Engine/Transmission (1994 - 1998) average mpg?

[ddechris]

Ran the same highway route both directions Sat. morning. Temp was about 50 or so. At 70 mph on the speedo, I was seeing a shade under 2000 on the tach, about 620 egt, and 8 psi - 6 psi boost depending on the direction. Doesn't seem too extreme. Again, I'm running 265's and 3. 55 gears.



Checked the brakes on Friday after getting home from work and rear drums were warm. The front rims were warm, but not excessive. But, I have to slow down on a steep hill before turning onto our street.



I emailed TST about my fuel plate and they agreed that it shouldn't have an effect on mileage. He did recommend advancing the timing to 15. 5. Which I'm considering once I round up the tools.



We did some highway running over the last few days and when I drop to 65 mph from 70, the boost drops to 3 psi. Egt's are still around 600. There is a definite difference in noise between 65 and 70 mph.



I've got 429 miles on this tank, which has been more highway than usual. I'll post when I fill it up. I hope to do a fuel filter change then too. This tank is my first run with 5% biodiesel.



- Dave

 

[arthr31]

We did some highway running over the last few days and when I drop to 65 mph from 70, the boost drops to 3 psi. Egt's are still around 600. There is a definite difference in noise between 65 and 70 mph.



I've got 429 miles on this tank, which has been more highway than usual. I'll post when I fill it up. I hope to do a fuel filter change then too. This tank is my first run with 5% biodiesel.



- Dave

absolutely different noise at that speed differences. at 70, close to the 2200 rpm you get the drone and excessive noise thing going.



i ran biodiesel several times last summer, always keep a spare filter on hand 'cause of the detergent effects of bio, in my opinion...

 

[J.BURCHFIELD]

That is why I like the Gear Vendor. 1,500 RPM @ 70 MPH. Much quieter than @ 2,000 RPM. On a long trip it is a BIG difference.

 

[Ahopper]

do you get better mpg then since you r running lower rpms?

 

[J.BURCHFIELD]

do you get better mpg then since you r running lower rpms?

That is what puzzeles me, no difference in mileage. When I installed Marine injectors I got 3 mpg better towing but they made no difference not towing. It for me is a real head scratcher.

 

[Ahopper]

yeah that really doesnt make any sence at all. youd think it would with dropping the rps by 500

 

[J.BURCHFIELD]

yeah that really doesnt make any sence at all. you'd think it would with dropping the rps by 500

Maybe when you run an engine at lower RPM it puts more of a load on it. With gas I would say yes but with diesel you get more torque at lower RPM. It is too much for my old brain.

 

[EKlem]

It is possible that you are running too low of an rpm for maximum efficiency. If you are running with a large trailer or a lot of windage, you are definitely running too low of an rpm. When you have a large load, you want to be near the rpm that produces peak torque. Running empty, I would think that you wouldn't be loading the engine that hard and 1500 rpms would be good. Also remember that the overdrive is another source of driveline loss. Even though you are running a more efficient rpm, the engine is having to put out more power because the overdrive unit is producing some heat.

 

[J.BURCHFIELD]

It is possible that you are running too low of an rpm for maximum efficiency. If you are running with a large trailer or a lot of windage, you are definitely running too low of an rpm. When you have a large load, you want to be near the rpm that produces peak torque. Running empty, I would think that you wouldn't be loading the engine that hard and 1500 rpms would be good. Also remember that the overdrive is another source of driveline loss. Even though you are running a more efficient rpm, the engine is having to put out more power because the overdrive unit is producing some heat.

Peak torque in the 12 valve is 1,300 RPM. Running at 1,500 is pretty close to peak. In the 24 valve peak torque is much higher, I forget if it is 1,600 or 1,800. Good point that the OD unit is counter productive. The noise level is so much lower it is worth it for that alone.

 

[MMcCallie]

I just filled up on B10. Fuel economy for in town driving came to 13. 6. There is a lot of stop and go, most speed limits are 35 mph though there is a stretch of highway where i get up to 60 mph between stop lights for several minutes on my daily route.

I did flog a little, still getting a feel for things and practiced doing burn outs only a couple times. I know fuel is being wasted when i see the black cloud coming from my 5" tailpipe, but i wonder just how much. 13. 6 is compared to getting just barely over 15 mpg all interestate 70-80 mph. I'm very curious about the most efficient RPM.

