running a little extra timing in the 4.0 HO motor

any suggestions on adding timing to my XJ? I am at about 7000 DA, and curious to see if people have run more timing through their motors and how they seem to react to a few extra degrees.

Chris

Because the computer sets the timing you can't do much to vary it in the normal way, but there may be a high altitude crank position sensor available that will advance it a little. I think some others here have used these with good results. What I don't know is whether this is available for all 4.0's, or only the earlier Renix ones.

The high altitude CPS is available only for the Renix. For the HO, you have to go to one of those performance chip thingies (Jet Chip, for example). The big change they make is that they advance the timing.

They also require running premium fuel, because of the timing advance.

Turbo City have a high altitude CPS for the HO 4.0 but it's only applicable to stick shift models.