I searched thru one of the Dakota forums the other night. Found a few instances where people with 42RLE and 45RFE trannys complained about it slipping in and out of lockup. But nothing I could see from people with newer trucks that had the 545RFE with the EMCC, or any mention of symptoms like we're having.

Another reason I'm playing around with OD lockout - there should be an RPM region where this engine gets the lowest Brake Specific Fuel Consumption (BSFC). For instance, the oddity that Farmdiesel noticed when speeding up from 70 to 75 mph that EGT actually dropped nearly 100 degrees, where several of us have noticed that above 70 mph we're getting better than 30 mpg, etc. It could be that this engine actually gets it's best BSFC somewhere ABOVE 2000 rpm.

Ordered some of the TDR back issues, to check out their research on performance modules. One issue had an article on how BSFC had changed from the older 12 valve mechanical engines to the newer 24 valve electronically controlled engines (we're talking Cummins 5.9 L). On the older 12 valve engines, it matched up rpm wise with where it was rated for peak torque, 1800 rpm. On the newer 24 valve engines with all the electronic controls, while the peak torque spot was still the same, the BSFC sweet spot had actually moved up to 2000 rpm and above.

I remember somone on the forum recently did a test, running for 10 miles at 60, 65, and 70 mph, restiing their computer each time, and noting where they got the best fuel mileage. I wonder what the results would be if they repeated the test with OD locked out at 40, 45, and 50 mph. Would be interesting if in both cases the best fuel mileage was achieved at speeds where the engine was turning at the same RPM.

_________________
Mitchell Oates
'87 MB 300D Diamond Blue Metallic
'87 MB 300D - R.I.P. 12/08
'05 Sport CRD Stone White
Provent CCV Filter/AT2525 Muffler
Stanadyne 30 u/Cat 2 u Fuel Filters
Fumoto Drain/Fleetguard LF3487 Oil filter
V6 Airbox/Amsoil EAA Air Filter
Suncoast TC/Shift Kit/Aux Cooler
Kennedy Lift Pump/Return Fuel Cooler

You have to remember we're still dealing with a lot of unknowns on this beast. One friend at work is also ex-military and spent a good deal of time in Germany driving diesels on the Autobahn. When I mentioned achieving over 30 mpg at 75 mph on the interstate, his response was "Well, duh, this thing was probably designed for blasting down the Autobahn at 100 mph, that engine and turbo are probably just beginning to wake up at 2 grand". However, think I'd want a little more info before i put his theory to the test.

_________________
Mitchell Oates
'87 MB 300D Diamond Blue Metallic
'87 MB 300D - R.I.P. 12/08
'05 Sport CRD Stone White
Provent CCV Filter/AT2525 Muffler
Stanadyne 30 u/Cat 2 u Fuel Filters
Fumoto Drain/Fleetguard LF3487 Oil filter
V6 Airbox/Amsoil EAA Air Filter
Suncoast TC/Shift Kit/Aux Cooler
Kennedy Lift Pump/Return Fuel Cooler

sounds like though the problem is only when going up an incline? (the 'hunting' problem) If so, then you just turn it back on when you get up it. I don't think its going to hurt the motor.


I had a rant at another website I frequent (svt performance) about the rioting going on over a cartoon, its my avatar overthere, so I just put it up here too. It'll change soon, I go through moods.

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Ryan
2006 Ford F-250 PSD CC FX4
**GONE**
2005 Jeep Liberty CRD
SAMCO Hoses//GDE Tune//PML Trans Pan//TransGo HD Shift Kit//MBRP Exhaust

1986 2R Mustang SVO

*raises hand*

_________________
Ryan
2006 Ford F-250 PSD CC FX4
**GONE**
2005 Jeep Liberty CRD
SAMCO Hoses//GDE Tune//PML Trans Pan//TransGo HD Shift Kit//MBRP Exhaust

1986 2R Mustang SVO

Humm, done that for about 20 miles once with no in effect on the Magmum, but red line is 6500 rpm and she loves to sing those high note's.

Bet my old MB had 100,000 miles at 3800 to 4200 rpm's, it red lines at 4200 if I remember correctly. Had big oil cooler and huge radiator, and was the toughest car I ever owned.

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91 MB 300D 2.5L Turbo. Her's

05 MB E320 CDI. Mine

Just finished the third day of commuting with the OD experiment. Started at 3/4 tank 200 miles, tonight down to 1/2 tank 320 miles. 120 miles total.

MPG hasn't decreased, if anything it's actually went up slightly. I've got about 10 to 15 miles more at this point on the fuel gauge than I normally do. Beast does seem happy with living above 1800 RPM more often.

On part of the 55 mph section tonight, I tried leaving OD locked out and letting it rev up to 2700 at 60 mph. Some twisty curves in that part where you have to slow down out of OD and then speed back up. To me at least, it handled the road and curves much better. And to my ear, the engine sounded much better singing at 2500 than lugging at 1700.

I'm starting to believe my friend was right, that OD on this vehicle was meant for high speed blasts down the autobahn. Depending on the final results, I might end up reserving OD strictly for interstate driving.

