Running too rich or too lean, how its effected
02-13-2006, 02:10 PM
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Originally Posted by S2kracka,Feb 13 2006, 02:50 PM
I think you are confused on what the A/F ratio means. The lower the number the richer (more gas) the car is. The higher the numer, the leaner (less gas) it is. Going to 14:1 seems to be going in the oposite direction from what you want.
You can't just "unplug" the VAFC, the car will not run properly unless you uninstall the whole thing and reconnect the air meter wires down by the ECU. You would be much better off just setting everything to zero across the board (this is the best option in my opinion since who knows how well your car is really tuned, let the ECU figure it out). After buying the header you want (and driving around for a few days with the VAFC zero'd out so the ECU can make any adjustments its going to make) go get it a good dyno-tune on it.
You can't just "unplug" the VAFC, the car will not run properly unless you uninstall the whole thing and reconnect the air meter wires down by the ECU. You would be much better off just setting everything to zero across the board (this is the best option in my opinion since who knows how well your car is really tuned, let the ECU figure it out). After buying the header you want (and driving around for a few days with the VAFC zero'd out so the ECU can make any adjustments its going to make) go get it a good dyno-tune on it.
But I knew that 14 means leaner.... I heard low 13 a/f is best and I'm at a high 13 near 14.0 a/f ration at some spots in my rpm range so I was asking if thats over kill (too lean)...
I think I'm going to add some fuel and bring it down to nearly 0 across the whole board to be safe like S2kracka and other people suggested...
looks like i wont be racing for a while now! Need those damn megan dyno's so I can make my header decision!!!!
02-14-2006, 08:13 PM
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My car runs best at an A/F ratio of ~13.25:1. Each engine like something a little different, but the combustion chamber shape, piston dome shape, spark advance, and ratio of Intake/Exhaust flow play the major role in determining optimum A/F ratio.
If you are not sure what the A/F ratio is you can check the output voltage of the oxygen sensor. The voltage ranges from 0.1 to 0.9 volts (as I recall). You can do a Google search to determine the correlation between the voltage reading and the A/F ratio (I have the chart at home, but I'm traveling right now).
IMHO an A/F ratio of less than 12.8:1 is too rich for any N/A application and an A/F ratio greater than 13.7 is too lean for any application (at wide open throttle, tuning for max. HP and torque). Since the combustion efficiency is the greatest at max. torque it can typically stand to be the leanest at this point.
If anyone has any other data I would like to see it posted.
If you are not sure what the A/F ratio is you can check the output voltage of the oxygen sensor. The voltage ranges from 0.1 to 0.9 volts (as I recall). You can do a Google search to determine the correlation between the voltage reading and the A/F ratio (I have the chart at home, but I'm traveling right now).
IMHO an A/F ratio of less than 12.8:1 is too rich for any N/A application and an A/F ratio greater than 13.7 is too lean for any application (at wide open throttle, tuning for max. HP and torque). Since the combustion efficiency is the greatest at max. torque it can typically stand to be the leanest at this point.
If anyone has any other data I would like to see it posted.
02-14-2006, 08:20 PM
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Originally Posted by Greenlight,Feb 14 2006, 09:13 PM
My car runs best at an A/F ratio of ~13.25:1. Each engine like something a little different, but the combustion chamber shape, piston dome shape, spark advance, and ratio of Intake/Exhaust flow play the major role in determining optimum A/F ratio.
If you are not sure what the A/F ratio is you can check the output voltage of the oxygen sensor. The voltage ranges from 0.1 to 0.9 volts (as I recall). You can do a Google search to determine the correlation between the voltage reading and the A/F ratio (I have the chart at home, but I'm traveling right now).
IMHO an A/F ratio of less than 12.8:1 is too rich for any N/A application and an A/F ratio greater than 13.7 is too lean for any application (at wide open throttle, tuning for max. HP and torque). Since the combustion efficiency is the greatest at max. torque it can typically stand to be the leanest at this point.
If anyone has any other data I would like to see it posted.
If you are not sure what the A/F ratio is you can check the output voltage of the oxygen sensor. The voltage ranges from 0.1 to 0.9 volts (as I recall). You can do a Google search to determine the correlation between the voltage reading and the A/F ratio (I have the chart at home, but I'm traveling right now).
IMHO an A/F ratio of less than 12.8:1 is too rich for any N/A application and an A/F ratio greater than 13.7 is too lean for any application (at wide open throttle, tuning for max. HP and torque). Since the combustion efficiency is the greatest at max. torque it can typically stand to be the leanest at this point.
If anyone has any other data I would like to see it posted.
Thanks for the good info!
02-14-2006, 08:57 PM
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Originally Posted by kayvan_pour,Feb 13 2006, 10:54 AM
We leaned it out to around an average of 13.6 A/F ratio (too lean?) and I was happy with that...
02-14-2006, 09:04 PM
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At some point if you add to much fuel you will be flooding it and not burning all of it. If you go to lean you can possibly get to a point where it will be a lean misfire. Like I said before 14.7:1 is the perfect ratio for AIR and Hydrocarbons (gasoline) to burn the most complete. To extract the most power as you can a little more rich is probably better. Though being a smog technitian and seeing you are in California you will have problems with smoging it in the long run becasue you will be working your cat a bit harder. 
ON the other hand good news, soon you will only have to smog newer cars every 6 years !!!!!!
ON the other hand good news, soon you will only have to smog newer cars every 6 years !!!!!!
02-14-2006, 09:05 PM
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Originally Posted by s2kBryan916,Feb 14 2006, 09:57 PM
Uhh last time I checked stoichiometric (probably wrong spelling) is 14.7:1. Now a ratio of 13.6:1 is a rich ractio being that you have less air than the best ratio. A lean ratio will be the other way on the scale 15:1 and so on....
02-14-2006, 09:21 PM
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Originally Posted by kayvan_pour,Feb 14 2006, 10:05 PM
hmmm.. I think for the s2000 a good air/fuel ratio i around 13.4... So any where in the 14.0+ range would be veryyyy lean and cause damage to the engine.
But then again thats what your tuning it for, more power with no worries about emissions. 
02-14-2006, 09:25 PM
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Originally Posted by s2kBryan916,Feb 14 2006, 10:21 PM
At a 14.7:1 ratio O2 and HC (air and gas) have enough molecules between each other that most all the O2 molecules will be used up and only little HC and CO (in complete combustion byproducts) will come out. With this ratio you need the correct compression and heat (fuel vaporization, liquid fuel will not burn) provided by the piston and spark. I know for sure a HUGE majority of cars in the US today do run around a 14:7.1 ratio OR are trying to be at the ratio. It will lean it out when it needs to, like many ULEV (ultra low emissions vehicles) in fact the Honda Accord will lean it to a 22:1 ratio WAY lean, but it is able to do so because it has an air fuel sensor rather than a O2 sensor. It may also go rich in times it needs power, "under load". I am pretty sure I have this down by now, Honda training school and being a driveablilty tech. I am not saying that the s2000 doesnt run at a richer mixture than what is normally done by most cars now adays. Im saying I would put my money on that the computer is always trying to keep it around 14.7:1. But then again thats what your tuning it for, more power with no worries about emissions.
But then again thats what your tuning it for, more power with no worries about emissions. But I'm almost 100% confident on the s2k engine, high compression engine that rev's so high, if you run anything over 14.0 the engine will blow...