How does SCTA calculate disp. for 2-cycle,as below or ?
Tim Schoeny
Richard Fox wrote:
> Dave and all; To the best of my knowledge 2 stroke engines have always been
> classed by the same bore x bore x .7854 x stroke x number of cylinders. Or
> Pi R squared X stroke X number of cylinders. There has never been a standard
> based on number of turns V power strokes. Rich Fox
> -----Original Message-----
> From: Dave Dahlgren <ddahlgren@snet.net>
> To: Gary Allen <gallen@relia.net>
> Cc: land-speed@autox.team.net <land-speed@autox.team.net>; Dan Warner
> <dwarner@electrorent.com>; Lee Kennedy <leekenn@pacbell.net>; Mike Cook
> <beauty1@hughes.net>; Mike Manghelli <mmanghel@hughes.net>
> Date: Tuesday, December 26, 2000 03:55 PM
> Subject: Re: mazda rotary engine factor
>
> >Gary thanks for replying.
> >The two strokes I agree on completely no question on that.
> >Displacement X 2 as they process twice as much air and fuel
> >as a 4 stroke engine of equal displacement in 2 revs. I had
> >brought this up with Dan Warner a long while ago on this
> >group. But I fail to understand your logic on the rotary.
> >From what i can see your logic is not based on facts at all.
> >It is based on what it looks like rather than how it works.
> >The engine sizes have been historically based on 4 cycle
> >piston engines. That infers that it is the amount of air and
> >fuel that can be processed in 2 revs as this is typical. had
> >you picked the amount of air and fuel that can be processed
> >in 1 rev then you would have had cylinders left over over.
> >had you picked 3 revs you would have been short cylinders.
> >Is an engine that processes 175 cu in of air and fuel in 1
> >rev with 4 cylinders not done yet, the same as a 350 cu in
> >engine in 2 revs and a 525 that processes all the air and
> >fuel in 3 revs? I suspect they are as they are all 350 cu in
> >engines using the standard displacement per 2 revs.. It is
> >just a matter of how you measure them and the only fair
> >yardstick is how much air and fuel in a given # of revs.
> >Just like it is miles per hour and feet per minute and
> >gallons per hour so is displacement per # of revs. Otherwise
> >there is no comparison at all. If you get a fuel pump do you
> >as for a 100 gallon pump or do you ask for a 100 gallon PER
> >HOUR pump???? Is your car is going 150 miles or is it going
> >150 miles per hour.... The relationship of displacement per
> >2 revs has always been inferred and not written out. I am
> >asking for finish writing it out. No more and no less. It
> >all seems very logical to me and ought to to everyone else.
> >I think you have to compare things that are dynamic in a
> >dynamic situation not a static one. What something seems
> >like while stationary has little to do with how it behaves
> >dynamically.
> >
> >In other words.....
> >What you are saying is, if I understand correctly, the
> >rotary is like a 6 cylinder because it has 6 faces total
> >from the 3 rotors. But in only has 2 firings per rev. That
> >means it takes 3 revs to fire them all. Well I have a 4
> >cylinder engine that has 500 cc per cylinder. In 3 revs it
> >fires 6 cylinders... 500 x 6=3000 cc. can I run against the
> >F class records too then? If you do not compare engines by
> >the amount of air and fuel that is processed per revolution
> >then how do you compare them fairly? The simple thing about
> >using that type of comparison is that it is all encompassing
> >and no new rules have to made no matter what type of engine
> >is run. It is the reason that SCCA and FIA use factors of X
> >2.1 and X 2.2 because that is a fair way to compare
> >engines. It also matches by the way the relative amount of
> >power from this type engine also. If I had a 1300 cc piston
> >engine and a 1300 cc rotary I would expect the the rotary to
> >make about twice as much power as the piston engine. A good
> >1300 cc piston engine makes about 220 hp. ask any of the
> >bike guys i bet i am pretty close here. if anything a little
> >conservative. A 1300 cc rotary makes about 360 hp. I have
> >dyno sheets of some of the better ones on hand here. using
> >those #'s it puts the rotary at a disadvantage at X2. If the
> >rotary was truly twice as good it would make 440 hp. with
> >your factor it would be expected to make 660 hp. Does this
> >seem realistic? I suspect not! That is because the engine
> >only has 2 firings per rev and the only place and time that
> >any power came be generated is when there is a firing. The
> >rest is a lot of monkey motion with parts going around and
> >around but no power being generated. I hope to hear back
> >from you on these comparisons.
