[Leroy Hastings]

My beater Ranger has a 2.5 Lima that is on it's last legs, and I have though about replacing it with a 2.3 Lima for the better rod ratio (my 2.5 has bad piston slap which I have been told 2.5's are prone to do because of the longer stroke).

My question is: can the ECU compensate for the .2 decrease in displacement OK? I would expect to see fuel trim showing a minus number, but I do not know how much. Not enough to effect drivability or set a MIL?

Any input much appreciated.

[cgrey8]

While seemingly only a slight change in CID, there may be far more different between those engines that the EEC will need to know about. For example, changes in cam, head design, valve size, injector size, and if equipped different MAF sensors. Any of these will affect how the EEC needs to control the engine and most will not be simply compensated for by automatic means. There could be other less obvious differences not mentioned that will cause you grief once you attempt the swap (e.g. wiring differences, fuel plumbing differences, sensor differences, etc). And if the trans is also controlled by the EEC, then you'll have torque/shift tables to modify which is always fun.

It's possible the 2.3L tunes were based on the same strategy as the 2.5L and thus used the same EEC hardware, just loaded with a different tune to fit the 2.3L and how it was outfitted. Although it is equally possible that they are nothing alike.

So short answer is most likely the tune CAN be modified to support the 2.3L especially if you reuse as much of the 2.5L's parts as possible/practical (specifically injectors and MAF). And if your EEC's strategy is well broken out, it should be possible to do. The question is how doable is it for a DIYer. I don't know. If you are adventurous and don't mind the prospects of mystery and lots of "learning opportunities", then it might be kind of fun. However if you care more about driving the vehicle than you do in tinkering with it, then tackling the job might be something best left to a tuner or just rebuilding/replacing the 2.5.