With Direct Injection a Reality. Why dont we bring BACK the Two-Stroke Engine? Might be time?

I was reading through one of my old books in my garage and was looking at a 1970 Kreidler UFO 50cc Race Bike. It had a Rotary Valved 50cc engine that produced a WHOPPING 25 Hp or so it claimed. That got me thinking…50cc and 25 Hp? Those are serious numbers to the uninitiated. Lets extrapolate that out a little further. 200cc and 100Hp ! Even further to 1 Liter… 1000cc and 500HP…now if that doesn’t impress you…then you don’t know engines very well and or you haven’t had your daily dose of whatever motivates you. Now of course the Hp may not be linear or be able to hold to the magic 25Hp per 50cc formula to be expanded so neatly…but hell even if its close those are impressive numbers. Also…the fuel consumption would be massive…as it simply takes fuel to make those numbers…and the Two Stroke takes advantage of being able to make a power stroke on each revolution.

This made me think about the abundance of Direct Injected engines that are now currently in vehicles…people barely know what Direct Injection is…let alone how cool it is and also how important it is. Direct Injection is nothing new…as few things actually are these days it seems. The Germans were running Direct Squirt back in WWII in their Aero Engines. Direct injection is serious stuff especially in the gasoline burning environment of engines…it has so many advantages that we havent even begun to find out how far this technology will be able to go yet. I am definitely a fan of DI Internal Combustion Engines.

Does DI and computer controls make the Two Stroke engine a newly viable option again? Or is the Two Stroke Dead for other reasons aside from the dirty emissions. As I understand things…meaning…I understand a good bit but by no means ALL…DI should clean up the Two Strokes exhaust emissions by quite a large margin as it was the piston porting that got the 2 Stroke into so much trouble I Believe??

I would be very very interested to see what Honda or Toyota or GM could do with a Modern Take on the 2 Stroke engine…Throw ALL of our current tech at it and see what comes out the other side. I mean what am I missing here? Small displacement…huge power numbers when run in a full bore type of manner… I wonder if the 2 cycle could actually be fuel efficient as well as a power maker? Don’t you guys think its something to look into… I’m sure people far above my pay grade would be doing this if it WERE something to look into. I know that we actually have 2 flavors of Diesel Engine…a 2 and a 4 cycle Diesel. I dont know too much about the Diesel world however…nor why they used a 2 cycle Diesel Over a 4 cycle…or what characteristics were exhibited by these two different power plants. Why make the 2 and 4 cycle Diesel…what were they looking to achieve when they did this? I will need to do some research on this myself.

What am I missing guys? Why don’t the big boys push out an Eco Friendly 2 Cycle? Is it not possible with all the tech we have available today? Wouldn’t it be really really cool to see a FULLY Modern 2 Cycle? I mean I still fire up the 2002 Honda CR250 that is in my back shed…and each time I do…I marvel at the light weight…and the MASSIVE POWER this machine can lay down… If you have never ridden one of the last to be manufactured 2 cycle Dirt bikes…I suggest you give one a little romp… They ruled the world for a good little while for a pretty good reason. LOL

Just another idea I wanted to weigh against the Finer Minds out here in the Car Talk shop…because I know that collectively we “regulars” on this site could probably launch a rocket to the moon if we all put our heads together and received Govt Funding… So I value your collective opinions…

SO…What say you “Regulars” on the Modern rendition of the 2 Cycle?


Way too dirty.

But I like the idea of putting our heads together and getting government funding. The Department of Labor awards many millions in grants for special projects. I once applied for a $2.1million grant from them for a microwave project. Their site has a section that lists all of the available awards. Perhaps a perusal there would prove fruitful.

I admit that I don’t know enough about engineering and so on to be able to provide much of an opinion as to whether this would be feasible or not.

Assuming emissions could be controlled, etc the one thing that might stand out to me would be performance characteristics regarding how the power was applied. I’ve ridden 2-stroke motorcycles and driven SAAB 2-stroke cars.
They rev to the moon and rev quickly with the power coming on in gobs but I don’t know if many motorists would go for that.

The most glaring example I can think of was the old Kawasaki Mach III which I had an opportunity to ride back in the day. It was 500 CCs and was so-so until about 4500 RPM. Once it hit 4500 there was a hard kick in the seat, the front wheel would start coming up, and the eyeballs started smearing. Pleasant to ride? No. There was also the comparatively very short lifespan of the motors to deal with.

The SAABs were essentially the same way; ZING and gone like a runaway Weedeater. If the powerband could be spread properly I suppose it’s feasible; assuming emissions get tamed.

The car makers would have to have a system in place to assure that the drivers kept the oil tanks full and not lead to a trashed engine due to no metered oil.

Too Dirty? Isn’t that what the Direct Inject would cure to a large extent tho? Hmm I havent thought of what to do with the Oil in the fuel yet… I wonder if that couldn’t be eliminated by modern lube systems.

