Big Blue24
Comp Diesel Sponsor
- Joined
- Jan 5, 2008
- Messages
- 6,310
I have been tracking the fuel economy on my 98' 12 valve Quad Cab 4x4 Long Bed Automatic ever since I purchased it in early October of last year.
**Truck weighs 7150 without driver.
**I built up the automatic transmission with a stock stall torque converter with billet triple disk cover, a few misc. internal upgrades, basically my version of a 600 HP transmission.
**3.54 gear ratio, 285/75/16 Bridgestone Tires, no leveling kit, AFE panel filter in stock air box, boost elbow set to 40 psi max.
**It has a 2095 rack plug, no plate, and modified AFC. Stock governor springs, 60lb marine valve springs, stock valve lash, and unknown mileage marine (330) 4x.013" injectors.
**I checked the timing and was surprised to find that it was not stock and is set at 26.4* BTDC.
I have been trying everything to get my fuel economy to come up, played with tire pressure, adjusted the valves, changed the fuel filter, altered driving habits, etc.
No matter what I did, fuel economy unloaded always came in around 16.5 to 17.7 MPG, usually upper 17's when coasting to stops, easing into the pedal, etc. In fact, my running average since I purchased the truck is 17.3 MPG.
Today I drove over 500 miles on a work trip, and since my employer was paying for the fuel, I drove faster than my normal conservative 65-70 MPH.
One the first leg of the trip, I drove 72-80 MPH, probably averaged 76 MPH and blasted up every pass exact opposite of someone trying to set fuel economy records. Averaged 19.53 MPG, huge difference.
On the second leg I purposely drove faster and drove 76-85 MPH, climbed several passes from 1000' to 4700', some head wind and cross wind as well. Averaged 19.51 MPG.
All that I can come up with is the combination of injector spray angle and high timing makes this motor most efficient in the 2000 - 2150 RPM range because it's a well-known fact that the wind resistance exponentially climbs with cruising speed which should make the truck get much worse mileage at 80-85 MPH.
I feel confident on my documentation of MPG in the 60-70 MPH range at the current timing so I'm now going to retard timing back to 20* BTDC and see if I can get 20- 21 MPG in a normal cruising range of 65-70 MPH.
Thoughts, experiences, theories?
And for those not interested in fuel economy, why did you click on this thread after reading the title???
My 95' Junker Drag Truck averaged 8MPG and 1-1/2 sets of tires on the last fill-up so I do have a real oil burner in the garage for those who only care about performance.....
**Truck weighs 7150 without driver.
**I built up the automatic transmission with a stock stall torque converter with billet triple disk cover, a few misc. internal upgrades, basically my version of a 600 HP transmission.
**3.54 gear ratio, 285/75/16 Bridgestone Tires, no leveling kit, AFE panel filter in stock air box, boost elbow set to 40 psi max.
**It has a 2095 rack plug, no plate, and modified AFC. Stock governor springs, 60lb marine valve springs, stock valve lash, and unknown mileage marine (330) 4x.013" injectors.
**I checked the timing and was surprised to find that it was not stock and is set at 26.4* BTDC.
I have been trying everything to get my fuel economy to come up, played with tire pressure, adjusted the valves, changed the fuel filter, altered driving habits, etc.
No matter what I did, fuel economy unloaded always came in around 16.5 to 17.7 MPG, usually upper 17's when coasting to stops, easing into the pedal, etc. In fact, my running average since I purchased the truck is 17.3 MPG.
Today I drove over 500 miles on a work trip, and since my employer was paying for the fuel, I drove faster than my normal conservative 65-70 MPH.
One the first leg of the trip, I drove 72-80 MPH, probably averaged 76 MPH and blasted up every pass exact opposite of someone trying to set fuel economy records. Averaged 19.53 MPG, huge difference.
On the second leg I purposely drove faster and drove 76-85 MPH, climbed several passes from 1000' to 4700', some head wind and cross wind as well. Averaged 19.51 MPG.
All that I can come up with is the combination of injector spray angle and high timing makes this motor most efficient in the 2000 - 2150 RPM range because it's a well-known fact that the wind resistance exponentially climbs with cruising speed which should make the truck get much worse mileage at 80-85 MPH.
I feel confident on my documentation of MPG in the 60-70 MPH range at the current timing so I'm now going to retard timing back to 20* BTDC and see if I can get 20- 21 MPG in a normal cruising range of 65-70 MPH.
Thoughts, experiences, theories?
And for those not interested in fuel economy, why did you click on this thread after reading the title???
My 95' Junker Drag Truck averaged 8MPG and 1-1/2 sets of tires on the last fill-up so I do have a real oil burner in the garage for those who only care about performance.....
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