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Old 02-12-2021, 05:55 PM   #114 (permalink)
wjohn
EcoModding Lurker
 
Join Date: Apr 2014
Location: KS
Posts: 15

Hatchback - '90 Honda Civic DX
90 day: 44.98 mpg (US)

GTS - '90 Dodge Dakota 4WD Base
90 day: 18.63 mpg (US)

Topless Brick - '66 MG MGB Roadster
90 day: 27.19 mpg (US)

Sedan - '91 Honda Civic DX
90 day: 40.66 mpg (US)
Thanks: 1
Thanked 4 Times in 4 Posts
Quote:
Originally Posted by ps2fixer View Post
I found suggested shift points for the diesel in the owner's manual (diesel supplement), wow I was really over reving it according to their figures. I was shifting into 5th at around 50mph, all the other shifts were based on rpm @2k. I'll have to see what kind of rpm the shifts are at. Same book also suggests idling for 5-7 mins after a long trip to cool the engine, but only 15 seconds after starting a cold engine before taking off. It basically says to wait for oil pressure to rise to normal range. The book doesn't say what year it's for, but clearly it's for a 99+ truck. Looked at the axle ratios in the book, it doesn't even list a 3.55 as an option. I guess I got the highest gearing possible for a factory f250 with the diesel.

EDIT:

Took the truck for a quick drive (still warm from doing some work on it and keeping the batteries topped off). Every gear shift suggested in the manual for best mpg is around 1500rpm, 2nd into 3rd is around 1900rpm (bigger jump in gearing). I'll have to target the 1500rpm shift and ~2000 rpm shift for 2nd into 3rd to see if I get good results. The truck seems fairly happy with those shift points, I think when I was testing before the shift I watched the most was 2nd into 3rd which is the big jump and 1500 is too low for that shift.
A little late with my response here but I was going to mention I shift at 1500-1800 RPM (generally higher RPM to jump between the higher gears) with my Cummins-powered Ram when unloaded. That's about what I shift my '90 Civic at, too, so I didn't have a hard time adjusting. My Dakota has no tach but I can tell I rev it higher between shifts... Although it's pretty worn out.

Anything over 2000 RPM in the Cummins sounds like screaming to me by now, so when I tow (not often lately) I have to remember to force myself to leave it in gear a little longer.
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