Archives

It suprises me that with the technology that they are employing with new "clean diesel" technology, that there hasn't been any real rumblings from the two stroke engine. They are cheaper to build, easier to run, and have ~ almost twice the power of a same size 4 stroke engine due to the virtue of a power stroke every other stroke (instead of one every four).

The way they are taking particulates out of diesel emissions to comply with Cali regulations, you'd think they could easily do something similar while increasing fuel economy and power. Not to mention reducing engine/component size and weight.

For those who don't know, two stroke engines have had a long standing ban on US roadways due to the amount of polution they create. Basically, the lubrication is mixed in with the fuel in a ratio anywhere from 1:36 ~ 1:50 and therefore burned and emitted moreso than a conventional 4 stroke. Also, there is an issue with blow-by, where some the unburned fuel/oil mix can pass through the combustion chamber and evacuate unburned. In it's primitive form it's a dirty little pig, but it's got one helluva oink!

Hi MAXX:

___You hit it on the head. It’s the emissions. The Two stroke is not only the worst emitting pig of any engine you could possibly run but they are not overly miserly little beasts either. Adding to the negatives is they are not known to run 10’s of thousands of miles without major rebuilds either. The Motocross industry started their transition to 4 strokes well over a decade ago and even though you can purchase a 2 or 4-strokes in most std. class engine sizes (the 2-strokes are still quicker), the emissions regs even for off-road use are catching up with them fast.

___Good Luck

___Wayne

Years ago GM had a CLEAN 2 stroke engine. It did not use mixed gas. It used a small supercharger to blow the fresh charge and clear the exhaust. Made allot of power for its weight, was VERY compact and did fair on fuel mileage, BUT its useful life was 60,000 mi and the test groups did not want a vehical that needed an engine at 60K even if it was easy to change and cheap.

Oil injection 2 strokes are easy to get. Relatively FE. However, have they ever even tried to put a Cat. Converter on a 2 stroke? I know they've solved the TBO problem (as much as any engine running 13K rpm will last). However, to my knowledge basic emissions tech has never been tried on a 2 stroke.

The mid 1980's-84-85 I think- Yamaha RZ350 had a cat com, but it wasn't a big sales success.It made about 39 rear wheel hp weighted about 386 lbs wet,and was slower than the 4 cyl 4 stroke 550's and 600's of the day.I think it did mid 13 second 1/4 miles according to the mags.A 550 Seca-1981 vintage weighed about 435 lbs, made 50 hp,did 12.9 1/4,and probably sold for less.Same story on the 600 Radian-a mid late 80's bike.
Of course folks immediately pulled the stock exhaust, put on aftermarket items,and got about 49 hp(nothing to brag about).Of course they could be made much faster more powerful by adding large amounts of $$$, but they are nothing like the current 4 cyl 4 stroke sport bikes-100+hp.
2 strokes are dead except for lawn implements-weed eaters-and huge 2 stroke diesels in ships(that are supercharged,I think).By the time you clean them up enough to use,they are almost as expensive as 4 strokes,and they still require require ring changes more often if the valve remains a hole in the cyl.
Usually 4 strokes can rev higher,and get "some" of that hp advantage back.By displacement they do have about a 50% advantage, by weight about the same, but by fuel used per hp produced the 4 stroke wins.
BESIDES-RINGDINGS SOUND LIKE %4#&^%!! I never liked the sound!
Huge ships have to get as much power in as small a package as possible,since they make $$ by hauling cargo, not hauling excess engine.Besides,I doubt they have much in the way of pollution regs to meet.They rev so slow that there isn't a heck of a lot of ring wear,I guess.
Charlie

2 Stroke imports were banned or severly limited in 2005 (atleast for mopeds, and most lawn equipment). If you have ever blown a cylinder in a car you'll find out how fast it will foul a catylitic converter. Oil in a cat will cause a clogged, or cover the emissions burning platinum. My friends 50cc moped, gets ~80mpg where as my although heavier 4 stroke 50cc, got 110 MPG. And as previously mentioned without a dedicated lubrication system, you have tons of wear and tear, which requires a rebuild.

On average a 2 stroke will burn 1 GALLON of oil per every 1000 miles. That's when I would change 1 quart on my 4 stroke (which can be recycled, where-as the 2 stroke puts it into the environment).

Kermit,
I'm about 99% certain that the USA spec RZ350 had a catcon.Now, they didn't have them for very long,since everyone pulled the stock pipes off to get the 10 hp or so the aftermarket pipes gave.The canadian spec RZ350 pipes were worth about 7 hp more-maybe they didn't have a cat con? I would guess that 2 stroke oil is a bit easier on cat cons the 4 stroke motor oil-maybe it doesn't have the zinc or other metals that 4 stroke motor oil has; probably doesn't have the buffers that the 4 stroke oil has.
I would bet the stock cat con didn't last very long-maybe 10,000-20,000 miles,and the oem pipes- with the integrated cat con- were very expensive
The RZ350 was a bust here because it was slow.It would have been a bust even if it did give the 50 hp,since the 4 strokes were putting out as much hp with a broader torque curve(which is why they were as fast despite being 40 lbs heavier).
I hope my memory the cat con RZ350 is correct.Sorry if it isn't.
Charlie
2 strokes just sound soooo bad(and I mean bad bad, not good bad).They always sounded broken,and stunk(like diesels,but without the benefit of good FE)

The original SAAB Sonnet was a 2 stroke. If you ever heard one coming down the road you'd never forget it.