Engine/Transmission (1994 - 1998) 300 HP Injectors

[JesseGray]

I recently purchased a1997 W250 quad cab. I have begun building my unit for better trailer pulling. I have finished the K&N Filter and installed a 4" turbo-back exhaust. I was planning to install a larger turbo, but several people have suggested installing 300 hp injectors first.



In my simple mind, it seems that this would increase my already high fuel consumption. On a recent trip (Ariz to Oreg) i only achieved 12 mpg with my 12K fifth wheel. My 1991 W250 pulling the same trailer I could achieve 17-18 mpg.



Would like to explain this, or perhaps list the TDR issues that discuss this?



Thank you.

 

[CumminsPower98]

Those mileage numbers don't compute from my experience and lots of reading on here. 12 is a really good number for a load that size. I pull for a living right now and I average between 10 and 11 with all types and sizes of RV trailers. Are you sure you were calculating things right on that '91 because that is impossible in my mind.

 

[MEby]

I recently purchased a1997 W250 quad cab. I have begun building my unit for better trailer pulling. I have finished the K&N Filter and installed a 4" turbo-back exhaust. I was planning to install a larger turbo, but several people have suggested installing 300 hp injectors first.



In my simple mind, it seems that this would increase my already high fuel consumption. On a recent trip (Ariz to Oreg) i only achieved 12 mpg with my 12K fifth wheel. My 1991 W250 pulling the same trailer I could achieve 17-18 mpg.



Would like to explain this, or perhaps list the TDR issues that discuss this?



Thank you.

Couple of thoughts here, it is my understanding that the diesel engine uses the same amount of fuel to accomplish a job whether it be a 200 hp or a 400 hp providing the load on the engine is exactly the same. an example of this would be if you had a 6bt powering a generator. load the generator to x amount of watts, ambient temps the same for both tests, etc making sure everything is exactly the same for both tests. now up the hp from 200 to 400 and it should use exactly the same amount of fuel. Now, there are variables to this. Most of us use the extra power available therefore lowering mpgs. If for instance your old injectors are worn the new ones could give you better fuel economy. I am sure there are a lot more variables than I can think of right now. Somebody else care to explain or correct me?





The first gen trucks seem to get better mpgs than the newer trucks. I am assuming this probably has to do with epa regs and the trucks weighing less.

 

[JesseGray]

CumminsPower 98: My mpg on the 91 is accurate. Since a kid, I have kept mileage and fuel logs. It was equipped with a Banks kit, and I went to a larger turbine and compressor. I have owned the 91 since 2003, and the mpgs have been consistent since the Banks and Turbo mods. Before the mods, I could barely get 55 mph in fourth with this same trailer. After the mods I could easily run 75 in fifth. My thanks to Paul Gibbons at High Tech Turbo.



MEby: Thank you for your explanation. My simple mind just had trouble wrapping around that idea

 

[dpuckett]

Your timing and valve adjustment can make a big difference- it'd be worth chekcing into. I had a 93 D350 that I had tuned to about 240-250hp (rear wheel estimate- peak boost was 28-30psi with a stock H1C and 12cm housing, approaching 100deg post turbo). Hauling hay from south central KS to ColoSpgs, I averaged 13-15mpg going 65-70 with a GCVW of 24-25K. So, IMO, 17-18 isnt too far fetched for a lighter load. Aerodynamics would be about the same- terrible.



I would keep the stock injuectors if you have a manual transmission. The 215s combined with the pump on there will make some good power with a plate change. You might want to check your valves and timing, and then your injectors to make sure they are popping at the right pressure and atomizing well. If you need new ones, there are MANY options out there. I'd only go to a bigger turbo if EGTs warranted it.



You're on the right track to open the intake and exhaust flow, though.



Daniel

 

[Vaughn MacKenzie]

Wow, I wish I could get in the ballpark of those MPG numbers with either of my 12-valves!! I typically get 12-13. 5 towing my single axle camper (about 4000 lbs) with either of my trucks driving 65. I can tell you Jesse at 12mpg it's doubtful there's anything wrong with your '97.

To your original question, 300 injectors shouldn't hurt your MPG. I have run them in both my trucks with no noticeable affect on MPG. The only thing though is they're so-so injectors, don't have the optimal spray pattern and only have 4 holes. I am thinking about trying the 330 injectors which have 5 holes. 370s are too much IMO if you want to keep it reasonably clean.

Vaughn

 

[JesseGray]

Thank you Vaughn. The Fellow down the road has my 91, and I would go get it back---but it is only a regular cab. The dog needs a seat of her own-vbg.

 

[CumminsPower98]

All I can say is wow! I wish I could get such numbers as I could make a lot more money. I had one other guy say he got 19 with his '03 pulling a 29 foot travel trailer and that I have a VERY hard time believing also. Are some trucks just a huge fluke? I just don't understand some of these numbers.

 

[MEby]

All I can say is wow! I wish I could get such numbers as I could make a lot more money. I had one other guy say he got 19 with his '03 pulling a 29 foot travel trailer and that I have a VERY hard time believing also. Are some trucks just a huge fluke? I just don't understand some of these numbers.

The thing is there are dozens of variables to makeing fuel economy. weight, wind resistance, drivers right foot, tire size, lift kits, auto v manual, gearing, ect. You can usually count that emisions equiptment works against fuel effiency. (the more you have the worse it gets. ) Personally I think this is one of the reasons that the old cummins got better mpg's. My dads 90' reg cab 4x4 for instance averages around 22 mpg empty and has never gotten less than 13 mpg with any load we have put behind it. From my experience, the newer the trucks get the worse the fuel economy. I probablly should note the newer trucks are also heavier.

 

[hsmith]

I am real happy with 11-11. 5 pulling my 14k trailer, empty weight. Usually around 18 empty.

 

[JFaughn]

Do you know what gear ratio you have in either truck ?
That could make around 3-5 mpg diff. between the 2 trucks , amongst other factors .
I get 17. 5 - 20 mixed hwy & in town with tools , maybe 200-300lbs .
Towing 32' Airstream 5,000 + lbs & bed loaded 600-800 lbs , 15 mpgs .
Not sure but it seems that I'm getting about 2 mpgs varying , I'm guessing the fuel is doing that , no other changes , daily driving .

 

[Vaughn MacKenzie]

One advantage the 1st Gen trucks with their VE pumps have over our P-pump trucks is dynamic injection timing. Timing advances as RPM rises, whereas the P7100 is hard timed and stays the same at all RPM. That may be part of the MPG advantage.

Vaughn