2 stroke thread (with occasional F1 relevance!)

[J.A.W.]

What is the type of lubrication on the Evinrude E-TEC?

Electronically controlled oil injection, a current iteration of the 2T mechanical 'injectolube' systems,
which have been in use for decades - which deliver accurately metered quantities of lube
- to specific points in the engine, according to power setting/emission control sanctions.

[J.A.W.]

Hello J.A.W.

You write:
“No Manolis, both engines were 225 hp models.. & as I noted, the 250 hp E-TEC has more power yet.”

OK.

An engine maker offers an outboard engine as making 225HP ... output power, but the engine actually makes 250HP...

The engine maker could simply say that for similar capacity their two-stroke has a 27% torque advantage over the four-strokes.

I wonder how the PatRoVa four-stroke would behave with the E-TEC direct injection of the Evinrude / Rotax.

Thanks
Manolis Pattakos

Hi Manolis, the horsepower ratings of marine engines do not directly relate to specific cubic capacity such
as applies in motorsports, or even in passenger cars, viz '2 litre, 3 litre' or what have you.

If you want a 225hp outboard, & it actually is capable of making 250hp, that is hardly cause for complaint..

As for a PatRova engine, surely the question is, why bother with the 'lazy' four-stroke cycle at all,
- if it is capable of supporting two-stroke port/time/area requirements?

Perhaps an approach to BRP R & D?

[FW17]

What is the type of lubrication on the Evinrude E-TEC?

Electronically controlled oil injection, a current iteration of the 2T mechanical 'injectolube' systems,
which have been in use for decades - which deliver accurately metered quantities of lube
- to specific points in the engine, according to power setting/emission control sanctions.

Does that mean the oil used on the cylinder walls partly gets collected and burnt off at the ports, while the rest of the oil is recycled?

[J.A.W.]

What is the type of lubrication on the Evinrude E-TEC?

Electronically controlled oil injection, a current iteration of the 2T mechanical 'injectolube' systems,
which have been in use for decades - which deliver accurately metered quantities of lube
- to specific points in the engine, according to power setting/emission control sanctions.

Does that mean the oil used on the cylinder walls partly gets collected and burnt off at the ports, while the rest of the oil is recycled?

No, the engine oil is not recycled, & though it may take time to be consumed, fresh oil is always injected as required.

[FW17]

Electronically controlled oil injection, a current iteration of the 2T mechanical 'injectolube' systems,
which have been in use for decades - which deliver accurately metered quantities of lube
- to specific points in the engine, according to power setting/emission control sanctions.

Does that mean the oil used on the cylinder walls partly gets collected and burnt off at the ports, while the rest of the oil is recycled?

No, the engine oil is not recycled, & though it may take time to be consumed, fresh oil is always injected as required.

Is that because the engine is placed vertically and the crank case is directly mounted with a intake manifold?

Also what is the system used on a Detroit Diesel? Is it wet sump, dry sump, combination of both?

[J.A.W.]

FW 17, for basic crankcase scavenged 2Ts, oil pressure as such is not even required.
Really simple designs such as chainsaws rely on simple 'premix' - lubricant oil in ratio with fuel & it is carried
through the engine internals - rolling element bearings require little & such 2T pistons always have down force.
A chainsaw can be operated at various angles as needful, with no sump or oil tank to be concerned about.

More sophisticated crankcase scavenged 2T mills have oil injection as a convenience ( no 'premixing') & for
accuracy ( lubricant is metered directly to points within the engine as it is required, & thus in the smallest
practicable quantities for economy/emissions reasons).

Tribology-wise, 2T lubricants have been steadily improved to focus this process efficaciously.

The Detroit Diesel - like other large 2T engines utilizes an external blower for scavenge, so can also use a
typical wet-sump/pressure lube/plain bearing bottom end - set up.

[manolis]

Hello J.A.W.

The most fuel efficient two-stroke, so far, seems the Evinrude E-TEC G2 outboard engine.

It is quite oversquare (the 250-G2 has 98mm bore and 76mm stroke, giving a bore to stroke ratio of 1.29)

In comparison, the Tilting OPRE (Opposed Piston) prototype engine:



with its 84mm bore and the 30+30=60mm stroke has a bore to stroke ratio of 1.4 which is less than 10% bigger.
Imagine it with an E-TEC direct injection system.


