This website uses cookies to improve navigation. No personal data is held. Do you agree to the use of these cookies?    
Classic Engines, Modern Fuel

Comments on Topic: Fuel Ageing Re Fuel Systems

Share this topic item by email
Submitted by Jules

I do'nt own a classic car, but I use a number of 4 strokes and 2 strokes to maintain my garden. One 4 stroke is an older Honda ATV bike used as a trailer tug. Whilst aware that E5 affected the bikes starting/running if not fresh, it failed entirely this year, following the flooding of its carb'. Investigation revealed substantial fine granular crud in the float chamber and around its needle valve, in addition to the anticipated white aluminium oxidation, and more was found in the fuel tanks on/off petrol cock. It is true that the ATV would stand for quite a while between use, and that its E5 fuel front end component would have evaporated, but I was surprised to find such a large amount of fine granular material in the float chamber. I replaced the fuel cock with its large fine mesh filter, and because of comparative individual parts cost, the whole carburettor also. After thoroughly cleaning out the fuel tank, I now use Aspen Alkyl fuel for the bike and the two strokes, as they are most affected by E5 in terms of even running and starting. This is impracticable in cost terms for classic car owners.

A question the "book" does not directly answer is whether modern ignition systems automatically compensate for combustion cyclic variability? I am aware that Lambda sensors are placed at the front and rear of cat' converters to compare the exhaust gas and alter the ignition advance.

Share this topic item by email
Submitted by The Author

I would guess the white crud is, as you say, aluminum oxide. This is probably due to water getting into the petrol. This could be rainwater or condensation from storage. As I say in the book ANY ethanol content in the petrol will cause this.

From what you say it looks like you do not make a lot of use of these vehicles. I suggest you buy R Storage Plus fuel from Anglo American oil. While this is more expensive it does not contain any ethanol and it is not as volatile at room temperature. This means it will not "go off" like pump fuel. As a final benefit the test engine performed very well on this fuel.

Modern ignition systems and cyclic variability. Modern engines do suffer from cyclic variability but it is not as severe as in classic engines. There are a number of reasons for this:

  1. Fuel injection produces a much finer and better dispersed mist of petrol droplets than carburettors. These evaporate and mix better during the compression cycle and give a more consistent mixture around the plug when it fires.
  2. Modern inlet manifold and combustion cylinder designs are optimised to increase turbulence and mixing.
  3. Direct injection engines add a small second charge of fuel around the plug just before it fires to produce a consistent mixture at the optimum mixture to maximise the flame front growth speed.

The anti knock sensors and Lambda sensors are only used to control the mixture and ignition advance. I suspect the ones before and after the cat are used to control how and when the cat is "purged" by running a rich mixture through it.

Share this topic item by email
Submitted by Jules

Hello Paul,

Many thanks for your feedback, it is sincerely appreciated.

The ATV was previously owned by a friend suffering complex health issues who succumbed to a stroke. He gave me the bike which is now 18 years old. I remember seeing three jerry cans all with their lids open belonging to my friend in an adjacent field - - -.

I had assumed that only the white powder in the carb was aluminium oxide, but from what you are saying it seems that the fine granular material in the float chamber is also aluminium oxide. I recovered about 70% of it, and I think I will weigh it for reference!

Thank you for all your painstaking work to produce a really informative book, I can imagine that it is the first time that work of this type has been researched in the round.

With kind regards,

Julian Lindley

Please wait .....