Toyota - Two stroke cars.

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Wed 25 Jan 2012 15:49
Toyota - Two stroke cars. - Oli rag

I know toyota and orbital have developed 2 strokes, but has everyone given up on them? I also know that long term emissions seem to have been one of the problems with them. Evinrude the outboard manufacturer seem to have been having success and critical acclaim for their etec range, could this technology not solve the previous problems?

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Wed 25 Jan 2012 16:05
Toyota - Two stroke cars. - craig-pd130

The problem is NOx emissions, if I remember right, hard to manage with 2-strokes although techniques like variable exhaust port heights (varying effective compression ratio) help, and work is ongoing.

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Wed 25 Jan 2012 16:18
Toyota - Two stroke cars. - jc2

Another problem is the lubrication of the moving parts without the oil getting to the combustion process-a California firm was working on an engine where the crankcase was separated from the combustion chambers-this appears similar to the Evinrude E-TEC-whether this technology could be reliably tranferred to motor vehicle engines at a reasonable cost is another matter.Intererestingly,Evinrude are owned by Bombardier Group and Orbital technology is used on Mercury Outboards.

Edited by jc2 on 25/01/2012 at 16:26

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Wed 25 Jan 2012 16:54
Toyota - Two stroke cars. - unthrottled

Marine engines are subject to much laxer emission controls than highway engines. It is not possible to run a two stroke in closed loop in conjunction with a 3 way catalytic converter-which rules out its use in petrol engines.

The critical acclaim is mainly from the companies' press offices!

Diesel engines?

The only company making high speed two strokes is Detroit Deisel-and they've spent twenty years desperately trying to get out of the two-stroke business. They know more about two strokes than anyone else-and the fact that they're not interested should tell you something...

Detroits were horrendously noisy, had a narrow rev range, slobbered oil and had worse emissions than a four stroke. The kicker was that weren't as fuel efficient as 4 strokes either. Absolutely no reason to revisit the concept.

Once turbocharging and high pressure injection allowed 4 strokes to reach the same power levels as two strokes-the detroit was dead.

The 2 stroke has one major advantage: because it fires twice as frequently as a 4 stroke, the torque delivery is smoother and it imposes less stress on the clutch and drivetrain. But the list of negatives is just too long.

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Thu 26 Jan 2012 07:56
Toyota - Two stroke cars. - craig-pd130

Yep, it's a shame because a stroker just feels so ... alive. Especially triples, their power characteristics are bewitching.

I've only ever owned 2-stroke bikes, with one exception. To me, they're just more fun to ride.

The exception was a 1968 TR6 650, which actually used more oil that my Suzuki GT250 did :)

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Thu 26 Jan 2012 09:03
Toyota - Two stroke cars. - dervdave

Yep, it's a shame because a stroker just feels so ... alive. Especially triples, their power characteristics are bewitching.

I've only ever owned 2-stroke bikes, with one exception. To me, they're just more fun to ride.

The exception was a 1968 TR6 650, which actually used more oil that my Suzuki GT250 did :)

Ah the Suzi GT250 one of the first road bikes to have a 6 speed box if I remember corrctly.

I had a new GT750 2-stroke triple.

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Thu 26 Jan 2012 12:02
Toyota - Two stroke cars. - unthrottled

I had a new GT750 2-stroke triple.

Very nice!

I think everyone has a soft spot for 2 strokes-even if, on paper, they are hard to justify.

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Thu 26 Jan 2012 12:46
Toyota - Two stroke cars. - craig-pd130

Sweet! Lovely bike, and even nicer with a Piper 3-1: youtu.be/XfHmJA9aQas

I have a GT380 with Allspeeds for summer fun ...

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Thu 26 Jan 2012 13:11
Toyota - Two stroke cars. - jc2

The Flying Kettle!! The air cooled 500 twin(GTA 500) was better-almost as much performance and much better reliability!The GS's were 380 and 550 triples and suffered overheating on the middle cylinder.Much lower oil consumption than a four-stroke particularly if oil changes were included.

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Thu 26 Jan 2012 14:58
Toyota - Two stroke cars. - dervdave

The air cooled 500 twin(GTA 500) was better-almost as much performance and much better reliability!

