Early M600 and E10 fuel

[tridentperu]

This is a saga that has been ongoing - my 98 M600 has always been tricky on small throttle openings - hesitating and spluttering slightly. Once the tap is open all good. No amount of carb fiddling helped much. Iridium plugs did help but didn't cure it completely. A good blast up the motorway helped but it always returned.

I have always used higher grade fuel, E5, as I do in my older bikes, reasoning that as the bike was built before ethanol came along the lower the E content the better....and the higher the octane too as the 600 is a fairly high comp motor at 10.5 :1.

On a recent 200 mile trip to Shropshire and back I needed fuel and all that was available was e10 - so, in it went. Performance was definitely improved. On the return more fuel went in, again e10 - the difference overall has been astounding.

Easier starting, no hesitation/ missing on small throttle openings and generally overall much smoother than before.

I wonder why? Does the ethanol burn faster? I have no idea but it's a result, and it's cheaper too!

Just my ramblings

Jim

[Nickj]

It's a bit complicated!
The issue is more the nature of ethanol and (a) it's effect on metals , rubber, semi and full sythetic materials and (b) it's ability to absorb it's own volume in water.

So on (a) older engines that weren't designed to use ethanol in fuel MAY use metals that it can corrode and MAY use gaskets and seals that will dissolve or swell. Potentially the biggest problem would be in the carbs. On later bikes it was the nylon fuel tanks that swell and distort, I know as I have some fuel tanks that have done this Ascerbis made of PA6. The really expensive damage is caused by corrosion
(b) is probably the biggest problem, ethanol can absorb it's own volume in water. It just sucks it in from moisture in the air and as fuel tanks have vents your fuel is continuously doing this. Water is denser than the fuel so it drops to the lowest point of the fuel tank. On a classic monster this is by the hinge at the rear where the tank starts to rust and eventually starts to leak. Any water in the tank can do this so even pre ethanol this happened frequently.
Also think a large tank full of ethanol laced fuel like your local garage has can have a layer of water in the bottom.
I put 5 litres of fuel into a new can, added some 2T oil for a power tool. It ran for a bit then bogged and stopped because there was water in the fuel so that came fresh out of the garage pump. Cue a quick strip down to clean the crap out of the motor

On the combustion front it's more interesting:
Raw petrol has a faster combustion rate and a higher peak heat release rate (HRR) under low engine loads, ethanol–petrol has a faster combustion rate and a higher HRR under high engine loads.
** An afterthought.. All the new car engines used in mild hybrids and designed to work with E10 and higher are all small with high rev limits, they're meant to be used at 3500 to 5000 rpm to hit the ethanol mix sweet spot??
Now what comes out of the engine on the ethanol mix is a reduced CO, the ammount of hydrocarbons is actually higher.
The burn rate is really complex, it down to how well it mixes with air, the intake designs, compression ratios, air temperature and pressure. Overall both mixes burn well enough to work in an engine.
The power output from an ethanol mix will be lower, take a unit of raw petrol and one of ethanol and ethanol makes about 35% less power. So an E10 mix drops up to 5% of your peak power and increases fuel consumption also drops. On yours that's less than 1 BHP so not really noticable.

It's probably just cleaned your low throttle circuit in the carbs to more like an 'as new' air/fuel delivery rate by melting any glase and crap that holds.
Check that there aren't any rubber tubes, gaskets or o-rings in the fuel line, if you're keeping the bike long term then change them if in doubt because they will eventually fail, either rotting away and shedding bits or swelling and blocking smaller passages.

[Mr Gazza]

Is it complicated though?
Surely this is just down to the octane rating and nothing to do with Ethanol at all?

E10 is 95RON and equivalent to 2 star also @ 95RON.
E5 is the same as 4 star @ 97RON.

As far as I can see, from what info I could find, the 600 should use 2 star and so would be more suited to E10.

I do remember filling my Honda 50 up many years ago with 4 star, it might have even been 5 star. My mate's Dad owned a garage and I needed some juice to get home on a Sunday, so he got the keys and filled me up with the expensive stuff saying it would be better.

Sadly the little bike ran like a pig, made less power and got hotter.
My Dad did a pretty good job of explaining to me how Octane ratings work and why I should stick to 2 Star, which I did thereafter.

If I recall correctly after all these years, he told me that the higher octane fuels have more anti-knock compound (Tetra-Ethyl lead in those days).
This makes the fuel burn more slowly and is to prevent knocking, pre-ignition, pinking or pinging as they say across the pond.

I think 5 star was 98Ron and Avgas is 100 Octane?

I don't really notice any difference in performance between E10 or E5 in my 900.
If I'm on a run I'll usually put E10 in as it will go through during the trip, but I have the habit of leaving the tank as full as possible with E5 when I put it away.

[jerry]

Never put any E10 in my carby monsters, but when E10 goes in my S4 its loses a lot of power and also uses more fuel 10% less mpg so I always put E5 in that too ,, I have seen what E10 does to carbs , destroying O rings , zinc, plastic and even brass not to add fuel lines, taps, etc etc had a nightmare with my wifes old 250 Honda even after it was rebuilt with Viton parts

[Kato]

Put very simply octane is a measured and/or calculated rating of the fuel's ability to resist autoignition, the higher the octane of the fuel, the harder that fuel is to ignite and the more heat is required to ignite it.

[Darren69]

Don't put E10 in old Ducati, E5 is bad enough but if you do add some Stabil the blue marine kind is better and reduces the ethanol reaction.

[spuggy]

Originally Posted by Kato

Put very simply octane is a measured and/or calculated rating of the fuel's ability to resist autoignition, the higher the octane of the fuel, the harder that fuel is to ignite and the more heat is required to ignite it.

And, different-but-related - higher-octane fuels burn slower. So the speed of propagation of the flame-front is also slower/takes longer. So timing is usually retarded relative to a lower-octane (faster-burning) fuel, in order that maximum cylinder pressure is not reached too soon - eg before the piston is "over-the-top" and the pressure can efficiently be converted into crankshaft motion.

Flame-front propagation becomes very significant with single-plugged (especially if offset from centre) and larger cylinder bores (in this context, 98-100mm seems to be a tipping point on 911 motors..). High-domed pistons also accentuate the effect.

Although I can think of one reason to run a more premium fuel than spec'd, at least from time-to-time. The more premium fuels often have a better additive pack.

[spuggy]

Originally Posted by Mr Gazza

I think 5 star was 98Ron and Avgas is 100 Octane?

100 LL (low lead) is the most common Avgas nowadays, replacement for Avgas 100 (which had twice as much lead).

Last track I went to had 110 and 120LL pumps. They all represent not-quite-instant-but-pretty-darned-accelerated death to your O2 sensor, if you have one.

And they made very little difference to detonation on (my) forced induction motor either (I run knock control).

It's really not a great idea to run Avgas at all, unless your motor is tuned to suit ("110 race gas" even has a different stoichiometric ratio, 14.9, than regular gas) - and then you shouldn't run anything else.

Optimal fuel formulation for an aviation motor turning RPMs in a very narrow range (many only vary by 500 RPM or so in flight), at high altitudes (you think your carbie 900s ices the carbs badly?) is very different to what is ideal for a car or bike motor...

Around here, if you insist on running 13:1 compression in an iron cylinder head and want 110 octane (quoted as (R+M)/2, roughly 114 "research octane") leaded race fuel for a boat, car or bike, you go buy it in 5 gallon pails. It's pretty expensive. And dyed lest you (god forbid) use it anywhere but a sanctioned race event...