110 Octane

[Editor_Reid]

A local gas station here in Portland, Oregon sells 110 octane gas out of 55-gallon drums. They can't pump it into your car, or let you put it in your car on their premises, so you bring an approved container and fill it, carry it away and then pour it in your race (or whatever) car.

I thought it might be neat to mix a couple of gallons of this stuff into a tankful of pump premium (93 or so octane), to come close to the high-test stuff they used to sell when Healeys were new as a way of seeing what he engine performed like back in the day.

Anyone else have any recent experience with this idea?

 

[Keoke]

HI Reid, yes I run mixed 100 octane produced by Union 76 at specific locations here in Southern California when I am going to do a long run ~200 Mi.Don't know how long this is going to last though.They also have 110 Octane.---Keoke

 

[aeronca65t]

I'm racing on Sunoco GT 100 octane unleaded.
I have 10.5 to 1 compression and I can run my total timing to 32 degrees advance (at redline) with no pinging.
It's almost $6 per gallon.
I can also buy Union 76 108 octane leaded at Pocono Raceway (pretty close to me), but it's like $10 a gallon and I don't really need it.
One of my friends runs an old Craftsman race truck in our enduro series. At Watkins Glen he burned almost $500 worth of 108 octane in the 3 hour event! I burn about $100 worth of gas in the same race.....that's bad enough.
For what it's worth, I think a stock big Healey will run pretty well on mid-grade unleaded (assuming normal compression and timing). Won't hurt, but I doubt the added octane would help in a stock engine.

 

[Editor_Reid]

[ QUOTE ]
...Won't hurt, but I doubt the added octane would help in a stock engine.

[/ QUOTE ]

Well, it's not exactly stock since it is a 100M with a fresh engine, but you're thinking I won't really notice anything with the increased octane?

 

[Keoke]

Reid, I think aeronca 65 is correct.However, if the stock engine runs a bit hot you may see a slight decrese in running temperature.In my case I just like giving the valves a bit of lead from time to time.Yes and at $6.00/Gal it isnt cheap.---Keoke

 

[Dave Russell]

[ QUOTE ]
I thought it might be neat to mix a couple of gallons of this stuff into a tankful of pump premium (93 or so octane), to come close to the high-test stuff they used to sell when Healeys were new as a way of seeing what he engine performed like back in the day.
Anyone else have any recent experience with this idea?

[/ QUOTE ]
I guess people will never give up the idea that "more is better". A couple of points:

Due to different rating systems, the present USA pump octane rating of 93 (R+M/2) is equivalent to the Euro rating of 98 (R). It is also equivalent to the old USA & the old British rating systems of 98 (R).
R = research rating method, M = motor rating method, R+M/2 = the average of the two ratings.

Using a fuel octane higher than needed actually reduces engine power due to slower burning. Higher octane burns slower. The present 93 rating should be adequate for any engine with 9.5/1 or lower compression ratio.

AV gas is rated on another entirely different system & it's octane is not comparable to automobile pump gas.
D

 

[Dave Russell]

Reid,
My opening comment above was not directed at you. Just a general statement. Please don't take it personally.
Regards,
D

 

[Deleted member 3577]

A very nice article on the subject.....recommended reading.

https://216.239.51.104/search?q=cache:MKj...t=clnk&cd=3

 

[200mph]

Reid,
Adding 110 octane race gas to 93 in equal amounts will give you an effective pump octane of (110+93/2) = 101.5

A few corrections/additions:
Since Jan 2004, 76 no longer makes racing gas (we were their northeast distributor). The 76 pumps in Calif have since been supplied with VP, and many are now being converted to Sunoco. The distributor there is C.L. Bryant.

Sunoco is the largest US maker of racing fuel, with 110 and 112 pump octane leaded (not street legal), plus 99, 100 and 104 octane unleaded (all street legal, though the 104 is not too stable).

Higher octane will allow the engine builder/tuner to build in more compression and/or more timing advance before detonation occurs, thus potentially producing more horsepower. In SOME modern cars, the onboard computer will advance the timing and take advantage of higher octane fuel. For street driving its not worth the added expense (cost is around $6 per gallon) UNLESS you are getting lots of knock/detonation and you have retarded the ignition timing as much as possible.

See also the thread below on the end of ALL leaded gas.
Mike

 

[vettedog72]

Dave:
How does the av gas rating diff from auto gas? I burned a lot of 115/145 many years ago (10.75 CR) and did not notice anything diff from high test pump gas except the av gas had a different smell.

 

[Dave Russell]

I didn't mean that av gas is inferior to auto gas. Just that the rating systems are different. To quote another source:
----------------------
"The octane of aviation fuel is listed as 80/87, 100/115, and 115/145, and are commomly called 80, 100, and 115 octane. The lower number is the motor number, the higher is the research octane. The numbers listed on gas pumps for cars are an average of the two. The corresponding "pump" octane for the aviation fuel would then be: 83.5, 107.5, and 130. 100 LL AV gas would be equivalent to around 110 pump gas."
----------------------
Your 115/145 would have an equivalent pump octane number of around 130. Certainly enough to handle a 10.75/1 compression ratio plus. The engine would have likely put out more power with the 100/115 av gas. The "high test" pump gas of that day was probably equivalent to a present day rating of 96 & would have likely caused no problems either.

Remember that the old av gas formulations were intended for use in high compression or supercharged engines which needed the very high octanes. In a low compression engine using higher than needed octane, the fuel burns so slowly that exhaust valves & manifolds can get very hot. A lot of still burning fuel can be pumped out of the exhaust valves. Obviously high compression or supercharging causes a quicker fuel burn & can take advantage of higher octane.

I recall trying av gas in old low compression engines. The only noticeable difference was some loss of power & a lot more exhaust popping.
D

 

[Jerry]

I have a high compression head (it was shaved and ported) for my 3000 engine. I had to run 2 gal of racing fuel mixed with Premium to just stop the knocking. It had a lot of torque and did well in the autocross at Tahoe. I don't know if it was the high compression (245lbs/ cyl) or the gas or both but it was fun to drive. I finally took the head off and put on a stock so I did not have to search for the high octane gas all the time. At $12 extra each tankful, it was an expensive "want". With the new head on the compression drops to a steady 175 per cyl. Now it will burn reg unleaded without pinging.

Jerry
BN4 with 3000 engine
BJ8 in pieces