Holley EFI

[eschaider]

Many EFI providers support MAF-based fueling models, although they promote speed density. If you elect to go with a Mass Air Fueling model (which I would encourage), you need to get a good MAF.

This is a link to a MAF test that demonstrates the difference between a good MAF and a great MAF, click here => https://www.youtube.com/watch?v=DAYAT-zTTRI&t=27s

The smoother and more repeatable your MAF voltage signal (the electrical representation of the air mass consumed by your engine), the better the fueling job the ECU can do for you. In addition to a good MAF signal, you need a set of good injectors with the least variation from injector to injector across their operating range.

This goal is achieved by buying correctly flowed injectors. Many injector suppliers will flow your injectors at max flow and perhaps even attempt to swap a few in and out to get a similar max flow, but that is only a part of the proper flow testing and injector matching you need to do.

In Detroit, there is a firm called Calibrated Success. It was founded and is run by Greg Banish. For those of you old enough to remember (that should be more than a few of you reading this), there was a 1950s or 60s half-hour TV Western called Have Gun Will Travel the protagonist was a character name Pallidin. He was a gun for hire that the little guys could use to put bigger bad guys in their place.

Greg is a modern-day Fuel Injection Pallidin. He does contract EFI Calibration work for the Big Three in Detroit to help their vehicles meet EPA guidelines, and he also does performance EFI education for enthusiasts like us.

One of his beneficial services is an Injector Calibration service that goes light years beyond the typical aftermarket maximum flow matching. Click here => https://calibratedsuccess.com/fuel-injector-test-bench/.

You need the correct injector performance, just like getting the proper MAF performance. Greg is the Undisputed Heavy Weight Champion in this category. If anyone is going to the PRI show this week, he will be there, and you ought to make a point of stopping by to see him. You will not be disappointed!

Beyond the fueling model you choose, the MAF you choose, and the injector characterization you decide to use, there is an additional consideration: whether or not to run a return style or a returnless style fuel delivery. In a return-style system, a manifold pressure-referenced fuel pressure-relief allows you to set your base fuel system pressure. Base fuel system pressure is the pressure your EFI system expects to see across your injector.

The fuel pressure across the injector is what the ECU uses to calculate (along with some other stuff) the required injector pulse width to meet your commanded lambda target for the engine's operating environment. On a n/a engine, it is important because it produces a predictable, smooth, and consistent fuel delivery necessary for reliable and easy-to-drive engine operation. On a supercharged engine, especially a supercharged gasoline engine, this separates the burned pistons and engine rebuilds from the happy country drives.

Unlike the return-style fuel system that requires a fuel return line to the trunk, a returnless system has none. Instead, the returnless system has variable-speed turbine pumps that the ECU controls based on the sensor data it reads off the running engine. Returnless systems are elegant, complex, and sophisticated. Along with a Mass Air Fueling model, they are the only way Detroit can meet emissions and performance targets anywhere on earth without a retune.

The anywhere on earth without a retune should ring like a bell on a cold winter morning for those of you who go through more than 1000-foot changes in altitude. Tony (TWOBJSHELBYS) has an unusually colorful way of referring to the Speed Density style EFI systems. If I remember correctly, he calls them an electronic carburetor (If I misquoted you Tony, please correct me ), and that is exactly what they are.

If you have driven a carburetted Cobra to or from low to high altitude, the change in throttle response and engine torque are virtually identical with a Speed Density fueling model. The only difference is your wallet is lighter by whatever you paid for your system, but, and this is a biggie, it doesn't perform any better than your old carburetted engine!

EFI is a big step but done correctly with some patience and a measure twice cut once approach can be rewarding beyond your expectations — especially if you are supercharged or plan to be.