Is Avgas a cheap alternative to racing fuel?

DirtyBird222 said:

we-found-the-narc said:

Did I miss the part of the article where it says it's illegal?  Why?  I think it's primarily because there are no road taxes put on AvGas.

The other aspect that seems to be missing is that AvGas is wildly more stable than car gas.  It takes way longer to go stale (don't know the stats). 

Obviously, don't put it in anything with a cat.

Bro the title says "alternative to racing fuel." Road taxes aren't applicable to off-road vehicles. Let's also take a look at the same gov't that ruined the fuel jug. 

They improved the fuel jug, the problem is the implementation.

David S. Wallens said:

dr_strangeland said:

Someone mentioned Home Depot. I like to pick up a gallon of Kleen Strip xylene and bring it to hill climbs in case the local gas isn't very good. It's 114 octane. I mix a gallon with 3 or 4 gallons of 92 for an effective octane of 97-99. It's $25 a gallon but totally cheaper than a bent connecting rod. Now I just keep a gallon with me. It can go straight in the tank, just don't get it on anything. I do add a tiny bit of ATF, supposedly for top end lubrication but I just like the smell. 

 

By far the best smell, though, is running silver tequila in the meth injection system. So good. 

Hey, we’ve written about that: Toluene or Xylene: Legit low-buck octane boosters?

Cool!

But you didn't actually try it, and the guy you quoted sells race fuel so kind of has a vested interest in selling race fuel, so it's like, the article says don't bother, basically. 

I think it works best if you're only going up a few octane as opposed to running straight xylene or toluene like an 80s f1 car or whatever. The car is definitely harder to start, but it isn't like it doesn't start, it kind of fires a couple of times and then gets warm enough to actually run. 

I like it, it's fun, and I think applied science is cool. Plus no lead in my lungs. What does race gas typically use to get to 100 octane? 

In reply to dr_strangeland :

The thing about race gas is it oftentimes burns faster, which helps prevent detonation.  Detonation is (loosely) when the flame front expands and compresses the remaining unburned air and fuel, which then spontaneously ignites all at once (detonates) from the compression and heat.  If the fuel burns faster, it is less likely to detonate because the flame propagates too fast to allow detonation to be possible.

Reread the comment about large bore, low revving engines... that is a recipe perfect to create detonation.

Now I am wondering what the bore and stroke are for the Waukesha engines used to test fuel.

Adding to my comment.

Most propellers on small, piston engine aircraft are turning at rpms between 2000 and 3000 rpm.

Unless the engine has a reduction gearbox, the engine is turning the same rpm.

The reason for this is to keep propeller blade tip speed below the speed of sound. Speeds above that generate excess noise and vibrations which can damage propeller blades.

A Cessna 185 is usually maxed out at around 2800rpm. That's a 470cid flat six turning really slow.

In cruise, the governor adjusts the pitch of the prop blades to keep the engine at whatever rpm you've chosen to keep it at.

All of this is the complete opposite of the requirements for a vehicle which is operated on the road.

This is also why I think those vehicles that someone has crammed an aircraft engine into are bloody stupid.

The fuels to operate these engines will be very different from the optimum fuel for auto engines.

In reply to ShawnG :

In the 30s and early 40s when there was a huge push for higher octane fuels (forced induction aircraft engines were generally knock limited for power, not airflow limited or internal strength limited, so higher octane fuel was a definite advantage) they had dual ratings on fuel like 115/130 or 130/140, for severe or mild engines. (Probably not the right terms used... my brain is still a fog after a 9 hour thrashathon at work)

Air cooled engines were severe, liquid cooled engines were mild.

IIRC they found triptane to have a rating of around 270, the problem was making enough of it.  Knock index numbers at the time were wildly different from what we are used to seeing today, I don't know how that translates to RON or MON.

In reply to Pete. (l33t FS) :

I always wanted to build a race car and run it on propane. Boost the hell out of it and have a bbq tank in the back. Gaseous fuel so no distribution problems, just a simple mixer does the trick. Might even run well in draw-thru systems.

The octane rating is supposedly around 110 or something silly.

As for Avgas, I'm just tired of the stories from non-car people or even uneducated car people of "ZOMG my dad ran his car on Avgas and it went SOOOO FAST!!!!"

It's nearly as bad as the stupid HHO idiots or the "100mpg carburetor suppressed by the oil companies hurr durr" stuff.

