What happened to the 2 strokes?

[dirtwarrior17]

In ROP we had a T-Rex which is basically a big green 2 stroke diesel dozer so i got to thinking.... why did they stop making 2 stroke diesels?

I still can't figure out why there isn't any gas 2 strokes on the streets. If they can figure em out for outboard's you'd think they would have em for trucks. I know the outboards are horizontally oppossed with a very short stroke for hp but it wouldn't be that hard to make a 2 stroke v8 or v6 with way more power per cubic inch than 4 strokes. Evinrude has basically revolutionized outboards by coming out with the e-techs. The use direct injection efi to make more power and burn cleaner and they developed their own mufflers to keep noise as low as possible. They also burn 64 times cleaner than the 4 strokes on the market today. Instead of scrapping the 2 stroke R and D they poured more into to it and came up with a lighter, faster, torqyer (is that a word?), quieter, cleaner 2 stroke that has all the rest of the 4 stroke and 2 stroke guys kicking themselves in the ass. Why can't they do that for cars and trucks?

Anybody have any explanations? I'm stumped.

 

[adamforsythe]

2 strokes don't have a good high end. Automotive companys / big rig companys will not put 2 strokes in there trucks because of that. Since there is almost no high end your MPG would hurt at high RPMs. The only good thing 2 strokes are good for is racing and pulling heavy loads at low speeds.
Thanks
Adam'

 

[bigjbear]

Two strokes run hotter for a given rpm, they fire on every revolution. But the big reason is many people won't buy diesel cars just because of the incovenience. Do you think those same people would mix their fuel? Now figgure the cost of r & d for a small market and you can see your own answer. Thinking outside the box is good, but the box is there for a reason.

 

[mikey_d05]

2 strokes don't have a good high end. Automotive companys / big rig companys will not put 2 strokes in there trucks because of that. Since there is almost no high end your MPG would hurt at high RPMs. The only good thing 2 strokes are good for is racing and pulling heavy loads at low speeds.
Thanks
Adam'

It's the opposite actually. Because of the fundamental design of a 2 stroke, it produces more power at high RPM's and hurts for low end torque. Usually the only time 2 strokes are used now is on recreational machines where weight is at a premium. Dirt bikes, quads, outboards, things like that where revs are important also.

 

[bdozeraz]

A while back I remember reading about Toyota working on a two strock engine for there cars but they couldn't get it to meet current emission standards.

Brent

 

[tiger9297]

It's the opposite actually. Because of the fundamental design of a 2 stroke, it produces more power at high RPM's and hurts for low end torque. Usually the only time 2 strokes are used now is on recreational machines where weight is at a premium. Dirt bikes, quads, outboards, things like that where revs are important also.

I read an article (I will try to find it and post a link) where two direct injected 2-stroke outboards were compared to two 4 stroke outboards. I think the HP was 135 and 200 IIRC. Anyway, the engines were mounted on identical boats so everything would be equal. The 2-strokes outperformed the 4 strokes in every category: top end, "hole shot" (low end), emissions, fuel economy, etc. The hole shot was what surprised me. Everyone says that 4 strokes have more torque than 2 strokes. I don't think this is true b/c of examples like this (and the fact that I have owned boats, motorcycles, 4 wheelers, etc. all my life). Torque is what launches the vehicle or gets it moving. Think about dirt bikes. You could take a 250cc 2 stroke dirt bike and race a 400+cc 4 stroke dirt bike on a dirt track and kill it. The reason is low end torque. I think the reason we don't see two strokes in cars is because up until now a two stroke was pretty much a "dirty" engine, and they just don't run as smoothly as a four stroke.

 

[dirtwarrior17]

who said anything about mixing fuel? 2 strokes have been oil injected for over 15 years...

2 strokes would be VERY usefull in a truck... yes they fire more but they make the same HP at half the size of the 4 strokes and if you compared two equal size motors one being a 4 stroke and the other a 2 stroke the 2 stroke would have it killed in tq and hp everywhere in the powerband. The whole e-tech speil on my first post was to prove that most of the R and D is already done... they just have to apply it to a car or truck 2 stroke and not an outboard... if you've ever seen an outboard without all the plastic off it looks just like a v6 tipped up. All they would have to do is put it horizontal and stick it in a honda then go from there.

 

[dirtwarrior17]

It's the opposite actually. Because of the fundamental design of a 2 stroke, it produces more power at high RPM's and hurts for low end torque. Usually the only time 2 strokes are used now is on recreational machines where weight is at a premium. Dirt bikes, quads, outboards, things like that where revs are important also.

I think he was talking about diesels but your right.

I think the reason everybody thinks 4 strokes have more torque is simply the dirtbikes... everybody watches the races and hears the announcer talk about the monster torque of a 450 but they never realize it only has more tq because its almost twice the size of the 2 stroke.

