Hi ,
Thought this might help .
Road fuels tend to be measured on a RON scale, for which unleaded fuels tend to be 95 - 98 RON but are only 85 - 87 MON. Avgas is measured on Lean Mixture (similar to MON) but also has a Rich Mixture Octane rating.
The Lean Mixture rating is 100 octane (15 octane higher than the comparable 85 MON for unleaded Mogas) but Avgas also has a Rich Mixture rating of 130 which allows higher supercharger boost pressures to be used without detonation occurring. This is particularly a problem when using high power settings at low altitude, for example during take off.
Cheers
JQ
Running 98 in a 22?
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- Silver Wings
- Posts: 23
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- 1st Dan
- Posts: 285
- Joined: Sep 2007
Re: Running 98 in a 22?
I've no problem using 98 Octane Petrol. It's the quality in which it's manufactured, transported and stored that's the issue for me.
Just because it comes out of a bowser, doesn't mean it's good quality fuel.
Just because it comes out of a bowser, doesn't mean it's good quality fuel.
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- Gold Wings
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Re: Running 98 in a 22?
Not to mention the unspecified and undeclared additives to the vehicle fuel, and the lack of additives anticipated in Avgas.
Keep it flying, don't quit!
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- Gold Wings
- Posts: 120
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Re: Running 98 in a 22?
If you look into the fuel stations standards 98 can be as low as 93 so you don't actually know what your using, avgas is also 80% less likely to grow bacteria
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- Silver Wings
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Re: Running 98 in a 22?
I have run 95-98 in 44's with no problems at all, in fact didn't notice a difference and some people I've talked to running it in 22's reckon they run better.
STC's are readily available for both types for not a lot of $ but not injection models.Shop around different fuel supplies to make sure you are getting a good product, Caltex was good from memory where I was and any ethanol is a no no.
Now here's the problem, pilots using it need at least a couple of brain cells because detonation & vaporisation are real problems so need to read literature and do their homework to understand this or it mightn't end well one day. This is what I used to do, once temp's got to late 20's start running a mix say 50/50 then once into 30's back to straight avgas, this worked for me & bear in mind that if you are working the machine hard with higher cylinder head temp,s even in the mid to late 20's degrees detonation could happen earlier with the lower OAT or this was my take on it anyway.
STC's are readily available for both types for not a lot of $ but not injection models.Shop around different fuel supplies to make sure you are getting a good product, Caltex was good from memory where I was and any ethanol is a no no.
Now here's the problem, pilots using it need at least a couple of brain cells because detonation & vaporisation are real problems so need to read literature and do their homework to understand this or it mightn't end well one day. This is what I used to do, once temp's got to late 20's start running a mix say 50/50 then once into 30's back to straight avgas, this worked for me & bear in mind that if you are working the machine hard with higher cylinder head temp,s even in the mid to late 20's degrees detonation could happen earlier with the lower OAT or this was my take on it anyway.
- with altitude
- Gold Wings
- Posts: 120
- Joined: Mar 2007
Re: Running 98 in a 22?
Can have the same argument running diesel in turbines.... I know people who do it... makes the machine much more dirty but the diesel rebate if your a farmer is worth it against the jet fuel prices....
Never take life seriously. Nobody gets out alive anyway.
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- Silver Wings
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Re: Running 98 in a 22?
Interesting thread, I've heard of people doing it and remember brief conversations about it when in training just hadn't seen it in the flesh. I think for the small price difference I'd rather be putting in the leaded bang juice if I owned a machine.
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- Silver Wings
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Re: Running 98 in a 22?
To use Alice Springs as an example.
98 ULP bowser price $1.98 per litre
Avgas tanker price $2.44 per litre
So for a R44 $27.60 saving per hour using 98.
98 ULP bowser price $1.98 per litre
Avgas tanker price $2.44 per litre
So for a R44 $27.60 saving per hour using 98.
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- 2nd Dan
- Posts: 373
- Joined: Jul 2012
Re: Running 98 in a 22?
Sheldon,
(Great name).
Mate, that's 2 beers (in Sydney per hour) ! And all to ensure you get the right fuel and the big fan keeps going.
I'm happy with AVGAS...but I am also happy to put 98 in those machines IF I need to and IF I get the LAME's permission.
Arrrj
(Great name).
Mate, that's 2 beers (in Sydney per hour) ! And all to ensure you get the right fuel and the big fan keeps going.
I'm happy with AVGAS...but I am also happy to put 98 in those machines IF I need to and IF I get the LAME's permission.
Arrrj
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- Silver Wings
- Posts: 37
- Joined: Sep 2011
Re: Running 98 in a 22?
I had the opportunity to do a direct comparison a few years ago flying a radial air tractor on a large seeding job. I was alternating between 98 and avgas. was not any noticeable difference in performance but was definitely had a big difference in how smooth it ran between the two. I would imagine running an avgas engine on 98 will eventually shorten it's lifespan.
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- Silver Wings
- Posts: 38
- Joined: Jul 2011
Re: Running 98 in a 22?
The lead in the fuel also acts as a lubricant on the seat and face of the intake and exhaust valves of the engine. Newer vehicle manufacturers have used different metals on the valves to avoid burnt valves but those lycomings are reliable, however old technology. There is a small amount of lead inherent in Pump gas anyway, but obviously not at the Avgas levels.
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- 3rd Dan
- Posts: 601
- Joined: May 2010
Re: Running 98 in a 22?
While I'm all for saving money in the operation of my helicopters, if you need to save $27/ hr, then maybe you need to reassess if you can afford that helicopter. The short term saving always cost more in the long run.
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- Silver Wings
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Re: Running 98 in a 22?
Food for thought. R44 raven 1 in Victoria
Avgas $2.35
Mogaas $1.53 minus road tax $0.19
Say $1 difference.
$60 per hour x 2000 hours = $120000
Not taking Into account the odd splash of avgas required every 75 hours.
One could replace the engine @ 1000 hours with a new one out of a crate and still be potentially $50-$60kbetter off@ 2000 hrs Not to mention the flexibility of remote operations. There are a few trick f#*ks. But nothing an educated pilot can't manage. The only problem I have encountered was the "maintance person" decided to advance the timing. I did a top inspection @ around 600 hour with no signs of any adverse wear or damage.
Avgas $2.35
Mogaas $1.53 minus road tax $0.19
Say $1 difference.
$60 per hour x 2000 hours = $120000
Not taking Into account the odd splash of avgas required every 75 hours.
One could replace the engine @ 1000 hours with a new one out of a crate and still be potentially $50-$60kbetter off@ 2000 hrs Not to mention the flexibility of remote operations. There are a few trick f#*ks. But nothing an educated pilot can't manage. The only problem I have encountered was the "maintance person" decided to advance the timing. I did a top inspection @ around 600 hour with no signs of any adverse wear or damage.
Jarrod Janson
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