autogyro wrote:I cannot agree Chris when you say that comparisons cannot be made between engines of very different design concepts.
Then you must be comparing them in a very unscientific way. With multiple variables you cannot attribute what components cause gains and what cause losses. Basically you know what the differences are but not why they are different.
This is common sense, when you test something you change one thing only at a time and measure the difference.
You cannot compare a 4 stroke naturally aspirated poppet valve engine to a 2 stroke boosted sleeve valve engine and conclude anything meaningful about specific components. You can conclude that one package is better based on specific criteria, such as power to weight, power per volume etc.
So unless you are suggesting basically using a mini Crecy for an F1 engine and not just the sleeve valve arrangement, then a comparison is fair. If you are comparing both and using the Crecy to site an example of how superior a sleeve valve is the comparison is meaningless.
Even then you've got to look at the gains and weigh them up against the disadvantages. The BMEP performance of that setup is inferior to the boosted F1 engines of the 80's and only slightly higher than those of today. From what i've read the BSFC is higher for a sleeve valve than the equivilant poppet valve, and a 2 stroke doesn't burn as well as a 4 stroke.
So the idea is not just from a power, but from an emissions point of view does the switch have a net gain?
An interesting question to be sure.
rotaryvalveman wrote:is the SAE paper you refer to headed titled, "Rotary Valves for Small Four-Cycle IC Engines", paper number 891793. If so it is sitting on my desk in front of me and was written for the 1989 small engine technology conference in Milwaukee, Wisconsin. If you like I could scan it and send it to you for your review.
The one I saw was newer than that, it was early 2000's, but if you don't mind scanning it i'd love to have a read.
EDIT: As an asside, I love this thread. Makes me wish I was an innovative person who comes up with wacky new ideas, but my skills lie in rigorous analysis (which although important is rather boring).