2 Stroke fuel consumption

[Soleair]

My MiniMax Eros is fitted with an MZ202 engine, and I thought I'd better do an accurate check on fuel consumption.

 

I use sight glasses in my cockpit as a gauge, but they're pretty useless. I rely on dipping my tanks before takeoff, with the tail raised on a sawhorse to bring the wingtanks level.

 

But for this test (the 2nd one I've done with the same result), I filled the starboard wing tank right to the very top - it overflowed actually, which was a bit messy. D'Oh!

 

I did this immediately before I went flying yesterday morning. It was hot & sunny, with a slight crosswind. Temperature was 27 degrees. Engine time was exactly 60 minutes on the Tiny Tach, though this includes warm up & down times, so say a bit over 50 minutes actual air time.

 

I did a mix of flying, mostly around 4000' QNH: steep turns; stalls with & without flap; max speed runs (seems to be about 85 mph level); slips at various throttle settings; a couple of touch-and-goes. About half the time was just pootling around at between 65 - 75 mph, about 4500 - 5500 rpm

 

I topped up the starboard tank once again to overflowing, so fuel used was accurately measured from that needed to fill. Result was almost exactly 8 litres per hour. Not bad for a 2-stroke: the MZ 202 is 625cc and maxes out at 6000 rpm, so it's a relatively big lazy engine in 95:10 terms. And maybe all my drag reduction mods are having some useful effect.

 

But it does show that 2 strokes aren't all gas guzzlers!

 

Bruce

 

 

[Methusala]

Fuel consumption is related to work done. Your engine, being 625cc is probably capable of producing 65hp or so. But the air-frame is relatively light and fairly aerodynamic. So it is not doing a great amount of work. 2-strokes do use a significant proportion of their fuel to run rich and control internal temperatures. I fly a Kitfox and a T300 Thruster. Both are quite draggy and consume around 18l/hr on their 582's. Not very efficient! Don

 

 

[facthunter]

If a two stroke gets real good fuel economy, it usually seizes up. I think the last fuel figures I recall with a 582 in a SB Drifter on general circuits and "air work" was about 13 litres /hour. Some draggy planes fly on almost full throttle. That will certainly affect your figures.. IF you are doing cross country work and have established a consumption pattern for your particular aircraft over a period of time that is consistent, if its documented it should be used for your flight planning. IF the POH figure is greater you CAN use it (not if it's LESS than actual, double emphasis) . If you want to be conservative use the REAL figure as a good practice and carry the extra as margin fuel (reserve). Your plan more reflects reality then and your flight progress and fuel situation, is easier to keep tabs on Nev

 

 

[Soleair]

I'm not really sure what your point is in that post, Nev. But as regards seizing up, my EGT's were respectively not above 1050 & 1000 deg F, & my CHT's never went over 350 deg F. My plugs are all light cocoa coloured. So I don't think I'm in any danger of imminent seizure.

 

Your other statement is to the effect that a Drifter with a 582 returns 13 litres per hour. Well, that was why I posted my test results: to show that not all 95.10 aircraft powered by 2 stroke engines are necessarily thirsty. The 582 anecdotally does not produce as much power as the MZ engine, so would need to be operated at higher throttle openings, implying greater fuel burn. As to the aerodynamic qualities of the Drifter versus my MiniMax, I invite you to compare the 2 photos attached.

 

Your comments on cross country fuel planning hold good for any combination of airframe and engine, so they not particularly relevant to 2 stroke fuel consumption.

 

 

 

 

[facthunter]

I don't seem to have pleased you at all. Sorry.

 

Generally two strokes are not good at specific fuel consumption figures Hp/Hr/litre. It's the nature of the design. I wouldn't like to see people chasing fuel economy with their two stroke engines..

 

My comments are general. for anyone to read. If you want comparisons of engine figures you have to have an apples with apples situation.

 

Two strokes are great for certain applications. In Power/weight they beat all others , Cheaper too. Simple , unbelievably so. Nev

 

 

[Soleair]

Not pleased or displeased. Just trying to work out what you're saying.

 

All I'm saying is that for my engine, in my airframe, under the stated conditions, I accurately reported my fuel burn, for general interest.

 

 

[Yenn]

Excellent fuel figures, but I wouldn't rely on one flight s figures.

 

I have recorded over 100 hours of consumption in my RV4 and it can vary vastly, depending on flight duration and how hard it as been working. Not a 2 stroke, but the same principles apply.

 

I used to allow 16 L/Hr for my 503 Rotax powered Thruster. It had a problem with wear on the pins in the floats and went up to 20 L/Hr.

 

 

[Hargraves]

I was getting an (average) fuel consumption in my 582 GT 500 of 17 lts hr but i say average because flying windows down was differant from zipped up as was cruise speed of course. But more noticable was, because of my tendancy to fly high when theirs a choice, the added consumption required to get to cruise hight at each climbout I think around 21 or more would be more realistic at those times. So that even befor factoring in winds enroute theirs a potential for large discrepancies in twostroke fuel usage making it harder to get a handle on.