Now I read this part somewhere, can't remember where, but there is a beautiful formula for the diesel motors for injection/air mix.
1.9L motor = 1897cm^3
1897/4 cylinders = 474 cm^3
This translate the maximum amount of air can be held in 474cm^3.
Assuming we are at sealevel, we can say that air density is 1mg/cm^3, which means that the cylinder at sealevel, will suck in 474 x1.0 mg of air at every stroke.
Now for most turbocharged cars, the MAF sensor is completely useless, but the only reason it exists on them, is to measure and compare the EGR flow to the intake flow. This means that if the MAF sensor reads 200mg/stroke of air flowing in, but the engine requires 474, then the EGR must be producing 274mg of it. To make my life, and the engines, easier, let's assume the EGR is disabled (it is).
Now, 1000 mbar of pressure is whats known as atmospheric pressure, or no boost. In order to get some boost, let's assume the turbo charger produces an extra 1000mbar of boost, to a total pressure of 2bars. Now we know for a fact that 1000mbar, the cylinder contains 474mg of air. That means that we can have 948mg @ 2 bar.
Now, we all know the magic number of 14.7, well sadly with diesels its a whopping 14.6. Huge difference, right? Anyway, to those who are not supposed to be coming close to tuning because they don't know this, Fuel to air ratio has a perfect burning efficiency at a ratio of 14.7 mg of air to 1 mg of fuel.
In this case we're running at 14.6:1, which means 474/14.6 = 32.5mg of fuel can be injected to produce an efficient mixture when the engine has no boost. Now, this does NOT mean that the engine will be injecting 32.5mg of fuel at every stroke, that would simply create shit ton of black smoke at idle. On average at idle, it is about 6mg of fuel. 32.5 is just the maximum amount of fuel for efficient burning at best of conditions under no boost.
I'll write up the theory behind driverswish/injection quantity an such a bit later on when I get back.
The only change I've done so far to the MAP per customer request:
EGR orig:
EGR new:
