Originally Posted by Skull31
Ya i have no idea on what you just said,lol.
"The only thing that can be done for any performance feel is lean the stock pig rich fuel trims out and firm up shift points. The only timing that can be added is very minimal with 87" Can you explain what all that means?This is what i am talking about for those of us who dont know much about this kinda stuff
But who wants to learn about it
First off: If you REALLY want to grasp the concept of tuning, buy and read that book I posted. It is an excellent way to spend 20 bucks.
As the truck comes from the factory, the tunes that come with them are VERY safe. There is a ratio called the air/fuel ratio that is based off a concept in chemistry called stoichiometry. When you are just cruising around driving normal the ratio will read 14.7. This is a perfect ratio for a gas motor. However, when you go full throttle, more fuel is added and the ratio changes.
Basically the higher the stoichiometric number, the leaner(hass more air and less fuel) the motor will run. The factory makes the tune so that at full throttle the A/F ratio is rich, meaning a lot of fuel added. Iv seen readings as low as 10.5 for a stock tune. That is PIG rich.
tuning your car in the fuel trims to get your wide open throttle A/F ratio around 12.5-13 is optimal for a naturally aspired motor. It provides some of the best, safe fuel trims for performance; it also saves some gas.
You get these numbers from measuring your exhaust gas with a wideband A/F meter. DO NOT GET THIS CONFUSED WITH THOSE POS NARROW BAND GAUGES RICERS USE TO LOOK COOL! THOSE DO NOTHING.
So to recap Ch.1:
your A/F ratio is a stoichiometric relationship where the higher the number the leaner the motor, and vise versa.
14.7= cruising A/F ratio, always unless your front o2 sensors are bad*
Now, to address the timing:
87, 89, 91, 93 octane gases are not just distinguished by the different added detergents. The fundamental difference between them is whats called their heating value. the higher the octane, the higher the heating value for that gas. This higher heating value means that the gas takes longer to completely burn. Consequently, it also has more internal energy to yield from the combustion.
when you increase the timing, you fire a spark sooner. This is good for 93 octane because it has longer to burn before its fully compressed in the engine. When you increase the timing to much on an 87 octane fuel, the fuel is burnt to fast and a condition called detonation occurs. FYI, detonation, just like it sounds, is not good.
87 octane does not posses enough internal energy to utilize more than 2-3* of advanced timing without starting to detonate. So the fact that a company calls an 87 octane tune "performance" is basically a lie. LOL
Ch 2 Summary:
Octane rating tells you in a nutshell how much timing can be added.
To much timing= boom
* Natural fluctuations occur from about 14.3-15, the average is about 14.7