74 Dart Swing 225 Electronic Ignition Module

bee1971 said

1972

Engine Speed Limited

Where all the factory Chrysler part # ECUs Engine Speed Limited ?

Was always curious on those RPM limitations that we all seem to talk about

4111850 when they went to a 4 - Pin to replace or superceded everything previous and RPMs

Click to expand...

Only two ECUs in the 1972 model year as shown in the table were intentionally speed limited.

The red heat sink unit, part number 3656127 limits RPM to 5000-5200 and was used on 400 and 440 high performance manual transmission applications.

The blue heat sink unit, part number 3656128 limits RPM to 5300-5500 and was used on 340 manual transmission applications.

The intentional limits were dropped in 1973. However, all ECUs are limited based on the electronic component parameters used, similar to point ignition contact points float or bounce limitations when the RPM exceeds those parameters.

Chrysler generally, and potentially conservatively in some cases, rated other production ECUs, including 4111850, as good to 5500 RPM or 6000 RPM depending on the coil and ballast resistor used, as well as the application itself.