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TDIwyse

Joined: 01/10/2009 06:58:20
Messages: 54
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Good morning. Got a couple MPG questions regarding cold weather and your tune.

What would be considered a normal drop in MPG's for a ~15 mile commute in winter with winterized fuel?

How about long highway trips?

Is your tune's efficiency better with warm fuel or cold fuel or does it matter? I had disabled the fuel heater due to some concerns over leaking but am wondering if better efficiency would be had if I had it enabled.

Thanks for your time.

2006 Liberty Limited CRD
2004 Ram Quad Cab 4x4 Cummins
2001 VW Jetta TDI
1990 YJ with 2006 Cummins B3.3T
GreenDieselEngineering
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Joined: 10/07/2009 07:25:47
Messages: 357
Location: Southeast Michigan
Good questions. The fuel economy drop in the winter can drop significantly in the winter. We see a general decrease around 10%, but this can vary based on conditions. The fuel tends to be the largest factor. You might see an additional 5% drop if the vehicle is strictly a commuter due to having a cold start in the morning and a cold start returning home. The cold oil requires a few minutes to warm up. The lighter viscousity 0-W40 oil helps reduce the FE drop.

We are noticing that with the tune the warm-up is quicker with decent heat in cabin in about a 1/2 mile of city driving. The advanced timing helps transfer more heat to the coolant, should be directionally correct for improving the FE.

Fuel temps can effect efficiency, but it is usually not a big factor. Temps in the range of 30C to 50C at the engine fuel inlet are optimium, colder temps may have slightly more ignition delay and this will tend to drop the fuel economy. With the tune, the higher injeciton pressures help to increase the fuel temps in the common rail and minimize the ignition delay. The pressurizing of fuel in the rail can add between 30-70 C to the inlet fuel temps. The return fuel temps are also slightly higher to help warm the fuel in the tank faster.

The fuel heater has minimal impact on increasing the system temps. The injection system heat load is at least 100 times greater and probably more. We will instrument one of our KJs to see the temperature difference across the fuel heater and the return line to the tank. After a few weeks of monitoring we should have some hard numbers for you.
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WXman
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Joined: 29/01/2010 14:53:49
Messages: 28
Location: Kentucky
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My MPG figures have been very low lately. I'm lucky to get 20 MPG. This is a 50/50 mix of city/highway and driving very conservatively. In fact, this current tank looks like it'll work out to around 18 MPG. That's pretty horrible for a vehicle like this. I'm wondering what affect using anti-gel additives has on fuel economy. Have you guys done any testing on this? The other thing that could be hurting me is that the temp. has been staying below freezing quite a bit lately. It's been a cold Winter here relative to average.

'05 Liberty CRD Limited
Factory Off-Road Package
Daystar spacer lift/Conduit washers
Skyjacker H7088s in the rear
Renegade wheels
255/70-16 General Grabber AT2s
GDE HOT Tune
EHM
No clutch fan
"Euro" TC
flman
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Joined: 28/08/2009 19:59:32
Messages: 74
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WXman wrote:My MPG figures have been very low lately. I'm lucky to get 20 MPG. This is a 50/50 mix of city/highway and driving very conservatively. In fact, this current tank looks like it'll work out to around 18 MPG. That's pretty horrible for a vehicle like this. I'm wondering what affect using anti-gel additives has on fuel economy. Have you guys done any testing on this? The other thing that could be hurting me is that the temp. has been staying below freezing quite a bit lately. It's been a cold Winter here relative to average.


Maybe you should try plugging in the block heater? Lucky for me, the place I bought has a 2 car garage for the Jeeps, and a large shop for my truck. None of the spaces are heated full time, but it is alot better then out doors.

PS, Kind of funny I fell in love with the place before I even saw the inside of the house, it was going to be my first place with two bays, a shop with a 10' bay, and a large bungalow I converted to a shed to boot.

Still Burnin Oil since 1992!
2010 John Deere 2305 3 cylinder Yanmar
GDE HOT!! Tuned 2006 CRD LTD Silver, Euro TC, GDE Tuned TCM, B&M Trans drain kit
GDE ECO Tuned 2006 CRD Sport Black, B&M Trans drain kit, Front and rear hooks, Full Skids
GDE ECO Tuned 2005 MB 2500 Sprinter Van
2010 MB 2500 Sprinter Van
Dave

Joined: 26/01/2010 13:56:59
Messages: 27
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WXman,
Do you get the same result with different fuel brands? Their method of blending winter fuel varies. Most blend in #1 fuel oil (kerosene) to lower the cloud point, which will lower mpg, more or less, depending on their ratio. Not enough #1 and customers will complain of gelling. Too much and they will complain of loss of power/mileage...junk fuel. Other companies have additives that have less effect on power/mileage. They all start out with pretty much the same base stock, it is their blends and additives that vary. Either way, they do a pretty good job of protecting us from gel, and you shouldn't need to buy any extra additives.
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WXman
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Joined: 29/01/2010 14:53:49
Messages: 28
Location: Kentucky
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So far the only place I have been fueling up is Murphy USA (Walmart). They have a sticker on the pump that says "guaranteed not to gel to minus 20 degrees". Holy cow that's hard to believe so I put anti-gel additive in anyway. So Friday I'm going to hit a Flying J truck stop for some good diesel and I won't use any additives so I can see if the Walmart fuel and/or additive is my problem. I bet if I use good fuel with no additive I'll see better numbers. When the weather finally breaks it'll surely help too. Right now I'm just disappointed.