I dunno about the reliability but I remember a mate who put his beloved GT 250 in p/ex of a GT 500 twin and absolutely hated it.The test reports at the time (1977) weren`t very favourable either.

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Thu 26 Jan 2012 15:03
Toyota - Two stroke cars. - unthrottled

Much lower oil consumption than a four-stroke particularly if oil changes were included.

Really? Two strokes always chuck a lot of oil out of the exhaust.

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Thu 26 Jan 2012 15:12
Toyota - Two stroke cars. - Oli rag

I had a kawasaki triple and judging by the amount of blue smoke it chucked out when you thrashed it, I expect that I was solely responsible for most of the global warming and pollution that's gone into the air since the 70's!

I once rode a mates kettle and thought it was fantastic - smooth ,torquey, I want one!

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Thu 26 Jan 2012 15:13
Toyota - Two stroke cars. - craig-pd130

The Flying Kettle!! The air cooled 500 twin(GTA 500) was better-almost as much performance and much better reliability!The GS's were 380 and 550 triples and suffered overheating on the middle cylinder.Much lower oil consumption than a four-stroke particularly if oil changes were included.

The middle-cylinder overheating / seizures is an urban myth, to be honest ... even on the more highly strung Kawa triples. Suzuki and Kawasaki built them VERY strongly indeed.

Lack of maintenance, or ignorant teenagers, was the real killer of these engines (setting the ignition timing wrong, running out of oil, removing air filters / baffles etc because their mates told them it would go faster, etc etc etc).

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Thu 26 Jan 2012 15:32
Toyota - Two stroke cars. - unthrottled

removing air filters

Thanks to K&N, that myth never goes away.

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Thu 26 Jan 2012 15:45
Toyota - Two stroke cars. - craig-pd130

Yep, and it will seize a 2-stroke (or add extra ports in the pistons) in short order without suitable rejetting ...

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Thu 26 Jan 2012 15:51
Toyota - Two stroke cars. - unthrottled

add extra ports in the pistons

:-)

Extra ports=extra power, right?!

And if the con rod exits the crank case then you reduce the reciprocating mass which makes even more power.

Is the pressure drop across an air filter really going to affect the air-fuel ratio? The pressure drop is pretty small.

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Fri 27 Jan 2012 09:21
Toyota - Two stroke cars. - craig-pd130

Is the pressure drop across an air filter really going to affect the air-fuel ratio? The pressure drop is pretty small.

It wouldn't matter so much on a low-power commuter, but even late 60s / early 70s strokers like the Suzuki X6 and Yam YDS etc had specific outputs approaching 120bhp / litre, which was phenomenal for a road bike at the time. In contrast, a '68 Bonneville was 75bhp / litre.

These more highly-tuned strokers are somewhat fuel-cooled as well as aircooled, with the nice fresh oily mixture cooling the underside of the piston before going up the transfers into the cylinder. That's why my 371cc Suzuki does 40mpg ....

While removing the air filters probably wouldn't make a big difference at medium speeds and light throttle openings / loading, at wide-open throttle and high rpms, even a 5% weaker air-fuel mix will be near the knuckle with such high specific output.

If the piston expands too much with excess heat and removes the oil film separating it from the cylinder at 7,000rpm, it'll only be a few hundred strokes before a seizure happens.

Likewise, once a hot spot develops on the cylinder crown (usually under the spark plug, where the flame kernel starts) it can melt the aluminium in seconds ...

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Fri 27 Jan 2012 09:41
Toyota - Two stroke cars. - unthrottled

I understand the theory of fuel cooling! But, the maximum pressure drop across an entire air intake system might be considered bad at 10" H20 or 25 millibar.

You get bigger swings in pressure from varying atmospheric pressure which might be as low as 980 millibar or as high as 1020 millibar-a difference of 40millibar. Do you consult the barometer before jetting the carb?! Air temperature also affects air density-which a carburettor cannot 'see'. A cold winter's day might lean the mixture out by more than 7%.

In short, high output engines ae normally jetted for about 11.5-12:1 and can tolerate leaning out by half a point or so.

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Fri 27 Jan 2012 14:18
Toyota - Two stroke cars. - craig-pd130

Agreed - and varying the jetting according to altitude, weather conditions, etc is exactly what racers had to do with their strokers in the 60s and 70s, the bikes were that fickle.

