2 stroke thread (with occasional F1 relevance!)

[manolis]

Hello Tommy Cookers.

You write:
“the PatBox seems to be useful for cycle manufacturers - and for enthusiast motoring types who like to play at shifting

does the auxiliary belt concept help in some way to mix transmission with motorgenerator functions ?”



Yes.

A couple of years ago a company had asked whether such an application is feasible (and how much it would cost), i.e. to drive the generator, the A/C compressor and other auxiliary equipment at optimum revs, no matter how fast, or slow, the engine rpm is.


The transmission ratio from the engine crankshaft to the electric generator pulley has to be so long that, when the engine idles, the generator to spin fast enough to provide the necessary electric power for the lights, the ECU, the recharging of the battery, etc.

But this way, at the medium revs (say 3,000rpm) the electric generator revs some 4 times faster than what is necessary, consuming useful power into friction, while at higher revs (say 6,000rpm) the electric generator revs some 8 times faster than at idling.


For instance, the pattakon VVA-roller version Honda Civic VTEC prototype car idles at 330rpm:



wherein the original transmission from the crankshaft to the electric generator is not long enough to spin the generator at revs wherein it can provide electric power for the car, causing the progressive discharge of the battery and the stall of the engine after an hour or so.

A reasonable solution would be to replace the pulley of the generators by a half diameter one.
But then, at the 9,000rpm of the rev limiter:





the electric generator would spin at extreme revs (just imagine the aerodynamic losses) and, reasonably, would fall apart due to the extreme centrifugal forces.


With a PatBox like:



the transmission ratio from the crankshaft to the electric generator (and to the rest auxiliary equipment) can vary so that, at the lowest revs of the engine (idling) to maximize, and at the highest revs of the engine (rev limit) to minimize. The auxiliary equipment (the electric generator etc) gets simpler, cheaper, more efficient and more reliable.

Think how easily such an application would be implemented, how useful it would be as a fuel saver, and how cheap it would be in mass production.

Thanks
Manolis Pattakos

[manolis]

Hello all.

Regarding the PatBam HCCI (for 2-stroke and 4-stroke engines), the following are added yesterday in the http://www.pattakon.com/pattakonPatBam.htm :


In the following GIF animation it is shown the (calculated) pressure and temperature (adiabatic compression and expansion) in the main chamber and in the auxiliaty chamber of a PatBam:



The compression in the auxiliary chamber is as high as required to auto-ignite the fuel used; when the two chambers unite, through the transfer ports, the burnt gas streaming into the main chamber:
1. increases the pressure (shock wave),
2. increases the temperature (heat wave),
3. and injects the radicals into the main chamber.

Thanks
Manolis Pattakos

[manolis]

Here it is shown one:

TWO_STROKE
OPRE-TILTING
PatBam HCCI :





The extended piston dwell at the Combustion Dead Center (it provides some 40% extra time to the HCCI combustion, increasing proportionally the useful rev range wherein the engine runs on HCCI),
the compact and fully symmetrical structure (vibration free),
the absence of spark plugs / high voltage system for the ignition (reliability),
the extreme capacity to weight ratio,
the absence of reed valves, etc,
are among its characheristics.

More about the PatBam HCCI: http://www.pattakon.com/pattakonPatBam.htm

More about the Tilting valve (no need for reed valves): http://www.pattakon.com/pattakonTilting.htm and http://www.pattakon.com/pattakonFly.htm

Thanks
Manolis Pattakos

[manolis]

Hello all.

Here is a "more conventional" HCCI PatBam 2-stroke:



wherein the piston-ring of the auxiliary piston slides permanently onto the cylinder liner of the auxiliary chamber.

Thanks
Manolis Pattakos

[tok-tokkie]

This last idea overcomes the alignment problem of the auxiliary piston entering the auxiliary cylinder.

[manolis]

Thanks Tok-Tokkie.

