LeSving wrote:
That’s what ULPower said, and they have tested them, neck to neck with MOGAS 95 which was OK (fresh MOGAS 95). This was during a training course I had there. It was said, but the official statement is UL91 is OK, because it should be OK
Sorry, but for me this is just hearsay…
europaxs wrote:
Sorry, but for me this is just hearsay…
Well, refineries cook and mix and sell whatever they think they can get away with. There’s no one there checking them and what they do. That ULPower share with us their own test results, even if they are “politically incorrect”, is nice and honest by them. They have nothing to gain by limiting the fuel on their engines. It’s the exact opposite. Recently they re-mapped the ECU on their i-series engines, enabling them to run on RON 91, it was RON 95 earlier. Older engines must still use RON 95 unless the ECU is re-mapped.
aart wrote:
All a bit puzzling
It’s more like a big mess if you ask me. But, in some way or another it’s dependent on the fuel we put in the tanks. This is good, because that part we can do something about ourselves. My decision is 98 E0 or 100LL.
refineries cook and mix and sell whatever they think they can get away with. There’s no one there checking them and what they do
I don’t think so.
The lower the engine speed, the higher the lateral forces on the piston and the higher the bearing pressures on the connecting rod and crankshaft bearings. The lateral piston forces must now be “dissipated” via the cylinder wall, and this they will do into the crankcase.
One can perhaps imagine that these forces lead to a continuous internal movement of the crankcase. Since we have two crankcase halves, it leads to possible frictional movement within the parting lines.
That to me sounds like a bad (marginal) design.
Some limitation on RPM (not go below x RPM if MP is above y inches) is common on aero engines and is to do with stress on the crankshaft flange, and possibly counterweight / resonance stuff.
Peter wrote:
I don’t think so.
Me neither. After all UL91 is AVGAS. AFAIK this must have certain properties, same as 100LL.
Some limitation on RPM (not go below x RPM if MP is above y inches) is common on aero engines and is to do with stress on the crankshaft flange, and possibly counterweight / resonance stuff.
While lugging the engine has a mechanical effect (affecting bearing loads) I believe this limitation is primarily related to detonation margin when running on the lowest grade certified fuel with fixed ignition timing.
The stated Rotax 912 tendency to run lean when running high RPM with low manifold pressure is puzzling as mentioned, if it is real. The Bing carb slide height and therefore fuel needle position are the same at a given power level and associated inlet airflow, irrespective of whether the inlet flow to achieve that power level is achieved by throttle opening or RPM. That’s what a CV carb does by design, and why the design exists.
It’s more like a big mess if you ask me.
From a regulatory point of view, the current Rotax situation (if it exists and isn’t just an out of control urban legend picked up by the bureaucrats now involved) is in my view a creation of the current chaos in certification and regulatory standards, with standard category certification having been over regulated to the point where nationally varying microlight/LSAs categories were created, plus very high, arbitrarily and politically motivated fuel taxation levels driving people all over the map to find the lowest taxed fuel without the understanding that fuel certification for a given aircraft should exist and should be be a function of both engine design and airframe design. I think it’s a case study in how overregulation and competing bureaucracies create chaos and the opposite effect of that intended.
My decision is 98 E0 or 100LL.
I think that’s rational as long as you are careful with calendar storage time for the E0. A previous owner of my certified plane got it field approved individually to run on 91 AKI E0 unleaded auto gasoline. I spoke with somebody who was involved the other day and he told me that was possible because the previous owner was employed as chief engineer in charge of emissions compliance at an auto manufacturer, in other words he knew exactly how to read the certification standard, how to test to meet it, and how to present the data to FAA bureaucracy. In spite of that being done, even if I could buy E0 fuel I wouldn’t run it. 100LL is about the same taxed price as premium auto gas in my market, everything about it except the lead is much better, and the lead isn’t a significant problem for my engine and roughly 25 hr oil change practice.
For my use the best technical solution would be 100LL minus the lead, but it’s not available to me.
IIRC, one can get rid of detonation just by running at a higher RPM.
But if you are getting detonation at all, even briefly, you will have loads of engine problems in the long run; no way around that.
There is a long story behind the 91UL or UL91. Lots of past posts e.g. here. TOTAL tried to split the market and kill off 100LL, stupidly hoping for, what, nobody knows… They failed, because 100LL is the main product in GA and about 2/3 of its sales volume is in engines which cannot use anything else. Stupid arrogant company. Had they been a bit smarter and tried to sell it for less, they might have got somewhere, but they didn’t. It is 100LL with TEL removed so it should be cheaper.
IIRC, one can get rid of detonation just by running at a higher RPM.
That’s because of fixed angle ignition timing and thereby reduced time per cycle at higher RPM.
It is 100LL with TEL removed so it should be cheaper.
I would love to able to buy it (UL91). My engine was certified on 80/87 Avgas.
LeSving wrote:
There is no good reason to use 95 E10 when 98 E0 is readily available.
Is E0 still readily available across Europe? In Ireland there is no E0 nor E5 available. It’s E10 or Avgas only.
No E0 here. Premium petrol and diesel are E5 and nobody knows how long this will remain. A friend in the business thinks E5 diesel may resist the pressure longer than E5 petrol. I pay extra for E5; obviously it is worth it. E10 is junk; the engine simply does less MPG in proportion to the lower price and runs less well.
Most chains sell E0 in Estonia (even 95).. As somebody wrote, the EU regulation is to sell some % of biomethane out of total fuels sales,so they are selling biomethane, HVO diesel or green electrycity..
