Piston crowns
Piston crowns
(OP)
I need to test piston crown shapes for better efficiency is there any substance that will handle the combustion temperatures,pressures for short term experimentation purposes, EG a few quick dyno runs. I am after something that can be reshaped & renewed quickly.
Thanks.
Thanks.





RE: Piston crowns
RE: Piston crowns
Agreed aluminium is soft & easy to machine.
If you have any suggestions other than using numbers of pistons i would appreciate your thoughts.
I thought of welding them then machining, shaping etc but i thought they would distort to much, especially if it was done more than once.
They are only cast pistons unfortunately, if you could tell me a welding proceedure that would not distort them i'll give it a go.
I have Mig & Tig welders.
RE: Piston crowns
RE: Piston crowns
Bore is 81mm, i don't think there is a forged piston available for this,it is an ugly dished cast piston that has to be used---rules.
What preheat temp 200-250deg C.
In my original post i should of wrote, piston bowl shapes.
Thanks
RE: Piston crowns
I would think you might need 6 or 8 small screws to do the job.
This would allow you to remove the inserts to modify them.
You would need to think about thread strength of the aluminium at high temps and the inertia over TDC on a trailing throttle during high RPM downshifts.
You might even consider countersunk head bolts from the top, but the heads of the steel bolts might form hotspots and cause detonation. If the bolts were from the top, and the original crowns had thread inserts, you could remove the inserts without removing the pistons.
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pat
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RE: Piston crowns
You have given me a million & one ideas with your post, theres plenty of material to play with. Well done once again.
Thanks
RE: Piston crowns
RE: Piston crowns
molten metal solidifes, then shrinks some more as it cools off.
Welding always = thermal stresses
Welding usually = distortion
Many distortion reducing welding techniques "balance" the stresses against each other to partialy cancel out.
Distorted ring grooves compromise piston seal.
I think my dyno tests with pistons modified by welding might be tests of how distorted the ring grooves became, rather than directly from chamber shape effects.