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Old 09-20-2007, 06:24 AM   #1
mfuess
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Default 112 Octane LEADED Gas

I couldn't help myself, I had to try some Sunoco 112 Octane racing gas in my DA-50. At $8.00 a gallon this isn't something one would do on a regular basis. But I figured it's worth a try one time.

The DA-50 fired up as usual, 4 choked flips & 4 open flips and it was purring. The first thing I noticed was, the idle had more kick. It had a slightly louder pipe noise also. After a warm up I nailed the throttle and she aggressively spooled up to top RPM. To my surprize, it didn't gain any more top RPM though. I could idle it down lower than normal holding a solid 1400-1440 RPM. The throttle transition is supreme as compared to un-leaded 93 Octane. I didn't see any appreciable cylinder temperature difference, although the 112 was hotter at the exhaust.

I did a minor re-tune to peak the fuel performance and the DA-50 responded well. From idle to full power is where the 112 really shines. It has a very aggressive throttle under a heavy load.

It was fun testing the 112 out, but in all reality this isn't the fuel I'd go spend $8.00 a gallon on... just to fly around.
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Old 09-20-2007, 06:41 AM   #2
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Default Re: 112 Octane LEADED Gas

Quote: Originally Posted by mfuess
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I couldn't help myself, I had to try some Sunoco 112 Octane racing gas in my DA-50. At $8.00 a gallon this isn't something one would do on a regular basis. But I figured it's worth a try one time.

The DA-50 fired up as usual, 4 choked flips & 4 open flips and it was purring. The first thing I noticed was, the idle had more kick. It had a slightly louder pipe noise also. After a warm up I nailed the throttle and she aggressively spooled up to top RPM. To my surprize, it didn't gain any more top RPM though. I could idle it down lower than normal holding a solid 1400-1440 RPM. The throttle transition is supreme as compared to un-leaded 93 Octane. I didn't see any appreciable cylinder temperature difference, although the 112 was hotter at the exhaust.

I did a minor re-tune to peak the fuel performance and the DA-50 responded well. From idle to full power is where the 112 really shines. It has a very aggressive throttle under a heavy load.

It was fun testing the 112 out, but in all reality this isn't the fuel I'd go spend $8.00 a gallon on... just to fly around.
In my experence with these industrial engines,and confering with Homelite engineers, 87 octane is all that is required for proper heat range and power output. In order to take advantage of the higher octane fuel, one must advance the timing, and increase the compression ratio, which will require a different piston design. Actually a petroleum engineer once stated that, "87 octane gasoline has more enegery per unit than 69 or 91-93." Happy flying. Jack
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Old 09-20-2007, 06:44 AM   #3
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Default Re: 112 Octane LEADED Gas

Yep....race gas does nothing unless the timing is different... if anything it "can" be counter productive and harmful.....

Use what the manufacturer recommends
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Old 09-20-2007, 08:31 AM   #4
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Default Re: 112 Octane LEADED Gas

Octane of the fuel is a number in which the fuel is rated as too how it resist detonation the higher the number the more detonation resistant, this is simply stated that the fuel will have more resistance to being lit. The reason 87 octane has more enegy per unit is that it burns hotter for the same air/fuel mixture than a higher octane fuel, the lower octane fuel is more explosive therefore it is more easily lit by something other than the spark plug at the correct time, which will cause detonation and if bad enough or prolonged will cause major engine damage. Racing fuel which has a higher octane resists detonation and therefore making a higher compression engine run hard without causing the ring lands to be hammered shut or burning a hole in a piston or wiping the rod bearings out. The reason your exhaust temps went up is explained in your statement that you adjusted for peak performance which you should have had to lean the engine with the higher octane fuel therefore causing a higher exhaust temp but keeping very similar cylinder temps .....The engine runs leaner without added heat and makes slightly more power.
The biggest benefit from "race gas" is that what you get today will be the same as what you get next week and it doesnt go bad in 30-60 days like pump gas. Plus it does not stink like pump gas for 2 hrs after you get it on your hands. Hope this helps people understand the difference in the fuels and thier benefits to the engine. Yes a stock engine will run well and for a long time on 87 octane but a hopped up high compression wild timing engine will live a short expensive life without the correct octane level being used with it.
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Old 09-20-2007, 09:00 AM   #5
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Default Re: 112 Octane LEADED Gas

The exhaust was higher because race gas burns slower and it's still burning in the muffler to certain degree. pun intended...
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Old 09-20-2007, 09:23 AM   #6
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Default Re: 112 Octane LEADED Gas

