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zero_psi 02-05-2012 01:01 AM

dsp best econ tune bad
so i tried all the caned tunes and noticed that the 89 tune with 91 octane i got the best mpg plus mds kicked in a lot more. i was getting close to 17 mpg average and it seemed faster then the 93 tune with 93 in it according to the butt dyno i don't get why i get such shitty mileage 13 mpg avg before the tune. and what makes me most upset is thats babying it. any ideas why i get such poor econ and what i could do to try and increase it.

FlyinRyan 02-05-2012 01:20 AM

Re: dsp best econ tune bad
The 91/93 tunes have problems with knock retard. Can't tune it out with the handheld, either.

The canned tunes, much like the stock tune, has a nasty WOT Delay that delays the triggering of WOT fueling. On most trucks I or David either tuned or watched logs for don't get true WOT fuel until after they hit 2nd gear, which, between running a ton of timing advance, targeting 14.7:1 AFR in closed loop in WOT, and the load of a 4800 lb surging forward after banging the 1-2 upshift, trigger KR that is off the charts.Even when WOT fueling is finally brought on, the KR takes time to be pulled out (for timing to be ramped back in).

In CMR we have control of this delay- and do so by removing it entirely.

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