Converting air meter to speed density

.....Hello childrens, today we are going to learn how to convert an air meter equipped car to speed density (can not be a frequency based air meter like the newer Corvette.)

.....First, we will need two matching voltmeters (tested for equal voltage) or a dual input – dual display voltmeter. You will also want alligator clips on the voltmeter ends. We will also need an SMT and a MAP sensor (2.5BAR or any other 0-5V unit rated for the pressure your engine will see) and a laptop.

.....What you need to do is connect the SMT to your ECU's wiring, all EXCEPT the air meter wire. The MAP sensor gets wired into the ANALOG-IN on the SMT (it can still be wired to the Map input) and a vacuum hose is ran to the MAP sensor from a manifold signal. The ANALOG-OUT is then connected to one of the voltmeters. The other voltmeter is connected to the air meter signal wire (you can stick a needle in the wire to attach an alligator clip to or you can strip a section of insulation for the connection). The goal is to be able to read the air meter voltage and the MAP voltage at the same time (analog vs. RPM tuning).

.....Now for the fun part…. You will try to match the MAP voltage to the air meter voltage so they both act exactly the same. This will involve some load tuning, so I recommend a second person to drive while you tune. The easiest way is to start with the car parked, rev the motor through all available RPM's and fill in the map positions on the analog tuning screen from the SMT. When this is done, you should move to low load tuning and slowly work your way up. If you get most of the tuning map filled in, you can pick a number half way between the number above and below to fill in a value that you cannot get the motor to stay at.

.....If this is done correctly, you should be able to watch both of the meters while driving around and see matching values. You are now ready to cut the cord! Cut the air meter to ECU wire; connect the SMT analog out to the end of the wire going to the ECU. You should be able to start the car and drive it with no problems, if you have dead spots that were not there with the air meter you should reconnect the air meter and retune the analog map.