Join Date: Nov 2000
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Re: Megasquirt: MPI or TBI on 258?
Blaze new trails and use the 4.0L head, mpi and exhaust. The majority of megasquirt applications are mpi and the batch firing works just fine. At idle, sequential firing makes a difference in emissions, at speed, the difference is negligible. You will have less work than I did, making my owner adapter and modifying the intake manifold. You will have yourself a 185+ horsepower motor that is fully tunable and easy to diagnose.
I went with a GM TBI because I wanted to keep things simple and didn't have easy access to a 4.0L head and intake. Nor did I want to risk the cost of replacing 6 injectors that I got from the junkyard. Also, I admire the fuel economy that TBI setups were getting and wanted that too. Despite the original design of the engine being sequential injection, you will like many others before you on the megasquirt list find that batch firing works great. There are lots of inline 4's and 5's (audi's), and 6's (BMS's I believe) being megasquirted and they all report favorable results.
Go for it! I believe the end result will be superior to the factory 4.0L because it will be fully tunable for any future mod's. And having an independant ignition system, you won't have the pinging problems associated with the Mopar kit.