2 stroke for drag racing cars?

[Mark Workman]

Taking the scaleability thing to the extreme....

At only .7hp/cubic inch, but 3.6ft-lb/cubic inch, this turbo 2 stroke is definitely compromised to the torque side of the equation, but at .278 bsfc (and other obvious reasons), it is still impressive.

http://people.bath.ac.uk/ccsshb/12cyl/

I know this link has been posted before, but I could not resist.

[Darin Morgan]

All the 2 cycle bikes I had when I was young and have played with through the years (Indian 80-MR50-YZ80-YZ400) had very narrow power bands and when you messed with the compression or porting it just seemed to make them nastier! I have the road rash and broken bones to prove that LOL. I remember taking my YZ400, porting it, lowering the jug to raise the compression and running it on racing fuel and oil. The thing would literally flip you when the power band hit. It was like an off and on switch and made it a bear to ride through the desert. You come up on a burm that you had to have some power to get out of and if you happened to be in the right gear at the wrong time,, you got a ride you where not counting on. I am sure some of that was my fault because I am not a good rider but any power band that acts like an OFF and ON switch is almost unmanageable.

P.S. Yes I am old enough that my fist dirt bike was an Indian 80. They where junk. Why do you think I learned how to work on engines. It was because of this bike. It was always broken!!!

[Larry Sockwell]

Are you possibly mistaken about Cummins 2 cycle engines?Ed

Yes, It was a Detroit 4 cylinder. Too many engines between then and now.

Larry

[Erland Cox]

It is not only the weight of the parts that changes when cylinders get bigger but also the surface to volume ratio. The volume increases with the cube while the surface in which the ports are only increases with the square. In a four stroke engine you can use a bigger bore and shorter stroke but this doesn't work in a two stroke as it would make the ports wide and low and give them even less area. A two stroke likes the same bore and stroke for a roadracer and longer stroke than bore for a motocross bike. You do'nt need to have a powerband like a lightswitch, it all depends on how you make the expansion chamber. Long shallow cones gives a longer more manageable power band. The transfer ports together with the compression ratio also are important for the hit of power. If you take the hook out of the secondary transfers the powerband is smoother. A modern 250 GP bike pulls from 8000rpm to 14000rpm. Even my old Zündapp pulls hard from 7000rpm to 12000rpm and it is piston ported with no reed valve or variable exhaust. It is even aircooled. 21.7 hp from 4.05c.i. I do'nt want a smooth powerband though, I love it when the engine comes on the pipe abrubtely and sends the front wheel sky high.

[putztastics]

I drew a few plans 15 years ago for a two stroke barrel type airplane engine (like a Dynacam) with valves in the double ended pistons and valves in the head. By design (sinusoidal cam) it would have been similar to a two stroke V-8 with a 2-1 reduction unit, perfect for a slow turning prop.

Then I got married and had a family.

[falcongeorge]

I ported and modified 2 strokes for 6 years. The power per CC attainable drops quickly with cylinder size. The drop is unbelievable when you get above 250 CC per cylinder. A similar 250 cylinder will have approx 75% of the power of a 500 CC. Tremendous power can be made at 80CC per cylinder but at that size 427cid would be like 87 cylinders.

The last two-stroke motorcycle I rode, 20 years ago, was a 4-cylinder 500cc Yamaha two-stroke sportbike my buddy smuggled in from Canada. At a smallish 125cc per cylinder (effectively two parallel twins with geared together cranks, not an inline four or V4), it verified your point... really nasty scarey acceleration... a bike as small and light as a 600 four-stroke with the power of a 1300(?)

RZ500. My dad had a first gen Suzuki RG400 Gamma. Berzerker machine. So peaky it took more skill than I had to be quick on it. My dad road-raced extensively in the late fifties-early sixties he had the skill to keep it "on the pipe" he could FLY on that thing. I remember chasing him on a twisty road I was on an FJ1100, by four corners in, he was GONE, couldn't even see him anymore. I'm on a bike with almost triple the displacement and way more grunt, he made me look like a chump.

