Avgas

it might be worth doing if lineaweaver can give you an advanced ignition index. i believe that he has said in the past that the ignition is correct at top end and ******** at bottom.

by advancing it at higher revs you may get some benefit and keep the benefits i have found in the lower revs.

otherwise, it's simple. you need a ridiculously high compression ratio to take full advantage of the stuff and so usually there is little point.

regards

Taffy

I did use the stuff for awhile during a period when I was storing my bike at the hanger of a friend's avaition repair business. We were mixing it 50/50 I think with premium pump fuel.

We seemed to think it was a good idea at the time but I can't say for sure that I really noticed anything special. I was accustomed to running VP race fuel so I was already used to having the benefits of good fuel. It certainly did not make the bikes run bad.

After reading the article in the link that McMucker posted, I am not sure that we were accomplishing anything. I would rather save my pennies for VP or something equivalent.

I have used the stuff in my DRZ250 (the pig) and, in this bike, there was a difference of about 10% more umph, but the jetting was not stock, I did lower the clip and added a bigger main jet and a T-4 exhaust. The bike even did great at Moab on the jeep trails (sucked on the single tracks). But it was ridiculously loud for a 250.

I have seen no difference whatsoever in the following bikes: my son's WR 250F, my Berg. Nothing, Nada.

There was a difference with the YZ125 and with my 125SX, but only when I put a Doma exhaust pipe on it. I guess it works better with unrestricted (motocross) 2-strokes.

Now that the stuff is over $3 a gallon, I don't even bother. Also from using it for about 10 rides in a row, the exhaust bits ended up being dyed blue (it is colored blue in the US, I guess if the color is gone, that means you need to discard it, better doing that than falling from the sky).

Everywhere I read about this stuff, it's the same: try and see if you feel a difference. But to take advantage of it, as Taffy says, you need a high compression ratio and to advance the ignition.

Also, McMucker, are the octanes the same in Europe? I thought your octanes were 5% lower than ours, meaning that AvGas there is 105? If you are in Northen Ireland (from what I guessed) maybe your measures are not continental.

100ll is going to be the same where ever you go in the world if it's avgas. That's one thing about aviation, many aspects of it are the same the world over, communication, fuel, etc... That way planes don't fall out of the sky, and people don't fly into each other!!

As far as octance goes, there are two methods, RON or research octane number, and ROZ. I don't know about ROZ. However, I do know that they are different. I believe, that research octane unmbers are arrived at by using a test motor at a set load and then the timing is advanced to the point of engine knock or detonation to determine the octane number. There are numerous articles about octane ratings to be found on the internet, so enjoy reading.

One thing I will point out is that there is a great misconception about high octane fuel. Just because you run high octane fuel doesn't mean that you're going to get any more power out of your motor. In fact, you will get less power, that's basically what Taffy was saying. The reason being is that high octane fuel has a slower flame speed, or burn speed than that of a lower octane fuel at a given compression ratio. And as Taffy also pointed out, one needs to advance timing as well. And, you will also end up with a motor that won't start very well either, especially when it's hot.

And let there be no mistake, LL avgas has a lot of lead in it. You will see a nice grey coating on the outlet of your exhaust pipe in short order after you've been running it. Possible benefits would include better ring sealing, and longer valve/valve seat life as the lead will act as a cushion. That's why there was a change in valve seat engineering when unleaded gas came on the scene many years ago, as the older motors relied on lead for the valves. This change to unleaded fuel was done b/c they found out that spewing lead all over the place was bad.

So, if you are going to be getting free gas, why don't you cut your free avgas with regular unleaded gas to give yourself high enough octane at half the price?

