It would be interesting to see a wide powerband de-stroked DS650, say 112mm bore x 66mm stroke = 650cc. If you could hold near peak torque to 12,000+RPM, you'd be making some ponnies, maybe 90HP on gas.

http://www.motorcycle.com/mo/mccompa...xr600dyno.html

 

This question probably has a very long answer, but is their a simple reason why a 4 cylinder 600cc engine can produce 100hp but our 650cc single only 40hp. Its interesting how low the torque curve is in relation to the HP curve.

 

hmm so this leads me to to a question that I have been trying to figure out for years. I was basically to the point where I would have to build both and just see the results. What is faster a motor built for torque and lower revs or a motor like shown above that has massive HP and so-so on the torque but revs to the moon? I have been told torque gets you there faster but HP keeps you there. I am sure gearing would be done differently and so forth to be able to handle the HP. We have all seen what a street bike motor does in quads and they rip but most of these are 150HP pluss motors. I have to think for us DS sand dragg guys a torque monster is what we need.

 

Demon,

Compare your basic diesel to your basic gas engine. The diesel has lots of low end power, the gas (comparitivly) revs to the moon. The gas engine is faster in the same vehicle.
A street bike engine is pushing almost zero resistance compared to what a DS650 is pushing uphill, in sand. So if you were dragging on street the rev engine would be ideal, but since we drag on high resistance surface we need the torque monster, which lots of hp. I think you've got the right idea.

 

I think alot of people get confused by torque numbers that get thrown around, especially when it comes to trucks. Torque is part of the mathmatical formula the HP,or amount of work that an engine produces in a given amount of time, is derived from. The statement that an engine is really torquey generally refers to an engine that develops its hp peak in a relatively low rpm range. Since the piston and in our case the only piston is what produces the power, more rpms or more opportunity to do the work in a given amount of time will always win out. Clear as mud? Take a guy on a bicycle and have him pedal at 100rpm and another guy on a bike who doesn't quite put out the same effort per stroke but pedals at 200rpm. Guy two puts out more work and if you can gear correctly, the more output wins every time.
Now, rpms rob hp due to drag and inertia of rotating parts + inneficiencies that develop but 2-85% power strokes compared to 1-100% and that winner would once again be obvious. I can't think of an example in drag racing where the rpms of an engine type haven't been pushed to the max while retaining some cost vs reliabiility and efficiency standards.

 

man it is getting fun to have a ds, high rpm low rpm which is faster? good stuff.

 

POTENTIAL.

4 smaller pistons all working together on one crank. each has its own carburetor and own set of 4 valves. These motors are much more effeciant(sp). and because of that they can make more power.




Bigger.

 

and they have a shorter ~60mm stroke which helps hold efficiency at higher RPM.

 

Not to mention crank mass. It would be hard to zing these engines quickly up to 12500 rpm with the existing crank otherwise you have a slow revving enging with no bottom end power.

 

also on a multi-cylinder engine power is actually being produced more often, with less relying on counterbalance - when one cylinder is exhausting another is firing to make power. its more efficient.

and a twin cylinder 2-stroke with opposing cyliners - well not just two stroke, but two opposing cylinders, firing 4 times to the single cylinder 4-stroke's one.... doesn't take alot of cc to get serious power there.

de-stroking the DS brings it closer to the predator motor - there's an interesting piece. same bore as us, shorter stroke, rides like a 2-stroke, gotta get the rpm up to get serious, but when you're there its fun man. those bikes got some good potential too.