2 stroke engines

[Alesi md]

I have a question regarding 2st engines. we all know that 2st produces twice as much power as 4st. That is why in motorcycle grand prix racing almost all constructors focused on 2st (back in the day of course) when classes were determined upon engine sizeses. It was natural that 250cc 2st would produce twice as much power as 4st 250cc. But why it never happend in automobile racing. Why manufacturers never produced 2st engines? Just imagine the power of 3.000cc 2st formula one engine, or 2.400cc 2st turbocharged indycar engine of the past. Also a question is, is it even possible to turbocharge 2st engine?

[Doctorindy]

In two-stroke engines like go-karts, etc. you mix the oil in with the fuel, thus it burns off. That would be a lot of oil consumption during the duration of a long race. The larger the engine, the more 'dangerous' the chances are of oil starvation.

Even in the early years, minimized oil consumption was often a rule.

[Alesi md]

In two-stroke engines like go-karts, etc. you mix the oil in with the fuel, thus it burns off. That would be a lot of oil consumption during the duration of a long race. The larger the engine, the more 'dangerous' the chances are of oil starvation.

Even in the early years, minimized oil consumption was often a rule.

yes but twice the horsepower is quite enough to compensate fo additional 10 liters of oil

also you could add oil during pitstops. both as in mixture or in a separate tank

I do not think oil was the reason to dump that much horsepower -we are talking about tons of horsepower here

2st grand prix motorcycles used oil too and they are smaller and lighter than cars

there has to be another reason. I am inclined to beleive that the rules strictly stated that it has to be 4 stroke engine

[rrrr]

I imagine the reasons were oil on the racing surface and visibility. Have you ever seen film of an early midget race when some of the cars had Evinrude Elto engines? It looked like mosquito sprayers were circling the track. WWI pilots flying early two stroke rotary engines would return from missions soaked in castor oil...cars would likely be no different.

[Alesi md]

I imagine the reasons were oil on the racing surface and visibility. Have you ever seen film of an early midget race when some of the cars had Evinrude Elto engines? WWI pilots flying early two stroke rotary engines would return from missions soaked in castor oil...cars would be no different.

I am interested was it rule or choice that prevented 2st from competeing?

because in 60s they tried to run almost everything. It didnt matter if driver was completely covered in oil. Neither safety mattered. In those days only horsepower mattered. thats why this is so intriguing

heck they even ran a turbine!

[Michael Ferner]

Two-strokes were tried in the teens (e.g. Amplex), twenties (Duesenberg) and the thirties (Cummins), and were not competitive. And yes, you can supercharge a two-stroke engine, and it's been done, too - w/o success. I wonder where your assessment comes from, that a two-stroke engine produces twice as much power as a four-stroke, all other things being equal. That's certainly not evidenced by existing designs. Two-stroke technology was banned in Formula 1 long ago, and at Indy sometime in the sixties, iirc. Nobody bothered anyway.

[Alesi md]

Two-strokes were tried in the teens (e.g. Amplex), twenties (Duesenberg) and the thirties (Cummins), and were not competitive. And yes, you can supercharge a two-stroke engine, and it's been done, too - w/o success. I wonder where your assessment comes from, that a two-stroke engine produces twice as much power as a four-stroke, all other things being equal. That's certainly not evidenced by existing designs. Two-stroke technology was banned in Formula 1 long ago, and at Indy sometime in the sixties, iirc. Nobody bothered anyway.

2stroke engine have twice as much productive strokes than 4 strokes. It has one out of two , while 4str has one out of 4 therefore it has to have twice the horsepower */- 10%

tell me why have then all motor cycle grand prix machines prior to 2002 been two stroke. the rules limited only capacity. and yet everyone but kawasaki went 2 stroke

you see it was banned in F1 and indy. And that is an answer to my initial question. Because if it wasnt everyone would go 2 stroke.

go on build 2 stroke 2.400cc engine and compare it to current F1 engine. It would blow it away. I can guarantee you

[Doctorindy]

2stroke engine have twice as much productive strokes than 4 strokes. It has one out of two , while 4str has one out of 4 therefore it has to have twice the horsepower */- 10%

I'm afraid that not how you calculate horsepower output.

