what will cause piston to break or melt

[gmh308]

Yes, Heywood says exactly that... leaner than stoich burns hotter (provided there is sufficient fuel, otherwise it won't burn at all... but that's pretty lean)... and the N2 (nitrogen molecule) requires quite a high temperature to oxidize

(...lol... otherwise our 79% N2 atmosphere would oxidize with each and every open flame...).

Lucky for us so far.....a % or 2 more O2 and we are in deep doo doo. :(

Glad my memory is serving me well after countless ales......

The lean/rich scenario is used a lot in go-karting. Hand on the needle entering the straight, lean it out for power, then turn it back in before the piston and the bore become one!

[gmh308]

Yes, Heywood says exactly that... leaner than stoich burns hotter (provided there is sufficient fuel, otherwise it won't burn at all... but that's pretty lean)... and the N2 (nitrogen molecule) requires quite a high temperature to oxidize (...lol... otherwise our 79% N2 atmosphere would oxidize with each and every open flame...).

Whats a Heywood?

[joecar]

John Heywood is the world's authority on internal combustion engine technology... he also teaches Mech Eng ICE classes at MIT.

See this book... it covers ICE theory/operation and is very mathematical and is considered an advanced engineering text.

[gmh308]

John Heywood is the world's authority on internal combustion engine technology... he also teaches Mech Eng ICE classes at MIT.

See this book... it covers ICE theory/operation and is very mathematical and is considered an advanced engineering text.

mmm...thanksyou! My memory is still mostly working. Must track one down and see how it improves on Ricardo, Irving, Yunick, Jenkins and McInnes. Must have some good up to date stuff on VVT/DI/Emissions etc. The Bosch blue book is a good little source of info too.

[joecar]

I don't think Heywood mentions VVT/DI (I might have not read far enough...)... he is a "traditionalist"...

he covers he underlying physics by which combustion occurs and how it is affected by cam/spark and anyything else...

VVT and DI still use the same underlying physics.

[DaddySS]

My understanding is also this:

It is easier to "light" a lean mixture and when it's too lean and you hear knocking it is because the compression is firing off the fuel (like a diesel) as the piston is on the upward travel - not good. That is why higher compression engines are more prone to knocking. Todays higher temperature engines have the added heat to make the problem worse. When you fire the fuel too early you expose more of the cylinder to the combustion which again generates more heat.

It is the same when the timing is too far advanced.

[Sid447]

mmm...thanksyou! My memory is still mostly working. Must track one down and see how it improves on Ricardo, Irving, Yunick, Jenkins and McInnes. Must have some good up to date stuff on VVT/DI/Emissions etc. The Bosch blue book is a good little source of info too.

David Vizard is worth listening to.

[joecar]

David Vizard is worth listening to.

Yes, he is very hands on.

[gmh308]

David Vizard is worth listening to.

Right on! David is pretty amazing. He has been consistently at it now for 25+ years producing very well researched, highly technical and objective books and articles. Certainly a pinnacle in the performance car space.

[joecar]

I have a collection of his books... good content and good writing style easy to read...