R U A LS1

I thought the higher the number the more rich the A/F ratio was. like a 12 is rich and a 10 is lean. But i just read a post where a guy had a 12.5:1 and everyone said that was waaay rich, and to lean it out to a 12.8:1 which is higher. So higher is leaner?

I ask because i am debating on whether to get a MAFT as ive posted in another post, or to get a $300 tune job <img border="0" title="" alt="[Roll Eyes]" src="images/icons/rolleyes.gif" /> Im new at ATAP and the brains of the LS1's PCM. So ill just tell you what i was looking for and what i know. At idle it was 14.6:1 and at WOT to 6000 it dropped to 11.1:1(5?). And i asked and my friend said there was no detonation (KR) (same thing right?)

<small>[ June 27, 2002, 06:37 PM: Message edited by: R U A LS1 ]</small>

Paul F

iTrader: (2)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by R U A LS1:
<strong>I thought the higher the number the more rich the A/F ratio was. like a 12 is rich and a 10 is lean. But i just read a post where a guy had a 12.5:1 and everyone said that was waaay rich, and to lean it out to a 12.8:1 which is higher. So higher is leaner?

I ask because i am debating on whether to get a MAFT as ive posted in another post, or to get a $300 tune job <img border="0" title="" alt="[Roll Eyes]" src="images/icons/rolleyes.gif" /> Im new at ATAP and the brains of the LS1's PCM. So ill just tell you what i was looking for and what i know. At idle it was 14.6:1 and at WOT to 6000 it dropped to 11.1:1(5?). And i asked and my friend said there was no detonation (KR) (same thing right?)</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Way rich is gas coming out of the tail pipe and way lean is holes in pistons. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> j/k

The ratio is air to fuel. So 1:1 would be way rich because you have 1 part fuel to one part air. Therefore 17:1 would be way lean because of the ratio of air to fuel. Or something like that. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

R U A LS1

so does anyone know why im would be so darn rich at idle??? or is 14 not too bad when it comes to 11 at WOT?

MelloYellow

14.7:1 is Stoich for emissions at idle and part throttle & is controlled by the PCM. Closed/Open Loop, etc.

WOT tuning, you want to be at around 12.8:1 with an N/A setup. 11.0:1 is TOOOO rich.

Get a MAFT and get that down. Did you change injectors or something?!

R U A LS1

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MelloYellow:
<strong>14.7:1 is Stoich for emissions at idle and part throttle & is controlled by the PCM. Closed/Open Loop, etc.

WOT tuning, you want to be at around 12.8:1 with an N/A setup. 11.0:1 is TOOOO rich.

Get a MAFT and get that down. Did you change injectors or something?!</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">No just got headers. I dont get how 11 is toooo rich but 14 is stoich? a higher number of A/F mixtures <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

Red2000SS

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by R U A LS1:
<strong>No just got headers. I dont get how 11 is toooo rich but 14 is stoich? a higher number of A/F mixtures <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The A/F ratio is the ratio of the mass of air to mass of fuel. People who replied above are correct, but you are not quite understanding it yet.

Stoichiometric is a term used to describe a chemical reaction in which you have exactly the right amount of two differnt chemicals that react to form new chemical compounds such that you have none of the original chemicals left.

In perfect (stoichiometric) combustion, burning hydrocarbons (gas), you have gasoline and air in the cylinder, ignite it and it burns completely producing CO2 and water (H2O). Hydrocarbons are broken down and combined with oxygen such that every single carbon atom is paired with 2 oxygen atoms (CO2) and every 2 Hydrogen atom is paired with 1 Oxygen atom (H2O). This reaction produces a lot of heat which is what powers our engines.

In reality even if you have perfect stoichiometric ratios of air and fuel going into our modern engines, they do not burn everything perfectly, and you can still get unburned hydrocarbons, carbon monoxide (CO), unreacted Oxygen, Nitrogen Oxides, Sulfur dioxide, and various other compounds due to incomplete combustion and additives / impurities in the gasoline.

Some of the engine gurus on here can comment on what A/F ratio you should have. My rough understanding is that too rich and you have unburned hydrocarbons going out your exhaust, possibly clogging your cats if you have them, as well as reduced mileage (if you care). Too lean, and you have higher combustion temperatures, and detonation problems, (holes in pistons, etc.).

Bottom line if you are running rich, you will have a lower air/fuel ratio (more fuel, less air). If you are running lean, you will have a higher air/fuel ratio (less fuel, more air).

Hope this helps.

MelloYellow

Like Red said.
Higher numbers are leaner, lower numbers are richer. It's ok to be leaner at idle and part throttle, but not at WOT.

Even that being said, you are still way too rich at WOT if you are at 11.0:1

<small>[ June 28, 2002, 12:45 AM: Message edited by: MelloYellow ]</small>

R U A LS1

RED
i got most of that.One point you didnt mention is that even though being rich causes unburn hydrocarbons clogging the cats (so what) running rich is what will cause your spark plugs to not run hot enough, dissableing its ability to burn of the carbon. This carbon buildup will cause fouling. So i guess ill get a MAFT and find someone to help my tune it. Either that or the pulley. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Nine Ball

iTrader: (38)

moving to tuning section <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />