Use AVGAS in car?

[gavinl]

AVGAS is a high octane low-lead fuel for internal combustion plane engines, could that be used in a cat-less car engine?

Will the low amount of lead build up on the valves if I use a 20/80 mix of AVGAS and regular gasoline?

I have access to lotsa AVGAS

The high octane will definitely help my Ford 2.3 turbo engine

 

[TooManyWheels]

Once upon a time Aviation Gas was regularly used in cars for racing use, before the advent of special purpose racing fuel. For what it is worth, I believe there is a Federal law against using it for street use.

 

[rob-the-oil-nut]

Granted it was in Canada and 10+ years ago, but a pilot that had access to av-gas told me it was NOT higher octane, just more accurate levels of this & that.
BTW how might one set up an engine so that they can go from 88 octane to 100 or so (or even more) and back again, on a weekly basis??
Thanks
Rob

 

[ralan]

The most common avgas available today is 100LL, which contains appr. 2.0ml/gal of T.E.L. and is dyed blue.(LL=low lead) 100LL is a replacement gasoline for the old 100/130 which had 4.0 ml/gal of TEL, and was colored green. Many WWII-era aircraft required 115/145 octane av gas which was dyed purple and had 4.6ml/gal of TEL. These same aircraft that are restored and operated today are running lower compression cylinders to facilitate operation on 100LL. Aside from 100LL, the only other avgas available today is 80/87, which is dyed red and contains .5 ml/gal of TEL. This stuff is getting scarce, though, so many of us Cessna 150 pilots have to settle for 100LL. Note that XX/YY octane means XX octane at lean best mixture and YY octane at rich best mixture.

Running 100LL will not cause problems in a car as long as you don't have a catalytic converter or an oxygen sensor. The lead may damage these. I have seen many low compressioned, gas-engined aircraft tugs, power units, start carts, generators, light stands, powered baggage ramps, etc. run just fine on 100LL for years. You may occasionally fowl your plugs with deposits from the lead, however. Also it will turn your oil grey and possibly screw up your UOA's. Be sure to tell the lab you are running avgas, if you pull UOA's. It's higher octane may enable you to advance the timing without fear of detonation.

I love avgas. I like the sweet smell, and the fact that if you get it on your person, you don't smell like gas for the next week, like you do with mogas. I especially like the fact that avgas seems to keep for a very long time in storage, and doesn't gum up needle valves, etc in the machinery that it is in. I winter my lawn mower with avgas, and my generator is fueled exclusivly with avgas for this reason.

Where are you getting this avgas? What airport did it come from? What flavor is it? I'm just curious, as I have a small use for it time and again.

[ November 20, 2003, 03:27 PM: Message edited by: ralan ]

 

[gavinl]

Hey Ralen, I'm getting the AVGAS from OSU's airport.

No idea what's the flavor but just wondering whether it'll work for my weekend racer.

No cat but has O2 sensor though....so perhaps AVGAS is not the best idea if it's going to screw up the O2 sensor and throw error codes to the ECM.

 

[DockHoliday]

When running 100 Octane, there is a risk of burning valves if the engine gets to lean. Probably only a risk if you tune your engine while running the 100LL.

 

[SteveD2]

It's really not necessary in an engine that isn't high compression...and I would guess that it is illegal for street use because you aren't paying road taxes with it. My dad has a '67 mustang with a 390 that will barely run on premium. He allways filled up at the airport, then one day they said he couldn't anymore. So he just got some gas cans and filled those up.

BTW - what's avgas usually cost? I'm thinking about getting a barrel to keep some in at my house to mix with premium crap gas for my boat...

 

[porterdog]

quote:

---

Originally posted by rob-the-oil-nut:
BTW how might one set up an engine so that they can go from 88 octane to 100 or so (or even more) and back again, on a weekly basis??
Thanks
Rob

---

Best way would be a full aftermarket ECU and separate maps for race fuel and street fuel. The race fuel map would have more timing and or (in an abnormally aspirated application) more boost.

 

[Jimbo]

100LL is currently selling here for about $2.30 a gallon, about half the price of race fuel. BP, Chevron and Exxon are the brands I most commonly see. It probably unlawful for highway use both because of the lead and road tax issues, but you are helping to support the FAA with the taxes on avgas.

Aircraft engines are actually very low compression (70 psi wear limit) but run a lot of spark advance, usually about 30 degress fixed with dual magnetos. Redlines are almost always below 3000 rpm. The smallest engines are 50 cubic inches displacement per cylinder. My point is that aircraft engines are vastly different from automotive racing engines.

 

[Drew99GT]

Isn't the "100" octane in avgas not the same octane rating system used at passenger car gas pumps? Wouldn't the equivalent rating of 100 octane avgas be much lower in terms of pump octane as we know it from your local Texaco, for example? I've always wondered about that while taking flying lessons! Why am I filling up a low compression engine that will be operating at lower barametric pressures with octane rated for a race engine

Also, why do aircraft engines still have to have lead in the gas? Is it simply to raise octane and because of the material that the valves and valve seats are made of (lubrication from the lead)?

 

[ralan]

quote:

---

Originally posted by Drew99GT:
Isn't the "100" octane in avgas not the same octane rating system used at passenger car gas pumps? Wouldn't the equivalent rating of 100 octane avgas be much lower in terms of pump octane as we know it from your local Texaco, for example?


I've always wondered about that while taking flying lessons! Why am I filling up a low compression engine that will be operating at lower barametric pressures with octane rated for a race engine

Also, why do aircraft engines still have to have lead in the gas? Is it simply to raise octane and because of the material that the valves and valve seats are made of (lubrication from the lead)?

