Thanks ghiaracer.

Also, thanks to Kento. I didn't realize that "avgas" is blended differently than automotive race fuels. My statements were made under the assumption that these fuels were developed the same way and for similar purposes. And that their octane ratings would be calculated the same.

You're right, in the cessna we are only keeping it around 2500 rpm give or take...

Maybe an unrelated subject, but why would high compression recreational/race boats be using the 100LL fuel? It doesn't seem very cost effective over the 93 octane.....

well....guess i'll be driving out to the track at Temple for my gas....

 

This statement may be right but I know a bunch of Big Block V-8s that are using PURE AvGas everyday on air boats. So Im guessing it cant be bad either, Ive heard of these Big Blocks lasting years before anything happens internally usually a head gasket blows or something before the motor does.

 

Once again...those engines run at very stable rpms (compared to any engine used on the road), and are low-revving, low-load use. A big-block V8 is not the same as 1.3L turbocharged rotary. Sure, it won't kill an FD engine, but why waste the money? And if you feel your engine warrants higher octane, if you're going to spend the $$ for avgas, you might as well spend the extra $0.50 or so a gallon for some decent unleaded racing fuel that will at least give you a performance gain.

Although not really the case here, it can be disastrous to use the "if it works on that, it must work on this" method of performance engineering. Akin to watching someone jump off a cliff and thinking, "shoot, if they did it, there must be something good down there. I'll do it too."

 

I am tuned to run avgas at 40% at 16 psi although a recent hot-side housing change seems to have led to a 2 psi jump in boost. I throw in some pre-mix as well. Super is costing $1.61, avgas is $2.29, and race gas is $7.00 or so at the track. I'm following this thread to try to get a better handle on things.

 

after 5 years and 2000+ hard track miles, I have never had a problem with aircraft 100LL. I mix in a bit of synthetic 2 cycle oil. I have had track days with temperatures as low as 40f and as hi as 95f. Car just keeps on runninng. Boosting 13 to 14 psi with all the bolt on mods you can get. I will continue this practice.
1R1

 

and believe me he can race!!!!!one of the fastest around the tracks, not to mention he's a pilot too.

 

Just one more point on avgas.... I owned a 1976 Piper warrior for 10 years that had a lycoming 0-320 E3D designed to run on 80 octane avgas. When that disappeared from pumps a few years ago, I had to switch to 100 LL (low lead) - a misnomer, since it actualy contains nearly 4x the amount of lead the 80 octane did. I had to more agressively lean the mixture at idle to avoid fouling of the plugs (2 per cylinder and not cheap!)

Guess this is why the O2 sensors don't do too well....

 

I love it.... try some acetone and maybe some methanol while you're there

 

Maybe the idea that higher octane yields more power stems from newer production cars running higher compression motors running "premium" unleaded. Most new cars today are fitted with factory knock sensors. If the ecu detects knock it will retard timing, thus lowering performance. Higher octane fuels don't burn as well, reducing the chance for knock, and the factory ecu advances the timing yielding more power. Thus the drawn conclusion-higher octane=more power. Like someone already said, it's all in the tuning. If your boost/timing is not set to take advantage of the higher octane, your just throwing your money away. A dramatic oversimplification, I know, but you get the general idea.

 

I was only wanting it to tune for 20psi, but I guess I'll have to pay more to get some actual automotive race gas to do that. If it would have worked, it would be a no brainer - the airport is literally a 10 min drive from my house. I am going to try and check out gas prices at the local redneck drag strip this weekend.

 

i don't want to do any name-dropping, but the guy who tuned my PFC on the dyno instructed me to use the avgas blend that i use when running at the max boost i am set up for. he did an outstanding job on the engine build and tune and i think i got what i paid for. that's why i go to them and recommend them w/o reservation; they're honest, knowledgeable, and nice. while others get bad engines or no engines or parts, and poor service and have great tales of woe to tell, i'm out running well all the time. a big thank-you to chris.

four of my friends here in the new orleans area have gotten burned bigtime by the idiots up there in the pac-nw who build and sell garbage. it's been terribly expensive and a big damned waste.

mark

 

That's some pretty damn expensive race fuel at $7.00 a gal. Even when I used to buy Sunoco Maximal Red leaded racing fuel (highest octane, and which used to be the most expensive...) for my two-stroke racing motorcycle, it only cost me $5.75 a gal, and that was buying it in small quantities; I'd get a major discount when I bought 55 gal drums. Pretty cheap price for avgas; I guess it's all region-related w/regards to price like anything else.

Hey, whatever floats your boat, it's a free country. Use avgas if that's what you wanna do. Like I said, it isn't going to kill your motor, although you can run 13-14 psi safely very easily with pump gas too.

 

Well, if you're really going to be tuning your engine for 20 psi, then you would be better off checking out real racing fuels. Your engine will be a lot happier (and probably live a lot longer) with actual race fuel. And I take it you're not going to be blending with pump gas either, so you may as well look into getting 55 gal drums of the stuff.

 

it's real handy living in vicinity of a small airport. the avgas is pay-at-the-pump. i usually load up after hours and it has never been a hassle.

 

na, I don't need that much. I am not planning on running 20 all of the time. It's just to make sure my AFRs are where I want them so I can run it later at the track and to play here and there.

 

Listen to the airplane mechanic. Don't put that in your car. It's very similar to high octane race fuel, but not the same. The grade is measured in single digit numbers. 8 being the highest I've seen. Such as JP8, etc. If you want high octane, go with actual race fuel.

 

JP8 is aviation turbine engine fuel....like what they use in F-16s

100LL, to be simple, is different