Avgas/ Premium Petrol (Read 4,980 times)

[4stree]

Had my car on the Dyno recently and was told that there was no advantage performance wise using Avgas opposed to Petrol. Any comments would be welcomed , I run on Avgas last year and have run on Gull premium this year and feel the car doesnt seem to be going as well as it should.

[nzf2stocks.]

At 10:1 compression there is no real gain from useing avgas/racefuel. There are other benefits though, the car runs slightly cooler, and avgas is more consistant in its rating, allowing finer tuneing of the motor. You wont see any increase on the dyno but the car will feel crisper in response.
The downside to racegas is that is more hydroscopic than pump gas, so you have to use it up sooner. Once a tin is opened you should use it within two weeks or it goes "stale". This doesn't cause short term problems, but the higher water content can affect the carb and other alloy parts of the fuel system. If you havn't used the car for a couple of weeks you should drain the tank and fuel system and replace it with fresh fuel.

[Deleted]

have also been told av better on motor as it leaded?
thinkingof running my new production on gull bio for something diff

[ross56y]

have found avgas to work really good on my vn
better the 98 or 91 octane gas

[strx7]

You need to advance the timing a couple of degrees to make the most of the higher octane rating of avgas, simply putting avgas in a engine tuned for a lesser octane fuel wont achieve anything, if anything you'd loose a couple of HP due to its slower burning nature

[wayne]

other advantage is its cheaper than 91 to buy

[Saloon29s]

wayneb said:

other advantage is its cheaper than 91 to buy

Cheaper? Where do you buy it thats cheaper than 91? Last season avgas was $2 a litre at the airport in Taranaki.

[nzf2stocks.]

Last time I checked if you buy a 206litre drum direct from the supplier it came to $258.00 inc gst, delivered to your door. You need to be GST registered and have a proper dangerous goods store to keep it. The price may have gone up a bit since then, but it allways been cheaper to buy avgas this way that pump gas at the station.

[nzf2stocks.]

gribbs said:

have also been told av better on motor as it leaded?
thinkingof running my new production on gull bio for something diff

Older motors benefit from the lead, but newer motors are designed to run without it. As a general rule, if the car has electronic injection don't use avgas as the lead buggers up the injectors, and if you still run the cat in a prod saloon (don't know the rule for this) NEVER use avgas as the cat will block up, overheat and catch fire in a very short space of time.
Lead is good for the valves, but most race car motors get rebuilds long before the valve seat recession becomes a problem.

[wayne]

stockcar29s said:

wayneb said:

other advantage is its cheaper than 91 to buy

Cheaper? Where do you buy it thats cheaper than 91? Last season avgas was $2 a litre at the airport in Taranaki
.

was paying 110 a litre last season and has gone up to 145 a litre now , i get it through a friends dad just drive out onto the runway and fill up like a plane

[Glenn, Ex 269s]

its $2.20 a litre at the aero club in new plymouth, yep just cruise out to the tarmac with the clipboard and fill your fuel container from the bowser, was paying $1.90 a litre last season in Blenheim

[Lucas Injection (72w)]

av gas buggers up the oxygen sensors used to control efi systems.

it does smell nice tho!, and yeah I had a problem with it going off and bringing water into the system

[strx7]

actually the only thing it buggers up is the oxygen sensor, the ECU is used to control the system itself. Find me a race car which uses closed loop 02 correction on the track.......

[nzf2stocks.]

Production saloons must use the o2 sensor if it part of the original system. The fix for this is to find one that doesnt work then retune the icu to suit.

I have heard stories from reputable sources about "race gas" supplied from less than careful outlets, ranging from so much water content you could use it for making coffee, to outlets running out of race fuel and substituting 98 and an octane boost (totally illegal in any speedway car), to stations that dont have a high volume in sales not mixing the fuel before dispensing it resulting in octane ratings of 115+ as the good stuff settles to the bottom of the drum. Get caught with that in your car and you'll have a long holiday.

In short, I wouldn't take the chance, the performance gains over 98 is not worth the hassle.

Also of note, dont mix 98 and 95, sometimes this will gain a higher octane, but will come up as a blended fuel in the tests, resulting in more time to do your gardens. I believe several ministocks have had this happen to them, resulting in bans.

T8-1-3 Fuel blending is not permitted. The addition of
Toluene to fuels is not permitted. The addition of
material to fuel or intake air to increase available
oxygen is strictly prohibited. Such materials include,
oxygen, water, nitrous oxide, nitro methane, nitro
propane, propylene oxide and nitropane etc.

[Lucas Injection (72w)]

Would one be better off running 98 in a production and get the computer reset to provide a 12:1 power mix and maybe a few extra degrees advance. This maybe against some rules but its no different than winding up the delivery on a mechanical system or rejetting a carb and rotating the dizzy a bit.

I just wonder how well an efi computer would perform without the oxy sensor. does doing away with the o2 sensor also nulify the air and coolant temperature sensors input?

cheers

[Sharns With Sparky]

is that in your standard stock rover8 ?? heard you cant run av in standards any more new rule?? old rule??

[nzf2stocks.]

rotaholic said:

is that in your standard stock rover8 ?? heard you cant run av in standards any more new rule?? old rule??

Technically this is correct, although people lump avgas and racegas into the same catagory.

T8-2 Approved Fuels:
(a) Solo, Sidecar, Open Wheel Vehicles, Modifieds, Super
Saloons: Methanol, Avgas 100, Petrol
(b) Saloons and Production Saloon, Super Stocks
Stockcars: Avgas, 100, Petrol
(c) Streetstocks: Petrol, Avgas 100; – no blending of fuels
allowed.
(d) Ministocks: Petrol Only

Racegas101 and similar products are illegal under this rule, and as most avgas is more than 100 octane this might be too. It all depends on the interpretation of the checker.

Rhis rule has been in for some time but was so grey that not much was done about it. Now that the SNZ roving Tech has more sophisticated testing gear they are coming down hard on it.
Use 98, its safer.

[strx7]

on a factory efi system (which i forgot about, due to there being no production saloons at baypark, and that any descently modified car runs an aftermarket efi computer) if there is no oxygen sensor, then the computer automatically runs rich to play safe. what is the car? why would you want to run 12:1 a/f ratio, thats a tad on the lean side for a turbo'd car and too rich for a n/a car.

[Lucas Injection (72w)]

yeah mate, sorry, the 12:1 was what I thort was the ideal fuel mixture for power

[Lucas Injection (72w)]

I posted a page ages ago re av gas on my www.saturdaynitefever.co.nz production website. its in the technical section. most of the content on the page is from bp fuels website. I added the bit re wellington airport.

by the way , Its not a commercial site . The sponsors supply prizes for the race series winners in return for space on the site.

cheers

dan