On the other hand, the new high-revving (165HP at 8,000rpm) Rotax E-TEC 850cc snowmodile engine is almost “square”:
82 mm bore x 80.4 mm stroke (bore to stroke ratio: 1.02).

Strange: the high revving E-TEC (i.e. the Rotax 850cc) is the one that more needs the oversquare design.

It would be interesting the comparison of the BSFC graphs of the two E-TEC engines (Evinrude and Rotax).


Spot on the wide opening of the titling valve in the above gif-video.


The substantially longer piston-dwell around the combustion dead center (some 30%) enables more fuel to be burned at higher expansion ratios, inside the compact combustion chamber:



Some people are confused about the gas flow in the Tilting OPRE.
The gas flow is explained at http://www.pattakon.com/tilting/pattako ... s_FLow.htm



You write:
“As for a PatRova engine, surely the question is, why bother with the 'lazy' four-stroke cycle at all,
- if it is capable of supporting two-stroke port/time/area requirements? “


The Evinrude E-TEC 250 G2 high-tech two-stroke with its peak BTE at 30% (268gr/kWh), is better than the Yamaha 250 four-stroke outboard engine.

The question is how good the E-TEC is when it is compared to other four-stroke engines.

For instance, the PRIUS 4-stroke 1.8Lt:



can operate consuming only 220gr/kWh.

At its best point the Evinrude E-TEC-G2 needs 20% more fuel per kWh of energy provided (268gr/kWh vs 220gr/kWh).

It would be interesting to have the BSFC graph of a, say, Ducati Panigale 1299 to compare.


The PatRoVa rotary valve can be used as the exhaust valve in two-strokes:



But in the two-strokes the Opposed Piston architecture (either with single crankshaft (PatOP at http://www.pattakon.com/pattakonPatOP.htm , PatPOC at http://www.pattakon.com/pattakonPatPOC.htm etc) or with two synchronized crankshafts (OPRE at http://www.pattakon.com/pattakonOPRE.htm , PatATi OP at http://www.pattakon.com/pattakonPatAT.htm etc)) offers similar advantages.

The PatRoVa rotary valve (at http://www.pattakon.com/pattakonPatRoVa.htm ) fits better with the four-strokes (for instance, think how cold the cylinder head and the rotary valve runs in a four-stroke).

Thanks
Manolis Pattakos

[J.A.W.]

Hi Manolis, it would be interesting to see the progressive designs you present fully integrated with current
ECU managed fuel injection & dynamic exhaust systems.

However while the Toyota Prius 4T piston mill is certainly an example of dedicated fuel efficiency, it falls down on other parameters of performance comparison with the muscular 2T E-TEC, the Prius being as intended - an 'econobox' car hybrid co-power plant - & sans any sporting capabilities worth noting.

That crankcase scavenged 2Ts make best power outputs at low operating temperatures would tend to mitigate
against matching a specifically economy oriented machine such as the Prius for BSFC - in any case.

As for the BSFC of the Ducati Panigale, it is doubtful that fuel economy was as such - a major design priority,
with performance while meeting durability & emissions regulations targets being of primary importance.
Its extreme bore to stroke ratio - needed for very high rpm - making for a less efficient combustion chamber.

4T cylinder heads which incorporate red hot exhaust poppet valves do have heat issues, I note the new large Harley-Davidson V-twin design with 4 valves per cylinder have now introduced liquid cooling within the heads, after over a century as air-cooled - this being needful to regulate the increased temperatures therein.

[FW17]

Etech boat engine is designed to operate in a narrow range. Bike and car engines are designed to work right through the rpm range so optimization as in etech is not possible.

A good comparison would be a modern gasoline generator, but not sure how much of modern technology is in it as the larger sizes tend to be diesel

[J.A.W.]

Etech boat engine is designed to operate in a narrow range. Bike and car engines are designed to work right through the rpm range so optimization as in etech is not possible.

A good comparison would be a modern gasoline generator, but not sure how much of modern technology is in it as the larger sizes tend to be diesel

I suggest you re-check the data recently presented on this thread FW 17, since your assumption is incorrect..

