Fuel Type Question (Please simple answers only)

[Rotor-Head]

I started a thread on this a while back but it got off track, and eventually off the subject. I'm looking for a simple answer...

I currently run 92 Octane non-ethenol fuel in my 503 DCDI... Can I go back and forth from the 92 to 100LL without any performance issues and is there a transitional break-in period to swap fuels from 92 to AVGas??

Thank You

[All_In]

Hi Shawn
Not sure about 2 strokes as they have rotary values but 4 strokes must use Decalin to reduce lead.

I would suspect it would help with lead in the 2 strokes not fouling plugs however 503 are suppose to use 87 octane so that may also be a problem with frequent use.

Here is a quote from Decalin:

667 Decalin RunUP Fuel Additive 32oz. Decalin Chemicals manufactures products for the experimental aircraft aviation community. Decalin Fuel RunUp Additive in a 16 ounce bottle, treats up to 320 gallons of fuel. Scavenges Lead in aviation fuel after combustion to prevent lead oxide buildup on valves but still allows the lead to perform the anti-knock function prior to combustion. It is an excellent additive for auto conversions, where it reduces buildup on oxygen sensors and plugs. If you have to use 100LL, then this product is for you. Prevents valve seat erosion from valve seat micro welding. It is equivalent to TCP (for experimental only). Does not contain volatile solvents so it is safe to ship and safe in the cockpit. You can carry it with you for out-of-town airports. Easy to use graduated measuring and dispensing reservoir built into the bottle. 1/2 oz. mixes with 10 gallons of 100LL Fuel. Tested and stable down to 0 degrees F. Decalin is not approved for use in the engines of certified aircraft.

[BEN S]

Shawn,
Simple answer is yes.
I have about 300 hours on my 503, and was nervous about using Avgas in it, but as you well know, if you land at an out of the way airport (like Needles CA) you aren't about to get any MoGas, only Avgas.
My first time using it was at a fly-in in Utah. I have found two things of note with the 503 and Avgas, first it will leave a strange/scary orange hue to the plugs....I'm told this is normal and more importantly I had to decarb/delead the piston heads at the 150 mark. However smarter people than I told me the lead on the piston head isn't such a bad thing as it can tend to lubricate the piston a little.
I just made my flight from Mexico to Nevada two months ago and used nothing but Avgas. I may not prefer paying for it, but I don't mind actually using it.
And when your done mixing the two in your tank as you fill up with the other seems to have no ill effects either. I now use them interchangeably when needed.
Hope this helps

[bryancobb]

I used pump gas (prior to ethanol) and 100LL interchangeably in my 503 equipped Tierra for years with no problems.

No science...just did it and it worked fine.

[scottessex]

I have run Avgas in the ArcticCat dominator (loves it) , I use Avgas for my generator (stores well) and avgas in all my gas powered lawn equipment. No ill effects plus it smells great!

[Rotor-Head]

Thanks for the info.. I appreciate it....

[Rotor-Head]

Okay my engine HATED 100LL. Temps were good but after about 5 minutes it got to 4000rpm and bogged down hard. Would not even make 4500RPM. I flushed the engine and tank and put my 92 Octane (non ethanol) back in and it ran absolutely perfect....

No AvGas for my gyro...

[BEN S]

Shawn, not that I LIKE using avgas, but that doesn't sound right. your engine should be running in the 6200-6300rpm range...maybe even 6500 or so, but I baby mine..
If you couldn't get over 4500 something sounds amiss...

[Rotor-Head]

Originally Posted by BEN S

Shawn, not that I LIKE using avgas, but that doesn't sound right. your engine should be running in the 6200-6300rpm range...maybe even 6500 or so, but I baby mine..
If you couldn't get over 4500 something sounds amiss...

I know.. It's strange, but as soon as I put the 92 back in, it ran perfect. Flawless. no idea.

[Redbaron]

Hey Shawn maybe the fuel filter is dirty, just a guess tho.

[Rotor-Head]

Originally Posted by Redbaron

Hey Shawn maybe the fuel filter is dirty, just a guess tho.

Nope. It's clean.. Here's the story....

Gas: 92 Octain-non-ethonol. RUNS PERFECT. CHT/EGT are right where they should be.

then
Gas: 100LL - Ran like crap... Could not get 4500 without it bogging. Temps were fine as far as I could tell at lower RPMs.

then
Gas: 92 Octain-non-ethonol. RUNS PERFECT.. NOTHING ELSE CHANGED No fouled plugs, fuel filter clean. I flew for over an hour with not a hiccup. CHT/EGT are right where they should be.

I know it's strange, but that's the story.

[Redbaron]

Keep running 92 octane and blame it on aliens for now. Maybe run some of that 100ll in your mower for a test. Water in the fuel? Let us/me know what you find out.

QUOTE=Rotor-Head;489248]Nope. It's clean.. Here's the story....

Gas: 92 Octain-non-ethonol. RUNS PERFECT. CHT/EGT are right where they should be.

then
Gas: 100LL - Ran like crap... Could not get 4500 without it bogging. Temps were fine as far as I could tell at lower RPMs.

then
Gas: 92 Octain-non-ethonol. RUNS PERFECT.. NOTHING ELSE CHANGED No fouled plugs, fuel filter clean. I flew for over an hour with not a hiccup. CHT/EGT are right where they should be.

I know it's strange, but that's the story.[/QUOTE]

[eddie]

My engine is a 2.5 subaru with a turbo,i ran av-gas for a year without any additives to the gas,ran just fine.I now use 92 octane mogas with alcohol still runs just fine,i did have to increase the mixture slightly for the mogas,still get the same RPM on takeoff as the av-gas. Best regards,eddie.....

[DennisFetters]

100LL is made for slower turning and longer bore-stroke engines.

The higher the octane lever the slower the burn, thats why it works better in slower turning and longer bore-stroke engines.

The lower the octane, the faster it burns, that's why it works better in your Rotax.

Thats also why you don't want to go below 87 octane, it will predominate and burn a whole in your piston.

With the 100LL, much of it is burning in your exhaust pipe because there was not enough time for it to finish burning in your chamber, so you will get less performance.

There is more involved, but this is the basics of it.

[PW_Plack]

Shawn, it's not impossible to get a tank of bad avgas!