School Me On...

[Zenobian_84]

The updated MPFI AMC 2.5.

 

Obviously the biggest difference is the multi-point fuel injection, but what else is different about it?

 

I assume it has 4 injectors on a rail VS the 1 inside the TBI on the old style engines?

 

If I were to swap one into my MJ, what would I have to change other than the complete wiring harness?

 

Any other useful tidbits about these things? I don't ever hear much talk about it, probably due to the fact that it was always more of a YJ engine than an MJ one. I figure I might go the MPFI route one day when this engine gives up the ghost; if the upgrade is worth the trouble. Hopefully that won't be anytime soon :crossfingers: ; but then again, Murphy's Law tends to strike at the worst possible times. :ack:

[Eagle]

That's pretty much it -- multi-port injection (one per cylinder) rather than a single injector in the throttle body. I don't know, but I would expect that the head got the same port revisions the 4.0L got when it went from Renix to Mopar. The change affects both injection and ignition, so you would need all under-hood wiring and the Mopar ECU to make it work. The MPFI version was rated for quite a boost in power -- The original carbureted version was rated as producing 105 horsepower at 5,000 RPM and 132 foot-pounds of torque at 2800 RPM. The throttle body injected version produced 117 horsepower at 5,000 RPM and 135 foot-pounds of torque at 3,500 RPM when it was introduced in the 1986 model year. This was raised to 121 horsepower at 5,250 RPM and 141 foot-pounds of torque at 3,250 RPM for model years 1987 through 1990. The final, multi-port injected version produced 130 horsepower at 5,250 RPM and 150 foot-pounds of torque at 3,250 RPM.

[Zenobian_84]

Figured that was probably it as far as revisions go. Definitely wasn't expecting anything like the 4.0 update for NVH. Thanks for the info Eagle. :cheers: