Bruiser.STi

Hi all, Is Aviation Fuel cause any damage to the engine of a scoob if used now and again for driving events, such as hill climbs, etc...20-30 litres at a time.

Do any owners use Avgas or racing fuel when doing track days???

The reason I use it is to aviod the risk of detonation, hence the 100+ octane.

dela

I did a high speed sprint at Silverstone a year ago.
I used some of their Elf Racing fuel, 103 octane and £1.30 a litre. Boy did it go!!

Don't know about effects on engine internals and not sure of what AvGas is made up of.

dela

Editted to say it was Racing Unleaded I used, and I suspect AvGas is still leaded

[Edited by dela - 28/05/2002 12:24:23]

Bruiser.STi

Yes, AVgas does have lead in it still. I run a link cpu so the fuel sensor can be bypassed so the lead doesnt kill the sensor, but apart from that Im unsure if there are any adverse affetcs??

Still looking for someone in the know!!!

Dark Blue Mark

One way ticket to meltdown I would have thought!

If its an import and designed to run on 100 octane you "MAY" be ok, howerver, as it has a higher octane rating the combustion effect will be larger and therefore you will produce more heat. if the explosion / combustion produces more heat than the engine intenals is designed for, you may start melting stuff.

On a UK car I expect you will be in trouble...

Yes, the car will go damn quick, but for how long. Most of the boysusing heavy amounts of nitrous don't last too long!

A mate used to run his Nova on the stuff...

MB

john banks

Puzzled why high octane would damage your engine and make it run hotter? My simplistic understanding of higher octane fuel is that it resists preignition better and produces a more even flame front propogating from the spark plug. The main benefit of this is that you can advance the ignition more without knock and gain more power. The engine should run cooler I gather? So what would be the hazard in running 103-107 RON as long as it was unleaded?

dowser

Bruiser,

I think it's more that the link doesn't care if you kill your O2 sensor as it doesn't use it. Leaded fuel will still damage the sensor I believe, as the lead content left in the exhaust will coat it.

Richard

Dark Blue Mark

John,

I'm no expert but the higher combustivity of the fuel the more heat you would generate when it ignites? I remember talking to some experts at a RR day, a guy had poured loads of octane booster into his car (same effect as a higher RON fuel) They told him they were concerend about the pistons melting etc...

I may not be on the right tracks here im more of a gas turbine engineer

MB

john banks

For the same boost and fuelling and timing I can only imagine that raising the octane improves safety and prevents pistons from melting. Perhaps the gentleman (women are too sensible ) was running too much boost and using octane booster as "insurance"?

Higher octane results in a smoother burn and less knock, I'm not sure it is more "combustible" - more that the burn is smoother and more progressive, whereas low octane fuel is more likely to combust in a haphazard high pressure, uneven, shockwave type pattern rather than smooth and extended? Knock is one of the principle causes of catastrophically high in-cylinder temperatures and holed pistons.

Certainly one of the marketing forces behind some octane boosters is that things run cooler - NF Europe told me that it cools both the oil and water side of the engine but I did not see any data to back this up. I know it makes my car run far less knock correction, and when I ran double dose octane booster I could only get the EGT to about 715 degrees when 1/2 hour before it was 740 degrees on single dose in similar conditions with the same map, but I can't pretend it was proper controlled conditions.

Are we saying that if you go too far with the knock resistance of a fuel it actually heats things up? Seems very unlikely to me, but as always I love being wrong

Besides, if you can run more ignition advance with the higher octane fuel then the EGTs tend to be LOWER.

http://www.dynopower.freeserve.co.uk...reignition.htm This link was recently posted in another thread and makes quite interesting reading. For me until I read otherwise, it is as much octane as possible/practical/affordable


[Edited by john banks - 5/28/2002 3:03:56 PM]

Dark Blue Mark

Ahh but engine work harder! More work = more heat. At least in an aero turbine.

Sorry, I know thats not too constructive but car engines confuse me.



MB

john banks

Anyone clever save us from our guessing ?

Perhaps Adam M will give us something from a book of the sort of size that one bash over the head would kill ?

The two options are compatible

Pete Croney

John

Some times you've just got to admit defeat. Its obvious that DBM knows far more about these things than we do.