 

[mikey_d05]

Well, this conversation could go deeper than it needs to. One of the things that people rarely realize is that torque is also a function of how much rotating mass you have and how much force it takes to stop that mass. The more rotating mass at a given RPM, the more torque is required to stop that mass. If you have an engine with twice the displacement, there is going to be more rotating mass.

I too have seen tests where two strokes outperform four strokes and while smokers do have their place, it's all relative. For example:

Almost all of the boat tests I have seen do not correct for the weight advantage of the two stroke over the four stroke. This can be a significant advantage to the two stroke when it's hung on a recreational craft that's 20-21 feet long and under. Also, as much as they test boat engines, I've rarely seen them prop a four stroke properly. Their different power curves need significantly different props to perform well. Most of the time they use well ventilated and/or racing propellers on both engines. This lets the prop "slip" in the water and the motor wind up faster. This benefits two stroke engines much more since they tend to produce more power at mid-high revs.

I don't watch many dirt bike races so I honestly don't know what the announcers say, but look at racing in general. Your engine is running up and down it's operating range so fast it'll make your head spin. Less rotating mass helps engines revs more quickly. Once again, advantage, two strokes. Combine this with a lighter weight because of less displacement and you have a winning bike.

Go to page 5 on this site: http://www.suzukimarine.com/sr02/images/01/df90115bro.pdf and there is a dyno comparison between two Zuki outboards. One is two stroke and one is four. Below 3,000 RPM's the four wins, between 3 and 5, the two stroke wins. After 5 grand, they're pretty well even, but these are also mid size marine engines. If I could find a comparitive dyno curve from a dirt bike manufacturer, I'm sure it'd say the same thing.

 

[h0nke]

.... why did they stop making 2 stroke diesels?

Emissions and fuel economy. I like the old 92 series Detroit 2-storke diesel's, but man the fuel rack on those things is a bitch isn't it?

I remember one guy in the shop was adjusting the rack and he rotated the motor over by hand with a breaker bar, it cranked over! He was scared but OK.

 

[dyeager535]

I have a sneaking suspicion that even with whatever advances Evinrude has made in 2 stroke technology, the simple fact is, a 2 stroke cannot meet the emissions standards of a comparable 4 stroke, ESPECIALLY when regulated as heavily as automotive applications are.

Stolen off of "howstuffworks":

* Two-stroke engines don't last nearly as long as four-stroke engines. The lack of a dedicated lubrication system means that the parts of a two-stroke engine wear a lot faster.

* Two-stroke oil is expensive, and you need about 4 ounces of it per gallon of gas. You would burn about a gallon of oil every 1,000 miles if you used a two-stroke engine in a car.

* Two-stroke engines do not use fuel efficiently, so you would get fewer miles per gallon.

* Two-stroke engines produce a lot of pollution -- so much, in fact, that it is likely that you won't see them around too much longer.

The pollution comes from two sources. The first is the combustion of the oil. The oil makes all two-stroke engines smoky to some extent, and a badly worn two-stroke engine can emit huge clouds of oily smoke. The second reason is less obvious but can be seen in the following figure: (you don't need this)

Each time a new charge of air/fuel is loaded into the combustion chamber, part of it leaks out through the exhaust port. That's why you see a sheen of oil around any two-stroke boat motor. The leaking hydrocarbons from the fresh fuel combined with the leaking oil is a real mess for the environment.

These disadvantages mean that two-stroke engines are used only in applications where the motor is not used very often and a fantastic power-to-weight ratio is important.

In the meantime, manufacturers have been working to shrink and lighten four-stroke engines, and you can see that research coming to market in a variety of new marine and lawn-care products.

Source

On top of that, even if they DID figure out everything else but the emissions problem, that would be another expensive investment to overcome. You can't just have oil and unburnt fuel going into catalytic converters as we commonly use now.

 

[tiger9297]

All of those facts are true of the older generation 2 strokes. However, the newer direct injected 2 strokes have overcome many of those problems. I love 2 stroke engines. In my opinion they make "fun" power b/c it's power you can feel. BUT, when I bought my 4 wheeler in '97, Polaris only made 3 four strokes and the rest of their models were 2 strokes. Without hesitation I bought a 4 stroke. Point being I think both engines have their place, and both have advantages over the other.

 

[sled_dog]

On a snowmobile give me a 2 stroke anyday. Skidoo has a 1000CC 2 cylinder with Direct Injection now, I really want to ride that beast. My buddy has a YZF 450 Yamaha fourwheeler, that thing is a sick little 4 stroke. Impressed me to no end. Most everyone is leaning away from 2 strokes(save for the boat industry I guess), I'd expect to see their demise in the not too distant future.

