Jump to content

Recommended Posts

Hey guys, new to the forum. I have a '98 Dodge Ram 2500 Cummins 5.9L 24valve automatic 2 wheel drive 3:55 rear axle ratio. I have done literally everything I could possibly do to my truck to improve the mpg. Yet, I cannot seem to get anything over 15-16 mpg in the city and hwy can vary from 16-22 mpg. Current mods are afe cold air intake, airdog 100gph pump, rv275 injectors, smarty tuner, 4" straight exhaust, IAT fooler, scanguage 2, tires are toyo m-55 245-75-16 filled to 80 psi. The truck would get 15 mpg city/hwy bone stock with a 3" exhaust however when the fuel pressure was tested I was told that it was at 9psi at idle. I'm wondering if its done damage to the already weak vp44 I seem to see other 4x4 trucks getting 18 mpg city as for me doesn't matter what smarty setting I am on or how much timing I give it if I really baby the heck out of it I can maybe manage to pull 16 possibly 17 city hwy mix. I'm planning on changing my diff oil to amsoil 75-90 same weight as I have in there now just hoping the amsoil will help also running 5-30 amsoil in the motor with a bypass. What could be causing the mileage to be so low? Truck shows no signs of starving for fuel I have the airdog set at 18psi now but if damage has already been done not knowing how long its been running 9psi from the PO is there any test I can do without having to pull the whole pump out?

Link to comment
Share on other sites

Your numbers are pretty close to what I get. 14 around town and about 19 highway. That is empty at about 7.3k#. I have personally never seen 18 mpg in town since mine was new. 9 psi of fuel pressure is to low. I am going to assume you do not have a FP gauge. Get one asap. Yes you may have damaged the VP from low pressure. But it sounds like it is still working fine for now. It might last 6 months or 6 years. Get the FP problem fixed sooner rather than later. Before i had a FP gauge I had problems and found my pressure to be close to non existent. I fixed the problem and the pump went 3+ more years before I replaced it There are many schools of thought on proper pressure. I personally run 19 at idle and 15.5 at WOT. Anything around 18 to 20 at idle and 15 to 17 at WOT is very acceptable. How old is your AD? .

Link to comment
Share on other sites

City mileage can really vary from one person to the next and from one truck to another depending on the number of starts/ stops, how much idling is taking place, how heavy your foot is from light to light, loaded vs unloaded, etc. Etc. Highway mileage is much more compare able between people because your simply driving down the road. The only factor now is speed and driving loaded vs unloaded. What speeds do you typically run. If your consistantly running 80+ then your mileage will suffer. Where I live I'm very rural so it's all country road driving and I consistantly run 50-60 mph sometimes if I jump on RT11 I'll run 65. If I run an entire tank without being hooked to anything I can flirt with 21 mpg And that's hand calculated. You can't really go by the ScanGauge, I have one and it just doesn't seem to be the most accurate. Close, but close isn't accurate. Another thing you have to consider is what others are telling you. Often times people will inflate their numbers just to make their truck look better. When people tell me they're getting really good mileage with a truck, I can usually take a closer look and find some holes in their story.

Link to comment
Share on other sites

  • Administrator

tires are toyo m-55 245-75-16 filled to 80 psi.

Too aggressive of a tire and over inflated will decrease MPG's. I would suggest next set of tire to drop back to a normal tread pattern and then with this set use the inflation formula to get the right tire pressures. Like for my Coopers (which are very close to your Toyo) you'll see the inflation pressures in the article. But for every 4 pounds of rubber you can ditch will require 1 less HP to keep rolling. My current 235/85 R16's are about 62-63 pounds per tire in weight. http://articles.mopar1973man.com/general-cummins/35-exterior/354-tire-inflation-formula

Current mods are afe cold air intake

Double check your actual IAT temps. Optimal point of IAT temp should be between 100-140*F roughly. For every 10*F below 100* you see you'll lose roughly 1 MPG.

I'm planning on changing my diff oil to amsoil 75-90 same weight as I have in there now just hoping the amsoil will help also running 5-30 amsoil in the motor with a bypass

I never used any synthetic oils in my truck I do well in the 20's for MPG's. So synthetics are not required to reach this point.

is there any test I can do without having to pull the whole pump out?

The only way to test a VP44 is to pull it out send it back to a Certified VP44 pump rebuilding like industrial injection and pay them $300 bucks to run the VP44 on the Bosch 815 test stand for 3 hours to certify if the pump is damaged or not. There is no test for the end user to verify the condition of the pump other than error codes and fuel pressure. Here is my fuel logs over the lofe of my truck. post-2-138698205497_thumb.jpg Now peek at my signature... :whistle:
  • Like 1
Link to comment
Share on other sites

  • Administrator
Hidden

tires are toyo m-55 245-75-16 filled to 80 psi.

Too aggressive of a tire and over inflated will decrease MPG's. I would suggest next set of tire to drop back to a normal tread pattern and then with this set use the inflation formula to get the right tire pressures. Like for my Coopers (which are very close to your Toyo) you'll see the inflation pressures in the article. But for every 4 pounds of rubber you can ditch will require 1 less HP to keep rolling. My current 235/85 R16's are about 62-63 pounds per tire in weight.

http://articles.mopar1973man.com/general-cummins/35-exterior/354-tire-inflation-formula

Current mods are afe cold air intake

Double check your actual IAT temps. Optimal point of IAT temp should be between 100-140*F roughly. For every 10*F below 100* you see you'll lose roughly 1 MPG.