For normal “progressive” combustion (as in the Spark Ignition engines), the “strange” shape of the combustion chamber (when the piston is at the TDC, the “dead volume forms a long “holed” cylinder) would be a problem (increased thermal loss etc).

But with HCCI combustion (they also call it: Low Temperature Combustion / LTC) there is no flame propagation, nor “flame front”; instead, the combustion is spontaneous (it completes into, say, 10 crankshaft degrees while in a similar Spark Ignition engine the combustion may extend along more than 50 crankshaft degrees) and by far colder (not allowing NOx formation).


The same design fits with four-valve 4-stroke engines, too.

The “cross shaped area” between the four valves (at the middle of this “cross” is where now the spark plug is located)



can be used as the bottom passage of the small diameter cylinder, leaving the poppet valves (and the intake - exhaust ducts) as big as they are now.


The over-square design of the Panigale 1299 (1.91 bore to stroke ratio) fits with the spontaneous HCCI / LTC combustion.

According the Internet, the big Ducati uses at some revs / load nearly 60 degrees spark advance.

It is interesting to think about it:

A spark occurs now, and a tiny fire-ball starts extending as it consumes the fuel it finds just outside its periphery.
But the pressure and temperature into the cylinder are still too low keeping low the rate of increase of the fire-ball diameter. The low volume to surface ratio of the fire-ball keeps its size small for longer.

After some 40 degrees (~20 deg before the TDC) the fire-ball is big enough and the pressure and temperature are high enough to accelerate the progressive combustion.

The progressive combustion,
which relates with high temperatures, increased thermal loss and relative reduction of the thermal efficiency,
cannot help completing substantially after the TDC (say 50 crankshaft degrees, or even later), causing a further strong reduction of the thermal efficiency: because the actual expansion-ratio of a fuel quantity burnt at, say, 30 crankshaft degrees after the TDC is about half than the actual expansion-ratio of a quantity of fuel burnt just at the TDC.

Thanks
Manolis Pattakos

[Pinger]

Major HCCI problem. The bottom end of the engine cannot withstand the very large nearly instantaneous rise in pressure when sufficient fuel to consume all the oxygen is supplied.Expect high NOx levels also.
That only leaves the possibility of running with mixtures so weak as to require a huge amount of excess air which is prohibitive in terms of 'air work' (the energy expended in filling the cylinder).

Who wants an underpowered, overweight, running at the ragged edge of durability and smoothness engine? I won't even broach 'control' issues.

[manolis]

Hello Pinger

You write:
“Who wants an underpowered, overweight, running at the ragged edge of durability and smoothness engine?”


Who?
Hyundai, Delphi, Mercedes, GM, Nissan, Mazda etc, etc, etc.


Quote from https://www.caranddriver.com/features/h ... gs-feature



Hyundai’s experimental engine—equipped with direct injection, variable valve timing, a turbo, a supercharger, and exhaust-gas recirculation—looks fairly normal on the outside. What’s weird are pistons with soup bowls cast into their crowns. With no spark plugs in the way, the injectors can squirt fuel into the exact center of each bowl. GDCI achieves auto ignition by heating intake air with carefully controlled amounts of exhaust gas followed by squeezing the dickens out of the mix with a 14.8:1 compression ratio. Injecting a small dose of gas just before top dead center, and the main fuel squirt just after that point, yields cylinder pressures that rise far more gently than those found in any diesel. This improves efficiency, since combustion pressure is working against a descending piston. Lean fuel-air mixtures, minimal heat lost through the cylinder walls, no throttling, and the large expansion ratio (the flip side of compression ratio) deliver fuel efficiency comparable to a diesel, according to Hyundai’s GDCI expert, the suitably named Nayan Engineer. (Mark Sellnau served as Delphi’s engineering manager on this project.) Best results derive from minimal swirl in the piston bowl. Fuel-injection pressures are in the gasoline-engine range, or only a fifth of what’s required in a diesel, yielding major savings in cost, lower parasitic losses, and quieter operation versus diesels. The supercharger delivers intake air at low speeds and loads when there’s insufficient exhaust energy to spin the turbo.”

