Real efficiency (or specific consumption) of a 2 engine time?

[Christophe]

How much can we estimate the efficiency (or the specific consumption in gr / hp.h or gr / kWh) of a modern 2-stroke engine with a carburetor (because 2-stroke injection is still too rare) and without a valve at the exhaust? So a modern 2 stroke but of a "classic" design?

I am obviously talking about the energy efficiency in%, not the "efficiency" in Cv / L (in fact that is the specific power or at a pinch power efficiency) which is an abuse of language often used ... In short I ' would like an average estimate of efficiency at 70% load.

I assume it's between 15 and 20% ... but I would like more precision ...

The info is quite difficult to find, as it is easy to find Cs curves for 4 times as much for 2 times I have trouble (but I may not be good?) .. hence my question here.

Thank you

[chatelot16]

the manufacturers show precise curves when they are favorable ... when they are bad we do not show them

the isoconsumption curves of a diesel are easy to show because they are reproducible, always the same (as good) without random variation

an engine does not have a constant output: it has a whole table which gives its output depending on the torque and the speed: for example a small car diesel does not have a maximum output better than a gasoline engine, but it has an area of ​​good performance much wider and which corresponds better to average use ... to caricature the gasoline engine has a good performance at bottom ... and the diesel a good performance at low power: so we save more by driving slowly with a diesel than with a petrol ... all that just to say that it is not the figure of the maximum output that counts but the whole isoconcomation curve

the 4-stroke petrol engine with carburetor already has a first problem: the simple carburetor does not know how to take into account variations in the quality of petrol which would require modification of the richness (what an injection with lambda probe does) therefore the first cause of efficiency variable ... the carburetor was good for the old gasoline with constant composition, but bad for the current gasoline with too variable composition

the 2 time has a 2nd problem: more or less good sweeping with gasoline air mixture which leaves by the exhaust ... it is very variable, the least fouling of the exhaust is a disaster

and not to mention the clamping system ... the engine sold with clamping (sabotaged exhaust) has a lousy efficiency, consumes a lot and does not move forward ... by putting the muffler in its normal state (but not legal ) the yield is much better

this problem is lamentable! is it acceptable to see the state cause a waste? ... limit the speed why not, but not by causing waste

[Christophe]

Yes but that does not answer my question: ultimately I think we are closer to 15% or maybe even lower ...

I'm not looking for an ISO curve (well if we have one it's better) but just an order of magnitude in% on the actual efficiency of a 2-stroke engine currently ...

[wirbelwind262]

Hello
see in Gordon Blair's books

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[Christophe]

Thank you, I'll see ... You are the first member to use the "hidden" function = reserved for registered members!

Was it voluntary?

ps: not finding such information on google FR quickly, it is still a sign of Google failure, electricity-electronics-informatics / google-the-engine search-is-he-crazy-drop-of-relevance-t14958.html

[wirbelwind262]

Yes

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edit: for gogol, I have the impression that it filters a little violently ...

[Christophe]

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Yes google kidding enough there ... Soon will have to say gogole ... but few specialists talk about it ...

[Christophe]

Yes

I flew over the more than 1000 pages (!!) of the 3 books ... these are real BIBLES of the 2-stroke engine!

I finally found some info on the specific consumption and the yield of 2 stroke ... but that in the file 2StrokeDesign, the other 2, nothing seen!

Page 382 efficiency of a 2-stroke chainsaw:

Rendement_tronçonneuse.gif (38.46 KiB) Viewed 12475 times

Page 499, yield of the 2 injection times, I add as a bonus an isopollution curve on CO:

7.4.1 Stratified charging with homogeneous combustion

(...)

The test results for the engine, shown in Figs. 7.32 and 7.33 as fuel consumption and bmep levels at several throttle openings, reveal significantly low levels of fuel consumption. Most of the bmep range from 2 bar to 5.4 bar over a speed range of 1500 to 5500 rpm, but the bsfc levels are in the band from 360 to 260 g / kWh. These are particularly good fuel consumption characteristics, at least as good if not superior to an equivalent four-stroke cycle engine, and although the hydrocarbon emission levels are not recorded, they must be significantly low with such good trapping of the fuel within the cylinder. The power performance characteristics are unaffected by this stratified charging process, for the peak bmep of this engine at
5.4 bar is quite conventional for a single-cylinder engine operating without a tuned exhaust system.

Consumption_2_temps_regime.gif (51.25 KB) Consulted 12475 times

These 2-stroke books are therefore the best for understanding design and performance, in particular an ENNOORM section on the acoustic tuning of pots (obviously: this is fundamental to proper operation), thank you wirbelwind262! We see that the 2-stroke injection does not date from yesterday and yet is still quite shunned I believe no ?? !!

Further on, we find consumption comparisons according to the type of 2-stroke injection:

Consommation_2temps_injection.gif (31.23 KiB) Viewed 12475 times

In short, I think that we can therefore start on an average specific consumption of a "classic" 2-stroke engine without injection towards 450 gr / kWh in a steady state close to ... i.e. an output of 3.6 / (0.45 * 47,3, 17) = XNUMX%

1 kWh = 3.6 MJ
PCI petrol = 47.3 MJ / Kg

17% for a classic 2-stroke is exactly what I had in mind, now we're on

On the 2 stages with stratified injection, the gain is high: we obtain almost the same yields as in 4 stages!

Medium at max load: 3.6 / (0.3 * 47,3) = 25.4%
Best efficiency at max load: 3.6 / (0.26 * 47.3) = 29.3%

Not bad at all for a cylinder with holes!

[The shadow]

Hello: I invite myself by force
for Google it's a story that gets worse and worse> I only use it rarely (site blocking and the last one it only wants HTTPS) MDR
For the yield having for some time use only 2 T but in other latitudes and you forgot some important points apart from the place ..... the type of oil to use (there are a few% not to be overlooked) the model of the builder (many are copies) and there is also the type of profile of the boat (I'm talking about what I use) if you use at sea or in rivers ????? and take it into account in a 2T
If by any chance my words are unrelated to your question> direction Poubelle
Thank you for taking the time to read me.

[wirbelwind262]

Bonsoir
Christophe, you're welcome, internets are there for that
(GP Blair is the pope of 2 stroke and racing engines http://www.profblairandassociates.com/GPB_Tribute.html )

direct injection on 2 stroke is not badly used on marine engines (Mercury OptiMax, Evinrude E-TEC, Nissan TLDI and Yamaha HPDI),
on road engines, there was Orbital, Aprillia (and I forget ...) but it is shunned by fashion effect despite a production cost 2 times less dixit KTM.
http://articles.sae.org/8157/
oil question, oils for marine engines rotate at lower T °, ​​must withstand humidity and salinity ... which oils for road engines can hardly bear, so do not invert.