Why would we even need to add oil to the fuel …couldn’t we sort of create a 2 cycle engine with a 4 cycle engines lubrication system? That would solve the oil in the fuel issue…

Hmmmm After a quick search on the topic… MIT is giving it some thought…

After reading that article and looking at the photos…that is pretty impressive and I must admit… I did NOT imagine anything like what I just saw there. Whoa


"I havent thought of what to do with the Oil in the fuel yet"
That’s what we need to government grant for. Three or four million should do it. {:smiley:

As long as there is an area in our funding for a few plots in Costa Rica (For Testing Purposes of course) we should have no problemos… Ha

Here is a moving diagram of the engine in motion… pretty cool eh?


I hate almost everything about a 2 stroke engine. I will pay extra for a 4 cycle engine any day of the week. I even tossed my 2 stroke weedeater in favor of a battery operated model now that the battery lasts long enough to do my yard. I think the sound of a 2 stroke engine is akin to fingernails scratching a chalkboard.

LOL…Really? I never minded the sound tho it can be annoying at 7AM when the lawn team is doing a “Group Blow” of everything around someones home. Then it sounds like an angry swarm of Hornets and is quite annoying. However properly muffled…it shouldn’t be an issue


Want money? Get DARPA interested in it. If you can tap into the $600 million DoD budget, you can get some serious funding.


There are some two stroke designs that have worked for Bombardier in the reinvented Johnson Evenrude line of outboards. Two stroke outboards use direct injection of the oil which minimizes the oil that is used to minimize pollution. They have been certified for use in our lakes and steams. Another possibility is to manufacture a type of oil that when burned, does not give off polutions. Direct injection is just a way of mico managing the combustion with a computer…I don’t see two strokes making a comeback in cars until burning oil after the fact can be made cleaner. Another alternative might be to treat like a diesel and use an expensive scrubber with urea…but, by the time you do all that, what ever two strokes have in lightness advantages, begins to fall away.

Here are some two steoke designs where in marine applications they have unique advantages…but in cas ? I don’t see they are worth the effort. Their simplicity begins to get pretty “complicated” after a while just to make polution standads…these are awesome motors though. The big problem is long term reliability of two strokes compared to four strokes…you can’t get around the lubrication problems they have. That’s why the Mazda Wankel has a problem.

There is no oil in the fuel of direct injection 2 stroke engines that use external charging. I have been curious about the lack of interest in 2 stroke direct injection of gasoline engines for a great many years. It’s such an obvious combination. Of course the phenomenal horse power per liter of dirt bike engines isn’t possible in larger engines due to limited RPMs of longer strokes but relative horsepower to displacement and weight would see a meaningful increase over 4 stroke engines.

It does not seem easily possible to vary valve actuation on a piston port two stroke engine to do what is being done now with four stroke engines to enhance power, fuel economy and minimize pollution. A two stroke might make more power per pound of engine weight but power to engine weight ratio is not normally critical for a land based motor vehicle. Next question: Why don’t small airplanes where power output to engine weight ratio is important use two stroke engines? Could it be reliability?

The Wartburg and I think the Trabant were two strokes. As an ad for a Wartburg says: " If tatty two-stroke engines, plumes of blue smoke, little actual performance and no real comfort are the pillars of a great automotive experience, than by all means do step right up and buy this Wartburg. "

Kinda sums up my view of two strokes.

There is a great deal of difference between externally charged and crankcase charged 2 strokes @Bing. The old Detroit Diesels had a good reputation and a strong following for many years


but they threw in the towel over emissions standards. Horsepower to weight and displacement was significantly greater than 4 strokes. They weren’t over sized chain saw engines.

Agree about the Detroits but they were awful noisy,the Rootes blower itself makes an heck of a racket,after you tame a 2 stroke to 4 stroke specs some of the advantages disappear.Even the old flathead had advantages,but apparently the current crop of 4 strokes are getting pretty close to perfection(maybe its time for something else,super thermal external combustion engines,etc)the infernal combustion engine has had close to 130 years of refinement and development,most of the low hanging fruit is gone.

The bottom end of a DI 2-stroke still needs to be lubricated and that means oil mist mixed into the intake air and getting burned, thus high hydrocarbon emissions: dirty.
“Valve” timing is fixed and far from optimum.

Well, if someone can overcome the problems of oil-burning, decreased durability due to engine parts having to make due with that little bit of oil in the fuel, general fuel inefficiency, and expensive special oil.
Also, the awesome power of those 2-stroke dirtbikes came partly through radical port timing that resulted in a very narrow powerband.

In surfing the net re 2 stroke vs 4 stroke diesels I find that like Chevy and Ford, there are camps of devoted supporters for each and they are quite loyal.

The reduction in moving parts might be worth the effort (much lower manufacturing cost) plus the reduction in weight that comes with lower displacement engines…

Never minded 2 cycle, but in the name of gas conservation there is no longer a throttle control on my mower, sure I would run at a lower speed if I wished, no more, that saves gas how? Changed the oil on the mower yesterday, no more drain valve, pour it out the filler, missed half, if 2 cycle might be logical, given the current state of things I doubt it will happen. Got a computer part the other day, wrapped in a plastic bag, “Remove before using” surprised there was no choking hazard attached. Anyone see the latest gm warings under the hood? looks like it is ok to chop off fingers but not your hand