Fueling - How to get it right

Once you have your cam angles set, your VTEC engagement where you want it, an ideal MAF Cal, (very important that its calibrated right from 2 g/s to Max g/s and the curve has no bumps or dips) then your ready to start looking at fueling.

And hence the age old question (well, at least as old as you've had your hands on an Access Port), how do I know if my fueling is right?

Thank goodness Honda chose to implement a Semi-wideband O2 sensor in our cars. Due to that little fact we can get close to optimal results without trying to convert Primary 02 voltages to corrosponding AFR's and worry about manufacturing variance and all that math. This tuning guide will try to show you how to use the stock primary 02 for tuning. A WB02 is best of course! But not everyone can afford one, or implement it as conviently into their logs. Also our stock primary is fairly accurrate when not operated for extended loads.

Theres a couple things to keep in mind though. Until it is proven otherwise it the growing concensus that the tables in ATR are labelled backwards for High Vtec fueling. Meaning the tables you should be thinking about adjusting for WOT fueling are the dual Primary High Vtec fueling tables. It is our opinion that the single Secondary High Vtec table is simply a fail safe table that the ECU uses for a short time after a reflash (while it learns fuel trims) or in the event it should lose the MAF sensor or other critical operating sensor. (*Update, its pretty much confirmed this is the case.) .The car runs so rich it that it can overcome a missing input from a failed sensor, thats the purpose of this failsafe table. It also appears to use this table on cold starts, until operational temp is reached as it slowly transitions (using averages) over to your dual primary tables.

So that being said I recommend leaving your ATR Primary fueling tables populated with stock values from 12.54psi and dwon. At least you will have the peace of mind that your car will run safe in the event of a failsafe mode being triggered. At the end of this thread I will explain how to put optimal values in this Secondary Table.

----------

For your first datalog, leave your primary tables at stock values as well and be sure to log:

1) AFR (For obvious reasons)

2) MAP (To get an idea which tables your ECU is using, 15.05PSI, 14.18PSI, 12.54PSI etc)

3) Knock (To run the knock spreadsheet hosted here to look for hidden issues)

4) RPM (For RPM specific fueling adjustments)

5) Ignition (To look for areas where the timing is pulled, ie 30,31,30,27,30, ties in with knock count)

6) MPH (To tell what gear you were in for each run, as higher gears appear to run richer due to excess heat)

This will allow you access to the information needed to adjust your fueling properly. The most important thing to keep in mind is that your primary 02 sensor will read richer then actual when it gets hot. *Update, its not that bad at all in 2nd and 3rd, its fairly close as long as you let it cool a bit. So allow the sensor one minute of idling or light driving to cool between gear runs. You are going to want to log 6 runs in total. Be sure you have had at least 10 minutes of driving time, and an engine restart (off/on) before trying this. Also for reasons explained later, if you have 10% ethanol gas (93-94 Octane) in your area, fill up on that first.

You are going to want to capture your logs as follows:

3 runs in 2nd gear. 2 of the 3 will be from 2500 RPM up to 8000 RPM and the 3rd will be a pop into VTEC from 5500-8000 RPM. Allow at LEAST one minute cooling time between each. The more cooling time the better, although 2nd gear is more forgiving for overheating the 3rd.

You want to repeat this procedure for 3rd gear as well. 3 runs, 2 of the 3 from 2500-8000 RPM and the 3rd from 5500-8000 RPM with proper cool down.

There will be 6 runs in total, respect your local traffic laws. Keep in mind if you don't have enough cool down time, for whatever reason, you will read rich, even though the may not be rich! This will lead to overly lean adjustments, so if your going to use the factory primary O2, you have to respect this fact. If you want to see what an overheated O2 sensor reads like, try a WOT run in 4th gear after cruising. You will be reading 10's or 11's on your primary 02 in no time, even though you are actually running leaner then that. Keep this in mind at all times.

-------------------

Now, when you get back home upload your datalogs into a directory with the name that corrosponds to your Map revision number so you don't get confused later. Open ATR and start comparing your fueling numbers. Your looking to run a 12.94 AFR -13.08 AFR at all times. For the area between 12.3 and 13.3 AFR, experience suggests that 10 ATR units is = to approx 1.0 AFR on the primary, but don't just jump in and subract 10 units because your 1 point to rich. The key is to make small changes and allow the ECU time to learn and correct for them, datalog in between and be sure. Running lean at WOT is the worst possible situation for ANY engine. It leads to detonation, knocking and in extreme cases pre-ignition. The difference between knocking and pre-ignition being that your NA engine can knock (post-spark activity) for many revolutions without extreme damage, however you'd be lucky to make 2 or 3 revolutions of WOT pre-ignition (pre-spark activity) without damage. So, theres the warning. Don't run too lean! In my opinion too lean is anything greater then 13.38 AFR at any time after VTEC engagement. Just because our engines are engineered well doesn't make them invincible.

