• Forum membership has its advantages....

AV Gas Pro or Con?

Junior

Well-Known Member
What are the effects of running AV Gas in a race motor? I have a JEEP which I use mainly at the dunes and the beach. It has a Chevy ZZ4 crate motor in it. The motor has 10.5 to 1 compression and is rollerized. I believe it is a non fuel injected version of the motor in the 2000 LT-1 Corvette. I ordered it from the Chevy Performance Parts Catalog. Some people tell me that Av Gas will make the motor run hot some say it will run cooler. Some say be sure and mix it with pump gas. Some say to expect valve damage etc. What is the scoop on running AV Gas. What are the Pros and Cons?



Junior
EJR Racing #244
 

Jimmy8

Well-Known Member
I am not an expert on the subject, but I have always heard never to run straight AV gas or it will burn the motor up. I always heard run a mix, like 1/3 AV gas and 2/3 92 octane. Also 76 now has a 100 octane race gas you can buy at the pump that is really good, or you can always add a little 110 octane race gas to your tank with the 92 and make it run like a champ.
 

ntsqd

Well-Known Member
Do some research on the web. I recall a site that stated the reasons why AV gas was not a good choice for race or high compresion engines. Partly had to do with the altitude the fuel's octane was rated at, as I recall. Not sure why altitude would affect the octane rating but appearently it does. The jist of it was that while 110 LL exists, it is rated to be 110 at 10k feet and isn't 110 @ sea level or something to that effect. Then there is something to do with lubricity of the fuel. Even the leaded AV fuel doesn't supply the valve lubrication most surface engines are designed to use. So burning it up as in fire, no, but burning the valve seats up, yes.
Not to mention that AV gas supposedly is illegal to burn in surface craft. Gov'ts got to get it's road tax.....

"Teach you all I know and you're still stupid"
-- Howdy Lee
 

BradM

Well-Known Member
What my engine builder told me echoes what Thom just said. Av gas lacks lubrication because it is designed for use at higher altitude. I don't really know how that effects lubrication requirements but I think there is a correlation. I have been told that some people add an additive to av gas like you would with alcohol just for lubricity. Hell, I add it to my diesel for lubricity. That may be a viable option. I know my engine builder made it abundantly clear that I if wasn't willing to spend the money for race gas he wouldn't put the compression in it. The zz4 isn't that high of compression, I would recommend you mix 110 leaded race gas with 92. There have been some really good articles on the subject in the past and some even had charts of mixing ratios. I would immagine that you could find that info on the web somewhere. If not, let me know and I can try to look it up. I recall one in Sand Sports within the last year or two.



Build 'em light, wind 'em tight
 

Waldo

Safehouse
I am going to attempt to address the controversy of aviation gasoline verses racing gasoline for use in race cars. Some racers use aviation gasoline which is fine for some applications but does have shortcomings. There are several grades of aviation gasoline (avgas) that we must identify before going any farther.

1. Avgas 80/87: this product is used in low compression ratio aircraft engines, contains little or no lead,is red in color, and should not be used in any automotive engine due to a low motor octane number ofabout 80.

2. Avgas 100/130: this product that can be used in some automotive engines. It has both research and motor octane numbers slightly over 100. Avgas 100/130 is green in color, contains four grams of lead per gallon, and is becoming harder to find.

3. Avgas 100 LL: the LL stands for "low-lead" which means two grams per gallon, low compared to the
avgas 100/130 that it was designed to replace. It has research and motor octane numbers very similar to the 100/130 product previously discussed. The color is blue. This product sometimes has a high level of aromatics which can contribute to lazy throttle response and dissatisfaction of the consumer.

4. Avgas 115/145: this product was developed for high performance piston aircraft engines used in
world war II and in the Korean war. It is very hard to find anymore due to lack of demand although it is of very high octane quality. The color is purple.

The remainder of this discussion will assume that our basis for comparison with racing gasoline is avgas100/130 and/or 100 LL since they are both available and have acceptable octane quality for limitedapplications. When the word "avgas" is used, it will refer to avgas 100/130 or 100 LL. Avgas is less dense than most racing gasolines. Instead of weighing about 6.1 to 6.3 pounds per gallon like racing gasoline, it weighs 5.8 to 5.9 pounds per gallon. The racer must compensate for this by
changing to richer (larger) jets in the carburetor when changing from racing gasoline to avgas.

The other major difference is octane quality. Avgas is short on octane compared to most racing gasolines. Many racing engines with "quick" spark advance curves or with no centrifugal advance have more spark advance at low rpm than avgas and some racing gasolines can handle. The result is
detonation, especially during caution periods in circle track racing because all of the spark advance is "in", rpm is low, and part throttle air fuel ratios are too lean for the operating conditions. If the driver does not "work" the throttle back and forth, pistons can be "burned" which melts away part of the aluminum piston material. Inadequate octane quality is one of the quickest ways to destroy an engine. Pistons can be severely damaged during one acceleration where detonation is present and the racer may not know what is happening until it is too late.

For maximum performance and power from a racing engine, racing gasoline will normally provide better performance than avgas. Avgas can be a good gasoline for some applications, but since most
racers do not know the octane requirement of their engines, they would be better off with a "real" racinggasoline that will give them the overall resistance to detonation that they need to protect their investment. If someone has spent from $15,000 to $50,000 or more on their racing engine, it is foolish to cut corners on gasoline be sure you have a gasoline with adequate octane quality.

P.S. Ya'll thought I was pretty smart, huh! Here is a link to answer "gas" related questions.'

http://www.osbornauto.com/racing/</A>


BRAAAAAAAAP!

