race gas revisited, why and when? Options

[Trekkor]

Bought a five gallon jug of leaded 110 octane "VP" brand racing fuel. (IMG:http://www.914world.com/bbs2/html/emoticons/ohmy.gif)

My motor seems to have higher than stock compression. Lowest is 160 PSI.

My speed shop guy says the valves will like the lead. (IMG:http://www.914world.com/bbs2/html/emoticons/chowtime.gif)

Maybe I just like throwing money out my open windows at speed... (IMG:http://www.914world.com/bbs2/html/emoticons/huh.gif)

KT

[scotty914]

well the leaded end of it acts as a lube on the valve to seat surface. the higher octane gives a higher resistance to compression ignition. as well as a slower more even burn, basicly the oppisite of running nitrogylicern ( sp ). the gives your pistons a push instead of a shove. in theory you will get more hp out of the higher octane, but i read a comsumer reports thingy a few years ago about it.

basicly they said a car will get 1/2 to 1 hp out high premium gas vrs regular, and 99 % of the cars out will not run better on the high grade stuff, at least once the computer adjusts for it. the consumer reports also said the best thing you can do is every 4 to 5 tanks run a name brand high grade gas for the cleaners then back to reg.

for what you want probably want out of it, mix a 50/50 mix race gas and regular, should bump your octane to around 100, and not affect jetting.

[Trekkor]

It'll be fun to try it, anyway.
Who doesn't like the smell of burnt race gas?

KT

[machina]

My motor is set-up for 110. We have a VP distributor here, got a 30 gallon drum. Its easier to move around when full than I thought, you just tilt it and roll. Just don't let it tilt to far or you'll have a 200 pound load to pick up.


Unless the motor is tuned for it, not sure its going to make a difference. At least tweak the timing (to start with)

One good note is that the race gas is supposed to do better in the lines, carbs, etc if the car sits for long periods like in between races. Some of the councours guys even put the stuff in just for that reason.

That stuff does smell good though. (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

[scotty914]

as david said it can handle some more advance too, like 5 degress or so. but thats one of the reasons why you should mix it.

BTW poor mans race gas around where i live used to be airplane gas, at the time it was 115 octane, and they would sell it to anyone who put it in a marked fuel bottle that said off road gas only, and it was half the price of race gas.

[Jake Raby]

An engine tuned for pump gas will normally make LESS power with Race gas!

This is because of race fuel having more viscosity and a slower burn to prevent detonation with higher CR.

When running race gas the engine can stand much more timing if its a medium CR based powerplant... Here is a "for instance" for ya.

My Hybrid 2316 was dynoed on pump gas (93) and race gas (110). With the pump gas the engine wanted a 140 main jet and 29 degrees full advance to crank out a 13.5:1 AFR and good fuel curve. When the race gas was added the engine liked 36 degrees of timing and a 155 main jet to attain the same AFR and similar fuel curve! This is a 10:1 street/track dual purpose engine.

So many times I see guys go to the track, add race gas and their cars run like shit..... Race gas isn't magical.
BTW- "AVGAS" is wayyy different than Race gas.. Aircraft engines operate below 3800 RPM, and accelerate slowly. They lack cylinder pressure that our engines must have for snappy acceleration. AVGAS also has lubricants in its composition that can harm normal fuel system parts that are not set up for it...

[john rogers]

As Jake noted, you may loose power since race gas burns slower so be careful about yanking that distributor around. When I ran 110 leaded in my stroker four we used 6 to 8 degrees more timming than with 100 octane unleaded. Also, if you have an O2 sensor the lead might bung it up.

[Trekkor]

My *plan* was to run a couple gallons on top of a full tank.

I know this motor is not build for straight 110.

[Jake Raby]

You'll still need some retuning... I have found that a mix of fuel is harder to stabilize tuning for because the mix has to be the same every time and thats kind of difficult.

[scotty914]

with av gas, i only used it in my motorcycle. it did run like crap with 100 % av gas but it ran great using a 50 50 mix. the area i was in at the time had a bunch of mussle car racers that set their engine up for 100 octane and almost all of em ran either a 50 50 mix with either the 110 race or av gas.

there was even 1 guy who dynoed his duster using the 50 50 av gas mix and got more hp out of it than 100 octane race gas. it was something like 10 hp, then while talking at the dyno shop he told the guy what his fuel was and there was a cop off duty standing behind him. he got a hell of a fine and the airport stopped selling the gas to anyone but pilots.

[Dave_Darling]

Anecdote, from my grandfather, retired A&P mechanic and retired FAA inspector:

Quite a while back, 80-octane AvGas was available. But then the refineries stopped making it. So the owners of the aircraft spec'ed for that stuff had two choices. They could either dump 100 (110?) in, or they could pay the $$$ to get the engines recertified for "MoGas"--that's automotive fuel to you and me.

The cheapskates just ran 100 octane. And guess what? They started burning exhaust valves left and right! It's not a good thing when you burn a valve at 120 feet on takeoff, BTW. Evidently the mixture was still burning on its way out of the combustion chamber, thus overheating the exhaust valves significantly.

The FAA came down pretty hard on folks who were doing that...


Next point: Compression pressure is not compression ratio. They are related, but rather indirectly. Lots of other stuff comes into play, far too many for us to really calculate the ratio if we know the pressures. So 160 PSI compression doesn't necessarily mean that you have a "high-compression" engine that will benefit from high octane fuel.

