-------------------------------------------------------------------------------- Been trying to dial in the A/F a lil better and it seems 1st and 2nd are dead on at 12.5 but when I hit 3rd it drops to 12.0 and may climb to 12.3...Should I pull fuel so 3rd is 12.5 consistantly? On a dyno dont they usually run them in a higher gear...Would that make more sense to dial it in ..in third
Hmm somethings wrong you should not drop that much, do this drive it in auto stick in 3rd gear and at 2500 RPMS nail it til it shifts and tell me what it reads, now there could be something that is being picked up at knock in 3rd gear that is false knock and the PCM is dumping more fuel, are you running dual wideband or just on the drivers side typically the passenger side reads leaner than the drivers side
I don't believe the PCM adjusts fuel in response to knock. It only pulls timing. Pulling timing could effect your a/f but not much.
Well should't the A/F reading at WOT stay pretty close to the same number I understand a .1 or .2 difference +/- but thats a big drop, mine used to do that after it hit 4th gear and went over 100mph and just keep getting richer but I dont see how custom tunes can be done in "GEARS", IDK where is a tuner whe have several on here but you can feel it, when my 60-80mhp punch read 11.5 A/F and it was a dog but when leaned out to 12.5 it was much better but my WOT was 11.4-11.5 in all RPMS so again?????
Well if you pull fuel you can only do it in certain RPM ranges and that will affect all gears, so if you do that it will lean out 1st and 2nd gear too much, 12.0 is really not that bad but there is some power left on the table but not a whole lot
The stoichiometric (STOICH) air/fuel ratio is the chemically correct ratio, theoretically all of the oxygen and all of the fuel are consumed. The mixture is neither rich nor lean. However, due to the fact that combustion is never perfect in the real world, there will always be a small amount of oxygen left in the exhaust. This small amount that is left is what the oxygen sensor measures. The smaller the amount of oxygen that is left in the exhaust, the richer the A/F ratio is, and the higher the oxygen sensor voltage is. The on-board computer or Powertrain Control Module (PCM) monitors the voltage from the oxygen sensor. If the PCM sees an oxygen sensor voltage greater than .450V, it immediately starts to reduce the amount of fuel that is metered into the engine by reducing the on time to the fuel injectors. When this happens, the A/F ratio starts to go in the lean direction, and the oxygen sensor voltage starts to go down. When the voltage drops below .450V, the PCM immediately starts to increase the fuel metered to the engine by increasing the on time to the fuel injectors to produce a richer A/F ratio. This occurs until the oxygen sensor voltage goes above .450V. This repeating cycle happens very fast (many times per second). The PCM is said to be in closed loop. It is constantly monitoring the oxygen sensor voltage and adjusting the on time of the fuel injectors to maintain a stoichiometric A/F ratio. This A/F ratio produces the lowest harmful exhaust emissions, and allows the catalytic converter to operate at peak efficiency, therefore reducing the exhaust emissions further. Since the oxygen sensor output is non-linear and very sensitive at the stoichiometric A/F ratio it will cause the A/F meter LED's to bounce back and forth rapidly. A very small change in A/F ratio causes a large change in oxygen sensor voltage as can be seen on the graph. This causes the A/F ratio meter LED's to rapidly cycle back and forth, and is normal operation when the PCM is in closed loop and trying to maintain a stoichiometric A/F ratio. The oxygen sensor is very accurate at indicating a stoichiometric A/F ratio. It is also very accurate at indicating an A/F ratio that is richer or leaner than stoichiometric. However it can not indicate what exactly the A/F ratio is in the rich and lean areas due to the fact that the oxygen sensor output changes with the oxygen sensor temperature and wear. As the sensor temperature increases, the voltage output will decrease for a given A/F ratio in the rich area, and increase in the lean area as shown on the graph. During wide open throttle (throttle opening greater than 80% as indicated by the throttle position sensor) the A/F ratio will be forced rich by the PCM for maximum power. During this time the oxygen sensor outputs a voltage that corresponds to a rich A/F ratio. But the PCM ignores the oxygen sensor signal because it is not accurate for indicating exactly what the A/F ratio is in this range. The PCM is now in open loop, and relies on factory programmed maps to calculate what the on time of the fuel injectors should be to provide a rich A/F ratio for maximum power. The A/F ratio meter should indicate rich during this time. During hard deceleration the PCM will command an extremely lean mixture for lowest exhaust emissions. This may cause the A/F ratio meter not to indicate anything. The A/F ratio is so lean that it is outside the range that the meter will indicate. A bit of clarification on how they work and what they look like when they are working. We get tons of calls, emails, and letters about what this gauge does and how it works, and what it is supposed to look like. In its simplest form, the gauge is a color coded voltmeter, which lights up the LED(s) that correspond to the voltage that the gauge is sent via its signal wire. On most late model vehicles, the sensors are quite sensitive, and capable of responding very