What is the ideal air/fuel ratio?
09-28-2010, 05:45 PM
#23
There is no IDEAL number. You have to see what your car likes and there are too many variables to say one number is IT. Agreed 13.0 seems to be a good target just dont assume because 30 people say 13.0 or 13.2 for example that your car may not like 12.8 etc. Got to allow for the possibilty that the measurement system (sensor, calibration, etc) may not be "dead on" also.
09-28-2010, 09:50 PM
#25
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There is no IDEAL number. You have to see what your car likes and there are too many variables to say one number is IT. Agreed 13.0 seems to be a good target just dont assume because 30 people say 13.0 or 13.2 for example that your car may not like 12.8 etc. Got to allow for the possibilty that the measurement system (sensor, calibration, etc) may not be "dead on" also.
09-29-2010, 01:32 AM
#27
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The whole idea of 14.7 being best A/F ratio is because it produces the lowest level of CO, HC and O2. High CO2 is desired by CA technicians because it is used to give a good idea of the cats efficiency. Black smoke does mean you're running rich; but i HAVE seen plenty of cars at the track throwin out black smoke.
So would everybody on this thread agree that the best A/F for power is 13.0:1?
So would everybody on this thread agree that the best A/F for power is 13.0:1?
09-29-2010, 09:57 AM
#29
No. See above post. Some will make better power richer and ignoring safety margins some better leaner than 13.0. Also you have to consider timing advance. If timing is far from optimum your "best" measured A/F for power can change.
Move it up and down a little and see how it responds. That is the only way you will know.
Move it up and down a little and see how it responds. That is the only way you will know.
09-29-2010, 09:13 PM
#32
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As has been said, ~13:1 is usually what will produce most hp on an NA motor that is not "knock limited". But part of the point of tuning is to see what works best for a particular combo. Excess fuel will cool the charge and supress detonation. That's why blower cars are often set up much richer. Going on the rich side of max power AF loses less than going to the lean side. Depending on the air when the tune is done, most tuners will consider this and set it up a little on the rich side to avoid it going to the lean side of the max power AF ratio when the air is very good.
09-30-2010, 10:23 AM
#33
There is no IDEAL number. You have to see what your car likes and there are too many variables to say one number is IT. Agreed 13.0 seems to be a good target just dont assume because 30 people say 13.0 or 13.2 for example that your car may not like 12.8 etc. Got to allow for the possibilty that the measurement system (sensor, calibration, etc) may not be "dead on" also.
As has been said, ~13:1 is usually what will produce most hp on an NA motor that is not "knock limited". But part of the point of tuning is to see what works best for a particular combo. Excess fuel will cool the charge and supress detonation. That's why blower cars are often set up much richer. Going on the rich side of max power AF loses less than going to the lean side. Depending on the air when the tune is done, most tuners will consider this and set it up a little on the rich side to avoid it going to the lean side of the max power AF ratio when the air is very good.
Can you even get E0%?
When you throw in E10% you need to scale the complete AFR curve.
You can have more than 14.1 to 1 (E10%) in none PE and 12.0 to 1 in PE.
What about PE 50% TPS @ X000 rpm's? You may not want 12.0 to 1 you may want it leaner.
09-30-2010, 05:52 PM
#34
Yes
Yes
Talking E0 here.
Yes
Talking E0 here.
09-30-2010, 08:29 PM
#36
Yes I am talking about E0 to simplify the discussion but can say E10-E15 is fine with me.
Have VP in stock by the drum but that has nothing to do with the point we are trying to make for the question that was asked... "Generally" 12.5-13.3 is considered best power. That is generally the reading that we see on the engine and the chassis dyno.
What comes out of the pump around here is about the same.
No I do not sample every one before tuning. That exact point is what we are trying to make, there are to many unknowns to say that "X" is the best measured a/f ratio for the most power, etc etc etc. The type of fuel and other factors have to be considered and that is why we dyno test it to see what it likes. Last one I ran today liked 12.8, and the one before it 12.2.
Have VP in stock by the drum but that has nothing to do with the point we are trying to make for the question that was asked... "Generally" 12.5-13.3 is considered best power. That is generally the reading that we see on the engine and the chassis dyno.
What comes out of the pump around here is about the same.
No I do not sample every one before tuning. That exact point is what we are trying to make, there are to many unknowns to say that "X" is the best measured a/f ratio for the most power, etc etc etc. The type of fuel and other factors have to be considered and that is why we dyno test it to see what it likes. Last one I ran today liked 12.8, and the one before it 12.2.
