Zero_to_69

Those of you using on-line calculators, be aware
of the "Piston Type" and "Piston Dome/Dish Volume"

There are several calculators on-line which require
you to input the Piston Type.

If you select "Dish" as the Piston Type, it will
automatically asign a negative value to any number
your enter in "Piston Volume".

If you are accustomed to using calculators that
don't have a "Piston Type" selection, you are simply
asked to enter a negative value for dish or valve relief.


So...if you are used to entering negative numbers,
you'll end up with a POSITIVE result (remember two
negatives make a positive!)

Example:

http://falconperformance.sundog.net/compcalculator.asp

Piston Type = Dish (program assigns negative)
Piston Volume = - 7 c.c.

Result = + 7 cc for dome!

Error = 14 cc of combustion volume. OUCH!


That should clear up any confusion. It turns out
my calculations were off by 1.5 points. That means
I've been running the wrong octane and timing for
the motor.

I'm probably missing out on a little bit of power
because of this.

amean94ta

thats cool i got a assumed 599 hp and 13.6 compression out of the 396 i just built. thats with the 50 cc combustion chambers we milled them too

Mindgame

Yes, little details... gotta be careful that's why I run my own calculations. One thing going for the the falcon performance calculator is that it doesn't just assume a gasket bore diameter.

Can't count how many times I've seen a calculator that just asks for compressed thickness.

-Mindgame

AdioSS

I like the calculators in DynoSim