> >Dave Dahlgren
> >
> >Gary Allen wrote:
> >>
> >> I diagree with your logic. I consider a 2 rotor, 3 lobe rotary engine
> the
> >> equivilent to a 6 cylinder engine with 654 cc in each cylinder for the
> total
> >> displacement of 3924 cc. This is the total swept volume (key term) of
> the
> >> engine just like piston engines are measured. If your recommended logic
> is
> >> accepted, then I would expect the 2 stroke engines to be measured as 2
> times
> >> their actual displacement because they fire on every stroke if one is to
> >> only count number of firings per revolution. Engines that run with an
> >> intermitant combustion cycle should be measured based on their total
> swept
> >> volume, not on the number of firings per revolution. Rotary and 2 stroke
> >> engines already have an advantage because they get more power strokes per
> >> revolution that the 4 stroke engines.
> >> Gary Allen
> >> ----- Original Message -----
> >> From: "Dave Dahlgren" <ddahlgren@snet.net>
> >> To: "Gary Allen" <gallen@relia.net>
> >> Cc: <land-speed@autox.team.net>
> >> Sent: Thursday, December 21, 2000 2:20 PM
> >> Subject: Re: mazda rotary engine factor
> >>
> >> > I did not even mention in my last reply what the issue
> >> > really is with the mazda rotary factor. It is currently
> >> > engine displacement times 3 for the class it has to run in.
> >> > This does not represent how the engine really works. it
> >> > takes 3 rev to complete 1 cycle for 1 rotor face. Typical
> >> > there are 2 rotors. This gives you 2 firings per rev the
> >> > same as a 4 cylinder piston engine. Each rotor face is 654
> >> > cc in a mazda 13b for example. That means that it processes
> >> > in 2 revs 654 X 2 rotors X 2 revs=2616 cc of air and fuel.
> >> > Exactly the same as a 2616 cc piston engine. Currently this
> >> > engine has a rating of 1308 X 3=3924 cc. I suspect it had to
> >> > do with the 3 faces on the rotors so everyone said just make
> >> > it times 3 or that it looks like it ought to be X 3....This
> >> > does not seem fair and reasonable to me. SCCA and FIA both
> >> > use an engine displacement Factor of just over 2 to adjust
> >> > the size of engines built like this when comparing them to
> >> > piston engines. In essence treating them the same as every
> >> > other 4 stroke engine by sizing them according to how much
> >> > air and fuel can be processed in 2 revs.
> >> > I would appreciate your thoughts on this matter
> >> > Dave Dahlgren
> >> >
> >> > Gary Allen wrote:
> >> > >
> >> > > I am not on the landspeed list but did know about the rule change
> >> suggestion
> >> > > from the rules meetings. It was rejected at the preliminary meeting
> >> because
> >> > > there was no data supporting the change. I am not sure where the
> >> request
> >> > > even came from and also not familiar with the current factor history
> or
> >> > > where it came from. Dan Warner is th best authority on the subject
> and
> >> its
> >> > > history.
> >> > >
> >> > > What is the issue / question? Gary
> >> Allen
> >> > > ----- Original Message -----
> >> > > From: "Dave Dahlgren" <ddahlgren@snet.net>
> >> > > To: <gallen@relia.net>
> >> > > Sent: Monday, December 18, 2000 1:33 PM
> >> > > Subject: mazda rotary engine factor
> >> > >
> >> > > > Wes Potter suggested i drop you a line about the current
> >> > > > dispalcement factor for Mazda Rotary engines.. Have you been
> >> > > > following the land=speed e-mail on this or do i need to
> >> > > > forward a bunch of it to you?
> >> > > > Dave Dahlgren
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