6,5TD injection timing / pulse width questions

[markrinker]

I have two identical 1994 3500 series 6.5TD flatbeds used for towing and snowplowing. Both came out of the same municiple fleet, both have 144K miles, both bone stockers except Turbo-Master wastegate controllers installed.

One truck significantly outperforms the other, and gets 12 MPG while the other gets 9MPG. The 'harder runner' is has more of the diesel rattle, while the other is smooth and quiet.

From the OBD computer at the dealership:

- Chips are both '9955' (assume factory stock?)
- Strong truck 8.5% injection timing
- Weak truck 8.3% injection timing
- Strong truck 1.88ms injector pulse width
- Weak truck 1.84ms injector pulse width

Could the .2% difference in injection timing create such a noticeable difference in power? What causes the variation in the pulse width - and is this significant to power?

Insite appreciated!

Mark Rinker

[ucdavis]

With stock timing chain slop @ 144k, I'd say the minute differences in these values mean nothing.
I'd be looking at make-up air blockage, possibly different rear end ratios and stuff like that. Some recent talk about fuel mileage on 1 ton units showed rear end ratios were significant.

[charliepeterson]

"TDC Offset Timing" makes a big difference in power and performance, more so than just timing degrees percent.

[markrinker]

Charlie - I got this information and started a new post on the topic of Offsets in hopes you could explain more.

Mark