Post by halkyon on May 23, 2023 16:59:02 GMT
I've just finished reading a book on this which I found very interesting. 
I'm hesistant to try and sum it up myself but a few things that haven't immediately fallen out of brain already:
- Modern fuels are more volatile, evaporating at lower temperatures.
This causes difficulties hot-starting vehicles as the petrol near the engine has vapourised. This can be tricky to prevent because the heat is not necessarily coming from obvious sources (hot manifolds, exhaust, ambient under-bonnet temperature) but bleeding back up from open inlet valves. - Modern fuels cause greater cyclic variability - the variation in burn speed and extent of the burn within the combustion chambers and cylinders from cycle to cycle.
This creates the impression that modern/unleaded fuels burn "hotter", which isn't true specifically, the heat comes from more of the combustion cycles taking longer on average (as if we were running with the ignition too far retarded). - Ethanol blended fuels improve this at lower RPMs (where we spend most of our time).
- Modern fuels are knock-resistant to the extent that with older lower compression engines we may be able to advance the ignition too far but not hear pre-ignition.
- Water ingress into the fuel system will cause rapid corrosion when ethanol blended fuel is used - true for both E5 and E10 and additives do not stop this.
A couple of recommendations that jumped out at me:
- E10 will likely require a small enrichening of the mixture as it contains more oxygen,
- The ignition advance can likely (every engine is different) be advanced 5 or more degrees to some benefit (cooler running and fewer cycles happening late),
- Do not ever allow water into the fuel system,
- Replace your hoses!
- Opening the throttle to rev the engine up slightly as you switch it off can help hot-restarts as the hot air inside will be cycled out the exhaust as the engine slows to a stop.
The book goes a lot further than the website, but it does have some info: classicenginesmodernfuel.org.uk