The E-TEC outboard engines are capable of very low rpm eco-running for trolling, as well as stratified charge
part throttle economy, on to WFO running as desired.. & the hi-po sports oriented variants are due to get ECU controlled 'power-valve' technology in addition, shortly too..
& FYI, the E-TEC injector is capable of supporting 10,000 rpm functionally ( which = 20,000 rpm in a 4T)...

It is the Prius 4T engine which is in fact - more akin to a generator...

[manolis]

Hello J.A.W.

Regarding the fast combustion in the compact combustion chamber of the OPRE Tilting, you may like to read the agreement between “Liquid Piston and DARPA”.

Partly quote from http://www.businesswire.com/news/home/2 ... -Efficient :

“BLOOMFIELD, Conn.--(BUSINESS WIRE)-- LiquidPiston Inc, a developer of advanced combustion engine technology, today announced that the company has entered into an agreement totaling $991,557 with the U.S. Defense Advanced Research Projects Agency (DARPA). LiquidPiston will use the funds to advance the development of its highly efficient, power-dense rotary internal combustion engine for portable and small-engine applications.

Under this agreement, LiquidPiston’s primary objective is to demonstrate a pathway towards a rotary JP-8 fueled engine that has the potential to reduce fuel consumption by 50% and to increase power density by threefold compared to today’s conventional heavy-fuel piston engines. JP-8, or Jet Propellant 8, is a kerosene-based jet fuel used widely by the U.S. military.

LiquidPiston’s Founder and CTO, and Co-Principal Investigator of this DARPA effort, explained: “Today’s diesel/JP-8 engines and generators are extremely heavy. For example, a typical 3kW heavy-fuel generator weighs over 300 pounds, requiring six people to move it around. LiquidPiston’s engine technology may enable a JP-8 generator of similar output weighing less than 30 pounds that could fit in a backpack.”



The ultimate goal of the funded effort is to demonstrate a pathway to a heavy-fueled engine that could deliver above 50% average brake efficiency, 57% peak brake efficiency and high power density (>1 hp/lb), using a test-bed environment. Such efficiency would reduce fuel consumption by approximately one half compared to today’s conventional piston engines. The effort will demonstrate key enabling components of the engine technology, as well as initial experiments with JP-8 fuel. As part of the agreement, LiquidPiston is investing 40% of the project costs.”

End of Quote.


They talk about 57% peak BTE.

At http://liquidpiston.com/technology/hehc-cycle/ they also talk about constant volume combustion: “A dwell near top-dead-center forces combustion to occur at nearly constant-volume conditions.”

In the Liquid Piston engine the compression and the expansion proceed, around the combustion TDC, in a pure sinusoidal way (i.e. some 15% slower than in the conventional reciprocating piston engine), i.e. exactly as in the Wankel Rotary engine. Here is the proof:



In the Liquid Piston engine the surface to volume ratio is a couple of times worse than in the reciprocating piston engines (increased thermal loss).


Compare the above characteristics of the Liquid Piston engine with the characteristics of the OPRE-Tilting-Valve two-stroke:



wherein the pulling-rod architecture makes the compression – expansion around the combustion TDC 15% slower than in the Liquid Piston and in the Wankel rotary engines (the green / "harmonic" curve in the following graph), and 30% slower than in the conventional reciprocating engines:



and wherein the surface to volume ratio is way lower.

A simple-minded, based on the agreement between DARPA and Liquid Piston, would start thinking about a much higher than 57% BTE for the OPRE Tilting.
However you know, and DARPA should know, that such figures are nonsense / impossible.

A 35% BTE from the OPRE-Tilting would be excellent for a Portable Flyer:





Back to the four-strokes:

You write:
“4T cylinder heads which incorporate red hot exhaust poppet valves do have heat issues, I note the new large Harley-Davidson V-twin design with 4 valves per cylinder have now introduced liquid cooling within the heads, after over a century as air-cooled - this being needful to regulate the increased temperatures therein.”


BMW also uses, in their boxers, liquid-cooled cylinder heads on air-cooled cylinders.

Rotax Boxers (912, 914 etc) also use liquid-cooled cylinder heads on air-cooled cylinders.

