Air Fuel Ratio Question

[mike britt]

So if the actual a/f is 13.0 and the target is 13.0 and the correction is -4.7% and in learning does that mean I need to adjust that cell or is it already correcting for me? Also if it is negative does that mean I need to take fuel out or add fuel?

[Dickens]

You ca go directly to learn table and the value will have been generated. You will then have to transfer it into the fuel map

[Jeff Niceswanger]

Originally Posted by mike britt

So if the actual a/f is 13.0 and the target is 13.0 and the correction is -4.7% and in learning does that mean I need to adjust that cell or is it already correcting for me? Also if it is negative does that mean I need to take fuel out or add fuel?

The Learn data is what has already been done to keep the 13.0 #. "Minus" is your system taking -4 % out to keep you on target of that 13.0 Setpoint. Just allow the transfer and your permanent map will no no longer need to take out -4% as it will be corrected in the main map. I recommend not allowing the smoothing (it will ask you if you want it done when you transfer) as the Holley will smooth the entire map and sometimes that will wreck your Idle areas,especially if your not using/running the Idle air control (IAC). You can go in and just smooth the affected areas by left clicking and highlighting that particular area and then hit smooth. And you will know the affected areas as the Holley will put a little dot in every cell that was changed when you allowed the transfer. Always rename and "save as" to your Global folder in the Holley. That way you still have your original tune. Make sure you actually "send" your renamed map to the ECU.

[Dyno]

Not wanting to hijack the thread, but has anyone compared the A/F ratio with the O2 sensor off a header tube compared to the sensor in the collector? If the collector sensor reads and corrects to 13.0, is the header tube reading 12.5 or 13.5 for example?

[Doug Hoven]

Originally Posted by Dyno

Not wanting to hijack the thread, but has anyone compared the A/F ratio with the O2 sensor off a header tube compared to the sensor in the collector? If the collector sensor reads and corrects to 13.0, is the header tube reading 12.5 or 13.5 for example?

I did this with an EFI car I was driving within the last year. We always tuned the collector to 13.0:1, and I realized the primary tubes were all around 12.5:1. However, the sensor used by the Holley is an NTK, and the sensors for the RacePak are Bosch sensors, so results may be different if the sensors are of the same mfg. Generally it seems that whichever tube is most directly in line with the sensor in the collector, that will have the most influence on the reading.

[e vassar]

So.. since all 4 tubes are dumping into the collector, wouldn't that sensor be the one you should tune from? Unless you have sensors in all 8 and attempting to tune each cylinder.

[Signman]

Hello all hope I can positively add to the conversation:

It's good to ask for advice but what works for me may not be optimal for you or even useless.

The proper way is to take the car to a chassis dyno with good tuner. Tune it for maximum power to the wheels, isn't that what is the ultimate goal? While doing so observe the AF ratio and carry that to your AF target map. You will now know what is optimal for you with all the various factors of choices made.

Locating the O2 sensor in the collector will see the average of all four cylinders but will appear lean due to reversion pulses of fresh air you cannot do much about.

When placed further up the primary tube closer to the exhaust valve there will be much less effect from reversion pulses AF will be slightly rich compared to in collector. You will see reading only from that one cylinder.

We did a test on the engine dyno with O2s in all 8 just to see how balanced or out of balance fueling was cylinder to cylinder and then do some individual cylinder tuning. What we found in my case (TPI) we were in good shape.

Then of course old school reading plugs really is not old.

Be Well!