End of Quote

In the above Quote, Hyundai and Delphi introduce their HCCI project with “great expectations”



Quote from http://www.motortrend.com/news/whatever ... ci-engine/

“Homogeneous-Charge Compression Ignition engines have been a fascination of mine for some time, promising as they do, diesel-ish economy with gasoline-ish cost and emissions. Following a Hyundai powertrain technology briefing back in November 2013, I was pretty convinced that Hyundai’s HCCI program (which they dubbed Gasoline Direct Injection Compression Ignition, or GDCI) appeared likely to beat both the Mercedes-Benz DiesOtto concept and the GM HCCI engine to market.
Well, at this year’s Hyundai powertrain-tech shindig, I got an update from powertrain honcho John Juriga as to just whatever happened to GDCI. He explained that under compression-ignition operating conditions, the peak cylinder pressures were so great that the block and lower end (crank and bearings) needed to be strengthened to what is essentially diesel specifications, adding cost and mass. All direct-injected gas engines have some issues with particulate emissions, and these were even worse with the GDCI engine, requiring a particulate trap not unlike what Mercedes is fitting to many forthcoming S-Class engines, which eroded the hoped-for emissions aftertreatment savings. The GDCI combustion process required considerable exhaust-gas recirculation, some of which was handled by retaining said gasses in the chamber using elaborate variable valve-timing mechanisms that added cost to the top of the engine. Achieving sufficient cylinder pressures at lower engine speeds demanded fitment of a supercharger in addition to the planned turbocharger, which added still more cost (and Juriga added that electric superchargers don’t represent much of a savings relative to mechanical ones).
This litany of cost overruns left a less expensive, lower pressure direct fuel injection system as about the only remaining cost savings relative to a diesel, so the program was deemed too risky and expensive. We suspect Mercedes and GM have come to the same conclusion, as all has gone pretty quiet on the HCCI front. But all hope is not entirely lost. Being able to vary the compression ratio is a real enabler for HCCI, and indeed the Infiniti folks suggested that a second-generation of their new VC-Turbo engine might employ HCCI to clear the next round of CAFE hurdles. Keep the faith!”

End of Quote


In the above Quote, it seems as the GDCI (HCCI) project of Hyundai / Delphi is now abandoned.
They are also mentioned the HCCI projects of Mercedes, of GM and of Nissan Infinity.



Quote from https://insidemazda.mazdausa.com/press- ... formation/

Mazda SkyActivX:

Range when HCCI could take place before the SKYACTIV-X:



SPCCI :



The expanded range of SPCCI (combustion ignition):






You also write:

“Major HCCI problem. The bottom end of the engine cannot withstand the very large nearly instantaneous rise in pressure when sufficient fuel to consume all the oxygen is supplied.Expect high NOx levels also.
That only leaves the possibility of running with mixtures so weak as to require a huge amount of excess air which is prohibitive in terms of 'air work' (the energy expended in filling the cylinder).“


The PatBam HCCI is different.

In the following PatBam HCCI design:



the diameter of the auxiliary piston is about 1/3 of the diameter of the main piston.

Similarly, in the following 4-stroke PatBam HCCI:



and from the "piston side", in case a Ducati Panigale is modified to PatBam:



the diameter of the auxiliary piston is about 1/3 of the diameter of the main piston.


This means that the surface of the auxiliary piston is about 3^2 times smaller than the surface of the main piston.

No matter how high the compression ratio in the auxiliary chamber is (say, it is 20:1 to cause the auto-ignition of the air fuel mixture at all conditions), the resulting loads on the kinematic mechanism are not heavy.

By the way: the HCCI combustion is not really instantaneous. It is some 5 – 6 times faster than the progressive burn in the Spark Ignition engines, but not instantaneous.