If you can get a copy, Mat Oxley's book "Stealing Speed" about Walter Kaaden, the MZ race outfit and Ernst Degner's defection is a brilliant read on the black art of tuning 2-strokes to specific outputs of 200+bhp / litre.

Obviously a roadgoing 2 stroke bike is nowhere near as highly-strung. But removing the airbox, filter & intake trunking on an RD or GT250 really does mess up carburation, making it fatally weak. I've seen the results (and helped rebuild the top-ends) of bikes were this has been done.

With piston-ported strokers the intake cannot be considered in isolation: the cylinder porting and exhaust pipe have a big effect on carburation too. You'd really need to experiment with this on a dyno with corresponding measurements for fuel and air flow.

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Thu 26 Jan 2012 19:54
Toyota - Two stroke cars. - focussed

Evinrude have had and are still having major problems with their engines and was a major factor in causing them to go bust the last time before Bombardier took them over-they are so finicky that the spark plugs have to be indexed -ie the earth electrode has to face a certain way in the combustion chamber-there is no earthly reason why anyone should buy an engine of this type-if you want a decent outboard, buy a Honda or Suzuki four stroke.

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Thu 26 Jan 2012 19:59
Toyota - Two stroke cars. - unthrottled

Quite.

Even with direct injection, you can't get round the 'four stroking' problem when the throttle is closed. Some people just won't let go of two smokes.

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Thu 26 Jan 2012 20:21
Toyota - Two stroke cars. - bathtub tom

>>Yep, it's a shame because a stroker just feels so ... alive. Especially triples, their power characteristics are bewitching.

Who can ever forget those Wartburgs?

;>)

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Thu 26 Jan 2012 20:27
Toyota - Two stroke cars. - unthrottled

I prefer detroit diesels myself but I see what you mean! I just don't understand why companies spend time trying to bring them up to 4 stroke standards since the task is impossible.

Best remembered fondly.

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Fri 27 Jan 2012 08:57
Toyota - Two stroke cars. - dervdave

Who can ever forget those Wartburgs?

I can remember the sound of the 2-stroke Saab like it was yesterday.

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Fri 27 Jan 2012 11:38
Toyota - Two stroke cars. - dieselnut

I used to race an ex GP 125cc Honda in club events in the 90's. It was a fantastc machine, weighed only 69kg & had 43BHP @ 11.5k revs, just single cylinder.

The power band was 9.5 - 11.5k which made for an interesting experience when trying to exit hairpin turns, especially in the wet, as my broken coller bone will attest to. You had to gear it for the fastest part of the circuit which would result in having to slip the clutch in 1st gear up to about 30mph.

Honda recomended changing the piston/rings every 200 miles & the crank every 1000 miles.

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Fri 27 Jan 2012 14:06
Toyota - Two stroke cars. - Collos25

Still plenty of two stroke motors here in Germany namely Trabants and Wartburgs where they have a dispensation when they go for a TUV test my son has a two stroke trabbie stashed away its awful to drive I have a four stroke estate stored away might be worth something in 100 years or so.

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Fri 27 Jan 2012 14:21
Toyota - Two stroke cars. - craig-pd130

One of my favourite sights / sounds / smells is the 250cc pack leaving Mere Hairpin at Olivers Mount and heading up the hill. Incredible clutch abuse :)

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Fri 27 Jan 2012 17:37
Toyota - Two stroke cars. - Oli rag

Honda made an interesting 1 off bike a few years ago, it was a V3 configuration, the rear pair of cylinders were 4 strokes and the front cylinder was a two stroke- to give the running characteristics of a V4 four stroke.

This is not to be confused with their nsr 400 triple.

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Fri 27 Jan 2012 18:21
Toyota - Two stroke cars. - Hamsafar

Some garden tools that were always 2 smoke are coming through as eco/green 4 smokes now. hedge clippers, leaf blowers etc...

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Fri 27 Jan 2012 18:22
Toyota - Two stroke cars. - unthrottled

How would that even run??

Pressure lubricated crankcase + crankcase scavenged cylinder? Firing pulses of uneven magnitude. Ugh.

Must be an April fool!

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