What Fuel to Use

[Tom Cole]

Get ready,  here comes a short book!
 
There is apparently NOT a rule about what octane you have to run.  I thought there was.   I am running Amoco Ultimate 93 Octane pump gas with Lucas top end lube.   I am going to add 4% Ethanol.  This is all legal.  Any fuel will be legal, as long as it meets the rule specs, which I posted a link to below.
 
Here's the deal.  Octane in dirt road talk is a measure of how long it takes to burn that grade of gas.  The lower the number, the less time it takes to burn, so you have a more volatile fuel that burns hotter and quicker than a higher octane fuel.
 
Increasing compression increases horsepower, but, compression, along with heat, can cause a volatile fuel to explode before the spark plug fires.  This is called pre-ignition (you know it as dieseling) and it is bad.  So, in order to counteract this problem, you use a higher octane, less volatile fuel.  Even though the fuel has less BANG, the net effect of the increased compression is an improvement in performance.
 
So the trick is to select the right octane for the job.  The first thing to consider is compression.  We are just under 10 to 1 with these cars, and my handy dandy chart tells me that 89 octane is the fuel to use.  BUT we have to also consider heat.  A racing engine sees higher RPM and heat than this engine was originally designed to handle.  It is also higher than what my chart is expecting.  Running a less volatile (higher octane) fuel will help keep it cooler.  Heat is the enemy!!!  But remember that less volatile fuel takes longer to burn, so it requires that the spark fires a little bit sooner.  So you have to advance ignition timing to compensate and give the fuel enough time to fully ignite.
 
There is not a huge difference between 89 and 93 octane, but it is plenty of difference to make up for the added issues we see.  The Ethanol will simple help it burn more completely, and the Lucas takes the place of lead in gas and keeps your valve faces protected.
 
 
Below is the new link to the new 2007 rules.  I copied and highlighted fuel related stuff.
http://probld.600racing.com/documents/2007%20INEX%20Rulebook%20-%20Legends.pdf

[Tom Cole]

http://running_on_alcohol.tripod.com/id36.html

Interestingly, it seems that premium unleaded actually has ethanol in it. 

[DARK AGE 53]

Thanks for the info, when you say Lucas top end lube is that the same as  Lucas Fuel treatment...how much do you add per gallon?

Al

[justfreaky]

 What engine size are you using? Sometimes, it's not all about octane. It's about burn time, combustion chamber size, compression, engine mods, etc...  Most pump gas  now days  ( depending on what part of the country your in) contains at least some ethenol. (I'm in the Pacific Northwest - Farm Country)  Any form of alcohol will usually consume more fuel. Therefore, you have jet size changes to figure in on the equation, weight (more fuel = more weight), etc...  There are fuel additives that will supply lubrication to valves and such. You also should give thought to wear on rubber parts (alky takes it's toll on rubber). If I'm wrong correct me, but I think most of us try to use the highest octane we can buy at the pump. Race gas ain't cheap!!! And it looks like pump gas is headed the same direction this summer.
 There is tons of stuff out there on the net, and race sites, about fuel - I'm not an engineer, and don't understand a lot
about that end of it.
 My 2 cents; for what it's worth.
 Steve

[justfreaky]

Found a tech tip on fuel.

 "Fuel For Legends Cars:
    Because race fuel has a slow burn rate, mix race fuel with 93 octane pump gas. This speeds up the burn rate and picks up hordepower and torque all the way up the power band."

[00h]

here in las vegas it has been made easy.the track requires us to use vp-98.it's the required fuel for the nationals and track management and 600 racing west decided to make it ours too.it hurts though, because at $7.00 a gal its about $3-4 more than say 100 race gas available locally.

[Tom Cole]

I have actually been real happy with Amoco 93 (from BP).  I ordered some VP 006 today that we are going to try next weekend as a test.  It is blended to meet INEX specs and is supposed to generate "substantial power increases compared with other fuels that meet INEX oxygen spec."  If I don't see an improvement on the tach and the stopwatch, I won't be buying it again.

[hundo24]

You'll be paying more then $8 a gallon for 006, more towards $15 . I think every engine builder will recommend racing fuels . VP110 is right in the middle performance wise , 006 being the best .

[Tom Cole]

It was $70 and change for 5 gallons before tax, so you are dead on target with the price.

[qweedqwag]

I blend 89 pump gas with VP 114 works great.

[gramps05]

Be careful what you run if you do not have a fuel test kit, was disqualified this past weekend running Sunoco high test, would like to know what was in that, could it have had ethanol in it?

[JGRacing]

If you live in an area where pump gas uses over 4% Ethanol, are you stuck having to buy race fuel to be legal? 

[legends13]

according to the guy that tunes my carbs ( and most of Nick Pistones cars carbs too), the best for these engines is 4 gallons of 89 octane, 1 gallon 110 race gas, and 1 ounce of lucas top end lubricant.

don't use 93 octane as it sits in the tanks at the gas station much longer then 89.

[Tom Cole]

Great input.  I like the 89/110/Lucas idea a lot.

[Shawnben]

I used to deliever gas to gas stations and most newer stations only had two tanks in the ground. One for regular, and one for high test. And the pumps mixed the mid grade?