Keeping low the compression ratio in the main chamber (say, 11:1), the near “constant volume combustion” triggered by the entering from the auxiliary chamber burnt gas, cannot cause excessive loads on the kinematic mechanism.

As the Diesels, similarly the HCCI engines run better on lean mixtures; the leaner the better.

In the road tests of the Mazda SkyActivX (an almost HCCI engine) the consumption gets better if the engine runs at higher revs and lighter loads (instead of the conventional: lower revs, heavier loads).


It is not possible to consume all the oxygen in the cylinder of a Diesel engine. This is the way it works: from lean to extremely lean (at idling).
Yet the Diesels with the lean burn achieve higher BTE than the Spark Ignition engines.

And because the Diesels and the HCCI engines fit better with turbo-charging and super-charging, they are able to make lots of power.


So, the PatBam separates the HCCI combustion in two chambers, achieving a simple, yet strong control.
The high pressures in the auxiliary chamber cannot create extreme loads.
Neither the near “constant volume combustion” in the main chamber, which runs at low compression ratio, can create extreme loads on the kinematic mechanism.
With a 11:1 compression ratio in the main chamber, a BTE similar to that of a Diesel having 16:1 compression ratio (and running in near “constant pressure combustion) is reasonable.
As for the fuel, a low octane cheap gasoline is the best fuel for the PatBam.


The basic problem of the Diesel engines is their emissions (NOx and particulates).

The direct injection gasoline engines have similar problems with the Diesels.

The HCCI is a solution. But the HCCI needs strict control And the PatBam offer such strict control over the HCCI combustion.

Thanks
Manolis Pattakos

[Pinger]

I looked at similar arrangements a while back. My conclusions were:

The greater surface to volume of the ante-chamber would (unpredictably) influence the point of ignition.
That the pre-TDC forces on even the smaller area of the piston protrusion would still be unwelcome.
That when applied to a 2T the homogeneous incoming charge would lead to fuel loss to the exhaust port and high UBHC (the usual 2T curse).
That any carbonisation in the small communicating ports of the ante-chamber would in service deteriorate the process.
That maintaining correct clearances at all temps was going to be problematic.
That maintaining geometrical integrity of the protruding piston after prolonged service was likely to be problematic.
That ultimately due to having to run (for reasons of lack of bottom end strength) lean mixtures no reasonable specific power output is achievable.

Some time prior, I also looked at divided chamber / torch ignition systems (which your (Manolis) PatBam is a a variation of). My conclusion was:

That there will always be throttling losses which degrade efficiency. That conclusion was reached at the same time as the launch of common rail injection systems which capitalised on dispensing with ante-chambers and deploying direct injection - with an immediate increase in thermal efficiency as a consequence. It never occurred to me (and probably never would) to reduce the ante-chamber volume to the levels so done with the TJI system. Not least because the prospect of employing an additional fuel injector to release such a very small volume of fuel isn't something the OEMs are going to be thrilled by.

At least one OEM that has investigated HCCI has concluded that their objectives can be met by using simpler and more familiar technology. The current market place (lack of saleable HCCI) endorses that view.

HCCI is infinitely better suited to free-piston designs such as those using the engine core as a gas generator to provide gas for a turbine (where the lean mixture is no handicap and nearly an asset) but the very low pressure ratios across the turbine(s) condemn such a configuration to poor thermal efficiency.

I really cannot envisage any bright future for HCCI - unless it is true that Honda are using it in F1 and it (Honda) make some breakthrough to curb all HCCIs negative aspects.
Does anyone know if Honda is using HCCI in F1?

[Pinger]

And, adequately scavenging any ante-chamber is by no means a given.

[manolis]

Hello Pinger.

You write:

“The greater surface to volume of the ante-chamber would (unpredictably) influence the point of ignition.
That the pre-TDC forces on even the smaller area of the piston protrusion would still be unwelcome.”


