06 5.9 New Injectors - questionable mpg - Dodge Cummins Diesel Forum
3rd Gen. Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission Ect...NO ADVERTISING

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post #1 of 29 (permalink) Old 03-29-2019, 10:06 PM Thread Starter
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2006 2500 5.9 with 175k. 4x4. 4 inch exhaust. Only cat. Afe intake. 305/70/18. Front 2.5 lift. Bullydog gt set to tow. 3.73 gears.

Contacted in house shop and had them order brand new injectors from bosch straight out of the factory in Germany. This is a guy i trust. No core charge. Brand new sealed Bosch box.
Noticed a ticking until acceleration with old injectors. After all 6 new injectors and tubes were installed (myself) i noticed less power. Mind playing games or not i guess there. I spent 4 months fine tuning my mpg on my bully dog and now i am within about 1% of accurate display it seems. Running 55-60 mph no load no wind it shows 16-18. Once i get on interstate and go 70 it drops to about 10 to 12. Maybe 13. Whats the deal with the massive drop?
Been debating internal fuel bypass leak. No hard starts. No hazz from exhaust minus during startup when exhaust is cold.(winter under 30 degree cold starts) lasts about 2 minutes. Seems typical.
I have not did any leak return test yet not 100% sure how. I do own a witech pod.
Just seriously surprised on a huge drop like that with just 10mph unless my 305's just throw off the gear ratio curve just in that 10.mph faster...
The new injector install went very smooth.
Just seems like the truck works harder.
Maybe stock injectors weren't the way to go...
Cylinder contribution test showed 100, 99, 100, 100, 100, 100 after install a few months ago. Id call that close enough. 🙂
Does anyone have any ideas. Hell with 305s id love 14 on the interstate running 70 but my last hand calculation with some random head wind was only 12.83 mpg
Disappointed.

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post #2 of 29 (permalink) Old 03-29-2019, 10:17 PM Thread Starter
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Debating on pulling everything back down here in the next month or so and just checking everything but i don't know what i would do differently. I spent a good 6 hours doing this job checking everything like a marine.
Today driving home at 75 with a head wind of roughly 10mph i was only showing 10mpg. Maybe 11.
I am seeing good rail pressure. Upwards of 19 20k running 75. Boost running around 15-18 running 70-75. Running 55-60 boost is around 8-10. Don't think is a boost leak.
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post #3 of 29 (permalink) Old 03-29-2019, 11:11 PM
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What transmission? Auto will out mileage a manual any day o you have to take it into account.

EVERYTHING impacts mileage, from the temp and any wind, tires, elevation, and especially speed. Speed is the killer on these trucks, you are shoving a brick thru the air, taller tires let more air and turbulence under the truck, and once you break 70 mph mpg plummets.

MPG calculators are notoriously inaccurate, they are called lie-o-meters for a reason. The ONLY way to calculate AVG mpg is as accurate as possible divided by gallons. Have you calibrated the speedo to a gps over multiple long flat runs and adjusted it within 1 mph of actual? Are you filling the tank the same way every time? If either of those is off or inconsistent your numbers are meaningless.

I have 2 05 trucks, auto, bigger injectors, running 400+ tunes. At 60-65 mph in 90+ temps at 3000 ft altitude or so they will make over 20 mpg, hand calculated and filled the same way every time. Either one in a 25-30 quartering head wind at 35-45 degrees temps running 70-80 mph won't break 12 mpg. Drive a reasonable 65-70 in warm temps, relatively dry, and they will consistently do 17-18 mpg or more depending on all those factors. I have towed grossing in excess of 21k and averaged 11 mpg coast to coast. I have towed heavy in hot humid nasty conditions and clocked less than 10 mpg.

EVERYTHING impacts mileage. In the north this time of the year if it stays running and gets over 10 mpg, count that as a win.

Oh yeah, based on your contribution percentages nothing wrong with the injectors or install.
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post #4 of 29 (permalink) Old 03-29-2019, 11:12 PM Thread Starter
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[QUOTE=cerberusiam;28941659]What transmission? Auto will out mileage a manual any day o you have to take it into account.

Sorry. Its a stock 48re.
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post #5 of 29 (permalink) Old 03-29-2019, 11:16 PM Thread Starter
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Thank you very much. I guess i will leave it alone. Yes i am in Minnesota so temps are hardly above 40 right now.
Everything you said makes sense. I won't bother pulling anything down. I will hope to see better fuel mileage when it warms up.
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post #6 of 29 (permalink) Old 03-29-2019, 11:21 PM Thread Starter
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Yes the speedo was calibrated and checked over the course of 2 weeks off and on. Everything is right on.
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post #7 of 29 (permalink) Old 03-31-2019, 06:41 PM
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Am I understanding that you have no idea if the old injectors were stock? It sounds to me like the answer is not and your ignition delay has changed... which will affect mpg.

Working from my trucks specs... when I had the 2" level and removed it I gained back ~0.8-0.9 mpg. But that s not enough to explain your mpg.

Cover up the front, monitor IATs and get them up into the 80-90* range and measure mpg. You can do this by making a CAC blanket to block all cooling efforts on the CAC which will raise IATs. You need to stay within 25* of ambient temps @ the airbox, otherwise the fan will kick on & all bets are off.

and monitor trans temps. when i went from AT -> MT I gained 2 mpg immediately...

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post #8 of 29 (permalink) Old 03-31-2019, 07:53 PM
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Quote:
Originally Posted by steve05ram360 View Post
Am I understanding that you have no idea if the old injectors were stock? It sounds to me like the answer is not and your ignition delay has changed... which will affect mpg.

Working from my trucks specs... when I had the 2" level and removed it I gained back ~0.8-0.9 mpg. But that s not enough to explain your mpg.

Cover up the front, monitor IATs and get them up into the 80-90* range and measure mpg. You can do this by making a CAC blanket to block all cooling efforts on the CAC which will raise IATs. You need to stay within 25* of ambient temps @ the airbox, otherwise the fan will kick on & all bets are off.

and monitor trans temps. when i went from AT -> MT I gained 2 mpg immediately...
I love learning new things from this guy ^^^^ Super knowledgeable!
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post #9 of 29 (permalink) Old 03-31-2019, 09:34 PM Thread Starter
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Yes the original injectors were stock. Bought the truck new.
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post #10 of 29 (permalink) Old 04-01-2019, 08:18 AM
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How long have the tires been on there before the injector swap?

Some of what your saying in post one isnt clear to me, relating to the 10 mph & tires...

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post #11 of 29 (permalink) Old 04-01-2019, 09:08 AM Thread Starter
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The tires have been on for over a year. Haven't paid attention much to mpg but was curious after the new injector install when i discovered this mpg issue.
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post #12 of 29 (permalink) Old 04-01-2019, 11:16 AM
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Assuming you corrected for the tire size difference, not sure why mpg would change much with new injectors. Custom tuning is really the best solution for running the motor.

AFE PG7 drop in filter, AFE Torque Tube, HTT 2.5 turbo, AFE e-mani, ATS Arc Flo, 50HP DDP , 415k, HPTuners, G56, 25.065 mpg, mpg threads ->
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