12V vs. 24V fuel economy?

[illflem]

How come 12 valves get better mileage?

 

[drawson]

It because of the P7100 pump!!!!!

 

[Rammin On]

EPA ... nuff said ... P7100 rules ... .

 

[Don M]

It dont help having to push 6 extra 30 pound springs and 6 extra 60 pound springs down. 540 lbs of extra effort.



Don~

 

[RHamner]

MPG

I tow a 10500# fifth and get 11. 5 to 13 with my 24valve at about 5MPH over the limit. Empty I get 19 to 23 depending on conditions and speed . What do you guys get anyway?

 

[Deezul1]

All them electrons and sensors eat fuel like crazy

 

[Cummins Corvette]

I don' think that there is much difference. I just filled up and got a whopping 14. 4. Par for the course (for me anyway). That is being nice to it too. In the summer it is way better NOT!!! (15. 5) My timing is at about 16 degrees, just changed the oil, put the BHAF on. Changed the fuel filter about 8k miles ago. I don't think diesels really get much more than a gasser. My old GMC got 11 mpg going 80 mph with a 10' camper. This truck gets 9. 8 towing my little TT at 65 mph. I really wouldn't have this truck if it wasn't for the cummins long life and reliability, that is all I get out of them. It really doesn't do that well with the fuel.

 

[Deezul1]

CAnderson



Thats too bad about your mileage being low. I had a 96 and my present 97 both with 3:54 gears and 5spd 2WD and both turned up some and got 17. 2 empty around town with 700lbs of tools in it and 21 on hiway at 77 mph, got 24 once when raining so hard I couldnt go over 50mph. Towing 6500lb TT it averaged 13. 9 over 3700 miles. Both trucks were very close on these figures.

 

[Cummins Corvette]

Ya, I don't know what the deal is. Everyone says that they get all those better numbers, but I only see them on long trips. On the highway at 75 mph, I usually get about 18-19 as long as the engine never cools down. Once I was REALLY nice to it and got almost 24, but that is only on the highway at 60 mph, with NO STOPPING, and no more than 10 lbs of boost at any time. To work and back 14- 16 is it. I log almost every tank of fuel, and starting at the last fuel up and working back I have: 14. 4, 15. 1, 16. 8, 15. 4, 15. 4, 14. 9, 23. 8 (the one I mentioned earlier, I went 103. 5 miles on 4. 34 gallons of fuel, an experiment to see what the max is), 17. 0, 18. 6, 17. 3, 18, 15. 7, 15. 2, 16, 16. 3, 14. 1, 15. 6, 16, 16, 19. 8, 18. 1, 16. 3, 18, 14, 20. 4, 18. 9, 15. 8, 13. 8, 17. 6, 18. 7, 22. 4, 15. 5, 17. 4, 13. 8, 16. 5, 22. 4. The last date is 7/16/01. That is just shortly after I bought this truck. The really high numbers are on short highway trips at low speeds.

 

[M Barnett]

I've had my truck since new, about 8 yrs. Its just about the ideal scenario, 5 speed, 3. 54, no duely, but it is 4 x 4. I think the worst I've ever got empty is 16 and the best 22. I probably average 19 - 20 and if there is a gasser out there that can match the power and mileage, I want to see it!

M Barnett

 

[Don M]

I only got about 8-0 with my v-10 gasser. Loaded it droped to 4-6.



Loaded now I get about 12-14 with the Cummins. Empty I have gotten 20-21.



Don~

 

[Champane Flight]

Low and high

My low is 12,pulling a 30'fifth and a 17' boat behind that,going up into the rockies with a headwind. High is 25 going empty across Nebraska with a tailwind. Average empty 22,average loaded 15.

 

[BCFAST]

To answer your question more directly, the 24v will suffer in economy because its operating rpm range is higher than the 12v. Like the 4v BMW's and Jap cars, the bottom of the rev range is pretty lackluster; the 4v heads need more airflow to work... just the nature of the beast.

CAnderson, you helped me figure out part of your mileage concerns when you said you drive 75 on the highway. The fuel curve in the P7100 is a bell curve: meaning that at just over 2000rpm, the efficiency goes away... if you slow up about 150rpms on the highway, I'd bet you would see a nice difference!

See my sig. and know that I got 22. 37mpg on my last tank. . and that's combo city/hwy driving.

 

[J.R. Adkins]

average

17. 5mpg between city & h-way. Best is 22. 5 from INDY to FLA.

 

[dalton4]

Look back in TDR issue #29. Brake Specific Fuel Consuption (BSFC) is covered for the 12 & 24 valve engines by Joe Donnelly and Robert Patton. This will shed some light as to why the 12 valvers can obtain better mileage when operated within a certain rpm range.



Jerry

 

[rrausch]

I generally get a little over 22 m. p. g. with a thousand pounds of tools in the bed, on I-40 going from L. A. to O. K. City. I've been temped to test it from Flagstaff eastward at about 58 m. p. h. just to brag... It's downhill!

 

[HoleshotHolset]

20. 3mpg going from Gardner, MA - Pittsburgh, PA last weekend.

19 and change on the way back... . faster speeds/more headwind.



The average speed was around 70-75mph on Rt. 80/84... slower on 81 and 28/66..... like was said earlier... slow it down just a little and you'll get better mpg. Keep your foot out of it too... . all that soot coming out the tailpipe doesn't come from the soot fairy, it comes from that wonderful hydrocarbon in your fuel tank.



Matt

 

[Deezel4x4]

well the long and short of it is that when I got the truck totally stock with 265/75/16 tires, I got 17city/21highway. with the addition of a BIG topper,305/70/16's and a #8 plate I get 12 city/still 19-20 highway. I took the topper off and I get the same 12-15 city but I am always getting on it pretty hard at times. I can't bring my self to baby it for a whole tank full. But I will say this that it get's excellant mileage towing my 7k trailer at 75 somewhere around 15-17mpg. I still don't know if I have the plate right where it should be. Everybody here in Jacksonville acts like they have no clue about a Cummins and how to make one faster. HELP I NEED SOME CUMMINS FRIENDS IN JACKSONVILLE!!!!!!!!!!

 

[BCFAST]

Deezul, you arent getting that low mileage with 305's on there... go to the thread on tire calculation and plug in the numbers; I'll bet youre doing a ton better!

 

[Cummins Corvette]

The 14 - 15 numbers are with the rpms always staying below 2000. Most of the time I go 70 on the freeway. Only 75 on long trips. Hopefully the BHAF will help.