Fuel Economy Series 60 Fuel Mileage battle.....

Hello. New guy here. I fix a lot of trucks and high end cars. As to your baro sensor throwing a code when it has failed, here are your parameters: Open or short. That's a hard failure. Out of range failure. This is the one that will get you. Lets say for instance the sensor provides a signal to the computer from 1-10. The computer is expecting an operating range of say 3-7. Any time it's out of the that range for a predetermined time it sets a code. On goes the light. What if the sensor sticks at 5? It's never going to set a code, as it's inside the operating range. I've experienced this problem with lots of other sensors. This is why datastream is so important. With a thing like O2 sensors, we simply read the O2 sensor voltage and add propane to the intake. If the sensor voltage goes high, we have a working sensor.

Hope that shed some light on sensor issues. Next time you're in Mount Vernon Washington, why not stop by and lets talk. I'm just east of I-5 on exit 230. Easy on and off. Always happy to help someone on the road. Oh, and screw diag fees. What a racket.
 
Since RPM on a diesel is determined by the amount of fuel, rather than the amount of air, a mass airflow system doesn't apply. Gas combustion is metered by knowing the amount of air to add fuel and control the ratio. Proper stoichiometric ratio for fuel air is 14.7 to 1 at cruise. At full power, 12-1 is essential to avoid burnt valves and pistons. You don't have these issues with diesel. A mass airflow sensor could be useful in a diesel by some form of tuning, but since fuel is the boss, it's virtually useless.
 
Since RPM on a diesel is determined by the amount of fuel, rather than the amount of air, a mass airflow system doesn't apply. Gas combustion is metered by knowing the amount of air to add fuel and control the ratio. Proper stoichiometric ratio for fuel air is 14.7 to 1 at cruise. At full power, 12-1 is essential to avoid burnt valves and pistons. You don't have these issues with diesel. A mass airflow sensor could be useful in a diesel by some form of tuning, but since fuel is the boss, it's virtually useless.

I understand what you're saying, but think about it a minute. With BAR and MAN sensors, they engine computer is likely calculating mass airflow already. Why not just switch to one. (And as I'm typing I realize the answer) They need to know manifold pressure to control the turbo to get enough exhaust back pressure for the EGR to work.
 
The fact remains, a diesel engine does not have a closed loop system. Until it does, its an open loop system with no true feed back to see how well its working g.
 
Interestingly enough, I don't see a way to utilize a mass airflow sensor on a diesel. Since baro data and air temp cover most of the bases, density is known to the extent that the computer can make the necessary calculations for efficient operation. Again, diesel is fuel driven, gasoline is air driven. A MAF could be employed, but it's expense and value would be questionable. I've been running some calculations this evening and can't get the MAF to make sense here. It doesn't mean you're wrong, it just means I can't find value for it. Maybe I'm missing something.
A
 
Upon further research and thought, I've come to the conclusion that a mass air system would have little or no value to the direct operation of a diesel. Again, the amount of air is a result of the amount of fuel injected into the engine. Unlike a gas engine that throttles the air and has to meter the fuel in relation to the amount of air coming into the engine.

However, I did come up with a great idea that would use mass airflow sensing in a diesel. Since all these EGR systems are now stuck on our engines and we have to remove all the soot from our intakes, a maf would be a great way to monitor flow restrictions caused by soot accumulation in the intake. Once flow is restricted a certain amount, then a service EGR/Intake warning would light up. That would take a lot of the guesswork out of maintenance.

In short, a closed loop system will never work on a diesel. You can't control mixture from the exhaust like you can a gas motor.
 
Injector dwell is simply the time the injector is open and spraying. The dwell is determined by pulse width. I did bring up stoichiometric, however it was just to illustrate the basis for mixture control in gas motors.

I'm not in this to have an argument. I'm liking this forum because everyone seems to be very respectful. I hope that I'm not offending you in some way.
 
Why can't you control mixture from exhaust?
 
I'm going to try to make this as simple as I can. If you reduce the amount of fuel that's injected in a diesel, you reduce the RPMs. Therefor, it's an exercise in futility to run a closed loop, MAF system on a diesel. However, your idea of running MAF got me thinking and I seriously think that it has some merit. Especially in light of the soot associated with EGR systems. Using the MAF to determine flow reduction is practical. That alone makes it worth the expense. I just can't see any way to do anything else for a diesel.

If you have any ideas, I'm open to looking at them. I just can't make that work. Might be my short sidedness. Let me know.
 
Since RPM on a diesel is determined by the amount of fuel, rather than the amount of air, a mass airflow system doesn't apply.

Well, not quite. It is a combo of boost, engine RPM overcoming low RPM rotational inertia, and exhaust flow that affects fuel consumption. I can, say, pull a hill at 1450 RPM and use less boost and less fuel than doing so at 1200 RPM. I use less boost, the EGT's are much lower showing efficient exhaust flow. Of course, it all depends on the engine, and I am speaking from a pre-egr Detroit 60 standpoint. Contrary to magazine articles and radio shows, higher RPM does not always equate to higher fuel consumption. It is a balance of factors.

Now let's take the DD15. Detroit would say operate it at 1250-1300 for max fuel economy as would the so-called "experts" that write articles. I chatted with Henry Albert a while back by phone call, who did a run from CA to NC for Freightliner in one of their newest Cascadias, grossing around 68,000 lb, and almost busted the 10 mpg threshold for the trip. Solid high 9's. What RPM did he do this at? 1375 - 1425. Which with combined with the 10 speed direct and the 2.47 rear ratio that was part of that truck specs, put him at between 64 and 66 mph with average 65 mph. Well outside what the so-called writers and "experts" would say is the "sweet spot" of the engine and tantamount to heresy (ask Prime) regarding the road speed. And Henry is just about the de facto expert in the U.S. on how to tweak out mpg. I have seen no one consistently match his mpg numbers. He could give anyone and inferiority complex when it comes to fuel mileage. That is why Freightliner uses him to prove what a truck can do.
 
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@Copperhead

Toss this by you.

Mileage is still hit and miss. Somewhat. Oct I was at 7.17, Nov 5.11 and Dec - 6.51.

Those are actual mpg calculated from fuel used against miles driven.

Early in December, I unplugged and plugged back in my SRS and trs sensors. I also started to notice that when its been off for several hours, the truck will fire right off. I'm talking bump the starter and its running. The dash will show 6.7+ mpg

After several hours, say running from des Moines to clear lake, I will have to crank it 8-12 seconds for it to start now. The dash will now show 5.9-6.2 mpg.


Thoughts?
 
Henry Albert has since slowed down, I believe. Never have seen the results of that though.

Sweet spot changes with conditions. Even freightliner advises higher rpm in Hills.

With a dd15, under 70k, not in major grades, I would stay over 9 all day long.

Give me his modified trailer, I guarantee I could have broken 10mpg.
 
It would have to he real recent, as in the last few weeks. I talked with Henry about that run not that long ago. Given the right situation, even with 70K gross, I can rest comfortably in the 8's with my pre-egr Series 60. Totally undoable most of the time during this time of the year. All I do in upper midwest, so these 30+ mpg winds, cold, and such really take a bite out of mpg. But it still is averaging in the 7's on a monthly basis.

Have never had the issue you describe mndriver, so have no real answer for you. I have heard of others doing similar to what you have tried, but have never done it myself.
 
I bought my truck in July 2012. Pretty much been battling a fuel mileage issue since then.
07 Century, 14L EGR Series 60, 13 spd, 3.42 Meritor 14X rearends.

Mind you, my mileage isn't horrible, it's 6.2 mpg for an annual average. All miles actual and all fuel counted for the year. My issues is the RANGE. I was seeing from a low of like 4.6 to a high of 8.87.

Things I have done.
3-axle and 5-axle alignment.
Gotten rid of ALL recaps and gone to GY 399L steers, Firestone FD695+ drives, BFG 720 drives and Double coin trailer tires on the trailer. All virgins. No recaps.

Exhaust Manifold gasket replaced. After the first Manifold gasket replacement, turns out my silicon boots between the Turbo and CAC were leaking. Replaced both of them with all new clamps.

Had the ECM tuned on a chassis dyno. Putting 550 hp and 2060 Ft-lb torque to the ground. Yop, it'll pull.

