Many in the know say that MPI is better, why (please be specific)?
I would think it would be for the same reasons as it is the preferred on everyday cars and trucks.
There is a injector for each intake port, (MPI) rather than on central injector (TBI).
For MPI systems:
A more balanced fuel mixture results because the fuel charge is shot at the back of each intake valve. On more complex systems the computer should be able to control the A/F mixture of individual or a bank of cylinders via a O2 sensor.
You don't get cylinders firing next in to each other starving the other for fuel.
A more radical intake design can be made (for lower hood lines) because the intake is "dry" and you don't have fuel sticking to the walls on intake runner turns or cold weather.
For TBI:
Less wires, less parts, cheaper to make, still outperforms a carb on cold drivability, starting, fuel mileage and engine wear(less fuel wash on cylinder walls over the life on a engine)
There are at least 2 types of systems of each also. A "speed density" and "mass air flow" with each having "closed loop" or "open loop" modes.
"speed density" basically uses a set of tables with the amount of air a engine will use at a given RPM.
A "mass air flow" system should use a airflow sensor to read the actual amount of air the engine is using at a given RPM.
In "Closed loop" mode a O2 sensor in the exhaust is used to adjust the amount of fuel to come up with a set A/F ratio. Also used is the engine load, RPM, crank position, throttle angle and sometime the air charge temp and amount of airflow into the engine.
In "open loop" mode a set of values programed into a chip is used to adjust the A/F mixture. Reads are taken of the engines RPM, temp, load(intake vacuum), throttle angle and sometimes the intake air temp itself. The O2 sensor is not used.(Most closed loop systems start this way until the O2 sensor is up to temp)
MPI also comes in 2 flavors "sequential" and "banked, or all at once" injection.
Sequential uses a 'crank position' sensor to fire each individual injector just before the valve opens or as the valve opens.
A banked system uses the same sensor or a distributor signal to fire the injectors all at once on every crank revolution.
A best of the best would be a "sequential" MPI, Mass airflow system that runs in a closed loop mode. It should have all the sensors posible:MAP(manifold air pressure), engine temp, air temp, crank position, O2 sensor, TPS (throttle postion sensor) mass air flow sensor, and engine RPM sensor.
I believe that the Edelbrock system is a speed density, non-sequential system based on talking to a tech once. Can't have cam lobes with alot of overlap because it throws the computer off the tables they program in it. Also can't run E-85 🙁:
Ok time for another beer :razz:
