nak%archie@att.att.com (Neil A Kirby) (10/26/90)
From: nak%archie@att.att.com (Neil A Kirby) In article <1990Oct24.115220.4396@cbnews.att.com>, Irving Chidsey <chidsey@smoke.brl.mil> writes: > > <From: rsiatl!jgd@gatech.edu (John G. DeArmond) > < > <If one wants to consided this in a different light, consider that 2 stroke > <engines run with oil dilution in the range of 40:1 to as little as 100:1. > > Hmm, how long do 2-stroke engines last compared to 4-stroke engines > of the same horsepower in similar use? I.e., lawnmowers vs lawnmowers or > outboard motors vs outboard motors? The guarantee that came with my new > mower implies that it will last longer than the old one. > > Irv Well, it depends! :-) Would you settle for comparing motorcycles to motorcycles? First lets look at same horsepower. Two stroke motors can have as much as two times as much power per liter than four stroke engines. A more normal figure is 1.5 times as much. How long do they last? Assuming proper oil flow, they both last forever. The normal* two stroke uses total loss oiling and always gets fresh oil if it gets any at all. Four stroke oil condition varies according to how long it has been since the last oil change. Comparing two bikes, the Yamaha RD 250 and the Honda CB350 of early seventies vintage, finds that both machines were reliable as bikes of the day go. The simpler Yamaha was more sporting to ride, and had fewer parts to break. The two had about the same power, although it was very easy to get more out of the Yamaha. The two stroke was better able to stand up to poor maintenence than the four stroke. It was also a very great deal lighter. *This doesn't go into cutting edge two strokes. Many companies have plans for fuel injected, turbo/super charged, wet sump two strokes. They deliver about 100 BHP per liter at 100 lbs/feet of torque, with low emissions. Two strokes don't run hot enough to get into Nitrogen pollution. Fuel injection eliminates high unburned hydro-carbons, the bane of normal two strokes. Exhaust gas recirculation comes for free in the design. Air induction into the exhaust is free also. Supercharging allows the use of a normal wet-sump crankcase and so gets rid of total loss oiling. Now that they no longer use total loss oiling, I suspect that the military might consider them. The Toyota design 3.0 liter V6 produces more power and torque than a 454 cu in V8. The three cylinder Chrysler 1.1 liter produces 110 HP and 100 lbs/feet of torque. It masses about three hundred pounds less than a 1.x liter 4 cylinder four stroke. Sources: Personal experience, Cycle magazine article on new generation two stroke engines. Neil Kirby ...att!archie!nak