Just two cents. I have found that using higher octane
would benefit for someone that does not ride allot.
By the time u used it for each month the octane
looses .5 points on its octane rating. Full tank and
5 gallon gas can can last ME 4 months.
I do not plan it like this when I buy the gas I plan on
riding every day but alass it does not work like that
>>>MAN<<< I need to ride more!!!!!
Earl

At $3 a gallon the stuff is so cheap I'd never use anything else. Just ask Taffy what he pays for the regular petrol in England. Be prepared for a shock.
A few years ago terrorists emptied the petrol stations through a refinery siege, it was amazing since the police didn't do a single thing to stop them. The whole country was paralyzed since the filling stations could not get any petrol and they had these large "CLOSED" signs that you could see from the road.
I was getting to a point here but now I've forgotten what that point was... :lol:

it's important that your octane reaches a minimum. i know that the bikes in the UK run happily on 98RON and there isn't much need for super unleaded when it's that good. then i went to the states and was told-and saw what thewy put in them there. i guess it goes back to the old jalopy days when the compression was 6 to 1 and you could run the bootleggers on pig sheeyut!

regards

Taffy

The best pump fuel available here is MON 91 which equates to about RON 95 .It is not great but it works.Price here to day is $1.08 per litre. OH yea...IRVING ROCKS

Taffy said:

then i went to the states and was told-and saw what thewy put in them there. i guess it goes back to the old jalopy days when the compression was 6 to 1 and you could run the bootleggers on pig sheeyut!

regards

Taffy

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Just whatcha tryn to say fella. The Moonshiners had the best of motors and knew how to hop them up. Where do you think the all american sport came from. Yes I'm talking about the great sport that has taken over Speed TV................NASCAR. :finger:
Our bootleggers might run some of their cargo in a pinch and you would never buy that good an octane at a pump!
I guess in Merry ole England they could use a jallopy with 6/1 cr cause they only had to outrun a Bobby on foot with a stick. :twisted:

Being a pilot myself, I can tell you a couple of things about avgas. One thing often overlooked is the deicers installed in the gas. Aircraft operate in temperature extremes running from 100f to -40 f. These fuels can aggravate vapor locking problems for hot-restarts. One reason that aircraft engines need such high octane is that they are bigbore engines that run at heavy loads and low RPMs ,air cooled, to, boot and are prone to detonation. Their cylinders are subject to hot-spots and dead spots that harbor this. They also generally have two spark plugs to help ignite this fuel better (and, of course, for redundancy). Add in lead fouling to some of these disadvantages, and it's not a dog-fall. You're better off using a commercial racing fuel designed for high-rpm engines, at least that's what they told me at High-Rpm-Racing-Fuel-School. :roll: :roll:

DaleEO
If I remember correctly RON was derived using a variable compression engine of sorts (compression increases until knocking) and MON is as you mentioned, constant load and advance timing until knocking. MON is I believe the more usable number, the higher the better. The octane number displayed at the pump is an average of the two methods.(RON+MON)/2 Part of the reason why some gas stations are better than others.

I don't remember where I read this but if I happen to remember I'll post a link.

sentinal said:

DaleEO
If I remember correctly RON was derived using a variable compression engine of sorts (compression increases until knocking) and MON is as you mentioned, constant load and advance timing until knocking. MON is I believe the more usable number, the higher the better. The octane number displayed at the pump is an average of the two methods.(RON+MON)/2 Part of the reason why some gas stations are better than others.

I don't remember where I read this but if I happen to remember I'll post a link.

Click to expand...

That sounds about right, it's been a while since I've read up on that subject. Thanks for the update.

from what I have read, avgas has high amounts of detergent (dont wanna foul plugs at 10000 ft I suppose), and this detergent factor supposedly makes it undesirable for running in motorcycles. For one, it washes the plugs clean, supposedly making accurate plug readings impossible insofar as jetting goes. The engine oils we use also may not be compatible with the detergents in avgas, and it may wash the critical oil away from the compression ring/top cylinder area, or simply cause an accelerated breakdown of the motorcycle engine oil, also not very desirable. Like so many things today, avgas is highly specialised, and is made to be compatible with the other aviation-specialised products. Like we dont use automotive oils in motorcycles because they contain moly( will fry a wet clutch), as well as not being suitable for use in gearboxes. Im thinking avgas isnt such a great idea. Id rather use the motorcycle-specific fuels from a company like VP, or just plain pump gas. Just my two cents, for what its worth.

Yes avgas is not cheap and must be used in very high compression aplications.i have a cheap solution with more power for little modified engines from avgas.go to my gallery and check also the measurint for husaberg.