Converting Lycoming 0-320-E2A from Avgas to Mogas?

[Pilatus09]

Hey Guys,

Just wondering has anyone any experience in switching an engine running on Avgas over to Mogas. Its a Lycoming 0-320-E2A

Any help would be greatly appreciated.

Regards
Pilatus09

[BackPacker]

The engine itself won't be that much of a problem. The problem will be in the fuel lines, fuel filters, pump, fitting etc. etc. etc. I'm not an expert, but I know that the experts will want to know what sort of plane the engine is currently fitted to, whether it's a CofA or permit plane, whether there's an STC for it or not, and so forth.

It won't be trivial if it's a CofA plane and no STC is available.

[Pilot DAR]

If Peterson or the EAA have an STC for both the engine and airframe, you're off to a good start (if there is no STC, forget it, it will be more effort than it's worth to approve). Be sure that you can obtain MOGAS manufactured to the standard specified on the STC. It might be that the STC specifies ASTM standard MOGAS, and your local supply is a different standard. In this case, you will have a regulatory gap, which could be a show stopper.

If alcohol or other oxygenate is blended into the MOGAS, it probably will not qualify.

Pilot DAR

[A and C]

I had an aircraft with a Lycoming O-360, the previose owner used AVGAS in one tank for take off and MOGAS for the cruise.

When the engine was switched from AVGAS to MOGAS the EGT went up by about 25F and the RPM dropped by 50 RPM.

I dont think that using MOGAS offers much in the way of economy as it requires more fuel flow for the same engine performance with the engine running hotter.

[ericferret]

If you go on the UK CAA website and look up Airworthiness notice's 98/A/B/C there is a list of airframe/engine STC's for most types.

There are often little or no physical modifications required for high wing aircraft. Although you still have to comply with the relevent STC and the UK AAN'S.

We have operated a Cessna 150 for about 14 years and 1200 hours with Mogas and no ill effects (as yet!!!).

If operating from strips as opposed to airfields avgas is a real pain as you have to travel to an airfield to buy it or ferry the aircraft to refuel.

[IFollowRailways]

There are usually no modifications required.



We have operated a Cessna 150 for about 14 years and 1200 hours with Mogas


What Mogas are you using?

Copied from AWN 98C on the CAA website -

GROUP 1
Any aircraft which has a valid UK Certificate of Airworthiness and has unleaded motor gasoline(EN228) listed as a suitable fuel in the CAA-approved Flight Manual or other approved document, may be taken as satisfying paragraph 1(a) of Schedule 1.

GROUP 2
These aircraft are listed below. To satisfy paragraph 1(a) of Schedule 1 the aircraft and their engines must be modified in accordance with the referenced FAA STCs and comply with AANs 27743 and 27744.




Cessna 150, 150A through 150M, A150K, A150L,A150M, 152 and A152; - aircraft withTCM O-200-A engines with STCSE2031CE, or low-compressionLycoming O-320 engines with STC SE1931CE



SA2048CE Petersen Aviation



Cessna 150, 150A through 150H, and 150J through 150M - aircraft with TCMO-200-A engines with STC SE634GL


SA633GL Experimental Aircraft Association


If your aircraft is not included in Group 1 above and your Cessna 150 is in Group 2 and it has not been modified and approved with one of the above STC's and you are using Unleaded Mogas I would suggest that you are invalidating your C of A and Insurance!

[Rod1]

Pilatis09

As has been said above, until we know what aircraft and what regulatory system we are not going be of much help. As a general rule most aircraft can run fine on pump mogas, provided you check it for alcohol, which is simple to do. I operate 80% of the time on mogas and only revert to avgas in very hot weather or if touring and no mogas availability. The cost saving is huge as I burn exactly the same in LPH terms and am paying £1 pl instead of £1.40

Rod1

[Pilatus09]

Hi,
The engine is in a MS892 Rallye 150GT, I looked through the CAA website and found that there is an STC for it:
(SE1931CE - Petersen Aviation SE800GL - E.A.Association)

But i'm not sure where to go from here, the aircraft is on the Irish reg, but as far as i know the IAA use the same/similar documents as CAA so don't think there should be a major problem.

Regards
Pilatus09

[BackPacker]

But i'm not sure where to go from here

Contact the IAA?

Seems you've got all the info you need, including an STC approved in a JAA country, to ask for the exact position of the IAA right there. Unless the IAA is monitoring PPRuNe and following up on posts here, I don't think we can be of any more help.

[Pilatus09]

Yes i suppose your right,

Thanks again for all the info, much appreciated guys

Pilatus09

[Pilot DAR]

I do not agree with A and C.

MOGAS has very slightly more energy per unit weight or volume. It therefore will not require more of it for the same performance in approved use. The engine will not run hotter, unless you're operating it differently than you did on AVGAS. If all else is equal, in an approved application, you will no be able to detect an operational difference between the fuels, other than smell, colour and cost. Now, if you were to use regular MOGAS, where the high octane of 100LL were required, and the engine was running hotter, you're probably having detonation, and are about to learn a very expensive and unsafe lesson!

If the airframe is not STC'd, it will require a considerable effort to assure SAFE operation is possible, then approve it. A Rallye is not a good candidate. I have done such approvals in the past, in particular, a Cessna 185, with a modified engine. Certain airframes should not be attempted.

Pilot DAR

[BackPacker]

Just out of interest, re AandCs post. Does mogas require a different mixture setting than 100LL? May that be the explanation for the engine running hotter when switching in-flight?

[Pilot DAR]

Any differences in ideal mixture between MOGAS and AVGAS would be so slight as to be imeasureable. The characteristics of the two fuels which make MOGAS not suitable for some airframes, are centered on volatility, and the presence of aromatics and alcohols which may cause deterioration of some fuel system elements. The energy content and burning characteristics of the two fuels will be about the same, as long as the anti-knock index is appropriate to the compression ratio of the engine.

I have previously posted considerable information in threads here, which a search should turn up for you.

Pilot DAR

[Pilatus09]

Hi Pilotdar,
Just wondering could you tell me why a Rallye would not be a good candidate for conversion to Mogas?? I know that there is an STC out for the rallye as you can see from above posts

Pilatus09

[Pilot DAR]

Hi Pilatus,

Typically low wing aircraft are less well suited to MOGAS use than highwing. This is particularly the case with a combination of hotter climate, and higher volatility fuel. There is a greater chance of vapour lock, as the engine fuel pump draws the fuel upward. A high wing aircraft has "head" pressure, and thus much less chance of vapour lock.

If there is an STC for the airframe, read it carefully, operate as instructed, and you'll be fine.

Pilot DAR

[Mariner9]

To avoid vapour lock, you need to maintain a net positive suction head (NPSH) at the fuel pump.

The fuel pressure head (ie high wing vs low wing) is only one of many factors that effect the NPSH.

High wings are in theory more suitable for Mogas, but the fuel pipeline diameter, number of bends/joints in the fuel line, fuel velocity, distance to the fuel pump, fuel volatility, & operating temperature all have significant effects, any one of which can easily exceed the "benefit" of high wing tanks. :8

[411948]

I am running an 0-320e2a. With Peterson Aviation STC SE1931CE. DJA is a 1974 Piper PA-28 Cherokee. There were no modifications to the A/C at all. Plackards indicating MOGAS use on both tanks.Unleaded or super. Minimum Avgas 80/87. Super grade petrol AKI 97. Unleaded normal or Premium Min AKI 87. Or any mixtures of these including Avgas.
Categories of operation are limited to Private and aerial work.
Carburettor icing will occur earlier than with avgas in the same atmospheric conditions. Carburettor heat is to be used as per A/C manual.
Under higher temperatures as in Aust' mogas will vapourise from your tank at a much higher rate than avgas therefore range should be given .
I constantly use 4.5 to 5 hour flying times. I tend to keep a 50/50 mix avgas and mogas in one tank and use it for T/O and L/ing
The 0-320 uses a fuel pump the same as a truck sucking fuel from a tank under the chassy.We are sucking from an air cooled wing to a pump in the open air behind the motor baffels. There is no more a chance of getting an air/vapour lock due to heat in an A/C than a car. However the PA-28 is fitted with an electric pump that is used for take off and landing.
If one is using unleaded continually some valve recession may occur. this can be remided by mixing 10 % leaded fuel with the unleaded.

If i were you i would go direct to Peterson Aviation via the faa web site quote stc SE1932CE They will give you your local contact and you can go from there.
Good luck

[gasax]

The 'modification' which is necessary for the majority of CAA approved Mogas types is the addition of a placard and an entry in the logbooks. That should tell you that the vast majority of 'technical issues' are theoretical at best.

The higher compression versions of even the O-320 are not cleared for Mogas and a number of airframes are in the same category, including IIRC some later Pa28s?

The addition of a fuel return line would address the vast majority of other suitable airframe types (with low compression engines) but on C of A aircraft the would be a major mod, allied with the use of Mogas as well the whole thing would just be too hard.

[Croqueteer]

:suspect:The only problem I've found with mogas over 20 or so years is that if you fly, land and shut down for a short time, the carb and the fuel in the lines heat soaks from the engine, and when you start up and apply power, the fuel in the now hot carb boils (I think the rough boiling figures for avgas is 80c and mogas 40c) and the only way out of the carb is through the main jet resulting in a vastly over-rich mixture and probably a rich cut. I think the gliding fraternity are well versed in this prob.

[Maoraigh1]

The group I'm in operate a Continental O-200 in a low wing (DR1050 with fuselage fuel tanks.) We always use EN228 unleaded, as per EASA, except when refuelling away. The only problem is carb ice, especially in moist summer air. Rarely do we have to use avgas because of the 21C temperature limitation.
I check the temperature of fuel drained from the gascolator if the aircraft has been parked into a warm wind with a hot engine. As the gascolator is behind the engine, I've had vapour lock on the take off run, as I opened the throttle. (Confirmed by using fuel drain after clearing runway - froth came out under pressure).
We've operated on EN228 since it was approved by the CAA/EASA.
You don't need to buy an STC, unless you are flying in FAA jurisdiction.

