Part throttle fuel tuning (MAP)

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This explains how to tune your part throttle fuel for speed/density (MAP) calibrations.  AFM calibrations do not use volumetric efficiency tables and so cannot be tuned this way.


You will need a quiet, flat, straight road where you can accelerate a number of times from 10 mph to 30-40 mph without causing nuisance or danger to other people.  The acceleration required is fairly low, so the main concern is being able to accelerate very slowly from slow starting speeds, and then slow down to repeat the process.



Open your calibration, and display the low speed cam fuel tables (F5).
Find what cam angles your calibration uses - normally it will be 0, 10, 20, 30, 40 or 0, 15, 30, 40, 50 degrees.


Cam angles

Cam angles


Starting with the first cam angle, lock the cam to the setting by setting the low speed cam angle table to this value.


Cam locked to 15 degrees

Cam locked to 15 degrees


Save the calibration using a different filename - we will want to load the old calibration when we are finished in order to restore the cam angles.
You do not need to switch the oxygen sensor off (open loop).  The software will read the fuel trims and actual lambda in order to calculate the fuel change.



Start datalogging & recording (F9), then accelerate in first gear with a light throttle to 5000 rpm.  The aim is to keep the throttle steady so that the engine load stays consistent as the rpm increases. You should be able to see the table tracing running straight down columns 3 & 4.
After reaching your target rpm, shift into second gear and slow down to approximately 1000 rpm.
Repeat in second gear with very light throttle.
Repeat in second gear a number of additional times, increasing the throttle each time slightly to run in a higher column.  It does not matter if you go over the same column again.
Your final datalog should look something like this:




Notice the straight lines of load, increasing with subsequent pulls.
The exact rpm range you use depends on your VTEC point.  The first and last rpm row tend to have incorrect lambda readings, from throttle tip in and release, so try to datalog from 1000 rpm or so to your VTEC point plus 1000 rpm.  Generally 1000 rpm - 6000 is ok.  In this example, VTEC is at 3200 rpm, so an upper limit of 5000 rpm is plenty.


Display the Lambda Overlay

Load the datalog, if it is not already visible.
Select the low speed cam fuel table (F5).
Select 'Fuel Change' (Shift-F3) to show the suggested fuel change.




The fuel changes should look something like this:




This shows that the engine is running lean in most recorded areas, and than fuel should be added.


Edit Fuel Tables

The aim is to analyze the recorded lambda and change the fuel table so that the suggest fuel change is close to zero.
In practice it is not possible to achieve a zero fuel change everywhere - changing temperatures etc will result in the engine running differently from time to time. A Hondata Heatshield intake manifold gasket will help by keeping intake manifold temperatures lower and more consistent.



Before editing make sure the correct cam angle is selected and that changes are not applied to all tables (unselect 'All').
When making changes we are more looking for patterns of changes to apply than changing each cell value.  The table needs to be smooth after applying the changes.



Here we have selected the whole of column 6 and will add 5% fuel.



5% fuel is also added to the whole of column 7.
2% fuel is added 2750 rpm to 8500 rpm, columns 1-5 (inclusive).
3% fuel is added 3500 rpm to 8500 rpm, columns 1-5 (inclusive).  This will be added to the previous change to give 5% fuel increase from 3500 rpm down.
2% fuel is added 4500 rpm to 8500 rpm, columns 1-5 (inclusive).
That is probably enough change for one datalog - we need to apply the changes to the ECU and re-test.



It is important to make sure that the changes keep the fuel table smooth.  Show the 2d view of the fuel table and make sure the load lines are smooth and equally spaced. If they are not, undo your fuel changes above and apply fewer fuel changes to larger areas to correct the lambda without making the fuel table inconsistent.



Once you have made fuel changes, save the calibration and upload to the ECU.
Repeat for the same cam angle until the fuel changes get close to zero - it may take 3-4 cycles of tuning.
Each time you edit the tables it is important to check the fuel tables are not getting distorted or bumpy.
After you have finished one cam angle, lack the cam to the next angle (eg 30 degrees) and repeat.



Restore your cam angles by loading the original calibration, copying the low speed cam angles, loading the tuned calibration, then pasting the cam angles.
You can also change lambda overlay options under Settings.