AAK Mega Bushman Engine Choice

[nickduncs84]

Last weekend I flew up to Taree to meet Ole and Brian at AAK. I've been looking at a STOL plane for a year or so and they are the top of my list. Even though I know better, I'm looking at a 4 place. As such, I need 250-300hp up front. This is a bit of a hang up as I ain't spending 80K on a new lycoming 540 series. So I think the options are either a mid time or even an overhauled Lyco or an experimental clone.

 

I've come accross the Titan R series. The R540 puts out 300HP in about 160kg which is quite a bit less than the Lyco. Obviously they are high compression cylinders, but what I don't get is how they are compatible with 91 octane fuel? From what I understand 91 octane is pretty close to BP 98. I was under the impression that auto gas was only suitable for low compression engines.

 

Can any of the resident gurus help me out as my brain is starting to hurt trying to make sense of all this stuff!

 

http://www.titanengine.com/rseries/

 

 

[Camel]

Did it say RON ?

 

Measurement methodsEdit

 

A US gas station pump offering five different (R+M)/2 octane ratings

 

Research Octane Number (RON)Edit

 

The most common type of octane rating worldwide is the Research Octane Number(RON). RON is determined by running the fuel in a test engine with a variablecompression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.

 

Motor Octane Number (MON)Edit

 

Another type of octane rating, called Motor Octane Number (MON), is determined at 900 rpm engine speed instead of the 600 rpm for RON.[1] MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern pump gasoline will be about 8 to 12 octane lower than the RON, but there is no direct link between RON and MON. Pump gasoline specifications typically require both a minimum RON and a minimum MON.[citation needed]

 

Anti-Knock Index (AKI) or (R+M)/2Edit

 

In most countries, including Australia, New Zealand and all of those in Europe,[citation needed] the "headline" octane rating shown on the pump is the RON, but in Canada, the United States, Brazil, and some other countries, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI), and often written on pumps as (R+M)/2). It may also sometimes be called the Posted Octane Number (PON).

 

Difference between RON, MON, and AKIEdit

 

Because of the 8 to 12 octane number difference between RON and MON noted above, the AKI shown in Canada and the United States is 4 to 6 octane numbers lower than elsewhere in the world for the same fuel. This difference between RON and MON is known as the fuel's Sensitivity,[4] and is not typically published for those countries that use the Anti-Knock Index labelling system.

 

See the table in the following section for a comparison.

 

Observed Road Octane Number (RdON)Edit

 

Another type of octane rating, called Observed Road Octane Number (RdON), is derived from testing gasolines in real world multi-cylinder engines, normally at wide open throttle. It was developed in the 1920s and is still reliable today. The original testing was done in cars on the road but as technology developed the testing was moved to chassis dynamometers with environmental controls to improve consistency.[5]

 

Also https://www.torquecars.com/articles/fuel-octane-ratings.php

 

This being very relevant.

 

Modern RON tests use computerized apparatus and the method has been refined so fuels with a RON greater than 100 can be assessed, but the basic principle remains unchanged.

 

Abbreviation Definition Notes

 

RON Research Octane Number UK, Europe, South Africa & Australia

 

MON Motor Octane Number Motor sport applications. Measured under more severe conditions than RON (higher revs etc). Usually 8-10 units lower than the RON.

 

RdON Road Octane Number Average of RON & MON. Usually 4-5 units lower than the RON. USA, Canada

 

AKI Ant Knock Index Average of RON & MON. Usually 4-5 units lower than the RON. USA, Canada

 

PON Pump Octane Number Average of RON & MON. Usually 4-5 units lower than the RON. USA, Canada

 

(R + M )/2 Average of RON & MON. Usually 4-5 units lower than the RON. USA, Canada

 

Octane number, Octane rating or octane Could refer to any of the above, if you can work out which country the article was written in you should be able to work it out.

 

 

[aj_richo]

The R series spec sheet says they run 10.5:1 compression and can use 93\100\100LL fuels

 

These guys make a product that is basically 100LL with no TEL, and mention 91 Octane = 94MON

 

https://swiftfuels.com/fuel/unleaded-94-mon-avgas/

 

I don't pretend to understand it either, but the R series spec sheet does not mention auto fuels

 

 

[facthunter]

Have you looked at the alloy Chev/Holden V8 with redrive. It's one auto engine I think deserves a place in an aircraft. (Suitably modified/converted). Nev

 

 

[facthunter]

There are some used for glider towing in Pawnee's Nev

 

 

[bexrbetter]

Ask Ross Farnham about opinions for suitable Chev V8 conversion, he is a member here; rv6ejguy

 

http://www.epi-eng.com/aircraft_engine_products/aircraft_engine_products_contents.htm

 

http://v8aircraft.com/

 

 

[fly_tornado]

just buy a used engine, like everyone else that builds.

 

 

[facthunter]

Why, when a new one is so cheap, in this instance. It would pay to look into the range of specs available. Nev

 

 

[Yenn]

There is one disadvantage to using a new engine with a new build aircraft.

