MAF Tune vs. Speed Density

[Vettezuki]

So I'm getting my injectors rebuilt and enlarged and it looks like I'll need to get a retune. I have a friend, who I originally got the motor from, who has built several motors, including his current twin turbo LS2, and he's pretty handy with tuning. He said he'd do it for me for free if I just pay for his tuning license (I guess it's per VIN), like $100. He has done and knows both MAF and SD tuning. My understanding is that SD, when done properly is a superior system, but requires rather more tuning skill and knowledge cuz you ust can't rely on the MAF. Also, that SD are technically illegal since it removes the MAF, though I think that's relatively easy to get around. :)

[jedhead]

The difference between the two was explained this way to me.
Speed Density is closer to tuning the mechanical fuel injection. Fuel is adjusted by the rpm of the engine. As the rpms go up so the demand for fuel. The system can also compensate for the density of the air; ie altitude.
MAF The amount of air going into the engine is measured. The amount of fuel injected is determined by a fuel map x amount of air equals y amount of fuel. In a closed loop operation, the amount of oxygen is monitored to see if any fine adjustments are necessary in the amount of fuel to keep the engine operating for least pollutions. When the engine is at WOT, the engine runs in an open loop and only the fuel map is used, usually causing the engine to run richer than in a closed loop operation.

I haven't had much experience in comparing the two system, but many people replaced the SD system with a MAF system on EEC-IV ECU Mustangs.

Bob

[94cobra69ss396]

Read this. If you are going to change to speed density make sure you have your exhaust done before you have the computer tuned.

http://www.carcraft.com/techarticles/electronic_fuel_injection/index.html