How To Hack Your AFC in a Turbo Honda

How To Hack Your AFC in a Turbo Honda


There are a couple of ways to hack your Super AFC or Apexi VAFC for use in your turbocharged Honda. We’ll be showing you both ways of how to hack your AFC in a turbo Honda, perfect for bolt on turbo kits. You may have found this page from our How To Turbo a Honda article or looking for a cheaper alternative to Hondata.

Whatever your reason for wanting to learn how to hack your AFC in a turbo Honda, you’ve come to the right place. But in order to understand exactly what you are hacking, you’ve got to know what the AFC does.

Turbo B16A

Put in the simplest way possible, the AFC gives you a way to alter your fuel trims when you are adding anything to yur engine. Whether it’s fuel or pressure above atmospheric pressure, the AFC will give you a way of altering your ECU fuel trims.

A piggyback device like the Apexi Super AFC is an easy, cheap alternative that allows you to get the job done with minimal hassle and cost. By splicing into either your TPS or MAP sensor, the AFC gives you the ability to adjust the amount of air the sensor reads.

Our Time Attack EG

The first method of how to hack your AFC in a turbo Honda, is to reference the Manifold Absolute Pressure signal as your throttle position. This is a common hack for the AFC for vehicles that do not utilize the standard 0-5 volt range for the throttle, like the turbocharged Dodge SRT-4.

The most common hack for the SRT-4 is included in our How To Install a Super AFC in a SRT4, and it requires turbo Hondas to utilize a MAP clamp. This clamp will prevent the ECU or PCM from seeing pressures over what the stock MAP sensor was designed to see. If you do not have a clamp in place here, your check engine light will go off after 10.5 psi of boost.

How to Hack Your AFC in a Turbo Honda

Install a MAP clamp or similar device that will limit the amount of pressure your sensor will see. After installing this “missing link” style unit, wire in the throttle position wire into your MAP signal wire. You will need to program it with the instructions below, and then you are ready to tune part throttle and boost separately.

You can also use a VAFCII, like our How To Install on a Acura RSX article

To setup your AFC or VAFCII, go into the menu options and select your engine type as 4 cylinder. Then move the cursor right and make your throttle arrow point upwards. Then you will want to go into the “TH-POINT” part of the ETC MENU and select your low settings for 20% and high settings for 80% throttle.


You can fine tune this to some degree by tuning the low and high fuel maps separately. If you want to clean up a certain part of your powerband, you must think a little differently when tuning. Instead of tuning by rpm and throttle, you are referencing boost as the throttle, anything less than 20 percent of the pressure will be the low throttle map.


Do not deviate too far from either map however, because your SAFC or VAFC will interpolate the two maps between the signal ranges specified.

Low boost – Since your vehicle will not be seeing full boost at part throttle and closed loop duty. Take your upgraded fuel injectors and calculate it using our Fuel Injector calculation writeup. For example, if you are installing a set of DSM 440cc injectors, you will be using taking this 440 value and dividing it against your stock injector flow. The result should be a value you set across the board for low throttle, giving your Honda ECU the best chance at orchestrating your motor.


On the dyno and on boost this method of turbo Honda AFC hack will work excellently. Giving your tuner the ability to tune by boost and not really caring about much else. He will need to keep a steady eye on peak timing as well as make adjustments to your base timing.

What will this turbo Honda MAP AFC Hack do?

By referencing the MAP sensor as a Throttle position point, you will be programming the throttle input through the Super AFC ETC programming menu. Go to Menu > ETC and throttle position input. The Super AFC will ask you for a zero throttle condition, which can be off boost. When the Super AFC NEO asks you for full throttle position, you can use an air compressor or simply go wide open throttle at full boost.

Tune your throttle position range using your MAP sensor

By using this turbo Honda AFC hack we are utilizing the AFC NEO as a tuner based on engine load as opposed to throttle, which is what Apexi intended.


What is the problem with this kind of hack?

Because your AFC NEO will be completely blind to the actual throttle position of your vehicle, closed loop tuning will be extremely limited. You will not be able to tune the part throttle part of your map, without going into boost and trying to hit a moving target.


You will have to take the cap off your ignition timing and retard your base ignition timing in your Civic. Check our How To Adjust Your Civic Timing article here. Because you are doing this to your base timing, it’s crude and not efficient. Driving up hills or putting unusual ranges of load on the motor will result in poor fuel economy and sluggish driving.

At best however, because of the limitations of your AFC not truly knowing throttle position as well as the MAP sensor overrun, this hack is not ideal for part throttle tuning. Serious lean conditions can occur when driving the car with high loads such as hills or mountain regions.

How to Hack Your AFC in a Turbo Honda Method 2

The superior way of hacking your Super AFC for performance and tuning convenience is otherwise known as “40% hack”. This method is installing the AFC as a MAP vehicle and starting the base tune as -40% across the board to begin with.

Called the “poor man’s Hondata” the Super AFC hack works for Turbo Hondas


The thinking behind this ‘hack’ is that you will be removing the 40% in airflow the Manifold Absolute Pressure sensor would see. In a funny way this is exactly what the AFC was meant for in the sense that it is tricking the Honda ECU to see that full boost is atmospheric pressure.

You can tune your maps from this starting -40 percent tune at your leisure but we’ve found this solution to be plug and play. If you are tuning with a datalogger make sure you do not cross the 3 volt threshold for the MAP sensor, otherwise you’ll be clearing check engine light codes.


Using a set of Mitsubishi Eclipse or Eagle Talon used fuel injectors would net a 440cc injector size, and using the Honda ECU curve the 40 percent rule gets the job done for modest PSI. At 8-10 lbs of boost this is a very good system to keep your turbo Honda reliable and potent with the right supporting mods.

How To Convert OBD0 to OBDI Honda
How To Convert OBD0 to OBDI Honda

Used injectors from Evolution VIII or IX engines can get you in the 520cc range and from 10-12 lbs of boost would be the range for this type of setup. Be aware however you will need to wire these injectors in with some sort of converter, to change the type of resistance for your fuel injector.

For more on how to install fuel injectors, or even how to size fuel injectors check our the How Tos behind each one that every DIY’er can do.


Tuning closed loop operation is easy and simple even for a solo driver and tuner on a closed road. Never attempt to drive a vehicle while tuning however, ask a friend to drive or take it to your nearest dyno. If you don’t know how to tune for closed loop control, check out our article here.

That does it for our How To Hack Your AFC in a Turbo Honda Guide, please let us know if you have any questions or comments below.


  1. I have a b16 with a to4e and I have a map clamp on my car now with a afc. How is this hack any different and do I keep the map clamp. Thanks

    • Hi Barry.

      You will not need the clamp if you are going to do the -40 hack.

      The purpose of this is to not go over the 3 volt limit

      With the MAP clamp removed you should follow the guide’s instructions and have someone tune you for wide open throttle.

      This is of course assuming you have the same injector range and fuel upgrades. Check with your local tuner, or if you are in the Bay Area give us a call and we’ll be more than happy to schedule you.

      Thanks for reading.