Last edited by DynoDR; 09-30-2010 at 08:44 PM.
09-30-2010, 09:07 PM
#37
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Yes I am talking about E0 to simplify the discussion but can say E10-E15 is fine with me.
Have VP in stock by the drum but that has nothing to do with the point we are trying to make for the question that was asked... "Generally" 12.5-13.3 is considered best power. That is generally the reading that we see on the engine and the chassis dyno.
What comes out of the pump around here is about the same.
No I do not sample every one before tuning. That exact point is what we are trying to make, there are to many unknowns to say that "X" is the best measured a/f ratio for the most power, etc etc etc. The type of fuel and other factors have to be considered and that is why we dyno test it to see what it likes. Last one I ran today liked 12.8, and the one before it 12.2.
Have VP in stock by the drum but that has nothing to do with the point we are trying to make for the question that was asked... "Generally" 12.5-13.3 is considered best power. That is generally the reading that we see on the engine and the chassis dyno.
What comes out of the pump around here is about the same.
No I do not sample every one before tuning. That exact point is what we are trying to make, there are to many unknowns to say that "X" is the best measured a/f ratio for the most power, etc etc etc. The type of fuel and other factors have to be considered and that is why we dyno test it to see what it likes. Last one I ran today liked 12.8, and the one before it 12.2.
This is case in point for why engines need tuning. You have to give them what they want, not what you think they want. And to do that, you have to find out what they want.
If you are tuning with E10, E85, M100, etc. and do NOT recalibrate your wideband for the specific fuel, it will still read 14.7 at stoich, even though the actual AF ratio will be different. Similarly, 13:1 will still be a bit more than 10% rich and so on. I don't recalibrate - it just gets too confusing. I tried it on an M100 car and I just couldn't get used to seeing mid 5's as the best power AF ratio, so I switched back. Before you start to argue with me about this, think about it. A wide band is not really measuring an AF ratio. The sensor does not actually measure oxygen concentration, but rather the amount of oxygen needed to completely oxidize any remaining combustibles in the exhaust gas. This has nothing to do with the fuel being used per se. When you change the meter calibration, all you are changing is the number it displays for a given output (voltage). The voltage is the same for stoich no matter which fuel is being used. So, using any of the common fuels, unless you recalibrate, you will still see max power in an NA engine at ~13.1.
If you wanted to measure AF ratio directly, you could do that with knowing fuel flow and MAF.
I just thought of another way to explain it. If you going 60mph, you are also going 97kph. Regardless of how the speedo is calibrated.
Rich
Last edited by rskrause; 09-30-2010 at 09:12 PM.
09-30-2010, 09:08 PM
#38
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CalEditor, If you are going to start throwing out different stoich ratio fuels, you should really use proper units like EQ. For this discussion you would be shooting for between 1.17 to 1.12 EQ.(or 0.86-0.89 lambda)
09-30-2010, 10:15 PM
#39
X2
If you are tuning with E10, E85, M100, etc. and do NOT recalibrate your wideband for the specific fuel, it will still read 14.7 at stoich, even though the actual AF ratio will be different. Similarly, 13:1 will still be a bit more than 10% rich and so on. I don't recalibrate - it just gets too confusing.
I just thought of another way to explain it. If you going 60mph, you are also going 97kph. Regardless of how the speedo is calibrated.
Rich
If you are tuning with E10, E85, M100, etc. and do NOT recalibrate your wideband for the specific fuel, it will still read 14.7 at stoich, even though the actual AF ratio will be different. Similarly, 13:1 will still be a bit more than 10% rich and so on. I don't recalibrate - it just gets too confusing.
I just thought of another way to explain it. If you going 60mph, you are also going 97kph. Regardless of how the speedo is calibrated.
Rich
I have seen typically that a tuned car with E10 tuned properly for E10 and a Wide-Band installed after the fact will read slightly lower than 14.68. About 14.45 to 15.5 and it is actually 14.1 to 1
thanks rskrause
10-01-2010, 07:30 AM
#40
power differnce As has been said, ~13:1 is usually what will produce most hp on an NA motor that is not "knock limited". But part of the point of tuning is to see what works best for a particular combo. Excess fuel will cool the charge and supress detonation. That's why blower cars are often set up much richer. Going on the rich side of max power AF loses less than going to the lean side. Depending on the air when the tune is done, most tuners will consider this and set it up a little on the rich side to avoid it going to the lean side of the max power AF ratio when the air is very good.
Thanks