Well since our Dyno Day really didn't happen I decided to make a post about how to tune the VAFC for those who want to learn to tune it themselves. This will be a complete how to, with tuning techniques I have learned and used. I don't go into any other forum accept this so that is why I am posting this here.

What is an Apex'i VAFC - Basically it is a digital fuel controller that can adjust Fuel and Vtec engagement. It actually cant adjust fuel it adjusts air correction, but I didnt want to confuse people.

How does it work - The VAFC is soldered/connected into the existing wiring harness right before the ecu. When enabled the AFC changes the map sensor voltage that the ecu sees. Basically you use a 1.75bar map sensor on a stock honda which reads between 0-5Volts. When you accelerate the map sensor is sending a voltage reading to the ecu telling it how much pressure is coming into the intake manifold. By manipulating the voltage you can change the air correction which in return changes fuel.

Whats tunable with the AFC? Here is a common misconception with the AFC's that I see all the time. People believe that they can tune their car in all aspects with this device. It is just not true. The only thing you can truly tune with this is vtec engagement and Open Loop (WOT) tuning. Partial throttle tuning is worthless.

You have two ways the ecu works; closed loop (ecu reads from o2 sensor) and open loop (No o2 feedback). When in closed loop (normal driving) your ecu takes readings from your o2 sensor to adjust for better mpg and daily driving. So when you change the voltage signal to try to adjust closed loop operation the o2 sensor will send a signal back trying to compensate to get back to a stoich (14.7:1 A/F) reading. That is why its worthless to change this, but when in Open Loop or Wide open throttle your ecu reads straight from the map sensor and uses pre-programmed maps from Honda built into the ecu to run the car. This is where making adjustments will work well.

Ok now that you have an understanding of what, why, and how. I will get into the basics of setting up and control of the device.

Here is a pic of all the functions of the VAFC and how to get to them.

Now you can see there are 3 main modules: Monitor, Settings, and Etc.

Key functions: This is a basic description of the buttons of an AFC. You have the 4 arrow keypad and then the next/prev buttons. Basically you move around the main screens with the next and previous buttons, then the keypad is used for manipulating the functions within the modules (ie. NE points/vtec/etc are functions)

Monitor: This is where you can monitor all the sensors (Up to 4 at a time). They can be displayed in numerical, graph, or gauge form. I usually just monitor two at a time because you can change the mode to peak and hold (explained later). The rev. -y is a graphing trace mode. I never really use it but its a cool feature.

Setting: This is the module that controls many of the functions like NE Point/ Vtec/ WOT/Narr throttle corrections. You will use this the most since this is where you will adjust the % changes and correction values for tuning.

Etc. Finally this is where you setup all the sensors and car type. Make sure for all hondas that the sensor type is 6in 6out, the car select is 4 and the arrow is pointing northeast. Then you can go to sensor check and make sure the AFC is reading them all correctly. After the initial setup is done you are ready to setup everything in the Setting module.

**If your AFC isn't reading the sensor voltage or isnt working go back and check your wiring**

I am going to assume that your VAFC is now working properly and the car is all ready to go. Keep the car in accessory mode while you setup all your sensors and beginning settings.

Where to Start?: Well now that you know how and where you can tune you have to setup the NE points. These are the points that will let you adjust the changes. The AFC only gives you 8 so you have to choose wisely where you put them. Any points in between will be extrapolated (meaning the AFC will pick the closest value in between each point). NE-HVT are the only points we are going to adjust since the LVT we wont be tuning. HVT meaning high cam (after vtec). For an S2000 since they tend to run rich up top I would say put the points anywhere from 5500-9000. You will have to do each point from lowest RPM to Highest.

Now that you have that you want to setup the TH-Point. This is the point where you go from low throttle to high and high to low. Some people do them high like 90% but I usually do around 70-80% since thats usually around when closed loop is disabled by the ecu.

Now you can set VT-Cont. Stick with a stock value (I believe it is 6000rpms) and make the vtec exit rpm like 200rpms below.

VT-Unmt - This is used when you have switched your vtec different from stock. I have changed vtec and adjusted this and seen no gains, and then some gains. It really depends on the car. I don't use this feature as much as some.

Now you are all set to tune the car. Using Wide Thr setting you can change the %. Remember +% adds fuel (richens) and -%subtracts it (leans). **Do not make changes without being able to verify with a wideband or dyno you risk your engines life**

Tuning Tips:

Vtec: Best thing to do to tune Vtec is change the vtec point to like 4000 rpms and do a dyno pull. Then change it too 8000rpms and do a pull. Where the torque curves intersect is where you want to put your vtec. This is where the smoothest curve will be. It may not sound or pull as hard as your butt dyno thinks, but you will be making more power. Vtec is supposed to have a nice linear pull without dips or spikes in the graph.

Fuel: Do a pull on the dyno to see what it looks like with all the points at 0%. Then make small percentage changes in areas that are rich. Ideally for an N/A motor you want an A/F ratio around 13-13.5a/f. This is where most N/A engines make the most power. Again this can change between motors. Some like it richer where some like a little leaner. Once you are around a nice A/F flat line you are done tuning.

Final Notes: This is a really helpful device for those who have a decent setup. Using it on a stock S2000 you will see minimum gains (5-10whp) if that. Don't expect to tune this and get 50whp with boltons. It is not going to happen. Well I hope you all benefit from this post. I know it might be a little confusing to some, but once you play around with it for awhile you will get the hang of it. I used this device for 2 years before I went with a standalone. I have used it for N/A and Turbo Setups.

Happy Tuning,

-Nate-

 

And remember boys and girl to always use a wideband O2 ..... and this is not a toy.......use only under adult and professional supervision.....
Nice post Nate

 

Did you get your car back yet? I saw it sitting there lifelessly (sp.?) as I got my Buddy Clubs installed. Now mine is sitting there lifeless because we had to send one of the coilovers out

Chris

P.S.-good write up Nate Dizzle

 

the car is still dead... waiting for the head studs from AEBS and the turbo from turbo city.....should be done next week( fingers crossed).........I heard johns car is in....
John, whats this I hear about the using tee same BOV.... Super sequential BOV from HKS huh?????
Chris, I saw your car last week.... at least it still has an engine..its like your car has a sprained ankle, mine needs heart surgery....
Beroz

 

Yeah you both are boostin'.................well at least one of you. J/k Bro. Hurry up and get that roach done will ya

Good comparison with the sprained ankle and heart surgery I should hopefully have it soon enough.

Chris

 

great post

 

All thats left is to get one

 

Damn Nate all I know now is that I'm completely confused and if I plan on any mods I'm asking you first!

 

Just let me know and I'll help you out