The small size of the cooling fins on the cylinders and at the big size of the cooling fins on the cylinder heads of the air-cooled Ulpower engines makes clearer the problem:




The elimination of the exhaust poppet valves from the cylinder head is a significant step ahead.

It is one of the advantages of the two-strokes.
The Evinrude E-TEC two-stroke is rid of hot spots in the combustion chamber.

In the combustion chamber of the four-stroke PatRoVa there are no hot spots, at all, allowing the engine to run colder.
Every point of the combustion chamber walls is equally related with the intake and the exhaust.
The cooling system has a much easier work to do (less thermal energy to pass to the ambient air).

In the Bishop F1 rotary valve engines the “knocking” was unknown (even at 17:1 compression ratios).

The PRIUS engine needs a higher expansion ratio for the sake of the BTE.
And it pays for it with its lower specific power: a 1,800cc engine making only 98HP. The intake valves stay open for a good part of the “compression stroke” allowing to a significant part of the entered gas to return back to the intake manifold.

With a substantially higher compression ratio (say 15:1 or 16:1) the BTE of the PatRoVa can increase above that of the PRIUS, without compromising to low specific power (the friction in the cylinder head decreases at high revs, the breathing is more free, the combustion is faster).

If you don’t need to apply the LIVC (late intake valve closing) “policy” in order to avoid knocking, you have it all: top fuel economy combined with top specific torque and top specific power.

And this is the real challenge for the PatRoVa four-stroke:



Thanks
Manolis Pattakos

[gruntguru]

DARPA must have a lot of money to waste and their fair share of fools to decide where it should be wasted.

[J.A.W.]

DARPA must have a lot of money to waste and their fair share of fools to decide where it should be wasted.

Yeah... it is odd..
..almost seems implausible - that they would 'put the bucks on the barrel head' for a fundamentally defunct design.

I know that a Wankel rotary piston mill powered Toyo Kogyo 'Mazda' is still the only Nippon car to have won
the Le Mans 24hr race, & that such designs do offer high power in a compact unit - at a profligate fuel consumption.

But when the Pentagon has already paid for much more advanced designs.. it is strange..

http://www.google.ca/patents/US8127544

[Muniix]

Hello Gruntguru.

The architecture of the Bishop rotary valve puts some limitations as the bore to stroke ratio increases.

With the same mean speed for the piston rings and for the rotary valve sealing means, the relation of the external diameter D of the Bishop rotary valve with the piston stroke S is:

D= S * 4/pi

Suppose that the “intake duration” T is 300 crank degrees (reasonably it is less even for extreme revs).

If f1 is the angle occupied on the periphery of the rotary valve by the “intake port” and f2 is the angle (about the rotation axis of the rotary valve) of the window in the roof of the combustion chamber (f2 is less than, or equal to, f1) then the duration T is:

T= f1 + f2

With f2=f1 the “window” area maximizes and the duration T gets 2*f1.

With T=300 crank degrees, the f1 is 150 crank degrees (i.e. 75 degrees around the rotary valve periphery, i.e. the width W of the intake port on the Bishop rotary valve is:

W = D * sin(75/2) = S * (4/pi) * sin(37.5) = S * 0.78

With a length of the intake port on the rotary valve equal to, say, 83% of the bore B
(and the same length for the window on the cylinder head), the window port area P is:

P = B * 0.83 * W = 0.65 * B * S = 0.65 * r * S^2 , wherein r is the bore to stroke ratio.

The P is the area of the rectangle hole at top right:

http://www.pattakon.com/tempman/Bishop_Rotary_Valve.jpg

For constant cylinder capacity, the product S * (B^2) remains constant,

so the S * (S*r)^2 is constant,

so the r^2 * S^3 is constant, say C0,

so S = CubicRoot (C0 / r^2).

I.e. P = 0.65 * r * (CubicRoot (C0 / r^2))^2 = 0.65 * CubicRoot(C0/r) = C1*r^(-1/3), wherein C1 is a constant.

So, the P is inversely proportional to the CubicRoot of the Bore to stroke ratio.