_________________
Mitchell Oates
'87 MB 300D Diamond Blue Metallic
'87 MB 300D - R.I.P. 12/08
'05 Sport CRD Stone White
Provent CCV Filter/AT2525 Muffler
Stanadyne 30 u/Cat 2 u Fuel Filters
Fumoto Drain/Fleetguard LF3487 Oil filter
V6 Airbox/Amsoil EAA Air Filter
Suncoast TC/Shift Kit/Aux Cooler
Kennedy Lift Pump/Return Fuel Cooler

When we bought the CRD the wife thought we should drive in town w/o the O/D on, and only use O/D when on the highway. I told her to try it with O/D on first and see how it does, I just now asked her and she said she had been turning the O/D off in town for about a month now. So I went back and looked and that corresponds to the slight increase in mpg's that I had written off to breaking in of engine. Looks like I may hay been the wife's idea to leave it out of O/D like she did on the old '87 4L Cherokee in the daily in town driving. Only time I ever drove the car was on trips, so I always used the drive position for O/D use on highway. She also always had the power switch on and I would turn that off when I drove.

So looks like the OD should only be used when hitting the highway where you will be doing 75 mph or more if any hills are involved. I guess someone driving in a 65 mph speed zone with hills should not be using O/D, this I guess would mean someone in CO would seldom be using O/D. In some parts of the country this would not apply, like some flat areas of TX or KS I have been through in the past.

Another thing that has crossed my mind is the EGR out put is highest at low rpm's, probably below 2000 rpm's and at highest EGR out put the engine would be idle. If this is correct, then not using O/D in town would greatly reduce the smoke out put or as we diesel heads are fond of, the soot we smoke people with.

Any thought or corrections are most welcome.

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91 MB 300D 2.5L Turbo. Her's

05 MB E320 CDI. Mine

That was one possible theory i advanced about why Farmdiesel saw nearly a 100 degree decrease in EGT going from 70 to 75 - EGR flow was already at maximum, and any further increase in air flow had to come from the intake system. EGR becomes a smaller percentage of total air flow into the cylinders, more cold air equals lower EGT. Also, looking at the Cummins data from TDR, we may also be hitting the point of lowest BSFC at that RPM, using the least amount of fuel for the power generated - in other words, the engine's peak efficiency point.

Instead of going by speed, I'd go by RPM as whether or not to lock out OD, trying to at least keep it above 1800 rpm.

I went back and read the TDR article again. They talked with Cummins, and confirmed that for the older 12 valve mechanical engines BSFC was at 1600 - 1700 rpm, the intital 24 valve engines 1600 - 2000 rpm, and for the high pressure common rail versions it moved up to 1900 - 2100 rpm.

So far, it looks like the CRD is falling in line with the Cummins HPCR engines as to where it's "sweet spot" is. Now, if they'd just put a bloody 6 speed manual behind it, where you could keep the engine in that sweet spot, you might see some impressive MPG results.

A suggestion to everyone - visit the Turbo Diesel Register website and spend the $35 to subscribe. The quarterly magazine they put out is a gold mine of diesel info, and you can order back issues as well. The first issue I received detailed a factory mod kit for worn out lift pumps, and it saved my friend in TX an expensive repair bill when his went out and Cummins covered the mod under the engine warranty.

_________________
Mitchell Oates
'87 MB 300D Diamond Blue Metallic
'87 MB 300D - R.I.P. 12/08
'05 Sport CRD Stone White
Provent CCV Filter/AT2525 Muffler
Stanadyne 30 u/Cat 2 u Fuel Filters
Fumoto Drain/Fleetguard LF3487 Oil filter
V6 Airbox/Amsoil EAA Air Filter
Suncoast TC/Shift Kit/Aux Cooler
Kennedy Lift Pump/Return Fuel Cooler

I've been a TDR member since December 1997.....that $35 per year subscription is peanuts for the value received.

Greg

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2015 Jeep Grand Cherokee Limited 3.6L and A8
*SOLD*2005 Jeep Liberty Limited 4x4 CRD, Bright Silver Metallic, Dk/Lt Slate Gray Leather w/bun warmers, 5 spd auto, 22G pkg, Trailer Tow, 3.73 Rear Axle w/Trac-Lok Differential, P235/70R16 Firestone Destination LE's, Power Sunroof, Selec-Trac 4WD, Infinity 6-Disc In-Dash, Magnaflow #15870 System.

I would like to see the OD button work in 2 stages. The first click of the button would lock out the 2nd OD which engages at 58 mph and the next click of the button would lock out the 1st OD which engages at 50 mph. That would give you control over all the gears. I wouldn't think that would really be a big deal as far as programming goes but it would fix many of the gear hunting issues. I find the tranny hunts between the two ODs more than anything. This engine has little trouble with the 1st OD but the second is hard for it stay in on twisty roads/hilly roads.

Is there a way to suggest such a mod to DC???

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'05 CRD Sport

I live in Colorado and NEVER turn the OD button off on the tranny. WHY? Shutting it off doesn't take advantage of the low rpm torque. I love it when it kicks into 5th and is buzzing along at around 1600 rpm at 55 mph.

I guess I'm lucky, I don't get any shudder at all in my 06 model. I do get an occasional "not so smooth" shift from 2-3rd gear.