 

[ryoken]

not too many places to buy 2-stroke outboards anymore.. pretty sure they're outta production from all manufacturers these days.. i know they've been illegal in Comufornia for years now..

the 4 strokes are better in every category except weight.. heavy sob's...

 

[desertrat67]

the Army's HETT and HEMTT use a detroit 8V92TA(8 cyliders, V configuration, 92 CI per cylinder, Turbo charged, Aftercooled), which is a 736 c.i. 2 stroke diesel. I just went through a course learning ho to trouble shoot these big boys. THey are TURBO CHARGED AND HAVE A BLOWER!! Turbo sits on top of the supercharger. They make a good amount of power. The HETT is used to tow the M1 Abrams main battle tank, and the HEMTTs range from 11-16.5 tons for cargo trucks and a little more for the wrecker.

 

[rjfguitar]

A 2 stroke 250cc dirt bike you say? What the heck you going to do with that weed wacker motor?

How about 800 and 900cc's of 2 stroke power. 150+HP a piece. Put the pansie 250cc's back in the trailer.

The main reason why 2 strokes are dying off is because of emmissions and fuel economy. Even with today's latest two stroke tech. (like our snowmobiles pictured) they will not run near as clean as a four stroke machine. You HAVE to have oil in the gas, obviously, or it will burn up. That oil will smoke no matter what.

Out of all the recreational big boy toys out there, snowmobiles need 2 stroke power more than anything else. Jet skis, ATV's, dirt bikes, nothing can match the terrain of deep mountain snow country where you drop in to a gulley 20 feet deep at 2,000RPM's and shoot almost strait up the other side and ext the top of the gulley at 8,000RPM. I would bet all my money that the last production two stroke engine ever built will be in a snowmobile, or a chain saw. The few turbo'd 4 stroke sleds out there just can't run like the two stroke sleds.

 

[muscle]

8V92TA Detriot

Good fire truck engine

 

[gravdigr]

I would bet all my money that the last production two stroke engine ever built will be in a snowmobile, or a chain saw.

My money is on a string trimmer. And I'm here to tell ya that the 2 cycle is crap for longevity. We burn through 3-4 trimmers every season. 31cc of weed shredding power

And it is my understanding that the 2 cycle shines in high rpm situations simply due to it's design. But when I put a 250cc 2 stroke 4 wheeler next to a equal sized 4 stroke with the same gearing and hook them up to a load...well you have to rev the piss out of the 2 stroke to pull the load, 4 stroke made power from idle. 2 stroke didn't really make power until you hit the power band, then hold on to your ass.

 

[rjfguitar]

My money is on a string trimmer. And I'm here to tell ya that the 2 cycle is crap for longevity. We burn through 3-4 trimmers every season. 31cc of weed shredding power

And it is my understanding that the 2 cycle shines in high rpm situations simply due to it's design. But when I put a 250cc 2 stroke 4 wheeler next to a equal sized 4 stroke with the same gearing and hook them up to a load...well you have to rev the piss out of the 2 stroke to pull the load, 4 stroke made power from idle. 2 stroke didn't really make power until you hit the power band, then hold on to your ass.

The trimmer is done my friend. I may be wrong but the majority of trimmers now are 4 stroke. Right?

I will agree on longevity with a 2 stroke, with small dinky engines. Our sleds will go for a LONG time. I've seen a Yamaha Phaser 480 with 10,000miles on it. I also saw a Polaris RMK 700cc with 16K on the original motor. That like 160k in auto terms.

A 4 stroke 4 wheeler will always out pull a 2 stroke in the lower RPM's. Like you said, 2 strokes make their power in the upper RPM band. My 800cc Polaris Liberty in my Vertical Escape sled makes peak HP at 8,000RPM. The great thing about snowmobiles is there is no "gears" to shift. You pull the throttle wide open and the clutches that consist of a helix and sintrifical clutch allow the engine to rev to 8K almost instantly. Kind of like a torque converter, just much more extreme. It's an awesome feeling to slam the throttle to 8K and do a 1/4 mile on 11-12 seconds.

 

[Thunder]

not too many places to buy 2-stroke outboards anymore.. pretty sure they're outta production from all manufacturers these days.. i know they've been illegal in Comufornia for years now..

What? 2 strokes are not illeagal in Calif.
2 strokes may be illeagal to use in some of California lakes like Tahoe and lakes that suply drinking water.. But they are not illeagal in the whole state. There are quite a few 2 stroke direct injection engines that meet California's CARB 3 star low emission certification and are sold all over the state. I fish in Calif all the time in a boat powered by an old Mercury 2 stroke.
All outboard manufactures have large lines of 2 stroke outboards. I doubt they will ever go out of production.
With the new cleaner burning 2 stroke OBs Cal may even allow them on some lakes they were banned before.