A MPG Tale of Two Trucks

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Just doing my part to increase postings!

If any of my fellow First Gen'ers have read any of my recent postings you know that a prestine '92 W250 Dodge was purchased in Connecticut last weekend. My '92 W250 was also in Connecticut getting some work done on it by Ted @ JRE. This left us Drafting each other back to Nashville for a 1000 miles! What kind of MPG did we get? There was quite difference to my surprise.

Keeno's ride: W250 5 spd. 3. 54 gears, LSD, 14cm2 housing with 12" x 32. 7" mud tires

C. X. ride: W250 5 spd. 3. 54 gears, Open Diff, 16cm2 housing with 9. 5" x 36" highway tread

Both trucks have been identically set up by JRE and have enhanced injector pumps, HO injectors & modified Banks 3 1/2" exhaust utilizing a Walker straight thru muffler. Besides the difference in tires the 'Keeno ride' has a 2 1/2" front suspension lift while the 'C. X. ride' has a 4+" lift in all corners.

Now for mileage over 1000 total miles:
Note: All MPG calculated using Keeno's odometer readings as a baseline.

Keeno: 19. 0 mpg average
C. X. : 21. 7 mpg average

I talked to Ted Jannetty about the MPG differences between 2 identically modified trucks in the engine department. He stated that the overall gear ratio differences between my almost 33" wide aggressive tires & the 36" narrow highway treaded tires is significant for a 1 to 1. 5 mpg advantage for the 'C. X. ride'.

Ted also mention that the differences between the 14cm2 VS 16cm2 housing is more significant than the tires. He mentioned that at highway speeds the 14cm2 housing builds more boost than the 16cm2 housing therefore resulting in more fuel being burned for a given speed. So I went home and check on the identical Banks boost gages and sure enough there is a 5-6 PSI difference. The 14cm2 is building 7-8 PSI of boost over the same strech of highway & speed while the 16cm2 housing is somewhere in the 2-3 PSI range.

When you add the differences of tires (height & width) with the different housing sizes you get significantly different MPG!

Just my observations over the last 1000 miles!

... ... ... Keeno



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1992 W250 5spd. 3. 54 gears, LSD, JRE enhanced VE Injector Pump, BD High Output Injectors, Banks "Stinger Plus" consisting of a 14cm2 wastegated housing, 3 1/2" JRE modified exhaust/muffler, pyro/boost gages, K&N, Skyjacker 2 1/2" front suspension lift to clear 305/70R/16 Goodyear MT's, Mag-Hytec, Amsoil

 

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KEENO and C. X. :
It appears that you are making good efficient Cummins Diesel POWER. As a matter of fact, I KNOW you are. The BEST to you both!
As you compare the 14 vs 16 housings, you'll see the best attributes of both. (remember about the 16 running within it's wind)
I'm certain the '92 with the power will feel as much at home hauling the white water/ocean kayaks of yours as it did hauling the surfboards (10' guns) of mine.
The empty spot in front of the garage is about to be filled with 12 valves of Cummins again. Accept no substitutions.
Ted J... can you dig it?

 

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To the top for a little story on MPG observations once again!

 

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As I reread this posting I want to mention a couple more things.

A few weeks after I originally posted this thread I got an email and an apology from Ted Jannetty. He mentioned that he had continually thought about the MPG differences between the two trucks and mentioned that when my pump was spec out during the rebuild/enhancement that the truck was assumed to have a 16cm2 and not the 14cm2. I didn't leave Ted much time or information to have the pump rebuilt & delivered to his shop for installation on the one day I was to be in Connecticut. Ted suggested that I needed to 'tighten up' the AFC 'star Wheel' because I was over fueling the midrange due to the increased boost that the 14cm2 puts out over the 16. I have since made this adjustment and I'm now realizing better MPG than the 19. 0 I had reported during this trip.

As a reminder, This adjustment needs to be made to anyone considering going to the 12cm2 housing to preserve fuel MPG. I will have to tighten the 'star wheel' once again when I replace the 14cm2 with the 12cm2 sitting on the workbench.

I would like to thank Ted once again for his incredible customer service! How often do you get a call or email from someone that worked on your truck two weeks prior saying, "I've been thinking about your truck and... ... ... ... ... . " I envy those of you that live in the Northeast for this great Cummins resource!

Keeno