For instance, for r=2.5 and for r=1.5 the ratio of the resulting port areas is: (2.5/1.5)^(-1/3)=0.84
This means that for constant cylinder capacity, the area of the window at the top of the combustion chamber of the Bishop rotary valve decreases substantially as the bore increases.


For instance:

with Bore 90mm, Stroke 60mm (i.e. r=1.5 and 382cc cylinder capacity) and 30m/sec mean piston speed and 30m/sec mean speed for the sealing means of the rotary valve (which means 15,000rpm), the external diameter of the Bishop rotary valve is D=76.5mm and the window area is P=34.9cm2 (46.8mm x 74.7mm).

while,

with Bore 106.7mm, Stroke 42.7mm (i.e. r=2.5 and, again, 382cc cylinder capacity) and 30m/sec mean piston speed and 30m/sec mean speed for the sealing means of the rotary valve (which means 21,000rpm), the external diameter of the Bishop rotary valve is D=54.4mm and the window area is P=29.4cm2 ( 33.3mm x 88.5mm), which is 16% lower than in the previous case wherein the bore to stroke ratio was 1.5.


Here there is another interesting thing revealed by the geometry:

with 54.4mm external diameter of the Bishop rotary valve, and, say, an inner diameter of 48mm (which means only 3.2mm width of the external walls of the Bishop rotary valve), the port area at the entrance of the rotary valve is only 18cm2, i.e. 39% less than the window on the combustion roof! (and 49% smaller than the 34.9cm2 window area in the case with the bore to stroke ratio 1.5)



With constant cylinder capacity, we decrease the stroke in order to increase the rev limit of the engine and so to get more power; the higher rev limit for a specific cylinder capacity requires freer breathing, i.e. bigger window area.

But in the case of the Bishop rotary valve what happens is the opposite: as the bore to stroke ratio increases, the window area reduces and the breathing worsens, which means the Bishop rotary valve is not good for engines having extreme bore to stroke ratio.


Worth to mention: during the combustion the piston rings move slowly while the rotary valve sealing means of the Bishop rotary valve move quickly.


Please do the calculations by your own and let me know if there is any mistake.

Thanks
Manolis Pattakos

You seem to be completely forgeting how one would approach the design of an engine with a Bishop Rotary valve.
Given the extensive knowledge gained during the CFD analysis of the BRV, the windows will be the full length of the bore minus a few mm, and the width will be determined by flow requirements for the engines operating range. The flow coefficient is the important issue, it is not just port area.
One would have again done some CFD to optomise this. But essentially is depends on the flow coefficient through the window and the valve as a whole, that is why the BRV has the throat to increase the pressure to avoid seperations as it turns around to flow into the cylinder.

Something that has never been done on your rotary valve, If I were you I'd be setting up Stanfords SU2 cfd code and doing some optimisation, You really need to work out how to get the air flow turned into the cylinder through your valve without restricting it. Some streamlines and a real idea of what the flow will actually look like, and its coefficient. Bishop valves actually flow better in higher bsr engines at equal cc's.

[Muniix]

Hello Tommy Cookers.

The theory has been already and analytically explained in the previous posts.
I don’t think there is something to be added.
It is simple mathematics. And there is no way “to argue with mathematics”.



Here is a partial quote from the link of Brian Coat ( http://articles.sae.org/5586/ )
It confirms everything the theory predicts.


“His (i.e. Furusawa’s) ideal would have been a multicylinder, even-interval-firing engine with minimum fluctuations in revolutions, thereby getting the maximum amount of propulsion without inducing tire slippage. Ultimately, he added, something like an electric motor.

He said that uneven-interval firing itself was not the primary purpose of his design and development team, but that the 90° crankshaft was a fruit of strenuous work in minimizing fluctuations in engine revolutions. The natural result was that combustion intervals had become uneven because of the crankshaft design.

Furusawa’s team then pushed the uneven-interval-firing envelope to an extreme in one variation of the M1 engine that had all combustion occurring in a single revolution, the “Ultimate Long Bang,” Furusawa described. The exercise produced a change in the bike’s total traction, but no improvement in lap times.

“Whichever the engine configuration may be, inline or V-formation, targeted weight distribution should be no different, about 50/50. It could be a fraction of that at either end, but I am not going into that,” Furusawa said. “I believe the inline engine is more advantageous when fitted within a shorter wheelbase, which is more agile. In the V-configured engine, the rear bank tends to shift the mass rearward, which must be offset by lengthening the wheelbase.”

