timing+air/fuel???
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Joined: Mar 2005
Posts: 248
From: angier; find it
timing+air/fuel???
I might have this completely wrong, but it hit me today as I flipped through one of my racing mags.
1) If I got a air/fuel guage to go in my car and it read from rich to good to lean, would that tell me when I sprayed if my car was running either way?
2)Meaning if I sprayed, it would say lean or possibly rich (since im running a wet shot).
3)If so, as long as it stayed in the middle (good) does that mean that my car is not having any detonation or such problems, and that Im running a pretty safe setup, and there would be no need to pull timing?
I hope all this makes since. I just thought it might be a good way to see if I needed to pull timing while I sprayed for pretty cheap($50), and also to get a cool A-pillar guage as well ($30). I might have this all wrong, but this is what my research lead me to believe; that one pulls timing in order to correct from running leaning or rich; therefore, reducing the chance of detonation or some other problem. If this is incorrect please correct me.
Thanks
1) If I got a air/fuel guage to go in my car and it read from rich to good to lean, would that tell me when I sprayed if my car was running either way?
2)Meaning if I sprayed, it would say lean or possibly rich (since im running a wet shot).
3)If so, as long as it stayed in the middle (good) does that mean that my car is not having any detonation or such problems, and that Im running a pretty safe setup, and there would be no need to pull timing?
I hope all this makes since. I just thought it might be a good way to see if I needed to pull timing while I sprayed for pretty cheap($50), and also to get a cool A-pillar guage as well ($30). I might have this all wrong, but this is what my research lead me to believe; that one pulls timing in order to correct from running leaning or rich; therefore, reducing the chance of detonation or some other problem. If this is incorrect please correct me.
Thanks
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Joined: Nov 1998
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From: Hell was full so they sent me to NJ
Re: timing+air/fuel???
No, doesn't make any sense.
The A/F gauge (assuming you are talking about one of the units that uses your stock narrow-band O2 sensors) is intended to show the stoichiometric A/F ratio (14.7:1) in the center. That's where you want your engine to run at part load, low load to give you decent fuel economy, and to allow the catalytic converter to do its job. That's not the A/F ratio you want when you spray.
When you go WOT, you want a much richer A/F ratio.... NA you will be in the range of 12.8-13.2:1, on a big shot of nitrous you may well want to be as rich as 11.0:1. So keeping the A/F gauge in the center (what you are apparently calling "good") is probably going to destroy your engine due to detonation.
And, you don't overcome the need to retard timing by pouring in fuel. Nitrous increases the concentration of oxygen in the air/fuel charge, and speeds up the combustion rate. You need to back off the timing primarily because of that burn speed increase, not because of the A/F ratio its running (obviously, running richer will alter the concentration of O2, but its not necessarily enough to offset the burn speed).
Finally, the last thing you want to rely on for setting a nitrous tune is a stock, narrow-band O2 sensor. They simply are not accurate at the A/F ratios you need for NA, N2O or forced induction applications.
The A/F gauge (assuming you are talking about one of the units that uses your stock narrow-band O2 sensors) is intended to show the stoichiometric A/F ratio (14.7:1) in the center. That's where you want your engine to run at part load, low load to give you decent fuel economy, and to allow the catalytic converter to do its job. That's not the A/F ratio you want when you spray.
When you go WOT, you want a much richer A/F ratio.... NA you will be in the range of 12.8-13.2:1, on a big shot of nitrous you may well want to be as rich as 11.0:1. So keeping the A/F gauge in the center (what you are apparently calling "good") is probably going to destroy your engine due to detonation.
And, you don't overcome the need to retard timing by pouring in fuel. Nitrous increases the concentration of oxygen in the air/fuel charge, and speeds up the combustion rate. You need to back off the timing primarily because of that burn speed increase, not because of the A/F ratio its running (obviously, running richer will alter the concentration of O2, but its not necessarily enough to offset the burn speed).
Finally, the last thing you want to rely on for setting a nitrous tune is a stock, narrow-band O2 sensor. They simply are not accurate at the A/F ratios you need for NA, N2O or forced induction applications.
Last edited by Injuneer; Oct 12, 2005 at 08:23 AM.