The PatBam architecture is tolerant to the “point of auto-ignition” in the auxiliary chamber.
Suppose the ignition happens 5 degrees earlier. The differential of the torque applied to the crankshaft is small because the auxiliary piston area is small and because the auxiliary piston is near its TDC wherein the eccentricity (from the rotation axis of the crankshaft) of the force applied to the crankpin by the connecting rod is small.



After its “spontaneous combustion” the burnt gas into the auxiliary chamber is further compressed (and heated) until the “transfer ports” open (which happens at a constant crankshaft angle, say 10 degrees before the TDC) allowing it to burst into the main chamber.
I.e. the “unpredictable” timing of the auto-ignition in the auxiliary chamber is not affecting the combustion into the main chamber.

A glow plug (like those used in the Diesels) can assist the cold starting (and not only).


You also write:

“That when applied to a 2T the homogeneous incoming charge would lead to fuel loss to the exhaust port and high UBHC (the usual 2T curse).”

The asymmetric timing of the 2-stroke PatATi / PatATeco / PatATE (more at www.pattakon.com )



wherein the transfer ports close after the exhaust ports, can solve this issue of all “non directly injected” 2-strokes.

The option for asymmetric timing in the Opposed Piston PatOP and OPRE (shown from 2’:36’’to 3’:48’’in the following video) solves this weakness of the conventional 2-strokes.



The PatOP and OPRE have also the advantage of the substantially longer piston dwell at the combustion dead center.


On the other hand, the direct injection even in the 4-strokes is related with problems like particulates etc; in the 2-strokes the time for evaporation and for mixing is shorter worsening things.


You also write:

“That any carbonisation in the small communicating ports of the ante-chamber would in service deteriorate the process.”

The “small communication ports” are the hottest areas in the engine, not allowing the carbonization therein.


You also write:

“That maintaining correct clearances at all temps was going to be problematic.”

In the OPRE Tilting opposed piston HCCI (animations in previous post), the two pistons are symmetrical and serve, both, the intake and the exhaust. Their motion is symmetrical. They slide inside the same cylinder that keeps them “coaxial”. These all allow the minimization of the clearances (for the moment it is not clear what the optimum clearances are; hopefully we will know soon).


You also write:

“Some time prior, I also looked at divided chamber / torch ignition systems (which your (Manolis) PatBam is a a variation of)”

Any images? Any photos? Any patent numbers?


You also write:

“It never occurred to me (and probably never would) to reduce the ante-chamber volume to the levels so done with the TJI system. “

The size of the auxiliary chamber depends on the fuel and on the operational conditions. If the main chamber is kept just below the threshold for auto-ignition and the auxiliary chamber is kept slightly above the threshold for auto-ignition, the auxiliary chamber capacity can be as small as in the TJI without the complication / cost associated with the TJI and with way better penetration of the burnt gas into the compressed air-fuel mixture in the main chamber.
The basic objective is to confine the high pressures necessary for the auto-ignition inside a small chamber and then to use it for the ignition of the charge in the big chamber which is intolerant to extreme pressures, to extreme pressure differentials and to extreme pressure “jerks”.


You also write:

“At least one OEM that has investigated HCCI has concluded that their objectives can be met by using simpler and more familiar technology. The current market place (lack of saleable HCCI) endorses that view.”

One thing is sure:
The specific OEM failed with the HCCI.
As for “their objectives that can be met (today) by using simpler and more familiar technology”, what about tomorrow?

In another OEM (Mazda) they think just the opposite; they seem as putting all their hopes on their SkyActive-X HCCI project.
Several auto journalists around the world have already driven / tested Mazda cars with the prototype SkyActiv-X engine inside, and they seem to like it (no matter how much fuel it consumes).
Mazda claims officially 20% lower fuel consumption than their current modern SkyActiv-G gasoline engines.

More at

https://insidemazda.mazdausa.com/press- ... formation/

and

https://www.caranddriver.com/reviews/20 ... ive-review

If this huge reduction in the fuel consumption (and over the CO2 emissions), without compromising with the power and the driver friendly, is true, what else is required to change your opinion about the HCCI technology?


