what does stoich mean???
 

I see this on alot of air fuel gauges,
one side is rich, the other is lean, I understand that,

but in the middle it says "stoich" !?!??!?!
wtf does that mean??

thanks!!

Re:what does stoich mean???
 

Lean = too less fuel
Rich = too much fuel
Stoich = Just about the right amount of mixture.

Re:what does stoich mean???
 

It's actually a measurement of the amounts all of the things that are in a chemcial reaction... basically a label that says "these things reacted evenly".

Re:what does stoich mean???
 

You react gas with oxygen to make water and carbon dioxide. These reactions happen at a very specific ratio. in the case of gasoline and air its 14.7 parts of air for one part of gasoline. if you have less fuel then you have a lean condition...extra oxygen has no gas to ret with and goes out your tail pipe. If you ave more gas then 14.7 then you all the oxyegen in the cylinder reacts with the gas and there is extra gas that has no oxygen and then also goes out the exhaust.

Stoich=stoichometery conditions which mans there is the just enough gas to react with the availible oxyegen, no more, no less.

When you say "just the right amount of mixture" it is very misleading since often you dont want to be even close to having a lean mixture. Hope this helps....Im a nerd i know.

Re:what does stoich mean???
 

ah ok,

very informative guys :)

Re:what does stoich mean???
 

No one said that. I said, "these things reacted evenly". Which is 100% accurate. :-\

Re:what does stoich mean???
 

hmmm,
question,
so with a normal cheap a/f gauge, on the stock o2 sensor,

if its reading exactly in the middle,
does that mean that its an exact 50/50 air/fuel mixture,
or not neccessarily 50/50 but rather the exact ammount of fuel to burn with the ammount of air supplied??

hope that makes sense.
thanks.

Re:what does stoich mean???
 

replying to ProjectZC, we know you knw your ----.

Re:what does stoich mean???
 

I dont think anybody said this but stoich literally stands for stoichiometric which is the air/fuel mixture 14.7/1 which yields the pretty much ideal emissions for cars. It is the perfect ratio for emissions, reducing HC, NOX, and CO.

Re:what does stoich mean???
 

It's also a tad on the lean side for boosted applications so don't run stoich for too long.
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Re:what does stoich mean???
 

so am i suppose to tune it until it shows kinda Rich?

Re:what does stoich mean???
 

You mean on a cheesy Autometer A/F gauge? Yes, tune it so it is on the rich side. Just to be safe I would suggest tuning further into the rich side since you aren't using the most accurate tuning device.
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Re:what does stoich mean???
 

Cheesy Autometer A/F ration gauge?!?! :o Good thing I haven't bought one of those things. ;) - Matt

Re:what does stoich mean???
 

..actually, stoichimetric is not an automotive term. It's a chemistry term, which again, means "a measurement of the amounts all of the things that are in a chemcial reaction". Applied to automotive theory, means a "perfect" air fuel ratio on gasoline, and that is 14.7:1 ratio..

Sorry for the symantics, but it's better to correct misinformation when it surfaces.

Re:what does stoich mean???
 

Good thing huh! Well, they are cheesy. I knew it when I bought it. They do give a "reference" point to work with. It's better than nothing. :-\ A wideband would be ideal, but money is always an issue. ::)
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Re:what does stoich mean???
 

Har har har ..... Money is ALWAYS an issue. :( - Matt

Re:what does stoich mean???
 

Re:what does stoich mean???
 

14.7:1 is for ambient air pressures (N/A Car), boosted stoich is 11-12:1. :)

Re:what does stoich mean???
 

iv got a summit racing a/f gauge,
its got 10leds, from bottom to top(bottom lean top rich)
4red/2yellow/4green
what would you guys say would be optimum for idle on an N/A car?

filled up to the 2yellow?
what would you say is the stoich range?
or approximate(i know these things arent that accurate).

Re:what does stoich mean???
 

That doesn't really make sense. Increasing air pressure does not change it's physical make-up. Which is what would need to happen to reduce it's ability to burn completely during combustion. The ratio of perfect air fuel combustion is still 14.7:1, however, during boost, it is recommended you run richer (~12-13.8:1) to decrease detonation.

..could you please explain your reasoning as to why you believe that pressurized air burns less efficiently than ambient air?

Re:what does stoich mean???
 

I thought you added extra fuel to "cool" the cumbustion process down and thereby not allow detonation.?

stoichiometry:

If you're lean=fuel is limiting reactant
If your rich=air is limiting reactant

that dude was NOT a mechanic(maybe he was I don't know...)