end result for me personally (if I am honest) but more for the journey that that the guys are going through. The shear determination, lessons learnt along the way and the fun and excitement of a project such as this will make it all worthwhile. I also hope that I get the opportunity to ride the bike one day as I think it'll be a unique little fella. Good luck with it all.

Crack on!
Lyndon Poskitt Racing
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