I was wrong about the MAP. My 89 doesn't have one,,and I'm not sure how ours measure pressure in the plenum , maybe it doesn't have to, just curious.
The '89 does have a MAP sensor.... of a sort.... it's actually not a MAP sensor since it doesn't sense "
manifold pressure - but an AP sensor incorporated in the MAF sensor as a barometric pressure sensor. All it does is sample the barometric pressure each time the engine is started and uses that value as an air density calculation in the fueling equation until you turn off the ignition. If you drove from sea level to say 10,000' in one trip, with the '89 (and many other vehicles) you would be wise to stop a few times, turn off the ignition and let the ECU reset to current conditions - that is if you wanted the best performance and economy.
Some of the '89s had high altitude sensors.... don't know if they were a one-time sample or on-the-fly correction - I suspect the latter.
The Diamante may have more MAP sensor control as in on-the-fly correction , but I'm not sure.
The thing on the Dia. Plemun is called "variable induction contol servo". It does report directly to the ECU. It sits at the oposite end of the plenum.
That should be the butterfly valve arrangement that alters the induction runner length. The ECU needs to know what position the valves are in for best performance, so that sensor is like a TPS.
If you use the Diamate engine with 10:1 heads and Diamante cams, you can probably do what Justice is doing and run 87 octane. At worst, 89 octane and a timing adjustment should be fine. The dynamic CR just isn't that much different than the stock '89 Montero arrangement. I would caution against using the Montero cams with the Diamante pistons though.... it would increase the dynamic CR to 8.3:1 as compared to 7.4:1 for the stock Montero and 7.8:1 for the Diamante pistons and cams. 8.3:1 is likely ok, but might require high test AND a distributor spark lead adjustment.... plus, the power would be lower than would benefit you. The 3.0L needs power at highway speeds (particularly with larger tires), so the Diamante 10:1 pistons and cams should be fine for a N/A engine that does very little towing.
Frank