You also write:

“And, adequately scavenging any ante-chamber is by no means a given.”

Follow the motion of the piston in this:



animation,
and take a look at the pressures at the upper side.

The high pressure the moment the two chambers seal from each other makes a big part of the air-fuel mixture to get trapped into the auxiliary chamber.

On the other hand, it is not yet clear which percentage of exhausted gas is the optimum into the auxiliary chamber for HCCI initiation.
According Honda’s EXP-2 with the active radicals etc, it is required a lot of exhausted gas for HCCI combustion, making the full scavenging of the auxiliary chamber a weakness.

Thanks
Manolis Pattakos

[Pinger]

Knock knock.
Who's there?
Mazda!

So Mazda are pinning their hopes on harnessing detonation - that well known piston killer whose MO is to strip the piston of its protective boundary layer and then heat it to the point of meltdown while simultaneously subjecting it to a rate of pressure rise it cannot cope with. Good luck with that. Hope it goes better than your last great leap forward, the Wankel.

Mercedes-Benz. Where is your DiesOtto engine you promised us 15 years ago? In a Mazda you say?

Mercedes-Benz, Why did you move the cam drives to the rear of the engine for longitudinal applications? To free up space at the front of the engine bay for pedestrian safety you say. Hmmm, wonder how an engine (HCCI) that cannot withstand load factors greater than 30% and will thus be three times larger is going to fit with modern day packaging requirements?

Mazda, With camless valve actuation, super high fuel injection pressure, a supercharger and a turbocharger, and a diesel strength bottom end - any idea of what this thing is going to cost to build?

[manolis]

Hello Pinger.

In the following, Alexander Stoklosa of Car and Driver writes (September2017) about the SkyActiv-X he tested on the road.


Quote from https://www.caranddriver.com/reviews/20 ... ive-review

Driving Mazda's Next Mazda 3 with Its Skyactiv-X Compression-Ignition Gas Engine
. . .

It’s . . . Alive!

In its current state of tune, the prototype engine is functional. That’s noteworthy only because the SPCCI tech is so unique that its working didn’t seem like a given until we had keyed the ignition for ourselves. . . .
They’re on the right track, because the X is plenty responsive and feels about as powerful as the current Mazda 3’s larger 2.5-liter four.

We had assumed the X’s zeal might sag during CI operation, with deadened responses like those felt in hybrids that can briefly run solely on their relatively weak electric motors. That does not seem to be the case, and the engine is relatively tractable running under compression ignition.
. . .
Even under compression ignition, the engine is smooth and quiet; the engine behaves so similarly in each ignition state that it takes concentration to detect which one is in play.

Traverse a smooth road at lower speeds in CI mode and listen closely enough, and you can just make out a diesel-like prattle. At higher speeds or on coarse road surfaces, you’ll never detect it.

Because the X is more likely to enter CI during lighter-load use and can stay in that ultra-efficient mode even at higher rpm, we’re told selecting lower gear ratios has little effect on fuel economy.

During our drive in the manual-transmission prototype, we could leave the shift lever in fourth or fifth gear instead of sixth and stay in CI while taking advantage of the engine’s sharper responses to dice through city traffic.

So far, the switchover from spark ignition to compression ignition is the only issue needing attention outside of final, production-ready engine calibration. The process is seamless, with zero vibrational cues that the X has chosen an ignition type and fully committed to it. However, it is audible, thanks to copious knock (detonation) that hangs around any time the engine isn’t fully in a single ignition setting.

During clean transitions from spark to compression ignition or back, the X emits its stuttered knocking soundtrack for about a second or two. However, whenever the computers move close to one ignition state from the other, the knocking drags on.
This condition, in which fuel mixtures aren’t quite set for the desired state of ignition, occurred whenever the engine was spinning at low rpm—a CI-favorable condition—but loads were moderate, favoring spark ignition.