[Steve.k]

The newer rotax twin 850 cc etec are almost 52 cubic inch. 165hp. Thats 3.17 hp/cube.

[SchmidtMotorWorks]

RZ500. My dad had a first gen Suzuki RG400 Gamma. Berzerker machine. So peaky it took more skill than I had to be quick on it. My dad road-raced extensively in the late fifties-early sixties he had the skill to keep it "on the pipe" he could FLY on that thing. I remember chasing him on a twisty road I was on an FJ1100, by four corners in, he was GONE, couldn't even see him anymore. I'm on a bike with almost triple the displacement and way more grunt, he made me look like a chump.

I had the RG500, it seemed fast until a friend rode my VFR 750 4 stroke and beat it is a drag race. Over and over again.

[SchmidtMotorWorks]

The newer rotax twin 850 cc etec are almost 52 cubic inch. 165hp. Thats 3.17 hp/cube.

That would be an interesting engine to put in a modern bike.

[Steve.k]

Yes and with the new etec technology im not sure why no one has. In the snowmobile world the etecs get as good or better fuel economy than 4 stroke equivalent. My nephew put a 583 rotax twin just over 100 hp in polaris quad. Suicide machine it was.

[SchmidtMotorWorks]

Yes and with the new etec technology im not sure why no one has. In the snowmobile world the etecs get as good or better fuel economy than 4 stroke equivalent. My nephew put a 583 rotax twin just over 100 hp in polaris quad. Suicide machine it was.

I wonder what a scaled up RD400 with the big Rotax would be like.

I think the blocking task is the transmission.
That always seems to be the problem for motorcycles.

[falcongeorge]

RZ500. My dad had a first gen Suzuki RG400 Gamma. Berzerker machine. So peaky it took more skill than I had to be quick on it. My dad road-raced extensively in the late fifties-early sixties he had the skill to keep it "on the pipe" he could FLY on that thing. I remember chasing him on a twisty road I was on an FJ1100, by four corners in, he was GONE, couldn't even see him anymore. I'm on a bike with almost triple the displacement and way more grunt, he made me look like a chump.

I had the RG500, it seemed fast until a friend rode my VFR 750 4 stroke and beat it is a drag race. Over and over again.

Drag racing wasn't even REMOTELY what they were intended for, that's why they had a relatively tall first gear. My FJ would have DESTROYED it in a drag race. Put a few bends in that 1/4 mile, and the 360lb wet weight tells a WHOLE 'nother story...

[ptuomov]

Gas exchange I think limits the rpm of two strokes when the bore size gets bigger, so there’s a rev limiter in there that goes down as displacement increase.

[Kevin Johnson]

The p-value of the null-hypothesis that you would not complete your studies by 2020 ?

Or are you really the reincarnation of Michel de Nostredame ?

985.jpg

[SchmidtMotorWorks]

RZ500. My dad had a first gen Suzuki RG400 Gamma. Berzerker machine. So peaky it took more skill than I had to be quick on it. My dad road-raced extensively in the late fifties-early sixties he had the skill to keep it "on the pipe" he could FLY on that thing. I remember chasing him on a twisty road I was on an FJ1100, by four corners in, he was GONE, couldn't even see him anymore. I'm on a bike with almost triple the displacement and way more grunt, he made me look like a chump.

I had the RG500, it seemed fast until a friend rode my VFR 750 4 stroke and beat it is a drag race. Over and over again.

Drag racing wasn't even REMOTELY what they were intended for, that's why they had a relatively tall first gear. My FJ would have DESTROYED it in a drag race. Put a few bends in that 1/4 mile, and the 360lb wet weight tells a WHOLE 'nother story...

Sort of, riding on 74 near Lake Elsinore, I compared it to my friend 1000cc Yamaha a couple years newer, vastly faster handling bike at least for my riding style.