This does however bring up an interesting point... all the explanation before me is correct, and the only way to have gained more HP would be possibly to advance the timing, but you would also have to advance the fuel ports. The idea is that you are igniting the fuel sooner before the cylinder reaches top-dead-center (TDC). So that knocking (detonation) you might hear, like in a car struggling to go up a hill, is the fuel pre-igniting from heat and compression vs. the spark. Higher octane resists pre-ignition. And essentially all you end up doing is sliding your HP curve up the rpm range as you advance the timing. Now here's my point... has anyone tried to use some sort of forced induction on any of their planes. supercharging or turbocharging is not realistic in these models due to weight concerns, but I could very easily see some of these speed planes incorporating some sort of ducting that would make use of it's speed. I doubt you would gain a tremendous amount of positive pressure, but any amount of positive pressure would be better than a vacuum. And I could see an application like this utilizing the higher octane of the race fuel.

One other thing not mentioned here is the added benefit of this race fuel being "leaded". Lead was originally added to act as a buffer/lubricant for the valve/valve seats of older cars. But cars do not use them today as they ruin O2 sensors and all cars today use hardened valve seats. (Not to mention... LEAD POISONING) I wonder how much of your RPM transition was due to increased lubrication as opposed to octane increase. I guess you could always get your hands on a few mattel toys and scrape the paint into some good ole' 87 octane and see what happens. (that was a joke) Any input though on forced induction?

JP
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Old 09-20-2007, 03:05 PM   #7
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Default Re: 112 Octane LEADED Gas

I have been running 110 octane racing fuel for many years. I have noticed no difference in power at all. It hasn't hurt any of my engines, they all run great. Cost is $4.75 per gallon.So why would I continue to pay almost $5 per gallon and continue to use this over regular gas for many years? Odor. I haul my planes in a van and store some inside the house. I cannot stand the smell of gas, however the racing fuel has very little odor and is not very offensive when you do smell it. Also, my wife no longer complains about smell when I bring one of my planes inside. For me racing fuel is the only option for flying gas planes.FWIW
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Old 09-20-2007, 03:55 PM   #8
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Default Re: 112 Octane LEADED Gas

Slightly off topic but would a guy be better off runing a higher octane fuel to produce better smoke due to the higher egt?
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Old 09-20-2007, 05:10 PM   #9
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Default Re: 112 Octane LEADED Gas

It's always been my experience that if you aren't having any detonation problems, then you don't need any higher octane. In fact, several of my engines will run a good bit hotter on 93 than 87... Go figure.

One thing you should watch out for is the leaded gasoline. The lead will actually foul your spark plugs.
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Old 09-20-2007, 05:48 PM   #10
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Default Re: 112 Octane LEADED Gas

It would be interesting to get a DA150 on Alcohol and see how much more power we could get....
two an'a' half times more fuel flow though right?
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Old 09-20-2007, 06:12 PM   #11
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Default Re: 112 Octane LEADED Gas

I'm currently flying a 3W170CS that requires 98 octane. I've been running Sunnoco 104 and now after breakin I'm mixing 104 and 93.
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Old 09-20-2007, 06:19 PM   #12
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Default Re: 112 Octane LEADED Gas

The Horizon boys are running two DA's on alcohol in racers. They sure as heck make some noise. The are not really able to be throttled. Its just half throttle and full and then stop. They run em out of gas to land them ans they would never slow down other wise.

I hate to think what RPM they haul but is wild thats for sure. I watched one throw a prop a year or so back and man did that make the crowd stand up on tip toes.
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Old 09-20-2007, 06:42 PM   #13
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Default Re: 112 Octane LEADED Gas

Jager, the 170cs does not need 98 octane, the manual says that, but in Europe they calculate octane ratings different than us. I am not sure of the exact number, but 98 octane in Europe is like 87 or 88 here. I use 93 in my 170cs.

Last edited by Flyinrazrback; 09-20-2007 at 06:55 PM.
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Old 09-20-2007, 07:30 PM   #14
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Default Re: 112 Octane LEADED Gas

what about using 100LL, there is no odor like pump gas and evaporates nice and quick without smell or residue.
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Old 09-20-2007, 08:03 PM   #15
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Default Re: 112 Octane LEADED Gas

I called DA a few months back and asked a tech what octane they recommend for all of their engines. Simply put.........87 is all you should use. That's what they are designed for. But hey, if you tried 112, that's cool! Makes this hobby more funner!
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