97 D90 Timing and Altitude Performance

[Oxcart13]

I understand those with distributors have had good effect by advancing the timing a few degrees to improve performance for trucks running at altitude. Has anyone modified the timing of a 97 truck? If so, please provide details - procedure and effect. Thanks. Mark

[Davis]

Your 97 self compensates for the altitude. You may be able to get an adjustable chip upgrade where you can program in individual settings to a degree, but I have not seen one for a rover.

[Oxcart13]

If it self-compensates, it does a poor job of it. Truck ran real well at sea level or there abouts. Up here it's a bit disappointing. I'm open to making some mods to get it to 'breath' better, but wanted to explore the timing option first. Thanks for the note. Mark

[Davis]

supercharger would do it. There are a few that have done it here...

[Oxcart13]

Thanks, Chris. I've read some of the posting on the superchargers. Right now I'm inclined to go down the route of head work, enlarging and lowering the stacks, and maybe a cam. However, wondering if the ECU can be modified to compliment the mechanical enhancements. Hate to go down that road only to be 'hand-cuffed' by the computer. Anyone else around that you can recommend besides PPR that can do this type of work? Thanks.

[Mike Hippert]

There is no easy way of advancing the timing on a 97. The 97s have electronic ignitions, and the computer sets the timing off of a sensor looking at a 36 - 1 tooth gear on the flywheel ( crank positioning sensor).

I believe the 97 guys (or OBD2) run bigger injectors when increasing air flow to compensate since the ECU may not be able too.