Txxxx@aol.com wrote:

I think people let language play tricks on them. I didn't learn the value of retarding the essentially fixed-timing Hitachi mags on TZs until 1977 (shame on me!), but in describing what I learned to others, it was hard to put across that "retarded" could possibly be better than "advanced". And on into the advance/retard curve ignitions, people were still thinking they would find god in piling on more advance. What ever happened to fast burn?

I agree about language - and semantics -

I just talked to an engineer for Visteon - (Victory mc and more) -
He kept talking about af ratios and o2 sensors... and relating that to LBT....
I told him that I could easily change his o2 readings and make him confused - He was disbelieving -
I finally told him that I would just retard the ignition and that o2 would rise and that he would richen the mixture to get his af ratio "correct" -
I said that then he'd  would be "fat, retarded and happy" 'cause the numbers matched -
I think that I had just pulled some rug out from under his "reason for being" -
Basically - he backed up and explained that he does tune to best power, using fuel and ignition - and not to af ratios -
Our dyne systems (EC997) do that by default -

There was a pro AMA team that raced a Ducati -

The ignition timing was retarded at 9500 rpm - They used silly, fragile, expensive, lead fouling, wide band O2 sensors to "tune" to an af ratio....
Their bike actually subtly rich misfired at 9500 - Power dropped there and you could actually see little puffs of black smoke when it happened -
I asked them (nicely and amazingly politically correctly for me) to, maybe, try advancing the timing at 9500 - "No! It's the right af ratio.".
Tuning to af ratios is a cruel hoax for the customer as compared to tuning to what the engine actually wants -

Lean for Best Torque???
What the heck is that!!!

If you are too lean the engine will make less power and if it's too rich it will make less power -
He started talking about power setting "plateau's"... and always setting things to the leaner side of the power "plateau"

I told him that if I can change v stack length by only 5mm on 2 of 4 cylinders or change the main air jet on 2 cyls by only .025mm and measure that power difference in a controlled setting - that there's not really much of a plateau, is there??  (that took average of 3 A-B-A-B tests each and was ~.1 hp)

So -
The bantered about, taught in engineering courses, LBT concept is only valid if the dyno equipment isn't as good as it should be, the test condition control aren't as controlled as they could be or the engine management equipment is limited in it's ability to provide sequential control -
Otherwise - it's a concept that's misleading to those who don't know more than what they either read without knowing enough about it or those who don't tend to ask that "Why?" question

Your 1977 comment - If only we could go back and redo what we did then with the knowledge that we have now.......   Oh well!!

Still cracks me up when R.O. showed up with 3.1mm btc on his tz which worked best on a self proclaimed "state of the art" dynojet dyno...... Some dyno's DO lie!!!  :-D 

Yep - 2.5mm to 2.6mm was actually correct on our EC997 dyno and on the track - Why anybody even tries to insist dj dynos are that "last word" can only be explained by inexperience with other dynos -
Just because it's a common dyno - doesn't mean it's right!

Signed -
Still learning - and ending up at odds with the dealership dyno sheep -

Factory Pro -
415 271-7239