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Tech Review—EFI Source MicroSquirt for Fox-body and SN95 Mustangs

The nifty little ECU controller and the EEC-IV adapter harness are included with EFI Source’s MircoSquirt system for pushrod Ford V-8s from 1986-1995.

By Miles Cook

Photos Courtesy of EFI Source

EFI Source is an intriguing resource for aftermarket late-model EFI setups, providing easy-to-install plug and play stand-alone upgrades. The company currently offers applications for GM LS and Dodge GEN III Hemi engines but it is rapidly expanding into the Ford market with the kit that is available here for EEC-IV Mustangs and more coming. In development are Ford Modular applications from the 1996-2010 era for both 4.6- and 5.4-liter displacements, and we’d reckon Coyote 5.0s are on the radar as well.

The GM LS and late-model Mopar Hemi coverage aren’t the only games in town as EEC-IV-era pushrod Ford V-8s are also in the mix as evident by the MircoSquirt system EFI Source offers for 5.0-powered ’86-’93 Fox Mustangs and ’94-’95 SN-95 Mustangs made for those two scant years. Yes, that’s right. This setup is offered for the less popular SN-95 5.0s from nearly a quarter-century ago as well as the now-classic ’86-’93 Foxes.

The MicroSquirt for Fox and SN-95 5.0s is a programmable engine-management system for air/fuel control and the kit includes the following:

• The MicroSquirt EFI controller configured for the EEC-IV with a TFI distributor

• A MicroSquirt-to-EEC-IV adapter harness

• A three-bar MAP sensor and adapter harness

The unit also comes loaded with a base tune for a stock SN-95 5.0 Mustang to facilitate a jumping-off point for subsequent tuning.

The MicroSquirt EFI controller is a pretty cool low-cost option for use in modified SN-95 5.0s. The kit’s easy-to-connect three-bar manifold absolute pressure sensor makes the speed-density system an ideal choice for modified cars and the mass airflow sensor is not used, which makes the conversion a good way to go for supercharged or turbo applications. It also uses a batch-fire system for the injectors and a waste-spark arrangement for ignition coil applications to further simplify the system. This allows the MircoSquirt ECU to be considerably smaller with fewer coil and injector drivers in play.

Some of the standard MicroSquirt features are:

• 12×12 tuning tables for volumetric efficiency, 12×12 for air/fuel ratio and 12×12 for spark advance

• A flexible spark advance table that allows different rpm and kPa bins than VE and AFR tables

• Wide or narrow-band oxygen sensor compatible

• Designed for use with high -impedance injectors

The MicroSquirt ECU is all contained in this little box that’s barely any larger than a deck of playing cards.

“Getting late-model engines into racecars and early model restomod street-car projects can be difficult,” said Mike Tomaszewski, who is EFI Source’s technical sales manager. “The biggest problem is trying to get the late-model ECU connected to the engine and the MicroSquirt line of components makes the integration process considerably easier.”

So clearly the EFI Source systems make things easier to either have a standalone EFI system work in a Fox or SN-95 Mustang 5.0, or retrofit the late-model engine and electronics to an earlier model car.