Estimating two-stroke Horsepower
Estimating two-stroke Horsepower
(OP)
I am looking for any equations or "rules of thumb" for calculating theoretical 2-stroke engine horsepower. I don't have access to a 2-stroke engine simulation program. I want to know the max power I can squeeze out of this engine, given the engine's bore & stroke, a tuned pipe, and playing with the port sizes and locations.
Thanks!
jake
Thanks!
jake





RE: Estimating two-stroke Horsepower
RE: Estimating two-stroke Horsepower
But I'm trying to figure out if the port area I have is enough to provide the flow required to produce this amount of power.
In contrast, if the port area is too large, the port velocity will be too low to fill the cylinders in the amount of time they are open. Any advice?
Thanks,
jake
RE: Estimating two-stroke Horsepower
200 bhp per liter with larger cylinders, much more with small cylinders.
If you are working with a single cylinder a look and measurement of a good 80cc motorcross cylinder is a start.
There are better designs that were used for gp racing but it is still hard to get info or a look at the insides.
RE: Estimating two-stroke Horsepower
Cheers
SACEM1
RE: Estimating two-stroke Horsepower
What do you guys know about squish band angles? The squish angle of the head should be roughly 1-2 degrees more than the dome angle of the piston, right? How critical is this with respect to detonation?
Thanks,
jake
RE: Estimating two-stroke Horsepower
If you look at the motorcycle industry, companies like FMF and Pro Circuit make their money off of not necessarily gaining more horsepower from the modifications and pipes they sell, but giving the customer more useable horsepower. The karting guys can get away with narrower power bands and compensate with clutches.
BTW, if you exhaust ports get too big you’ll start catching rings in them.
RE: Estimating two-stroke Horsepower
So is port sizing and timing normally done experimentally and from experience, or is there published data to get baseline numbers? What do these engine simulation programs derive their calculations from?
RE: Estimating two-stroke Horsepower
Port size, as I previously mentioned, is limited to what keeps the top ring from diving into the port. Port shape and flow direction plays a large roll, but with each set of cylinders you are limited with what what you have to work with from the factory. Basic port timing is fairly standard stuff with some room to play around with. You can get fancey with transfer port timing by allowing some to open sooner than others yeilding different flow patterns across the plug.
RE: Estimating two-stroke Horsepower
only new here so let me know if im out of line.
There are a few software programs available for 2 stroke simulations. The one i have been using is call MOTA, from Ian Williams Tuning. Specificaly written for go-karts engines, but will do any 2 stroke. It is also very good for expansion chamber designs.
Ken