In reply to ShawnG :

I used to read a lot about natural gas conversions in Australia on performance vehicles.  Fuel mixers and such, as you say.

I know for a while they were very popular with rock crawlers.  Fuel mixers work at any angle and the fuel pickup isn't going to suck air in the tank at extreme angles.

My personal experience is that it works great as long as it isn't so cold that the pressure drops too low.  IIRC the conversions we did would start on gasoline, and some of the fuel lines were routed with coolant heat.  It's been a while.  Probably not a problem in the high desert or Oz, kind of a problem in northern Ohio.

In reply to Pete. (l33t FS) :

Propane was popular here in Canada for quite a while as an alternative fuel but it's really gone away now. Cost of conversion and you can't really bodge it onto a modern engine like you could with old TBI and carbureted engines.

The RCMP used to run their fleet on natural gas but they stopped partly because the fill times took too long. From what I understand it runs much higher tank pressures. 2000ish PSI instead of 20ish PSI.

In reply to ShawnG :

Oh we were converting OBD-II port injected engines.   Eight fuel injectors on a rail connected to hoses that ran to the ports.  

I did some service work this week (complete front diff and suspension rebuild) on a fairly new 6.2 F350 that has a dual fuel conversion.  Second set of injectors and a patch harness at the PCM, kind of like the ones I did.  The biggest issue is the tank is large and heavy.

The appeal, for fleets, was that these were technically natural gas engines, and you could just connect your refill stations to the gas mains at your depot and the trucks would refill overnight, so time doesn't matter.  Kind of like how EVs are done.  I would imagine that the RCMP expected their vehicles to be available 24 hours a day instead of just during a day shift.

In reply to Pete. (l33t FS) :

Bingo! He was always chasing that sweet spot of power and longevity. Didn't have a lot of money and we had a small airport close by. 

ShawnG said:

This is also why I think those vehicles that someone has crammed an aircraft engine into are bloody stupid.

Not quite as stupid as putting automobile engines in airplanes, which happens far more often.  See, for example, the Porsche-powered Mooney.  Or the ever-popular Corvair-powered homebuilts.  The trend now, of course, is to put Rotax snow mobile engines in light aircraft, which requires a gearbox.

ShawnG said: The fuels to operate these engines will be very different from the optimum fuel for auto engines.

Eh, it seems like it, but in reality it doesn't seem to matter, and I don't think this is one of the major considerations in the formulation of 100LL.  Most of the piston-powered fleet runs just fine on automotive gasoline.  I myself run 91 octane ethanol-free automotive fuel in my airplane.  I have an STC to do so legally.  Hilariously, I run 100LL avgas in my Formula Vee, though I often mix it with ethanol-free 91.  The Vee runs fine on 91 octane, but we've done dyno runs that show 100LL does have a slight edge in these engines.  It is not clear to me why, and the difference is slight.  Possibly just because the carbs were jetted on the dyno with 100LL.

I regularly haul 25 gallons of auto fuel to the airport, put it in my plane, then haul 100LL back to take to the race track.  The big downside I've found to running auto fuel in the airplane is the vapor pressure of mogas is significantly higher than avgas.  My airport is at 6,800 feet and on hot days the auto fuel will boil as soon as it his the float bowl.  Carburetors are not great at metering fuel vapor.  So in the summer, I keep one wing tank about half-full of 100LL to avoid the problem.

Pete. (l33t FS) said:

In reply to ShawnG :

In the 30s and early 40s when there was a huge push for higher octane fuels (forced induction aircraft engines were generally knock limited for power, not airflow limited or internal strength limited, so higher octane fuel was a definite advantage) they had dual ratings on fuel like 115/130 or 130/140, for severe or mild engines. (Probably not the right terms used... my brain is still a fog after a 9 hour thrashathon at work)

Not quite.  The dual rating is lean vs rich, has nothing to do with air vs water cooled, and the rating system persists.  100LL is 100/130.  This means 100 octane when leaned out, 130 when full rich (as for takeoff).  Lean mixture rating is pretty close to MON.   My Cherokee specifies 80/87 avgas, which is no longer available.  80/87, 91/96, 100/130, 108/135, and 115/145 all used to be available, but we simplified the distribution with the introduction of 100LL in the '90s so that's all that's readily available now.  It's "low lead" compared to the original formulation of 100/130, but still has a bunch of lead as compared to the lower grades or typical automotive leaded gasoline at the time.