'05 Liberty CRD Limited
Factory Off-Road Package
Daystar spacer lift/Conduit washers
Skyjacker H7088s in the rear
Renegade wheels
255/70-16 General Grabber AT2s
GDE HOT Tune
EHM
No clutch fan
"Euro" TC
GreenDieselEngineering
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Joined: 10/07/2009 07:25:47
Messages: 357
Location: Southeast Michigan
WXman,

Is the CEL off? Any changes in starting the engine stock vs. tune? Were you using the additives pre-tune? Are the mileage figures hand calculated? and not EVIC as it has some accuracy issues on most KJs. Have you noticed an improvement in city driving, launching and passing? Hopefully the mpgs will increase for you, the extreme cold will rob a few %, but nowhere near where you are running. What driving mix is typical for your KJ, city/highway?

Thanks for the feedback.
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WXman
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Joined: 29/01/2010 14:53:49
Messages: 28
Location: Kentucky
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GreenDieselEngineering wrote:WXman,

Is the CEL off? Any changes in starting the engine stock vs. tune? Were you using the additives pre-tune? Are the mileage figures hand calculated? and not EVIC as it has some accuracy issues on most KJs. Have you noticed an improvement in city driving, launching and passing? Hopefully the mpgs will increase for you, the extreme cold will rob a few %, but nowhere near where you are running. What driving mix is typical for your KJ, city/highway?

Thanks for the feedback.


Yes, CEL is off. I use block heater when temp. hits 15°F or below. Engine starts fine, spikes to 1,000 RPM immediately, then idles normal. I do hand calculate my mileage and use EVIC too. Pre-tune my EVIC was always very accurate. I still haven't gotten a good feel for how close it is post-tune.

My driving is 50/50 city and highway. I have a 15 mile commute to work, most of which is 55 MPH. I drive very conservatively. Right now I have 250 miles on this tank...and I'm at the tick above 1/4 tank mark. Not looking good at all.

Running synthetic oil, new filters everywhere, clean MAP sensor, 35 PSI in the tires, only run defrost when I need it. Other than the quality of fuel...I don't know what else could be causing this horrible economy.

As far as power, yeah it feels a little stronger but not what I expected 65 lb./ft. to feel like. Maybe my TC and/or pump is holding me back? The engine is very quiet now. Even pulling up a hill at 2 MPH it's very quiet whereas before it sounded like a tractor.

'05 Liberty CRD Limited
Factory Off-Road Package
Daystar spacer lift/Conduit washers
Skyjacker H7088s in the rear
Renegade wheels
255/70-16 General Grabber AT2s
GDE HOT Tune
EHM
No clutch fan
"Euro" TC
GreenDieselEngineering
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Joined: 10/07/2009 07:25:47
Messages: 357
Location: Southeast Michigan
After running a couple tankfuls you will have a better idea of the real fuel economy, there is some variability in the gauge so don't worry too much about it yet. Any chance you are having some dragging brakes? We lost 3mpg due to the front brake calipers binding on the support pin.

As for the torque, it is not a huge step up as the engine is still limited by the turbocharger, but it is much better than stock and provides a more linear, connected to the ground feeling. Keep us posted when you refill and come up with some hard numbers. Thanks.
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WXman
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Joined: 29/01/2010 14:53:49
Messages: 28
Location: Kentucky
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Dragging brakes... that is a possibility. I noticed that my right front caliper was leaking where the banjo bolt connects to the caliper. I replaced the caliper with a reman. unit and used all new hardware and greased the pins. I even installed new copper washers on both sides of the banjo bolt. The leak got better. I bled the brakes the old fashioned way.

Now, there are times with my Jeep will pull hard to the left under strong braking. Other times it's fine. The pedal also feels like it has more travel in it than it should. (My pads are all new). So I am very suspicious of my entire brake system right now. Perhaps it needs to be bled in a different manner since it has 4-wheel ABS??

In any case I will try to get some different brands of fuel and try them. I'll let you know what I find.

Otherwise the Jeep is running very good right now and I'm happy with the tune. Thanks.

'05 Liberty CRD Limited
Factory Off-Road Package
Daystar spacer lift/Conduit washers
Skyjacker H7088s in the rear
Renegade wheels
255/70-16 General Grabber AT2s
GDE HOT Tune
EHM
No clutch fan
"Euro" TC
TDIwyse

Joined: 01/10/2009 06:58:20
Messages: 54
Offline
This question is good timing as I was about to re-address this issue since I’ve been keeping track of many tanks and multiple changing variables.