. . .

A steady 115 mph on the autobahn sounded like 80 mph in our recently departed 2015 Mazda 3 hatchback.

End of Quote


Mazda SkyActiv-X review:




Provided the above journalists are true independent third parties, the HCCI is already here.
And it seems it is gonna stay, enabling substantially stricter emission regulations to which the Spark Ignition and the Compression Ignition conventional engines must comply or die.

The HCCI is better simply because it brings a huge reduction of the fuel consumption and of the CO2 emissions as compared to the Spark Ignition engines, and because it brings a huge reduction of the NOx emissions and of the particulates emissions as compared to the Compression Ignition engines.


To underestimate Mazda is a way, but not a clever one, unless you have a better solution / invention to propose.

After all, when all the other car and engine makers failed, Mazda insisted and finally achieved to make the Wankel Rotary reliable, keeping it in production for half a century.


If you can accuse Mazda’s HCCI SkyActiv-X for something, it is its complication and cost.


In comparison the PatBam provides strict control over the HCCI combustion, being by far simpler.

Here is an animation of a PatBam Cross-Radial PatAT :



Four-stroke-like lubrication, external scavenge pump, asymmetric transfer, full balance, no need for high voltage system, it runs better on cheap low octane gasoline, etc, etc.

It’s architecture makes it so lightweight that even when it runs extra lean (say, AFR=2) it still can provide top specific power.

Thanks
Manolis Pattakos

[Pinger]

Provided the above journalists are true independent third parties, the HCCI is already here.

So was MB's DiesOtto, Hyundai's HCCI, and a GM HCCI too.

And it seems it is gonna stay, enabling substantially stricter emission regulations to which the Spark Ignition and the Compression Ignition conventional engines must comply or die.

The HCCI is better simply because it brings a huge reduction of the fuel consumption and of the CO2 emissions as compared to the Spark Ignition engines, and because it brings a huge reduction of the NOx emissions and of the particulates emissions as compared to the Compression Ignition engines.

Yes HCCI offers advantages and if you paint it up as absolutely the future and claim to have mastered the technology - are you offering the public a new engine or propping up your share price? So many press releases are to benefit shareholders and offer no real picture as to what we'll be driving.

To underestimate Mazda is a way, but not a clever one, unless you have a better solution / invention to propose.

After all, when all the other car and engine makers failed, Mazda insisted and finally achieved to make the Wankel Rotary reliable, keeping it in production for half a century.

I'd ask RX8 owners about Wankel reliability before praising Mazda for failing as NSU did some 40 years earlier.

[manolis]

Hello Pinger.

For Mazda,
the Wankel Rotary project was a great success.
For Mazda the Wankel rotary was a blessing.
They made (and still are making with the spare parts they sell) money from it, they became worldwide known with their RX-7 and RX-8, they became reputable.


In comparison,
for all the rest OEM’s (Mercedes, Rolls Roys, Citroen, NSU, GM, etc, etc, etc),
the Wankel Rotary proved a disaster, a nightmare.
After spending several billions of dollars, they failed to put the Wankel Rotary to really work. Some bankrupted. The others returned to the conventional reciprocating pistons.



Quote from http://www.screamandfly.com/archive/ind ... 4-p-2.html :

“ I asked Charlie Strang. Here is his response:

Dear Sam:

I'm afraid the story about the reputed cleanliness if the rotary is a figment of someone's over active imagination! The primary problem with the engine was its extreme dirtiness. The long, flat combustion chamber created by the rotor in its somewhat triangular housing resulted in a "wet chamber" that could be cleaned up to meet coming pollution standards only by adding a very expensive catalytic converter to the exhaust system.

Aside from being dirty, the engine was expensive to manufacture because of the tool steel seals it required for any kind of life and the very expensive alloy coating needed in the trichinosis housing to withstand the wear created by the seals.