There is a factor of diminishing returns. Firing twice as many times does not in and of itself make the net power output double.

[jnormanh]

Modern 4 stroke engines make more torque and horsepower than any equivalent displacement 2 stroke due to far better adiabetic pumping efficiency. Not only do two strokes make less power, they use more fuel to do so. two strokes are horribly inefficient. It's an engineering thing.

Two strokes were popular in the (distant) past because they generally weigh less, have fewer moving parts, and are cheaper to manufacture. They powered lightweight motorcycles and a few lightweight, cheap cars.

They are still used in some low horsepower applications like leaf blowers where low cost and light weight are important and in smaller outboard engines where low cost and light weight are concerns.

Two strokes, almost invariably air-cooled (low cost and light weight) often have service lives of a few hundred hours, whereas any decent four stroke will last many thousands of hours, primarily because of better temperature control and superior lubrication.

You don't believe? Hop on a 4-stroke Suzuki Hayabusa and twist the throttle. You'll leave any ring-a-ding-ding two stroke in the dust.

http://www.youtube.com/watch?v=Ct1yr...eature=related

[Neshaminy]

I believe you may also find the air cooling of 2 strokes is very inefficient which keeps the theoretical horsepower numbers from ever actually becoming real......whoops, someone beat me to it. <emily latella voice on> Never mind.

[BADGER]

I am no engine expert, but there are a lot of inaccurate statements in this thread. You can have liquid cooled two strokes and in fact, most TAG karts use 125 cc liquid cooled two strokes. Also, two strokes, at least small ones do make more hp for a given displacement. When gp bikes went to four strokes, they went from 500 cc to 1000 cc for similar performance. In Mx, the 250 cc two strokes were replaced by 450 four strokes. The fours produced more hp so while it is not 2 to 1 hp advantage, it is significant.

[Michael Ferner]

you see it was banned in F1 and indy. And that is an answer to my initial question. Because if it wasnt everyone would go 2 stroke.

go on build 2 stroke 2.400cc engine and compare it to current F1 engine. It would blow it away. I can guarantee you

And if the moon was made out of green cheese, mice would've invented spaceships long ago to get there. You are right, I am sorry; I won't bother again.

[noivson]

Look into Honda's RC166.

[jnormanh]

Look into Honda's RC166.

Good point: RC166, 4 stroke, 250cc, 18,000 rpm, 60 horsepower.

Which 250 cc 2 stroke could touch it? None.

Back in the day (1930) Leon Durray entered a water-cooled, supercharged, 16 cylinder two stroke at Indy. Durray was a good driver and spent plenty of development money. The 4 stroke Millers ate his lunch.

[dirtfan]

Sure it's a powerful 2-stroke, but can it be used as a "stressed member".

[jnormanh]

It doesn't have a starter. What does it use, a 78 liter Cummins turbo-diesel?

[D-Type]

Although a 2-stroke has twice the number of power strokes, the combustion is not as efficient so it does not produce double the power.

Where the small capacity 2-stroke scores is in the phenominal revs it can reach as it doesn't have the inertia of [poppet] valves to limit it. peak power is confined to a very narrow rev band which is why the 2-stroke bikes had so many gears.

The emissions from the inefficient combustion (together with the oil in the fuel) led to the demise of this form of engine in production cars: DKW, Auto Union, SAAB, Wartburg, Trabant (admittedly all engines from the same family)

[Neshaminy]

On road tractors, Detroit Diesel engines were/are two strokes, but needed a ROOTS supercharger to encourage the air to move through efficiently enough to run.........some of the old 12V71TTs were sweet sounding machines albeit a touch heavy.....and the 855 ci Cummins diesels were their equal in many a racing competition for short duration.....the difference was only 3 cubes......but the weight of the V-12 created an issue of tire heat on round tracks. Man do I miss those sounds.