The Porsche engine in a Mooney is in a certified aircraft, so it's backed by all the testing which goes along with that.

Homebuilts and ultralights are experimental so do whatever but it's on you.

VW engines, see Pete's statement about being pretty much the same as aircraft engines.

As for the fuel boiling, yes, this is why there's different fuels and why you need to be approved (your STC) to run mogas in a certified aircraft.

Sure, the Porsche Mooney was certified, but it was still a disaster.  Almost all of them have been engine swapped to aircraft engines.

The STC testing process did try to address the different vapor pressure, but sadly it seems insufficient for hot days at high density altitude.  Some aircraft are worse than others, and most of the common types for which the mogas STC is unavailable was a result of this limitation.

The real question: is flying a plane the cheap alternative to driving a race car?

In reply to Olemiss540 :

Good question!  Depends on the plane and the race car.  I have pretty much the cheapest version of each (a Piper Cherokee and Formula Vee) and my annual costs on both are similar, but the plane is worse.

Formula Vee: Per race weekend is about $400 in entry fees, $300 in tires, $75 in fuel.  Probably about $1,500/year in parts/engine rebuilds, racing 6 times/year.

The airplane: $50/hour for fuel, $1,500/year in insurance, $1,500/year in annual inspections. Misc broken things have averaged about $500/year over the last 5 years. The engine should cost about $12/hour for a rebuild, but this was a $24,000 expense that I had when I bought the plane and it started shredding the lifters/cam in the first month I had it.  I share the plane, so my costs are only half of this, plus I pay $175/month to store my half of the plane in my co-owner's hangar.  I store the Vee in there in the off-season for free.

I'm not including the purchase price in either calculation since the Vee is still worth what I paid for it and the airplane has nearly doubled in value.

Olemiss540 said:

The real question: is flying a plane the cheap alternative to driving a race car?

I HPDE because its a LOT cheaper than owning even an old beater Cherokee 140.

In reply to Berck :

There are thousands of homebuilts that disagree with your assessment .

I was a 1/10 "partner" in a 172 that only had like 3 other active users of the plane. If I could get in on a track car, with similar terms for similar costs, I'd do it in a heartbeat. 

mfennell said:

APEowner said:

wae said:

I find it bizarre that I'm the guy to say this, but wouldn't it be a really good idea to not add to the number of engines that are sending lead particles out their tailpipes?

Yeah, I don't feel good about that.  In fact the whole racing thing is ecological disaster.  Driving a truck and trailer hundreds of miles to drive an old car around a closed circuit for hours before driving the truck and trailer back the same distance.  I try and mitigate that by being responsible in other aspects of my life but still.

FWIW, leaded race gas is worse than Avgas.  100LL is about 2 grams/gal of TEL.  Sunoco 110 is about 4.

I believe the new Avgas spec is 0.56 grams/gal.  I think that started in 1998.  I remember pilots complaining about their old Lycomings not being able to run with that low lead content without re-doing the valves and seats.

In reply to Appleseed :

There are thousands of homebuilts flying with automobile engines.  That doesn't mean it's a good idea.  After lots of research, I'll be putting a Lycoming in mine.

We should also consider that Avgas has fewer BTUs than Mogas.  Not an apocalyptic amount, but something like 120kbtu versus 125kbtu.

But, like someone said, I would rather make 10 fewer hp and not destroy rod bearings or hammer a piston.

I actually have burned Avgas in a car.  When I was getting my Private license, I realized when I was leaving the airfield that my 66 Bonneville was on fumes, so I bought a couple gallons of 100LL to get me to a gas station.  It ran the same as it did on 87 octane, of course.  It was a stock 389, so I wasn't expecting anything to be different.

Berck said:

In reply to Appleseed :

There are thousands of homebuilts flying with automobile engines.  That doesn't mean it's a good idea.  After lots of research, I'll be putting a Lycoming in mine.

Which reminds me... an LS really does go in anything.

In reply to ShawnG : Late 80's there was a guy in Wisconsin who ran a Ford Ranger in short course off road who ran propane. This was the start of the mini pickups in short course in the Midwest. He ran midpack. I really remember seeing the long tank mounted in the bed of the truck front to back

In reply to Berck :

When people are asking and getting $10,000+ for ancient C-65s, I understand why people do it. I don't have $37,000 to spend on a O-360. But you're also talking to a man who would have no qualms about cutting a VW in half to build a powerplant for a Hummelbird.