Pooder

The thing you are going to have to watch is Avgas has a lot of additives in it to stop it for example freezing at altitude. Aero engines of the type that run on Avgas are prone to carb icing and further chemicals are added to help prevent this.The typical aero engine running Avgas runs low rpm and is air cooled.,and have magneto type ignition,not at all like your scooby engine
Steve

Pooder

Aero turbines do not use Avgas they use something a bit like domestic heating oil

john banks

So should I stop using octane boosters when my engine runs so much better with it and runs less typically 3-5 degrees less knock correction if the timing is on the edge when running 2ml/L NF, and it appears lower EGTs? No I thought not Sorry this seems a no brainer to me. AVGAS additives/lead fine, different issue, but the article cited above says no risk damage from running excess octane than what you have mapped for. DBM?

Pooder

Avgas is leaded

john banks

Any comment about putting holes in pistons by using octane booster?

Pooder

John
I cannot see why you would hole a piston running higher octane unless you are running to lean
Steve

ChristianR

iTrader: (1)

i know of a scooby that did a 1/4run on 98octane fuel - it was in the 10's.

(not in this country though)

Pooder

lol

Trucker Ted

High octane fuel gives a more controlled burn under high compression or more advanced ignition timing without detonating.

Race fuel will also have a guaranteed RON rating which burns smoother and cleaner and will actually benefit from increased boost and advanced ignition timing.

Only drawback is the price of the stuff.
check out: www.76lubricants.co.uk

Pooder

Bruiser
I would keep away from avgas i can get it easily being a pilot but I would NOT put it in my STI. Do you have shell optimax in your part of the world?? Run your car on this and add octane booster for track days
Steve

Bruiser.STi

Thanks for the advice, I normally run a mixture of Avgas and our equivalent of Optimax which is BP Ultimate 98. Too ensure 100 RON.
I have been warned off octane boosters by many who say they wreck the injectors on turbo vehicles. Is this a myth???
Would be so much easier if we could just by Jap petrol, 100 unleaded!!!!

Bruiser.STi

Does anyone else have any "true life" experience in this area???

David_Wallis

As far as Im aware there is no difference between injectors on turbo and non turbo cars.... so sounds like a myth to me.

David

Bruiser.STi

I heard it wrecks all injectors, but turbo's are the worst hit!!!!

gene1

seems all non factory additions are bad for imprezas,from reading many off the posts in the other sections.but did race moto-x with a South african guy racing over here who used avgas in his bike and went like stink and swore by it.Mind you his dad was a millionaire and he had an ex-works Honda mecnanic work for him that re-built the motor after every three meetings.

JME

Hi Guyz,

Another of ppl here in perth (western australia) do use Avgas for the odd weekend hillclimb, khana etc. No side effects to report. Altho IT WILL KILL your o2 sensor fairly easily. Many a turbo (wrx, evo, gtr) are running avgas with std internals and having no trouble. Some mix with premium unleaded to lighten to concentrate, but a swing is towards the elf line or unleaded race fuels.....

i.e. avgas wont kill if used in moderation.

Jme

Bruiser.STi

Do you know any of the brands or companies that produce unleaded race fuel down under???

BugEyed

Hi Guys

An interesting debate appears to have gone on in my absence.

Avgas is leaded. So, it will destroy/poison any cats left on the vehicle and the O2 sensor. Our US cousins "invented" Avgas in the 1930's to allow them to run the Aero engines at higher temperatures without suffering valve seat failures. The lead effectively vapourises in the combustion process and the lead oxides formed lubricate the valve seats allowing the heat in the valves to be better dispursed. As an aside, if you find pictures of WWII carrier based aircraft you'll see the streaks of lead oxides down the side of the plane - they tended to run ridiculous amounts of lead in the fuel at the time (you don't want an engine failure when taking off a carrier as they have a nasty habit of running you over).

I personally would council against running Avgas in a race engine. As stated in previous posts it contains various anti-icing chemicals and will tend to give a very high combustion speed in the engine (which increases the stresses on the mechanicals). However, it will not produce more heat (unless you run more power as a result of increasing ignition advance or boost).

HTH

Duncan

NotoriousREV

We run AvGas in our race bikes (2 stroke) and it works great, our old TZ250 was running ridiculous compression (that would have made a diesel proud, think 18:1!!) without detonation. I asked my mechanical expert mate about running it the Scoob, he reccomended against it heavily in a 4 stroke car motor, reckoned it would burn the valves out in no time. However, he did say that he was no expert on Avgas itself, he was only interested in it's high octane rating. I suspect he only uses it because of it's pretty colour

Higher octane fuels do not produce more energy than lower octane fuels, octane is a fuels resistance to ignition, which allows you to run your motor in a higher state of tune without melting stuff (ie more boost or higher compression or more advanced ignition or a combination of all the above)