Okay, I'm NOT a tuner (this will be obvious in 2 ms)

WHY, please pray tell with excruciating detail, does everyone tune for 11.1 to 12.1???

Obviously there is a safety factor involved but I'd love to hear the wisdom behind it rather than just hear it spatted out as some law. (perhaps good law, but I just want to know how it was arrived at).

Basically, isn't 14.7 ideal air/fuel mixture? So why 12.1or 11.1? PLEASE don't be generic and just say for safety. or because of turbo boost.

 

The 11:1 A/F is a safe number for our motors. On a piston motor you can run a leaner A/F and still be safe. Here's why, The shape of our combustion chamber is pretty shitty being long and narrow. This causes the flame front to basicly start at one end and burn across to the other. As this happens the fuel/air at the far end in compressed and heated. What do that sound like? Right, a good way to light it off before the front crosses over and burns it in a controlled manner. So if it does light off on it's own bam! no more apex seal. So you use more fuel to a.)cool the charge b.) slow the burn so the flame front has a chance to get all the way across. THe 14.7 is for perfect combustion. But under high pressure/stress condtions it's to unstable and parts will burn just due the temp/pressure on it own in the chamber. You can Use High octane race gas at a lower A/F because it's more stable and does not need as much help to burn slow and smooth. ie high octane slower burn=more control. Plus all gas motors are heat engines it's the heat that turns the parts. Well, in a long narrow space there is alot more surface for the heat to go into the motor/coolant instead of turning parts. On a piston motor it's pretty close to a sphere and the lowest suface area possible. Plus if you put a spark plug in the middle(almost all good motors do) the distance is the same all the around. This and other factors are the reason our motors are very thristy or have a high BSFC number. But thats another long boring post

 

It seems as though, 7 eleven is still the smartest cookie I know!!! Just wanted to say hi!

 

true dat....... lol 7-eleven is a bible of knowledge

 

to add to 7-elevens post: even piston engines dont use a "true" 14.7:1 AFR. that is for perfect combustion and there arent too many engines that can hold a perfect combustion process due to the difference in air density and fuel. . . and the above mentioned "heat loss" characteristic that all engines share.

paul

 

dam.... seven 11 is smart........ without the arrogance of some other "smart" folks on the forum....