dished pistons make more hp than flat top?

[big block fiero]

Originally Posted by Stan Weiss

Matt the reason I ask how you were calculating VE was your 150%.
The effective cylinder volume is the same as swept volume only calculated using the dynamic stroke or stated another way the cylinder volume @ intake valve close.
I use that term on the 2 stroke page because somewhere I found that is what they (2 strokers) use. On the CR page for 4 strokes I call it "Total Volume".

I would not refer to this as being dynamic stroke. If you revolve the crank till the valve closes you then use this static piston position to calculate cranking compression ratio and cranking trapped volume. Dynamic stroke would be if at 6,000 rpms the crank flexes and the rods stretch to give an extra 0.50 piston stroke movement. Other two stroke tuners and a few in my circuit use the transfer port closing period to begin the dynamic stroke reference point as you suggest. Graham bell has suggested that this method got started this way because some of the cheaters have used this dynamic stroke to calculate dynamic displacement so as to justify a compensating increase in displacement that they then keep secret.

When I originally saw the trapped volume in your chart I thought this was taken dynamicly at maximum torque rpm so as to use the ram tuning and enertia to make this dynamic trapped volume bigger. I then thought we could plug in the dynamic compression ratio and volumetric efficiency but I hadn't realized that this number was in cc,s and that it was what I would call chamber volume. now that I know what you are trying to communicate my posts will also start to make a little more sense.

matt

[MilesTugoh]

In this thread the terms reverse dome and dish have been used. A discriptive definition of each would be useful. Thanks

[shrinker]

A dish is when the top of the piston has a shape in it like a soup bowl. you can fill the shape with liquid and it holds liquid when the piston is on the bench. A Dome is the opposite, the top of the piston has extra material added to it to create a bump up into the head chamber. The dome reduces the volume of the cylinder head chamber when it enters it near top dead center. You could create a dome by welding onto the top of a flat top piston, but this is not how its done. Hope that helps.

[DavidHarsay]

A REVERSE dome may be a more complex machined cut-out than a dish... but terms are pretty much used interchangeably.

[Stan Weiss]

Note the cut in the piston and how this is different from a dish which would cover much more of the top.
Lunati LS6 Reverse Dome Pistons (-14cc) 3.903" Bore [L65RT2SD] - $639.99

[rookie]

Originally Posted by Stan Weiss

Note the cut in the piston and how this is different from a dish which would cover much more of the top.
Lunati LS6 Reverse Dome Pistons (-14cc) 3.903" Bore [L65RT2SD] - $639.99

As compared to the two photos here dished pistons make more hp than flat top?

[Stan Weiss]

I guess the next question is when would you use a reverse dome and when would you use a dish?

[HPaddict]

its the trapped volume not swept volume that i was on about in the beginning of this thread. this has been a very interesting topic indeed.