~Waldo~
 

mustafa

Well-Known Member
Doesn't avgas adversely effect fuel consumption too?

I'm shaking the tree boss!
 

kurt

Well-Known Member
Quick Question - can you do engine damage or adversly affect performance by using a fuel with too much octane. Example if I use 110 race fuel in an engine that only requires about 100 octane, other then it being a waste of money is it a bad thing to do?
 

ntsqd

Well-Known Member
"Doesn't avgas adversely effect fuel consumption too?"

Yup.

"The racer must compensate for this by changing to richer (larger) jets in the carburetor when changing from racing gasoline to avgas. "

I knew about the lack of response issue with avgas, but had forgotten that aspect, Thanks BajaWaldo. Man once yer past 30 it's all downhill. First thing to go is the...........


"Teach you all I know and you're still stupid"
-- Howdy Lee
 

Waldo

Safehouse
Crap!...I just turned 30 in July.

BRAAAAAAAAP!

~Waldo~
 

Junior

Well-Known Member
100LL is the tye of Avgas I was considering. Sounds like mostly negative effects both in performance and engine wear. Why all the hype? Is it just because of the advertised 100 octane? There doesn't seem to be any reason why someone would use Avgas with the possible exception of it being lighter. I will check out my local 76 station looking for the 100 octane fuel.

Thanks for all the info and links.



Junior
EJR Racing #244
 

ntsqd

Well-Known Member
The hype is because it's available anywhere an airport exists and race fuel isn't always easy to find (geographically or otherwise, not withstanding the Trick Fuel station on Studebaker Rd.). Just because it's available doesn't mean it's good. Something Madison Ave. would like us all to forget.

"Teach you all I know and you're still stupid"
-- Howdy Lee
 

Waldo

Safehouse
Av gas is for planes at altitude.

BRAAAAAAAAP!

~Waldo~
 

BradM

Well-Known Member
Race gas isn't that hard to find if you really look for it. Besides, a lot of stations are starting to carry the new 100 octane unleaded fuels at the pump. I know of several in Ventura and Oxnard, they must be available throughout LA and Orange counties. If you want leaded fuel, find a dealer near you. Otherwise, go to your local circle track. There will be someone there selling parts and tires and fuel. Get a card and pick it up at their shop if you don't want to get it at the track. Or step up and buy a drum or two at a time. The price is better and you won't have to go looking for it. Hell, we usually take about 200 gallons with us when we go skiing..... I guess that's why we affectionately refer to the boat as "Thirsty".



Build 'em light, wind 'em tight
 

Junior

Well-Known Member
Here in Yuma the best deal I can find on Race fuel is 112 octane Sonoco for $6.95 per gallon. I guess I should purchase a drum from VP. Will race fuel keep?



Junior
EJR Racing #244
 

BradM

Well-Known Member
A new sealed drum will keep for a long time. Once the seal has been broken, the octane will drop off with time. It is also important to keep the cap screwed on tight and keep moisture out. If moisture develops in the drum, the inside of the drum can begin to rust. It ought to be plenty dry in Yuma so you shouldn't have to worry to much about moisture in the air if you get the cap tight. As for the octane, like I said it will drop over time. If you can use it within a few months, no problem. Over a year and the rating will drop pretty quick.


Build 'em light, wind 'em tight
 

BradM

Well-Known Member
Forgot to add, you should be able to buy it by the drum for about $4.00 - $4.50 / gallon. I buy Unocal 110 leaded for $3.95 at the pump or by the drum from Cosby Oil in Santa Fe Springs. They are also a CFN so you can have the business write it off. That's OK with you as an accountant, isn't it Junior? Actually, they require a special card for race gas but they have Unocal 100 unleaded, 110 leaded, 114 leaded, and 118 leaded all at the pump. Also, once you have a card, you can get in to buy it anytime. You don't have to go by there during the day like you would to pick up a drum. Also, most people will add a $20 drum deposit that is refundable when you return the drum.

I would think you could get it through EJR Racing. Where do y'all buy your fuel for the protruck?



Build 'em light, wind 'em tight
 

Junior

Well-Known Member
We get the Protruck fuel from VP. We usually pick it up at the race and it goes quick! I had never really considerred paying for race fuel since I had a REAL GOOD connection for the Avgas here at the airport.

Is it better to run the leaded or unleaded race fuel in my ZZ4? Nice motor by the way. Paid approx $3,000 for it over the internet, including shipping. Motor came complete. Only things needed were a carb, starter, oil filter and plug wires.

And yes, I love deductions!



Junior
EJR Racing #244
 

BradM

Well-Known Member
The unleaded only comes in 100. I use the leaded, even if I mix it with 92. I don't see where the lead will adversely effect anything and may add lubrication qualities.

I know those are nice engines. Just so you know, if you ask a really good engine guy he will tell you never to run a crate motor out of the box. Chevrolet is good but they are not perfect. I have heard many stories about the small discrepancies in deck height, line bore, balancing, clearances, etc. It depends on how hard you plan to push it and how much use it will see. If you expect to squeeze everything out of it, you might check all the clearances and if all is good, just reassemble it. If not, fix any potential problems before they create more problems.

Put in an order for an extra drum at the 1000 so you have it for Thanksgiving at Glamis. It's only money and you can't take it with you.


Build 'em light, wind 'em tight
 

Junior

Well-Known Member
Great idea. Thanks to all for the insight.

This sight rocks! Over 150 views of my inquery in an afternoon, great responses too! You know how long it would take me to ask these questions to over 150 people, without this venue? Personal reply's also......Engineers, Racers etc.........



Junior
EJR Racing #244
 
Top