“What the rider wants is combustion torque proportionate to the throttle work, not inertia torque,” said Furusawa, who drew an analogy to signal-to-noise ratio (SNR), an electrical engineering term. “Combustion torque is a signal, and inertia torque is noise. Unfortunately, noise increases proportionately to the square of revolutions, greatly deteriorating the SNR.”

A typical road vehicle inline four may go up to about 7000 rpm on the high end, which is well within the engine’s effective combustion torque zone. In the MotoGP application, winding to 15,000 rpm, inertial torque would be significant. The rider must make best use of the signal buried deep within a large noise, and that would do no good to the essential connectivity between the throttle and rear tire.

His theoretical SNR graph shows a 180° engine model at wide-open 15,000 rpm, assuming no fluctuations in rpm, in which noise/inertia torque is greater than signal/combustion torque. The compounded torque value that drives the motorcycle is, therefore, reduced. In the 90° crank engine, noise/inertia torque is almost negligible; what little is there is generated by the leaning connecting rods. Net driving torque nearly matches the value of combustion torque and is efficiently transmitted to the rear tire at the rider’s command.

Verification of the Yamaha SNR theory was performed by directly measuring fluctuations in rear tire revolutions during cornering using frequency analysis. In the 180° crank YZR-M1, speed fluctuations by second order in revolutions occurred regardless of throttle opening. The 90° crank version, on the other hand, displayed speed fluctuations of the second order in only 1.5 revolutions when the throttle was opened. Furusawa concluded that the 90° crank engine transmitted the signal/combustion torque singularly and effectively to the driving wheel.

Furusawa recounted racer Valentino Rossi’s first reaction to the YZR-M1 in January 2004. Rossi was the World MotoGP champion in 2002 and 2003, riding for Honda. The young Italian had just switched camps to Yamaha, widely rumored to prove that it was not the song but the singer.
Furusawa put Rossi on both the 180° and 90° crank YZR-M1. On the 180° machine, he commented that it was as power-oriented as his previous Honda mounts. On the 90° crank version, he responded, “Very sweet!” The bike responded precisely to his throttle command, producing optimal rear-wheel traction during cornering, and demanded less physical strain on a long run.

END OF QUOTE



In the first paragraph of the Quote it writes:

“(The) ideal would have been a multicylinder, even-interval-firing engine with minimum fluctuations in revolutions, thereby getting the maximum amount of propulsion without inducing tire slippage.”

If this primary transmission:

http://www.pattakon.com/tempman/Variabl ... _gears.gif

were used in a conventional I-4 four-stroke (plane crankshaft, even firing), the inertia torque would not be allowed to arrive to the transmission.
It is a mechanism that, without killing energy, keeps the “bad inertia torque” away from the rear tire.

With the above transmission, the angular speed of the flat / plane crankshaft fluctuates, while the transmission and the rear tire rotate at constant angular speed.

It is the ideal moto-GP engine according Furusawa (the technical director of Yamaha).


I don’t need to see it in practice.
The theory and the mathematics say it works.
Practice will just confirm the theory.

The funny thing is that the gear wheel with the uneven / strange teeth is quite easy to be made with the existing CNC cutting machines (say, with a wire EDM CNC machine). It is a matter of a couple of hours, if you know what you are doing. The other gearwheel is a conventional one.

But who listens?

Thanks
Manolis Pattakos

Using a microphone and signal processing, "confirmation bias"

"Verification of the Yamaha SNR theory was performed by directly measuring fluctuations in rear tire revolutions during cornering using frequency analysis."

Their are other issues that could explain the result they are not looking for!

The reduced crank mass, could be helping the bike turn-in and out faster, the effects on front suspension vibration and harmonics effecting grip and acceleration out of the corner.

Check out the Australian again Motocycle Innovation TS3 suspension, they have telemetry data that shows through mostly elimination of front suspension harmonics that their prototype goes around corners 1 whole second faster than a gsx750r using a 2002 Ducati Desmodue air cooled 900cc twin with 70'ish HP.