Don Terrill’s Speed-Talk

Seems to me there are two different approaches to this. You could try and pull some heat out of the piston crown with oil jets. This is often used with supercharged or turbocharged engines. Another completely different way would be to try to reduce the peak combustion temperatures if possible, with...

Gordon P. Blair's "Design and Simulation of Four Stroke Engines" SAE R-186 Page 474 onwards: How to calculate the effect of squish in terms of: squish ratio; squish geometry - bore area, squish area, bowl area, bowl volume, squish band volume etc; squish velocity; squish kinetic energy; c...

There were a number of us who fooled with trenches and chamber/quench pad "fixes" in the late 70's and early 80's in some race programs that were well-financed enough to permit extensive dyno and track back-to-back testing. With the exception of some small improvements in RPM ranges far b...

Too many variables to pick one "best" egt number. Fuel, cam timing, ignition timing etc. EGT's just show whats still burning in the pipe as opposed to exactly whats going on IN the cylinder. Steve, you touched on my question from another thread. Possibly higher compression engines complet...

Hello gents THis does not relate specifically to the grooves...but in Mr. Widmers speedtalk lecture - he specified creating a pulse wave/squish and aiming it to the flame kernal( towards the spark plug area ). I beleive he does this on his "roller pistons?". this interview was outstanding...

basically The higher the CR....the lower the EGTs the Lower the CR....the higher the EGTs So the high compression engines combustion is more efficient using the fuel to make power as oppose to generating heat. Or is the flame still burning in the exhaust of the low compression engine due to poor fl...

It looks like they were using the technology to determine where to add material to assure valve
relief pockets were sound and light enough for today’s race engines.

I noticed Larry Widmer's Super Squish Enhanced-Combustion Pistons on this thread have a very similar Radial Anti Detonation Grooves

viewtopic.php?t=5264&postdays=0&postorder=asc&start=15

Thanks Larry, The reason I’m interested in this is to run high compression with out the cost of high octane fuel. The reduced detonation tendencies and more power is exactly what has attracted me to this idea. The people running these pistons in air cooled engines have nothing but good things to say...

RT can you post a picture of that Honda piston?

strange looking piston

People that post information on other sites say valve timing is critical.

It looks like the idea is to create squish area with the piston dome and the intake valve it self.

Thanks to all that responded.

I was able to confirm Larry Widmer designed the piston for aircooled.net.

The drawing is the basic design the piston has a dome under the intake valve only.

This wiseco piston has radial grooves around the piston top above the top ring land.


What is the purpose of these grooves and how do they work?

Ed-vancedEngines wrote:... You might check the member list and send him a PM. Ed

PM to Larry sent

SchmidtMotorWorks wrote:

Could this be the "Super Squishy"?

Could 13:1 be made with that shape?

I suppose so with a 49cc chamber!

...Be interesting to know what are their minimum piston-to-head recommendations. As you would know, opposed and air-cooled V-dubs and Porsches are noted for substantial expansion from cold to hot. thnx, jv. From another forum For me, yeah I ran/run the squishies... ran them at 12.8:1 on an standalo...