When all was said and done it was far less costly to build a direct-injected two-cycle piston engine or even a four-cycle engine to meet the emerging clean exhaust laws.

As far as I know, OMC was the only company in the USA or North America ever to put a rotary into actual production. We built several thousand single-rotor engines and sold them in snowmobiles just before the onset of new exhaust laws finished the day of the Wankel. All in all. the engine was fun to work with --including our four-rotor racing engines -- but in the end it amounted to one big and expensive waste of time!!

Regards, Chas S.”



Quote from http://www.amsnow.com/how-to-tech/2000/ ... ry-engines


“Wankel Rotary Engines
An early casualty in our industry's efforts to build a better 2-stroke
By Olav Aaen*** October 1, 2000

The good old piston engine was "on its deathbed," read the announcement. Good-bye to pistons, rods, valves and camshafts; there was a revolutionary new engine taking over the automotive world. The new engine had only a rotor instead of pistons, was fully balanced and ran smooth as a turbine. The inventor was Felix Wankel, and the Wankel engine promised a bright new future as a sophisticated and compact power source.

It was the mid-sixties, optimism abounded, and most of the major car manufacturers jumped on the bandwagon. The largest licensee in the U.S. was General Motors, but the concept also found its way into snowmobiles. Both OMC (Evinrude & Johnson), and Arctic Cat produced snowmobiles with Wankel engines for a short period. Arctic Cat imported a Sach's-produced Wankel from Germany while OMC built its own.
. . .
For OMC to gain production experience it was decided to make a snowmobile engine first. OMC had a reputation for quality products in the outboard business, and it was felt that there would be a lot less risk if the unavoidable teething problems could be sorted out in a fan cooled snowmobile version.
. . .
At the time I was a young project engineer in the Snowmobile Division, and was assigned to coordinate the installation between the Outboard Division and the snowmobile chassis department.



Inherent Obstacles

It was not my first experience with Wankel engines, I had tested some in early NSU cars in Europe and had been impressed with the turbine-smooth power delivery. At my first meeting with George Miller, the project manager, I was advised of a potential problem he hoped we could solve.

The Wankel exhaust runs very hot, and it would be important to make sure it did not become a problem in the sled installation. What did he mean by hot? Cherry red metal glowing under the hood, just like a coil on an electric stove. This was obviously much hotter than a two stroke muffler, and could be a serious problem.
. . .
The only reported problem with this design was a tendency to melt snow and ice under the sled if you let it idle too long before you shut it off. Occasionally owners would come out after a dinner at their favorite restaurant and find the track frozen to the ground, as the melted snow turned to ice. As far as I know, there was no problem with the close proximity of the gas tank to this glowing hot muffler, because the gas tank compartment had also been well insulated.
. . .
OMC's Wankel-powered snowmobile lived up to its expectations as a test bed for the new engine concept. The Wankels were both smooth and relatively quiet for their time, and the power curve was a lot broader with lots of torque from a low engine speed. This made it completely insensitive to clutching. You could throw a bad clutch on this motor, and you would not notice it because of the exceptional four stroke-like delivery.
. . .
OMC got out of the snowmobile business in 1975. The Wankel design team was disbanded, and most of the team members left for jobs at other companies. Only the Japanese Mazda company continued to make Wankel-powered cars, better known as the RX-7 Rotary, a very quick sportscar which gained an enthusiastic following.
. . .
As it turned out, the OMC snowmobile rotary engine ended up being the only Wankel engine ever manufactured in the U.S., and as such has some historical merit.”

End of Quote


***Olav Aaen, the writer of the above quote, is the author of the famous “Clutch Tuning Handbook:





Look it from another viewpoint:

It’s not Mazda’s fault that the Wankel Rotary design had, and still has, significant flaws.

It was Mazda’s accomplishment to make the Wankel Rotary functional and increase its reliability not far from the reliability of the reciprocating engines.

Thanks
Manolis Pattakos