[IFMU]

:suspect:The only problem I've found with mogas over 20 or so years is that if you fly, land and shut down for a short time, the carb and the fuel in the lines heat soaks from the engine, and when you start up and apply power, the fuel in the now hot carb boils (I think the rough boiling figures for avgas is 80c and mogas 40c) and the only way out of the carb is through the main jet resulting in a vastly over-rich mixture and probably a rich cut. I think the gliding fraternity are well versed in this prob.

I've never seen this problem. My 200-ish hours of towing have all been on auto gas, except one time when I refueled at an airport during a retrieve. We do a lot of short-time shut downs as the next guy in the glider is not always ready. I am a big believer in auto gas for low compression engines. Our towplanes get worked hard and go to TBO. Our C140 used to foul its mags on 100LL, that problem went away completely on autogas. Plus it's a lot cheaper.

Typically low wing aircraft are less well suited to MOGAS use than highwing.
One of our pawnees has wing tanks, one has a cowl tank. I can't tell the difference between the two regarding the fuel system, except that the one with wing tanks has a boost pump. It is no more difficult to operate on mogas than the other tugs.

-- IFMU

[Croqueteer]

:confused:IFMU, My experience of this is at Aboyne about 20yrs ago, where they did have a problem of heat soak with the tug, a Rallye if I remember correctly. We also had it in our Stampe, where you could actually hear the fuel bubbling and could see it jetting into the manifold. Not a common problem up north, but on moving to the Midlands in a hot summer, it was significant. The positioning of the carb could have a lot to do with it. Just little bits of info to help the big picture. I use mogas myself.

[Mariner9]

I think the rough boiling figures for avgas is 80c and mogas 40c

Not quite right, and the true situation is more complex than simple boiling points (which of course vary depending on atmospheric pressure, although the reported values in analysis are corrected to standard pressure).

Dealing 1st with Avgas, initial boiling point (IBP) is not specified, and can be anything from ~30C (providing it meets volatility specs) up to a theoretical maximum of ~70C (based upon the maximum specified temperature for 10% of the fuel to have evaporated of 75C). In practise however, the IBP of an Avgas is usually 50-60C, though as I said above, this figure does not form part of the specs and thus is generally unreported.

For Mogas, the initial boiling point is also unspecified. Instead volatility is specified using a combination of Distillation data, Reid Vapour pressure (both of these specs change with the season), and Vapour lock index. The initial boiling point for Mogas could be higher than that of Avgas in theory (the lowest RVP specified for Mogas is less than the highest specified for Avgas, & the 10% evaporation limit is not specified in Mogas), although in practise it is typically around 30-35C.

M9 :8

[Mickey Kaye]

So if one is in the UK and get STC approval for a PA-28 say are they then allowed to use this aircraft on MOGAS for instruction.

Might save a bob or two?

[Big Pistons Forever]

I personally would not fly an aircraft on MOGAS because you have no idea what additives (MOGAS is loaded with brand and season specific extra chemicals) are in the fuel and what effect they will have on hoses and seals. Also the fuel is not subject to the stringent handling process required for AVGAS, therefore there is a higher probabilty it could be contaminated. Finally the lead in AVGAS helps lubricate the valve stems and is, I believe the reason for many reports of premature valve wear particularly in Lycoming engines.

If MOGAS is truely benign than why does it's use void the factory warranty for both Continental and Lycoming engines ?

[gasax]

It is not approved because Lycon would have to repeat the certification tests on their range of engines - given their present incompetent quality control there is every likelihood they would fail if they did that! These companies are very risk averse and in the US Mogas is a minority fuel so there is no driver to make them approve it.

Why do Lycomings suffer from valve wear? Again mixed quality control and poor geometry of the valve gear - wonder why there are so many after market modifications to these engines?

Put this in perspective. Lycons were designed over 60 years ago. The 'quality' of the fuel was pretty mixed then. Does your car cough to a halt every time you fill up at some rundown filling station? Oh course not - we fill up without a thought.

Additives? well singing the praises of tetra-ethyl lead whilst decrying non-oxidisers seems a little selective!

[Big Pistons Forever]

gasax

Sorry to wind you up. I prefaced my post with the caveat that I personally would not use MOGAS. If you feel comfortable using it than that is obviously your choice. I provided a different point of view to balance the discussion and trust that all readers will take any advice offered on an anonymous internet forum with the appropriate grain of salt.

[gasax]

Big Piston no problem.
You come from a land where petrol is cheap (and the land flows with milk and honey - well not quite). In your circumstances there is little point in using Mogas unless there are major problems in sourcing Avgas.

In Europe the cost of any fuel is by your standards horrible. The additional cost of Avgas (often as much as 40%) makes ths discussion very important to people on this side of the Atlantic.

Your points about seals and hoses though are well made given the potential increase in the amount of alcohol in Mogas which is coming due to the political directive for 'green' sourcing.

Hopefully most of the materials will be OK (they are in my aircraft because it was built to run on Mogas) but on the older spamcans we'll see.