RX-4X4

Would 100LL work as a fuel option. (Beside the price) It is a leaded fuel which would offer a sort of lubircant (spell) and it won't go bad no matter how long it sits. I use it in my mower when the carb gums up and it always runs like a champ afterwards. I know rotaries love low octane, but why? Anyway I saw a post from RX7Carl, talking about how he had to start is race car ofter because of fuel sticking up his carb. Thats would be a non issue if he used 100LL. Just asking questions and learning. Thanks

RX-4X4

I have done some reshearch and have determined that the lead would build up and cause some problems. But still might be good to run about a gallon of for a perservative. Not to mention it won't foul plugs.

BlackFireRX7

Am I correct in assuming you are in/around aviation?

100LL is an aviation fuel and is produced by a completely different process than automotive fuel. This is why it dows not go bad (I will spare you all the techno babble). Is the fuel of a higher quality? Yes, without a doubt, but what about the lead?

LongDuck

Forget about the lead - what about the COST!

Back when I was flying actively, the fuel costs were supported by the FBO, but fuel wasn't cheap in those days (~$2.50/gal). With fuel costs rising for just about everything, I would think that a gallon of blue 100LL would cost you about $3-4 now.

Plus that 100 rating is the octane equivalent, so you're essentially running very high octane fuel - bad for the rotary engine.

If you're interested in trying something, might be better to go with red 80 fuel which is lower octane than pump gas and will actually have a lower flash point. This may actually increase energy output of the fuel, but I still warn against running any kind of avgas in your car.

Aviator 902S

100LL (blue in color) actually contains about three times as much lead as the regular leaded auto gas used to have in the sixties. The "LL" stands for "low lead." The truth is that it is anything but. It's only low in lead content when compared to regular 100/ 130 avgas, which (if you can find it) is green in color.

Even in aircraft engines (which with their larger running clearances) this lead will foul the plugs during extended idle periods. In a close-tolerance engine like the rotary this lead fouls the plugs and clogs the apex and side seals in short order. It would be ok to run a tank of this stuff once in a great while, but there are no benefits unless you're running very high boost. For our N/A 1st gens anything more than 87 octane is a waste of money because detonation is not a problem and there is zero performance gain--- except maybe a "psychological" one for those owners who are mis-informed.

RX-4X4

Yea I am the line manager and A&P mechanic at a small FBO in NC. I can get the gas at cost ($2.54). The thing that got me wondering is that all the local 2 stroke guys run it an love it. The say they never foul a plug while using it. And my Maintence manager tell me to run some through the motor to clean the carb out. So it thought I would run this by you guys.

Aviator 902S

Congrats on the A&P licence. I've been a private pilot for 8 years and just completed the first 2 years toward my AME licence. David Atkins (of Atkins Rotary fame) reported several years ago about a trip from Seattle to Oshkosh, Wisconsin in his 13B-powered RV6 kitplane. Previously he only ran pre-mix autogas in this plane but since 100LL was the only fuel available en route that's what he used. He noticed no performance improvement (understandable, since octane boosters serve only to prevent detonation in high-compression and high-boost engines), but his plugs were fouled quite thoroughly.

Of course, the lead would provide lubricating qualities that may be beneficial in a rotary, particularly if lead scavengers are used, but since I've never used scavengers (and have seen lead-fouled plugs after extended taxiing in aircraft engines as a result) I'm in no position to confirm this.

As for 2-stroke engines, I'm wondering if a rather liberal pre-mix ratio is keeping these higher-revving, hotter-running engines clean by not allowing lead deposits to form on the plugs and in the rings. If so, then maybe this same strategy could work on rotaries--- just run 50:1 pre-mix instead of 100:1. (?)

dino1stgen

I used to be an A&P at an FBO with a flight school, and we were cleaning fouled plugs about every 50 hours or so because of the students' 3-hour preflight runups. Once we taught the flight instructors the finer points of the mixture control, it improved immensely.
Like Aviator said, in aircraft engines with their relatively large clearances(air-cooled) it's not really a concern. But in newer liquid-cooled engines with their closer tolerances and calibrated orifices and whatnot, it may be more of an issue.

LongDuck

Hey, I'm a pilot (SEL, Aerobat & Tailwheel) and have never heard of a "3-hour preflight run-up".

What is that?

My run-ups only lasted about 15 seconds while you're sitting on the apron adjacent to the displaced threshold (controlled tower), and they wouldn't take well to you sitting there for very long at all...

RX-4X4

A three hour run is a way for instructors to give instruction and have the hobbs meter going at the same time. LOL. Anway that is a long run up. The owner of the FBO I work at is usally putting on his belt and finding his head set while taking off. He also has like 10,000 hours. I wonder how long he is going to be around? LOL

Aviator 902S

I've never heard of a three-hour run-up either, although there are a few sleazeball instructors who will keep the hobbs meter running as long as possible for nobody's benefit but their own.

Still, longer than usual taxi times combined with flying circuits repeatedly with the mixture at full rich and low rpms (except during take-off and climb to 1000-ft circuit altitude) make for some quickly-fouling plugs.

Rx7carl

Well its also time in their logbooks ( I think thats what Aviator 902 was referring to).

Im not a pilot, Im an A&P. Been in the airlines for 20+ years. I dont have any opinion on running 100LL though. I see both sides of the argument as valid at this point. If you wanna try it, keep a close eye on the spark plugs.

What about 115/145 (purple)?

Aviator 902S

[QUOTE=Rx7carl]

Well its also time in their logbooks ( I think thats what Aviator 902 was referring to).


Yeah, it's primarily logbook time that's most valuable to them (Pilot-In-Command time, which makes them more employable sooner than would otherwise be the case), but the extra hourly wage doesn't hurt their cause either.

smokin_1320

you can add 1/2 - 1 qt of oil to a full tank of gas..that gives some lube..

dino1stgen

They don't really do three hour runup, I was just exaggerating. They do seem to do longer than necessary runups, and sometimes neglect leaning the mixture when not at full throttle.

RX-4X4

Hey waht about an aircraft oil cooler like off a twin commander. IO-540 oil cooler with electric fan? Maybe. I have a few cores laying around.

Rx7carl

The 540 is a big engine, and being that its aircooled it needs a good, efficient oil cooler. So Id guess that it would be more than adequate.

RX-4X4

And on the Commander it is plumbed in. So mounting is super simple for both the fan and the cooler

BlackFireRX7

how about that turbo on the 540?? lol My school had a Cessna 421 with two of those big boys...I think it was a 540...Lycoming(spell check) right?


yea I know this is an old post by this sites standards, but I havn't been on much...

dino1stgen

The 421 is one af my favorite aircraft... has a distinctive sound with those two big geared engines. You can actually hear the gears clacking at idle when it is cold.

RX-4X4

We actually have the STC to put turbos on commanders. But they are not like car turbos. They are used at altitude to keep performance normal. We also maintain a P-Navijo. Piece of ****. Look sweet as hell but breaks all the time. It has the geared motors. IO 540. It is a $3000 maintence bill everytime it flies.

BlackFireRX7

hey easy!!

quit the nit picking!! it was a joke...


besides a rotary's exhaust would pass right through that turbo w/o even turning it

...and yes thats a joke too!