My engine doesn't feel powerful until i hear it wind up (no tach. ) It smokes heavily down low if i apply more pedal so i figure at that point i must be lugging the engine at too low an RPM. Once the engine is spinning faster and louder, the truck surges to life and cleans up the smoke. Stock turbo, home ground fuel plate.

 

[DonTX]

Not sure if that was a typo, max torque according to Dodge in a 97 12v is 1500, not 1300 (just rechecked the sales brochure, that is where I get that) Maximum HP is at 2500.

Peak torque in the 12 valve is 1,300 RPM. Running at 1,500 is pretty close to peak. In the 24 valve peak torque is much higher, I forget if it is 1,600 or 1,800. Good point that the OD unit is counter productive. The noise level is so much lower it is worth it for that alone.

 

[J.BURCHFIELD]

Not sure if that was a typo, max torque according to Dodge in a 97 12v is 1500, not 1300 (just rechecked the sales brochure, that is where I get that) Maximum HP is at 2500.

1500 makes more sense. Puts it in line with the engines used in 18 wheelers. We were always told below 1600 we were lugging it. The govenors were set at 2100. There were different transmissions but a gear change was 300 to 400 RPM. The Fuller 10 speed was the transmission we saw the most. It evolved into a 13 speed which I liked better than a 15 speed (2 sticks). The last job I had driving was in 1982. I started in 1966. Diesel fuel was 19. 9 In 82 it was a dollar more or less depending where you were. I would say give me back the good old days but the advancment in medical science has kept me alive and quite well and the future looks good. The value of the dollar falling has had everythng to do with prices going up. Between that and fuel tax, we are being had.

 

[DonTX]

I can agree with all that for sure. Spent my years on the road behind my own Kenworth W900, 425hp cat, 15 speed ONE stick. Used to haul house trailers for a living with a gasser, had to quit when gasoline got up over . 50cents a gallon!

Lots of BS over lugging around, and it sure depends a lot on whose engine you are pulling with. You sure can't call max torque lugging for sure.

 

[J.BURCHFIELD]

I can agree with all that for sure. Spent my years on the road behind my own Kenworth W900, 425hp cat, 15 speed ONE stick. Used to haul house trailers for a living with a gasser, had to quit when gasoline got up over . 50cents a gallon!

Lots of BS over lugging around, and it sure depends a lot on whose engine you are pulling with. You sure can't call max torque lugging for sure.

I started with my own truck and after 10 years went to work as a company driver. My biggest problem was the big companies kept lowering hauling rates while cost of operation kept going up. When I saw I was making less than drivers wages I became a company driver. On the strength of my regular Air Force service (1948 to 1953) I was able to go to work for the Air Force as a civil service worker at WPAFB in Dayton OH (1983 to 1990) I retired in 1990. Been here in FL since 1992. Bought my 98 12v Ram in 98 and have made many trips to OH, 1050 miles one way. When I replaced the 4&1/4 turn steering box with a 3 turn it became a nice truck. Before that it was a pain. I plan to keep it now. REGARDS

 

[DonTX]

I think my 97 and I will probably never part. It is the sweetest ride I ever owned, just love driving it, still looks and smells brand new even. Going into the paint shop in the morning. .

 

[J.BURCHFIELD]

I think my 97 and I will probably never part. It is the sweetest ride I ever owned, just love driving it, still looks and smells brand new even. Going into the paint shop in the morning. .

I somehow got the idea 98 was the first year for the Quad Cab. Your 97 must be a late 97.

 

[DonTX]

NOT a quad cab. I intentionally wanted as new as possible without the back doors. Friends that had the doors found they leaked and rattled, the back seat is for the exclusive use of the cat and his box.

 

[J.BURCHFIELD]

NOT a quad cab. I intentionally wanted as new as possible without the back doors. Friends that had the doors found they leaked and rattled, the back seat is for the exclusive use of the cat and his box.

THANKS every cat should be so lucky

 

[JTEdieselram]

My truck has "race only" everything, look at my sig, and still gets 15. 5 average on the highway and drives like a dream, it did used to get over 20 before the injectors and 13mm pump, but I think the loss in mpg is worth the gain in hp! I drive my truck almost 100miles every day to work/school/home with no issues.

 

[LarryWard]

And I sometimes thought a '98 12v with those extra doors would be so much more convenient. Well they would no doubt, but did not know they rattled and leaked. Sad but now kinda glad until some quadcab 4doorers defend them extra doors. Larry