I'm planning on changing my diff oil to amsoil 75-90 same weight as I have in there now just hoping the amsoil will help also running 5-30 amsoil in the motor with a bypass

I never used any synthetic oils in my truck I do well in the 20's for MPG's. So synthetics are not required to reach this point. Food for thought... More Cummins engines have cross the 1 Million mile mark with petroleum oils. There are some head to 2 Million miles where no one has crossed 1 million on synthetics as of yet that I've know of...

is there any test I can do without having to pull the whole pump out?

The only way to test a VP44 is to pull it out send it back to a Certified VP44 pump rebuilding like industrial injection and pay them $300 bucks to run the VP44 on the Bosch 815 test stand for 3 hours to certify if the pump is damaged or not. There is no test for the end user to verify the condition of the pump other than error codes and fuel pressure.

Hopefully you not using any cetane booster or high cetane fuels. Higher the cetane the lower the MPG's. Lower the cetane the higher the BTU's and MPG's...

Posted Image

Here is my fuel logs over the life of my truck.

[ATTACH=CONFIG]5853[/ATTACH]

Now peek at my signature... :whistle:

Link to comment

mileage seemed about the same with the PO had a set of toyo highway tires really smooth tread design my iat fooler is set off of your idea 143* and to answer other question the truck had a bad lift pump when I bought it so I had the airdog 100gph its less than 30k miles old installed with gauges the gloshift gauges are junk but according to a shop im at 18-19 idle and under load of about 1,500 rpm (in drive foot on gas and brake) down to 14 psi i also drive 50-60 on the freeways never over unless on a road trip so either my vp 44 is damaged due to the PO running it with 9 psi for who knows how long or my auto trans being bone stock is the problem i imagine a low stall converter upgraded valve body would go a long ways but the trans is not ready to quit yet

Link to comment
Share on other sites

I don't think you will ever see much better with an automatic, your numbers mimic mine when it was an auto. Going to the nv4500 bumped my mpg up over 2mpg with no other changes. I wish you could see my fuelly numbers when it was an auto but I erased them when I put the 5 speed in.

Link to comment
Share on other sites

i could see a gain with city and having a manual but cant imagine gaining much on the hwy as the tq converter is locked up just like a manual? i use to have a zf5 speed in a 7.3 powerjoke :lol: and driving that truck around town got old real fast super stiff clutch to push down even after a new clutch don't know how the dodges are never driven a dodge stick but if its anything like the fords i guess i'll suffer with the 2 mpg loss im a tree climber so already killing my knees day by day and the stick only made it worse

Link to comment
Share on other sites

I'd like to get about 18 around town and 22hwy i did a run to the coast towing my little aluminum boat 500lbs and got 18mpg granted the roads are windy and has a few mountain passes I was going 50-60 mph I've often wondered would I benefit setting the smarty at level 1 and timing at 4? Last time I did that without the iat fooler didn't gain any mpg however my truck weighs in at about 8k I've got a 80 gallon transfer tank and big tool box with a buckstop bumper on the front :doh: also live in Portland,or so x2 on :doh:

Link to comment
Share on other sites

Hate to say it but 18 mpg city is just not realistic. 18-20 highway is more in the ballpark. I run my Smarty on SW5 with torque management maxed and timing at +2 above the catchers parameters. The biggest tires I run are 285/75/16 but for the most part I run my 4th gen wheels with the factory size tires. I keep a light foot for the most part and can break 20, may flirt with 21 On an extended highway run but that's as good as I've ever seen.

Link to comment
Share on other sites

I'd like to get about 18 around town and 22hwy i did a run to the coast towing my little aluminum boat 500lbs and got 18mpg granted the roads are windy and has a few mountain passes I was going 50-60 mph I've often wondered would I benefit setting the smarty at level 1 and timing at 4? Last time I did that without the iat fooler didn't gain any mpg however my truck weighs in at about 8k I've got a 80 gallon transfer tank and big tool box with a buckstop bumper on the front :doh: also live in Portland,or so x2 on :doh:

18 around town in a 8K truck is asking alot. I just dont see it happening. 22 highway, maybe. I have seen almost 21 once, But i was keeping my speed 65 max. As far as Smarty settings, I know nothing about them.
Link to comment
Share on other sites

  • Administrator

Another site I've got my hand in... :ashamed:

www.smartresource.com

www.smartresource.net

Give these guys a crack really good information on the Smarty programmers.

Note: the site was down with a MySQL server issue last time I checked it 07/07/2013 so it should be noticed by Monday morning and dealt with.

Link to comment
Share on other sites

I think I better stop complaining then last fill up smarty on level 1 hand calc 17 mpg 2nd with towing 6,500 for 30 miles of the tank yielded 16.8 hand calc did a run to Seattle to pick up a new fridge I'm guessing I was in the range of 24 mpg heading up there smarty on level 1 timing on 3 on the way back I didn't do so well according to the scanguage avg was 18mpg so combined run there and back just shy of 21mpg the fridge was standing up right so it made for a fantastic wind sail price you gotta pay unless you wanna lay it down and wait 12 hours for the freon to settle :whistle: my truck is also 2wd drive auto so the guys who have 4x4 sit a bit higher catch a little more wind however i do have a 300 lb front bumper and 90 gallon transfer tank

- - - Updated - - -

Also made sure to stay set at 60 for cruise unless I got frustrated with Seattle drivers had a few 65-70 speed ups

Link to comment
Share on other sites

×
×
  • Create New...