Look for trends in your datalogs. Compare 2nd gear runs to 3rd gear runs.You want at least 3 out of your 6 runs to concur on a fueling descision before you make it. Is 5800 RPM always 13.38 AFR? Try adding 2 ATR units to get that down to 12.94-13.08. Is 7400 RPM always 12.2 AFR? Be sure that its not just the 3rd gear runs reporting this (possible overheat) and if you see this in your 2nd gear runs too, try reducing by 2 ATR units. *Update, 2nd gear tends to read .1-.2 AFR LEANER then 3rd gear runs. Make sure your 3rd gears runs are not greater then 13.23 and your 2nd gears runs are not greater then 13.38. I'd aim for 12.94 in 3rd and 13.08 in 2nd myself.

Your first revision may have large changes (up 4-5 ATR units) however after that all changes should be limited to 1-2 ATR units. 2 units makes a big difference!

Keep in mind that ethanol gas makes about a ~0.4 AFR difference leaner in WOT, its also more resistant to detonation (spontaneous combustion post spark due to heat and pressure, the flame front does not spread evenly across the top of the piston). So if you tune your engine for 13.23 AFR on 10% ethanol, if you switch back, your going to run 12.94 or so AFR. This is good, if you tuned on regular gas for 13.08 AFR, when you switched to ethanol if would run too lean. The ECU MAY over time learn to correct for ethanol, but my experience has been that ethanol gas behaves just like normal gas at part throttle loads. It doesnt burn much leaner in those situations, so it makes it harder for the ECU to learn the true fuel trims to apply to WOT fueling. This means its a good thing you tuned on ethanol gas because should you switch back, if you car fails to adjust, it will just run a bit safer, or richer. Instead of vice versa. Also ethanol is more forgiving as it is slower burning, this does not mean it makes less power. Most engines make more power on ethanol gasoline due to reduced knocking and advanced ingition, and the sheer effect of cooling the extra fuel in the cylinder has. I remember watching motorcycle magazine make ethonal gas out of apple juice and they made 15% more HP on their bike with that gas then regular premium!

Keep the above in mind when tuning, and to get things right be prepared for 5, 10 or maybe even 20 revisions. Be sure to save your changes as a different file name and revision number, make notes what you changed. Keep at it, and remember small changes. I find it best to keep notepad open and log my readings textually as I review a run. IE:

Notes:

1 point too rich at 5800 RPM (1 run) 

2 points to lean at 6500 RPM (5/6 runs, 6th run suggested 1 point too lean).

---

This allows me to keep my concentration on the AFR's and not try to remember it all in my head. Write down what the logs are telling you, and make sure at least 3 of the 6 agree with the changes you are about to make, if they don't agree consider smaller changes. Your WOT fueling table values should typically be between 145-165. Of course exceptions apply depending on intake and altitude etc, but generally the stock values of 155 are very close to where you want to be (unless you have installed Cams or a very large diameter intake). Thats why your performance parts showed gains... on a stock tune. They were tuned to work, with a stock ECU, as it wasn't too long ago we had no tuning.

Remember both tables should be identical, both Hi-Vtec tables that is. Don't get confused and change the low vtec fueling tables. Those can be tuned with information from your logs, regarding lower RPM, PRE-VTEC AFR's, as long as the ECU was in OL (STFT's are all 0).

Its not an exact science yet, but with time and practice we may have a tool in the future that makes this less of a chore. And remember if you can afford a WB02, it will yield more accurrate results, and give you some peace of mind when you see your WB02 corrosponding to your Primary 02. You can also run an AP dyno after every revision to see if I made more or less power. I use the same numbers everytime and the same location for my revisions.

Keep in mind this guide is here just to get you started and dabbling with your tables, ultimately though it is your skill and ability or the person you choose as your tuner that determines how things end up. The more tools you have access to, the better you will do. There is no replacement for a dyno with a wideband 02 hooked up, however this is still a pretty good way to get things close to ideal.

To tune the secondary High Vtec Table... only edit the values from 12.54psi and up, IE the last 3 rows. Take the last 3 rows from one of your dual primary tables, and copy and PASTE that into the last 3 rows of the secondary High Vtec table. Then select those 3 rows and press "M", enter 1.01 and press enter. This will increase those values 1% and give you a 1% safety margin in 4th gear, when it switches to this table. Alot better then 11 AFR and still safer then a standard table. As you left the values below 12.54psi alone, you still get your cold start and limp mode values. The key here is to remember if you have a CEL and AER in limp mode, take it easy and avoid WOT, just incase there really is a problem, you want have a large safety margin at WOT anymore.

Thats all there is too it! Basically aim for 12.94-13.08 AFR at WOT, and by the top of 3rd, a good tune should be around 12.79 AFR on the stock Semi-WB02 due to the heat affect.

Happy tuning,

The AccessTuners Team