Had the overhead ran. No significant improvement.

replaced the ECM to firewall wire harness. If you drive a Freightliner, I'd pay REAL close attention to it. There's a 10 ga battery positive wire that runs through this bundle. The sheathing had rubbed through large areas of wiring where it makes sharp bends over the ECM and the starter. It WILL shut your truck down on the side of the road, and if that BAT+ wire rubs and shorts, I can see it being a fire hazard.

Found out my CAC was seriously leaking. Took some windex and just fast idle to find this issue. I had it in 4 times to have it tested for a bad CAC. No one found it.

Replaced the power divider. Input shaft bearings were TOAST. This was kind of suspected back in July after I got the truck home. My mechanic had gone in and tightened up the input yoke on the power divider. We just kind of ran it and kept an eye on things but it lasted 85,000 miles after I bought it.

Serious fuel issues over the winter. In Nov/Dec, I used 42 fuel filters. It took a 16 OZ Kill 'em, two 32 oz
CLEAR-DIESEL® Fuel & Tank Cleaner and one 80 oz bottle of Emergency 911. I have been averaging 28,000 miles on a filter now since I put in that fuel cocktail to 240 gallons. Prior to that, about 7,000 to 9,000 miles. I even made a filter setup so I could try and clean the fuel at night after driving for the day.



Replaced the entire exhaust manifold with new. Center section was showing hairline cracks and there was soot behind the manifold. Turns out it was the EGR to Manifold joint that was leaking.

I pulled my map sensor out and decided to clean it with ether. Seems to have helped. Since it helped, I just changed both the MAP and the boost sensors.

I was starting to show similar behavior to what happened the first time I replaced the exh man gasket so I checked all my clamps again. Yop, two clamps loose like 6 full turns and leaking. Big ol' bubbles blowing out.

As a result of the manifold replacement, I came down Bozeman pass in Bozeman MT and the exhaust pipe came off the turbo. I have no clue why other than there was NO nut on the turbo clamp. The pipe itself you could see was damaged from being tightened like it was installed incorrectly.

In Mt Vernon WA, I noticed I was up in fuel mileage again. I got to thinking...All my best mileages occurred in Boston, Florida and now Seattle areas. What do ALL those areas have in common compared to running in MN and the upper plains? Sea level vs 900-1000 ft in elevation. I pulled into the Freightliner dealership and asked them about if they could map the range on the Baro sensor. Yop, you guessed it..."deer in the headlight" look. "Two hour minimum to hook up the computer. $250 charge." And how much is a sensor? $113. Bought the sensor and put it in.

Fueled in Sumner WA and drove to McMinnville Or to Ontario OR. Gross weight, 70,0000. 7.21 MPG Hmmm.....Lot of 2500 ft pulls between 2000 to 4400 ft there. I remember 4 pulls at least in there.

Ontario OR to Laramie WY 6.54 mpg. Hmmmm... You climb to 7800 feet from 4000 feet in Ontario. SEVERAL times too. Three Sisters on I80 are in there too.

Today's fuel mileage according to the dash sucked. But across NE, there was a 20-40 mph cross wind at 90 degrees. I was still above 6.4 mpg according to the dash. I'll be fueling on Tuesday sometime and have a better idea what the mileage is.

Two things. I am pulling hills in a gear higher than I had before. The truck hasn't gone below 6.1 MPG on the dash yet. In the crosswinds I had coming across NE today, I would have been low 5, high 4's for mileage easy.


In a nut shell.....
replace your CAC when needed.
No exhaust or turbo leakes. CRITICAL here.
Replace fuel and air filters on a regular basis.
If you can't get any other things to better your mileage, consider $200 worth of sensors. MAP, BARO and boost sensors. They get dirty and seem to really make a difference.

So what do these sensors do?

Boost sensor is obvious. It tells you the level of boost the engine is seeing.

MAP sensor tells the engine how much load is on the engine. Compares the manifold pressure to atmosphere.

BARO sensor basically is telling the ecm what the altitude is. Changes the fuel and timing curves as a result.

I was able to find this in the EPA 04 EGR tech manual. Good luck it would seem getting a service shop to understand it.
 
Hey mn driver if u from Saint Paul mn area I been having issue with mpg since bought this 07 century Detroit 14 liter n like to talk to u. Maybe u can help me out . Thanks new to this
 

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