In general, if your engine is not pre-igniting (pinging, detonating) then high-octane fuel won't give you any more power.

--DD

[lapuwali]

One also shouldn't generalize and say things like "high octane burns slower". It *may* burn slower, it may not. VP 110 racing fuel very well may, but some other 110 octane fuel might not. Octane measures detonation resistance and nothing else. It does not measure flame speed, viscosity, energy content, color, taste, smell, or anything else. There are so many different compounds involved in what we call gasoline that there are no hard and fast rules about any property of higher octane gas other than it's more resistant to detonation than lower octane gas.

Even pump gas varies substantially from state to state. Pump gas in California, for example, is refined in California for the California market. It's not used in any other state unless someone buys a tankful and drives somewhere else. I'd not be at all surprised if Jake ran an engine on CA gas, he'd come up with different results than he gets with GA gas.

[TimT]

I rec3ently read an article in the NY Times. Gist of the article was we have few refineries, and the refineriies have to make over 17 different formulations of gas (to suit the various states and EPA gas specs), one of the small reasons gas prices are going where the way they are.

ok back on topic, we run 100 or 112 octane in our 700+ hp turbo motor, this motor has s static cr of 8:1, and we run boost sometimes as high as 1.6 bar. This engine would hand grenade on anything other than high octane gas. We learned this the hard way when we were dyno tuning the car, and ran short of 110, so we cut it with 94, and melted one of the heads (IMG:http://www.914world.com/bbs2/html/emoticons/screwy.gif) ( could of been us looking for to much power)

On close to stock cr engine 110 is pissing your money away. If you feel you need leaded fuel you can get 100 octane fuel for a few bucks less a gallon then 110, and it has that race gas smell

blend some 93 and 100 and advance the timing a tad..

my $0.02

[sixnotfour]

That motor is an older motor and 110 will perk it right up, and its not AV gas.
Didnt you get the VP fuel guide from the dealer ?
Back when the motor was new premium was 100.

It is not some smoggy late 70-80's motor.

[Trekkor]

OK, the motor is from a 1967 911. With 9.0:1 CR if it was stock.
The 914-6 shop manual says 125-162psi would be nice.
My lowest cylinder is 162. (IMG:http://www.914world.com/bbs2/html/emoticons/ohmy.gif)

No smog, webers, MSD, headers. It don't even have vac advance (IMG:http://www.914world.com/bbs2/html/emoticons/cool_shades.gif)

Can you smell it?


KT

[lapuwali]

QUOTE (trekkor @ Mar 18 2005, 04:37 PM)

OK, the motor is from a 1967 911. With 9.0:1 CR if it was stock. The 914-6 shop manual says 125-162psi would be nice. My lowest cylinder is 162. (IMG:http://www.914world.com/bbs2/html/emoticons/ohmy.gif) No smog, webers, MSD, headers. It don't even have vac advance (IMG:http://www.914world.com/bbs2/html/emoticons/cool_shades.gif) Can you smell it? KT

Like Dave said above, compression pressure measured with a compression tester and compression ratio are only vaguely connected.

I have to disagree with sixnotfour's comment. Running more octane than the engine was designed for is pointless. 100 octane gas may very well have been available at the pump in the US in 1967, but that doesn't mean a stock(ish) '67 911 engine would be able to use 100 octane (in fact, I very much doubt it could). My '67 912 requires 98 RON (the European measure), which is very roughly 93 (R+M)/2 (the US measure). Since 98 RON was and is "premium" in Europe, I'd expect the '67 911 required the same grade of fuel. It may actually require less, since a 2.0 six will have smaller cylinders and combustion chambers than a 1.6 four, and smaller combustion chambers are typically more knock resistant.

The only way to REALLY work this out is to run the car on a dyno on 91 octane pump gas and a mix of the 110/91 octane, and fiddle with the timing some. I actually doubt you'd notice the difference between timing that would not ping on 91 and timing that would require 93 to not ping.

[TimT]

That 67S distributor is a hot ticket! I sold mine a few years back for $500 (IMG:http://www.914world.com/bbs2/html/emoticons/cool_shades.gif)

Porsche required 98 RON ( not the same as the octane rating you see on the pump) for the "S" engines


Interesting reading

Another

The octane rating we see on the pumps is an average of RON and MON ( reasearch octane/motor octane respectively)

I think I saw 96 octane fuel at Lime Rock last year, that would be damn close to your engines requirement.. 110 is frivoulous, but its your money

[TimT]

I agree with assholes garage (IMG:http://www.914world.com/bbs2/html/emoticons/lol2.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/lol2.gif)

QUOTE

It may actually require less, since a 2.0 six will have smaller cylinders and combustion chambers than a 1.6 four

Actually the 2.0 /6 has a nasty cylinder head, piston crowns are quite tall, flame propagation sucks. Small ports

[Trekkor]

I dumped it in there and ran it tonight. (IMG:http://www.914world.com/bbs2/html/emoticons/ohmy.gif)

Seemed better...Maybe just my imagination, but this motor really pulls. (IMG:http://www.914world.com/bbs2/html/emoticons/clap.gif)

Stinks, too. (IMG:http://www.914world.com/bbs2/html/emoticons/lol2.gif)

See ya at the Marina.

KT

[redshift]

Dave is right on with the BURNED EX VALVES POINT


M