Engine/Transmission (1994 - 1998) Just keeps getting better & better

[fortunate1]

To kind of tailgate on "got smoke?"s thread, "should I bump my timing?", I'll post some actual results from 2 recent trips. About 2 weeks ago, I had to travel down to Charlotte, NC. Very hot: 98-99 deg. A/C on all the time. About 800 miles, almost all highway. Kept the speed between 70-75 mph most of the time (some faster). = 22. 1 mpg.



The timing was advanced to 15. 5 BTDC a while back, and that seems to have changed the "sweet spot" to about 1900-2000 rpm. That is typically not good for fuel economy on 12V's, but now there is no penalty for driving 75 mph (fuel-wise, that is ).



Last week I drove down through the Blue Ridge mtns and Smoky mtns into SW VA, eastern TN, and western NC. No towing, but loaded-up. Same speeds as above. A/C all the time. Over 1600 miles, with over 300 of that on slow, twisty, 2-lane, mountain switch-back roads. = 21. 2 mpg.



The final analysis: Bump the timing up to 15-16 degrees!! You'll be glad you did.

 

[TPCDrafting]

Did you notice any changes in Ex. Temps with the advancement of timing? Couldn't tell if you have a pyrometer from sig.

 

[fortunate1]

The exhaust temps have typically been cooler than before the timing advance. My pyro t'couple is post-turbo; cruising flat @ 70-75 mph the temp was 500*F, and the boost was 6 or 7 psi. Getting up some of the hills (5% grade?) brought the temps up to 650-750*F and the boost up to 12-15 psi. This is about 100*F cooler than the same hills before the timing went up to 15. 5*BTDC.



I'll point out that when Keith (Rammin On) did the timing, he found that the timing was at 10. 5* and the gear came off the tapered shaft pretty easily. My stock timing should have been at 12. 5*, so it had somehow loosened and slipped a little over time. Could only tell that top performance wasn't there; the engine still ran well enough. I did notice that I was missing 1 mpg, though.