My 1993 W250 has a 6-pin diagnostic port, and there are adapters to go from this connector to the standard OBD2 connector. Since OBD2 is a superset of OBD1, I was hoping I'd able to use such an adapter to look at real-time data. Has anyone else tried this? Also, is there any possibility of tuning the ECU in my truck to get better fuel economy? I have read that Dodge tuned these trucks very rich, because the high compression of the Magnum engines had preignition problems on 87 octane. I'd be willing to run 91 octane gas if it meant I could get decent fuel economy.

 

no no no. sounds like you really need to just do some research. why would they tune it rich? they got a o2 sensor for a reason. as long as the plenum is fine is should do just fine on 87 preferably ethanol free if you want better fuel mileage and it is available.

 

The why is obvious. To reduce preignition, particularly at WOT.

Which almost certainly doesn't get used at WOT, when preignition is the most dangerous. A lot of these older EFI systems operate in open-loop mode at WOT, using just a fuel map.

 

Even the new vehicles go to open loop at large throttle openings......

 

I suspected as much, but didn't want to speak beyond my knowledge.