Fuel

HansL

HansL

Senior member
Location
Netherlands
Does anyone of you of you have experience with high octane fuel?
I was told that Aral Ultimate 102 would do very good for our type of bikes.
With Bikers Classics approaching and the problems with the Gijs van Dijk bikes due to bad fuel in mind, I was thinking of buying some special fuel.
Also found stuff called Aspen on the net. Pretty expensive, but would it do good to the Monty?
Or maybe Avgas? Or just octane booster?

Hans
 
Put a drum of Avgas thru the Jota and 750 over the
HBBB w/end both bikes loved it  :-* didnt miss a beat,
plugs ran clean and pipes nice grey tinge  ;) just like
the good ol days of leaded fuel .
Pump fuel is faarken shit  >:D >:D

Just under 4 bucks a litre , great for track days.  :D
 
Ultimate 102 comes at a price, remember paying over ? 1,80 per liter last year, but it was the only higher octane stuff they had. Engine has no problems with SuperPlus which is rated at 98 octane and not as pricey.
 
I only use BP Ultimate if I can help it! Burns nicely.

It is also the only fuel that the fuel-level sender on my Audi A4 works with as well, I have tried every single fuel available - even normal BP unleaded doesn't work. Yes I tried changing the sender for ?40 odd and the new one is the same (wiring and instruments are fine as they work with the good stuff).

I have not resorted to octane boosters yet with the bike, but when I do trips I will take some with me.


 
I don't do track days and since Ultimate isn't available in enough places I use ordinary 95 plus a bit of Pro-ma. Have done for years, no issues in 79 Jota, 10.5:1, Witt ignition, original carbs. Probably works out around same cost per litre as Ultimate, typically get around 40mpg(imp).
 
What is the compression ratio on your Monty?
On our racers (10.5 or 11 to 1) here in Norway we religiously used Aspen (100 octane IIRC) but have gone over to pump 98 with no noticeable difference. My roadbike also has same comp ratio and is fine on the same pump 98. I?m told EU does not yet have the worst additives as some other countries do. Bad fuel Van Dijk had was more likely stale or contaminated than basically too low octane.
 
On my  (nominally) '79 Jota I have an RGS Corsa cr stamped head which was nos when fitted in about 2000. It has never seen leaded fuel or substitutes and has all but exclusively received the standard unleaded fuel available at whatever gas station happens to be open when needed!

I did for a while suffer from repeated cold fouling of plugs, particularly on the left hand pot. This was partially cured by Riccardo Oro turning down and balancing the action of the pumper jets, further cured by replacement of the coils with 3 separate modern Japanese units and finally solved by using 55 pilot jets and 130 main jets in the carbs (original 32 mm Dells c/w inlet manifolds spun out to 36 mm to marry with the head, original airbox and an un-oiled Clem Unifilter). Witt ignition. All works very well now. Have probably put 75,000 + miles worth of standard unleaded fuel through this motor and none of the problems I have had over the years can be attributed to fuel quality issues.

RGS, standard unleaded, no issues, 20,000 + km on top of previous owners mileage. It previous bar one owner only ever used it to travel to Morocco from the New Forest!

American Eagle, yep I am feeding him/her the same diet.

James
 
Tippie said:
What is the compression ratio on your Monty?
On our racers (10.5 or 11 to 1) here in Norway we religiously used Aspen (100 octane IIRC) but have gone over to pump 98 with no noticeable difference. My roadbike also has same comp ratio and is fine on the same pump 98. I?m told EU does not yet have the worst additives as some other countries do. Bad fuel Van Dijk had was more likely stale or contaminated than basically too low octane.
Click to expand...

I have never measured the compression ratio. The bike has Formula pistons and the head has been flattened once by 1,5 mm.
So far I've always used euro 98 and no problems so far, but was wondering what experiences people have higher octane fuel and if octane boosters do anything.

Thanks for the replies.

Hans
 
Mixing Avgas with some  regular fuel can increase the octane rating, I used to use 50/50 blue Avgas mixed with regular pump fuel. The problem with Avgas is that it has a slower burn rate than 'terrestrial' fuel and you can actually lose power with it. The other issue with Avgas is it comes in many different octane ratings, some of which are actually lower than pump gas so unless you know what you are doing you could actually cause more harm than good. If you're using Avgas you should familiarise yourself with the colour coding- blue Avgas is about 100 octane, I think green and purple are the highest ratings [don't take my word for this]

Always bear in mind that Avgas won't necessarily make your bike go any faster, what it can do is allow you to run more ignition advance/higher compression which in turn can liberate power. Just putting Avgas in won't magically make your bike go like a rocket.

In the UK Tesco 99 octane is about as good as you can get [as tested by various magazines] unless you go to specific motorcycle race fuels such as Sunoco.
 
You might find that skimping on the cost of fuel by buying lower octane stuff is a false economy.