 

With a new engine you have to break it in at the same time a you are test flying your new aircraft.

 

My first build I used an old 1600 jab engine. No problems with break in, but I did have other problems due to the engine being very tired.

 

My second build I had a brand new Lycoming and an aeroplane that was brand new and I hadn't flown that model before. It all went well, but there was a tendency to get the CHT too high. A but of a distraction for a first flight.

 

If you could get a good condition used engine I would suggest that is the way to go.

 

 

[facthunter]

You have no idea of it's history if it's out of a car.. Modern engines have fits and finishes that make running in hardly an event. If you give them too easy a time you often have problems with excess oil consumption. Just control your temperatures which tend to be a bit higher in a new motor, for a little while. Race engines don't really get a running in either. If your clearances are not right it will fail. Nev

 

 

[nickduncs84]

Thanks everyone. It seems I've narrowed it to a used o540 or an ls series v8. I never thought I'd consider an auto conversion but it seems like there are quite a few people with good experiences with the ls engine and an o540 isn't as reliable as the 4 banger lycos anyway.

 

Still a lot go through on the ls engines. The epi guys aren't doing them anymore although it looks like there is a seabee guy who is.

 

Progress at least!

 

 

[facthunter]

Once you get into the over 300 HP range it's serious money. The turbocharged O540s have to be operated carefully and best used all the time. (Not sitting around) and you have an expensive prop as well. The original Spitfires were fixed pitch wooden props so maybe that is an option if you are into saving money. Have you considered the Romanian radial in the Russian and Chinese planes we have plenty off around here. ? About the size you want, or a bit smaller 285 HP. and maybe firewall forward adaptions. Sukhoi engine may be a bit more power...Nev

 

 

[Oscar]

Nick - an LS conversion is a serious proposal for the power you want at reasonable weight - BUT you need to be VERY, VERY careful in regard to the PSRU you select. The late Terry Kronk had an LS conversion ( I believe) in his immaculately built 80% scale Mustang, the PSRU failure killed him. Suggest you look at: http://www.epi-eng.com/aircraft_engine_conversions/conversions_contents.htm

 

(EDIT: oh bugger - just saw the comment that epi are NOT doing them any more!.)

 

Terry Kronk was no cowboy, he was a damn fine aircraft builder. I and other family members bought some of the stuff from the disposal sale of his workshop after his death, and all my clecos (for a start) are ex-Terry. PSRUs are a really, really serious concern for auto-engine conversions and I doubt Terry did not take care in his selection. A good LS1 conversion with a reliable PSRU has every chance of being an excellent power choice - but with anything less than an excellent PSRU, not so.

 

 

[bexrbetter]

And then there's the thousands of PSRU's running around, tens of thousands of Rotax of course. I know Lycoming 540's have stopped also killing those onboard, etc, etc ....

 

I have always been surprised at the effect that singular incidents have in this industry.

 

Nick, one reason I mentioned Ross is because he was recently involved with a LS powered plane, and he's an honest, decent guy ...

 

http://www.sdsefi.com/

 

 

[fly_tornado]

these guys are using an airboat gearbox

 

 

 

[nickduncs84]

Thanks everyone. At the end of the day safety is the priority and is one of the main reasons I've opted for a stol plane over something more slippery. I'll see how I go with the ls route but if I can't be convinced of the reliability I won't be doing it.

 

 

[bexrbetter]

I had a miss in my car, started last week, darn spark plugs had to be replaced, got it back today runs like new.

 

Bit cranky they only lasted 10 years (almost to the day) and 256,000 kms.

 

Starter mtr, fuel tank filter, 2 batteries and now the spark plugs ... I think I got a lemon.

 

 

[nickduncs84]

Well even though the EPI guys aren't doing engines anymore, they were more than helpful with both the info on their site (which pretty much covers everything) as well as responding to emails. The long of the short of it is that a ls engine for applications of around 300hp or less doesn't make sense from any perspective. Perhaps the biggest issue is the weight as when it's all said and done, you're looking at 900 lbs or so. Compare that to the 360lbs or so for the 335hp titan r540 and you're talking apples and oranges.

 

So I'm back on aero engines. The options are, a mid time or overhauled o540, a classic style clone like the titan x540 or the titan r540 which from a power to weight perspective looks like a real beast. Originally, I wanted to run mogas, but 50lbs more and 100hp less is a big sacrifice. It's awfully tempting to suck up the extra $20 an hour for the avgas!

 

 

[diesel]

A friend built a murphy moose with a russian radial. Thats serious hauling. The biggest psru killer is too much propeller mass and light flywheel. Robin aircraft had certified peugeot V6 and porche engines. Mooney also used the porche. My pic would be the peugeot, jaguar,ford combined effort with their excellent V6 diesel. Chas

 

 

[facthunter]

If you can't find a reliable car engine conversion, unless you have a lot of time and the motivation go for the 285 HP Russian/ Romanian, Radial. Plenty around and not expensive. Bit thirsty but not outrageous. Nev