fast to a change in A/F ratio. This makes it appear that the LED's flicker in the different ranges, and this is normal. The gauge is showing the voltage it is receiving from the sensor, so more often than not it will appear that more than one of the LED's are lit, or that the readings are being shown to be in more than one section. Provided the gauge is connected properly (good power and ground) and that the connection to the O2 sensor signal wire is SOLDERED, this operation is normal. Usually, the only time the gauge will not show so many LED's is when the engine is at WOT. Instead, the gauge will pin the last few green LED's of the rich section. With time, as the O2 sensor degrades in sensitivity, the readings may be more spread out on the gauges display. Also, this gauge is not in any way designed to be used as a tuning tool, but more of an aid for the overall tuning of the engine. This gauge, when used in conjunction with either an EGT gauge or even 'reading' the condition of the plugs will help you determine the optimal A/F mix for your vehicle. Keep in mind the above only pertains to computer controlled, later model vehicles. For the rest of the carb fed engines out there, you will not see the exact same operation. Instead, the readings will be less diverse, as in the gauge will not illuminate a number of LED's, actually only a few or even one at a time will be lit. This is due to the lack of a computer in place to both monitor and adjust the A/F mix, so the readings are not quite as sporadic, and thus aiding with the overall tuning of the engine. A couple of things to look for when connecting your A/F ratio gauge to your vehicle are the O2 sensor itself, and it's current condition. Normally, an oxygen sensor is designed to last about 50,000 miles. However, its life can be shortened by contamination, blocked outside air, short circuits, and/or poor electrical connections.
I don't know. See the thread "Help me tune my engine". There are a number of factors that figure into it -- map, various temps, etc. If you just look at a/f and timing then (within reason) you can pick some a/f. Then you can advance timing until the point of knock at that a/f and, more or less, you should be getting the best power at that a/f. If you pick a different a/f you can do the same thing. There seems to be some debate as to whether our engines make the best power down in the very low 12's (like somewhere between 11.8 to 12.2) or in the upper 12's (like around 12.8). A dyno would tell and I suppose it could vary depending on your engine configuration. I would guess gas might make a difference too (yes, higher octane will take more timing advance but do you want more timing in the low 12's or do you want more timing in the high 12's). Given that, it does seem that tuners go for a fairly flat a/f through the rpm range and power curve. I don't know that tweaking a lightly modded engine for different a/f's at different places would make much difference if it does in fact make a difference in any engine. I (predator) tuned my basically stock (CAI and cat back) engine for a 12.0 to 12.2 a/f through the rpm range. Apparently with the gas I have I need to go that rich to get the timing up to 17*. I just assumed that there was some point that you wanted the timing over. When I tuned for 12.7 a/f I couldn't advance the timing much past 12* or 13*. So I was shooting for 12.2 (no particular reason) and ended up going to 12.0. After that I was able to add a bit more timing in the lowest range (which is only hit starting out in 1st) without knock which improved the sluggishness off the line. In the upper 2 rpm ranges the a/f stays the same in all gears (I haven't really watched it over 120mph). I don't know about the Jeeps. There's that thing about limiting throttle/power in first? to save the transfer case? Do the predator tunes remove that? That would be a gear difference thing right? although only in first. By the way, from what I saw the a/f is not constant with the stock tune. Seems to be a good bit leaner in first (that's where I got the idea for more timing in the bottom rpm range). Maybe with the engine winding up that fast it is under different load characteristics? I wish I knew something about tuning...
With the advent of emission concerns and catalytic converters engines are run at 14.7:1. This leaves some extra fuel needed for the chemical reaction in the cats. I believe our sensors/PCM are centered at 0.5v which maps to 14.7:1 a/f and it cycles between something like 0.2v and 0.8v (decreases fuel until it hits 0.2v and then increases fuel until it hits 0.8v... repeatedly). It does not instantly switch crossing the 0.5v threshold. small points.
Is this on spray or motor? Either way, I think the reason the AF goes rich in 3rd is because the motor is loaded down more and the rpm is much lower. See what rpm your jeep is at as soon as it shifts to third and lean the AF 1% in that rpm range. If thats not enough go another 1%.
Sorry busy work week...Temps have been 80's...I just put the 62 n2o and 26 fuel jets in...Bottle pressure about 800 and my A/F is 11.2-11.5 range...I think with 950 range bottle pressure I should be 11.5-11.8 ..SO I think it is finally dialed in...Till temps cool down...I will try that Centraltexhemi...Thanks... Also the 150hp jets made the Jeep feel so much stronger than the 125 jets..
Its leaning out as the rpm rises. Was that NA or on juice? If its NA I would try leaning it out 2% in the 1000-3800rpm range and 1% in the 4000-4800 range. If that was on juice I would add 1% to the 5000-7000 range.