A few years ago the standard fuel in Perth was 92, with an option to buy 95 or 98.
The 98 was 6% more expensive than the 92, but I got 25% more miles out of a tank full!
(72 Jag XJ6, and 83 Mitsubishi Magna).

I think that the difference is less profound in more modern cars, but our old bikes must have similar characteristics.
 
Once when I had the Laverda on the dyno, we tried different fuels in it to see how it affected the power curve. The result is that it didn't. The traces on the power curve overlaid each other exactly. You couldn't pick one from the other. I've found no difference in fuel consumption or performance on the road with different octane fuels either - not even any pinging on low octane (10.5:1 compression). So now I just go for the cheap stuff.

Cam
 
That said, Cam, what compression is yours? You will find Laverdas with 8.x:1 to 10.5:1 or more. With 8.x:1, you can run even 92 Octane without getting the bike to ping ever, at least not with the standard curves and with everything else to Laverda specs. with 9.x:1 or 10.5:1, there is a good chance a bike with 92 Octane will ping as hell...

Friend of mine has a 1000 SFC that had been re-worked by a known dealer. They sat the valve-seats a bit deeper into the combustion-champer, which caused pinging by self-detonation as soon as the bike was warmed up (no stress when cold, even not under load or without choke engaged).

So - please be careful to generalize, it really depends on what your bike's configuration looks like.

But I agree: 98 or even 102 Octane gas (alone) will NOT increase power or torque in any way. And without the according modifications, it is just a waste of money. Octane is nothing that BRINGS power, it is simply a required attribute of gas for certain engine configurations. As our engines do not have knock-sensors and no adjustment of the ignition curve, no TPS (except Cape's bike and 5 lucky other ones...), there is no benefit in giving the bike more than its actual configuration really needs.

the only thing why 100 or 102 Octane gas MAY make the bike run nicer are the additives that are claimed to be added to clean the valves and burn the combustion-chamber free. THIS might (!) make a difference, not the extra Octane...  ;)
 
Dellortoman said:
Once when I had the Laverda on the dyno, we tried different fuels in it to see how it affected the power curve. The result is that it didn't. The traces on the power curve overlaid each other exactly. You couldn't pick one from the other. I've found no difference in fuel consumption or performance on the road with different octane fuels either - not even any pinging on low octane (10.5:1 compression). So now I just go for the cheap stuff.

Cam
Click to expand...

Cam,

It's not about the power - as Bob said regarding Avgas.
It's much more about smooth burning, being able to advance ignition to provide a gain.
If you didn't advance the ignition on your test bench or anything else then ultimate power may well be largely the same.

The extra fuel economy gained by high octane fuel (I presume) is provided by more efficient burning at cruising speed.

As far as I know (and I prepared to be shot down) higher octane unleaded contains a good proportion of Cyclo Hexanes from the Benzine Ring family - famous for burning smoothly and evenly, thus raising octane rating.
Benzine = nasty stuff, but if burnt properly should cause no problems.

By testing a Cortina engine in a lab (yes I know) I determined that the most economical speed for the engine coincided with maximum torque NOT power. Also I learnt that higher compression ratio improved thermal efficiency - probably why diesel engines get better economy that petrol.

So with higher octane fuel the engine can be pushed harder.


 
Benzene was added to unleaded to boost octane rating when leaded fuel was deemed too hazardous to health..
I am surprised because it was disclosed (somewhere, somewhen, somewho) that the TLV (threshold limit value) for Benzene in the atmosphere is exceeded in most urban concentrations due to use of unleaded fuel.
So, you can breathe in your daily dose of Benzene in the city, but H&S won't allow that level in a work environment.
Green fuel?
Saving the planet?
Don't get me started on Ethanol in fuel (diverted from food crops).
Kiss my ora d'ora.
 
Grant said:
Lothar, if you read what he wrote he mentions 10.5:1 compression.
Click to expand...

sorry - jet-lack strikes obviously (just returned from the most south-west point of the USA...)

Still - another factor is: what ignition curve? Pinging is a result of to much pre-ignition. "To much" depends on rev and compression. As an extreme example: if you put ignition to ZERO pre-ignition, you will never have pre-ignition on 10.5:1 whatsoever, not even if you go down to 80 Octane...

32? at full revs isn't what counts, it is the pre-ignition at midrange mainly that kills an engine when you have the wrong pre-ignition for the compression and fuel grade you are using. Or the wrong octane for the compression and pre-ignition. Or the wrong compression for pre-ignition and octance-grade. It is mainly a combination of these 3 factors, which all need to be considered. Not talking about air-fuel ratio, which can - if to lean - can contribute to pinging, too...
 
Hi Lothar

Running an Ignitech box of sparks. Advance curve is pretty much a straight line from 9o at 1000prm to max advance of 29o at 6000rpm then flat 29o up to the rev limiter at 8500rpm. This curve was found to produce the best spread of power after a bunch of dyno runs. Bike runs pretty well and reasonably efficiently in terms of fuel consumptioon.

Cam
 
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