---

I have been told that 100LL has 100 octane minimum, using both research and motor methods. Sorry, I don't have any links as proof!! We all know that pump gas is an average of the two. I think the vapor pressure of avgas is less than pump gas, however.

Availablitity and certification dictate what you fuel up with in the U.S. 100LL came out as a low lead replacement for 100/130, back when the EPA mandated unleaded fuels for everything else. This was the best they could do at the time, because everything for aircraft must be certified by the FAA. Autogas S.T.C.'s do exist that allow an owner to use pump gas in aircraft with low compression engines. The EAA has several STC's and does ongoing research on this subject. There is current research going on to replace 100LL with a new standard based on pump gas, called (I think) UL92.

Your little trainer, (Hope you got your license!!) could have run on 80/87, if it was available, but it is unavailable in most parts of the country. That's why you were using 100LL. More advanced piston engine aircraft with higher compression ratios or turbo charging need higher octane.

The refineries produce comparitively little avgas with respect to auto gas. Only one or two produce 80/87. Hopefully, the new spec will get approved and lower avgas prices for everyone.

 

[ralan]

quote:

---

Originally posted by gavinl:
Hey Ralen, I'm getting the AVGAS from OSU's airport.

No idea what's the flavor but just wondering whether it'll work for my weekend racer.

No cat but has O2 sensor though....so perhaps AVGAS is not the best idea if it's going to screw up the O2 sensor and throw error codes to the ECM.

---

That's interesting, I wonder why OSU is throwing it away. You should try and determine the octane before using it. Since this is for a racer, why not ask around at the track and see what other people know about using avgas in their cars. I imagine that somebody has BTDT!

 

[Chumley]

Drew99GT asks:

"Why am I filling up a low compression engine
that will be operating at lower barametric
pressures with octane rated for a race engine?"

Aviation engines are air cooled and the cylinder
head temperatures typically run in the 350°F to
375°F range during full power at takeoff. Much
hotter than most water cooled engines. Aviation
engines MUST NOT DETONATE, ever. Because of the
additional noise levels from the headphones, the
engine, wind, etc., you can't usually hear it
until it's too late.

Imagine this. On a hot day you are taking off in
your Cessna at 65 knots at full power. About 50
feet above the ground, you hear the engine start
to detonate, it starts to lose power as you watch
the end of the runway pass behind you and the
trees beyond the end of the runway (which you
still can't clear and still in front of you)
approaching quickly.

What are your choices?

Bail out? No way. A 60 foot fall to the ground
then skidding to a stop from 65 knots doesn't
look too good.

Turn around? No way, your too low and going too
slow to risk a steep turn stall and there isn't
enough room to clear other ground obstacles.

Reduce the power to save the engine and stop
climbing or accelerating? No way, you'll for
sure crash straight INTO the trees if you do that.

Continue on at full power for a few minutes
hoping to gain some speed and altitude before
the engine blows up? Yep, for the most part,
that's your only hope. Then reduce power, level
off, turn around, and put the plane back on the
ground ASAP. (it's a little different than
driving a car because you can't just "pull over"
and stop just anywhere!)

Then you go over to the FBO (aiprort talk for gas
station) and yell like **** about the lousy gas
you just bought that almost killed you and should
have been thrown away instead of put in your tank!

Chumley

 

[wings&wheels]

A couple thoughts;

I've heard that avgas doesn't have as high a vapor pressure as car gas which could cause starting problems. I never had any actual experiences though. I use my sumped fuel in most of my lawn toys and have never had any issues.

Also, fully synthetic oil may not suspend the lead adequately. Mobil had issues w/ their M1 aviation oil and paid out a considerable amount of cash for overhauls on customer aircraft. Certain engines run w/ their synthetic accumulated deposits referred to as "grey paint sludge" from lead settling out of the oil.

I don't know how much Pilot technique (leaning) contributed to this of if it affected the Porsche engined Mooney PFM's that recommended Mobil 1 auto oil.

I'm an Aeroshell guy so I didn't follow the issue except to sympathize w/ a few friends.

 

[Drew99GT]

Why does av gas still have to have lead in it? Is it simply to raise octane level, or do most aircraft engines have to have lead to lubricate the valves?

 

[Jimbo]

It is primarily octane levels. As stated in other posts, turbocharging combined with high cylinder head temperatures increase detonation risk. Many non-turbo aircraft can and do run on unleaded fuels, where available. Lead contributes problems such as spark plug fouling and sticking piston rings. I have only seen 80/87 unleaded at Santa Paula, an airport that caters to antique aircraft. Here at Long Beach none of the four FBO's sell it.

 

[Drew99GT]

Then why can't they run 100 octane unleaded race fuel? Seems that would be the best of both worlds, and it's not much more expensive. Hell, in Denver, you can buy 100 octane unleaded at many Phillips 66 gas stations!

 

[ralan]

quote:

---

Originally posted by Drew99GT:
Then why can't they run 100 octane unleaded race fuel? Seems that would be the best of both worlds, and it's not much more expensive. Hell, in Denver, you can buy 100 octane unleaded at many Phillips 66 gas stations!

---

FAA Certification. Everything in aviation is bass-ackwards and 20 years too late because of the FAA!! Consider that we don't have an electronic fuel injection systems for piston engines, and ignition systems use mostly magnetos. We don't have air bags, etc. I think they are working on a newer avgas spec now, though.

[ December 08, 2003, 06:07 PM: Message edited by: ralan ]

 

[Drew99GT]

So it would basically be against the law to fill up a high performance aircraft engine with 110 octane unleaded race fuel?

 

[VaderSS]

quote:

---

So it would basically be against the law to fill up a high performance aircraft engine with 110 octane unleaded race fuel?

---

Yes.