How many degrees advance - change in RON

[ringram]

GreenV8S said:

Oh dear, why did I write that?

No problem squire, you certainly confused me at the time

Edited by ringram on Thursday 13th December 10:05

[That Daddy]

planetdave said:

The poor OP doesn't have an ion detector and is beginning to regret opening this can of worms.

When you guys have reached a concensus will you let me know?

Spot on.

[Pigeon]

GreenV8S said:

Pigeon said:

I once experimented with attaching strain gauges to the head of my MZ to see if I could detect the deformation due to combustion pressure and use that as feedback to adjust the ignition timing to give the pressure peak at 15 deg ATDC. Unfortunately I couldn't detect a thing...

You could put a pressure transducer inside the chamber, but you would need very fast monitoring to get the timing accurately enough. Ion detection seems to be the fashionable way to do this now.

"Fast" is a relative term; 5ms per cycle on a single-cylinder engine is time for a fair bit of processing Main limitations I came across were bandwidth/response time of transducers of any kind, and cost and availability of anything that would stand long-term use inside the combustion chamber. It's a bit offputting when the electronics consists basically of a microcontroller and a MOSFET and a voltage regulator, total cost about a fiver, plus a pressure transducer which costs enough to buy several MZs I'd read an article which talked about the use of a specially-manufactured piezo washer on the base of the spark plug to detect head deformation, so I figured that I might stand a chance with the strain gauge (an option on my air-cooled engine not readily available with the water-cooled engine in the article) but as it turned out I didn't get enough deformation to measure.

Ion detection might be worth looking into though...

[tristancliffe]

MBT does not, and never has/will stood for Maximum Best Torque. Anyone who says it does, post-graduate or not, is an imbecile.

MBT = Minimum Advance for Best Torque. Always has, always will.

Volatility has nothing to do with how it combusts

In the case of this thread, the timing should be backed off by a couple of degrees (from 12° to 10&#176 or thereabouts, but it would probably be fine at 12 anyway (as manufacturers took into account fuel MON/RON availability.

[ringram]

Sorry I didnt realise than an anonymous internet poster knows more than an MIT professor in advanced automotive engineering.
I guess we should all throw the text books out and listen to people on the internet.

Its also strange that a search on google returns 176,000 hits for "Maximum brake torque" and universities publish papers on the topic..
http://www.essays.se/essay/eecfd0564a/

But im sure you know best.

http://www.google.co.uk/search?q=MBT+maximum+brake...

Edited by ringram on Wednesday 19th December 20:22

[ringram]

tristancliffe said:

Volatility has nothing to do with how it combusts

Actually it does. In so far that its required to exist in the correct amount for the fuel to burn at all. A more vaporised mixture will burn more completely than one that has not.

Agreed its not directly related to octane, but then I was discussing a wide range of topics including cam timing etc.