[rrrr]

On road tractors, Detroit Diesel engines were/are two strokes, but needed a ROOTS supercharger to encourage the air to move through efficiently enough to run.........some of the old 12V71TTs were sweet sounding machines albeit a touch heavy.....and the 855 ci Cummins diesels were their equal in many a racing competition for short duration.....the difference was only 3 cubes......but the weight of the V-12 created an issue of tire heat on round tracks. Man do I miss those sounds.

I don't thing many people know those early Roots superchargers were simply blowing out combustion gases and not being used as an intake air charge method. The early drag racers did some amazing stuff with those blowers considering they were designed to run at a couple thousand RPM and move air at a good breeze...

A two stroke F1 engine...uhhhh

[Neshaminy]

I don't thing many people know those early Roots superchargers were simply blowing out combustion gases and not being used as an intake air charge method. The early drag racers did some amazing stuff with those blowers considering they were designed to run at a couple thousand RPM and move air at a good breeze...

A two stroke F1 engine...uhhhh

And the first race car in the world with a ROOTS supercharger? http://auto.howstuffworks.com/supercharger2.htm The 1908 Chadwick racer from Pottstown PA, http://theoldmotor.com/?p=12878 winner of the 1909 Indy 10 mile Open event and 1909 Founder's Cup Race in Philadelphia driven by Len Zengle...... http://purplesagetradingpost.com/sumner/lenzengle.html

Now back to two strokes as I've gone almost near enough for another thread.

[Sea Fury]

During the war, Rolls Royce built a two-stroke V12 "sprint engine," the Crecy, intended for interceptors like the Spitfire. They never could get it to put out more power than a Merlin or Griffon. It was also loud enough that the test runs caused the Royal Observer Corps spotters to turn on the air raid sirens in neighboring towns, thinking the Luftwaffe was on the way.

[rrrr]

It was also loud enough that the test runs caused the Royal Observer Corps spotters to turn on the air raid sirens in neighboring towns, thinking the Luftwaffe was on the way.

I had not heard that story...very interesting.

Kinda reminds one of the XF-84H.

The propeller of that aircraft turned at supersonic speeds and could allegedly be heard over 25 miles away.

I flew into Bakersfield around midnight back in the 80's and as I walked out of the terminal a loud squealing noise got my attention. Over on a traffic island on a pedestal sat the only surviving example of the turboprop driven XF-84H. A small electric motor was turning the propeller at about 30 RPM, and it sounded like a poorly maintained windmill on the prairie. I had heard of this experimental aircraft, but had no idea it was corroding away in the California desert.

Happily the aircraft has been removed and restored, and is now on display at the Air Force Museum.

[Sea Fury]

I had not heard that story...very interesting.

Kinda reminds one of the XF-84H.

The propeller of that aircraft turned at supersonic speeds and could allegedly be heard over 25 miles away.

I flew into Bakersfield around midnight back in the 80's and as I walked out of the terminal a loud squealing noise got my attention. Over on a traffic island on a pedestal sat the only surviving example of the turboprop driven XF-84H. A small electric motor was turning the propeller at about 30 RPM, and it sounded like a poorly maintained windmill on the prairie. I had heard of this experimental aircraft, but had no idea it was corroding away in the California desert.

Happily the aircraft has been removed and restored, and is now on display at the Air Force Museum.

The Thunderscreech. Supposedly it emitted a visible shock wave laterally out from the props powerful enough to knock a guy down. A crew chief sitting in a nearby C-47 was reportedly so incapacitated by the sound waves during a run-up that he had a seizure.

This web site has a sound file proported to be of the airplane starting up: http://aviationtrivia.info/Republic-XF-84H.php

[KnockOff]

Tempest in a teapot SAAB
http://youtu.be/dXVRdSbKDT8

[Neshaminy]

Tempest in a teapot SAAB
http://youtu.be/dXVRdSbKDT8

Fill the oil and check the gas please.....what a screamer that car was.