Variable 1 (and 2): Tires (and brakes).
Back in Oct I switched from the stock tires to Cooper Discoverer ATR 215/85R16 Load E tires and had a huge hit in mpg’s. Like 20-30% huge. Part of the issue was my brakes started dragging immediately after this switch and actually warped a rotor in the first few days following the switch. Tore apart the calipers, re-greased, bled brake lines, etc. which helped but still had a big loss in mpg’s of about a 10-15%. That was before temps got really cold.

Recently did an experiment and switched to General Grabber HTS tires (235/75R16) partially due to Consumer Reports (had rolling resistance data -- http://access.gale.com/widgets/cr/pdfs/suvtires.pdf) and TireRack ratings and got back close to 8-10% of mpg’s compared to the ATR’s for similar winter driving conditions (sold the ATR’s on Craigs List). However I still have what I consider to be a BIG hit in mpg’s when the temps fall below ~20 F.

Variable 3: Temps.
Looking at my mileage logs and trying to isolate for temp variability it looks like below ~15-20F I see a dramatic drop off in mpgs. At least a 15% drop compared to above 20F. I’m not sure if this is due to the automatic transmission or something with the engine properties or the tune?

I have a ~28 ml round trip (14 ml one way mostly 55 mph county roads) and on the mornings (after sitting overnight in an attached garage, being plugged in) it takes about 2 mls before the TC will lock up on cold mornings. After work sitting all day it takes about 3-4 mls to lockup the TC for the drive home. The colder the day the longer it takes to lockup. However, even when the TC locks the mpg displayed by the EVIC is dramatically lower on sub 20F days. I have cardboard covering most of the radiator to help warm up the engine and keep it warm. I’ve seen as low as 21.7 mpg hand calculated on tanks where the ambient air temps are averaging below 10F. But on tanks with temps mainly between 20-40F I get 26-27 mpg. Last fall (before the ATR tires) on the tune when temps were above 60F I was getting 28-30 mpg for back and forth to work.
I’ve played with enabling and disabling the viscous heater. Measured data shows better mpg’s on average for similar cold conditions with disabling the viscous heater (pulling the relay). The mpg hit for the time its running is really large and it only takes about 1 ml longer of my drive to get the coolant up to temp without it.

Sooooooooo . . . since I’m new to the Liberty CRD in winters, and new to this automatic transmission (mainly driven manuals where I get to choose what gear I’m in), is the cold weather mpg hit an artifact of the engine, transmission or tune? Or is it something else all together?

Confused in Iowa . . .

2006 Liberty Limited CRD
2004 Ram Quad Cab 4x4 Cummins
2001 VW Jetta TDI
1990 YJ with 2006 Cummins B3.3T
WXman
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Joined: 29/01/2010 14:53:49
Messages: 28
Location: Kentucky
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Your load range E tires are going to be really hard on MPG numbers because A) "E" tires are meant for 1-ton trucks and are VERY heavy tires and B) they are taller than stock and put more leverage against the drivetrain. I stayed away from "E" rated tires on purpose. Going with a "P" or "SL" rated tire is much more suitable for the Jeep. However, my Grabber AT2 tires did not get good marks from CR in the rolling resistence dept...so my tires are not exactly helping my MPG figures either.

I went out last night and verified my odometer. It is in dead lock-step with the speedometer. GPS shows my speedo to be 1 MPH too fast at highway speed. So my odometer is only 2% off. It appears that this tank is going to end up around 20 MPG. But...the temp. is 6 degrees this morning. It's been a cold winter. I'm very hopeful that when Spring comes...I can get at least 25 MPG average. If I can do that, on these AT tires, I'll be very happy.

'05 Liberty CRD Limited
Factory Off-Road Package
Daystar spacer lift/Conduit washers
Skyjacker H7088s in the rear
Renegade wheels
255/70-16 General Grabber AT2s
GDE HOT Tune
EHM
No clutch fan
"Euro" TC
flman
[Avatar]

Joined: 28/08/2009 19:59:32
Messages: 74
Offline
TDIwyse wrote:
I have cardboard covering most of the radiator to help warm up the engine and keep it warm.
Confused in Iowa . . .


Make sure the card board is not blocking air flow to the CAC?

Still Burnin Oil since 1992!
2010 John Deere 2305 3 cylinder Yanmar
GDE HOT!! Tuned 2006 CRD LTD Silver, Euro TC, GDE Tuned TCM, B&M Trans drain kit
GDE ECO Tuned 2006 CRD Sport Black, B&M Trans drain kit, Front and rear hooks, Full Skids
GDE ECO Tuned 2005 MB 2500 Sprinter Van
2010 MB 2500 Sprinter Van
GreenDieselEngineering
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Joined: 10/07/2009 07:25:47
Messages: 357
Location: Southeast Michigan
"Sooooooooo . . . since I’m new to the Liberty CRD in winters, and new to this automatic transmission (mainly driven manuals where I get to choose what gear I’m in), is the cold weather mpg hit an artifact of the engine, transmission or tune? Or is it something else all together?"





The cold weather does have a significant effect on fuel economy and is a combination of several parameters. Transmission has a warm-up cycle based on fliud temp and it usually lasts between 2-10 minutes depending on load/drive cycle. During this time it tends to hold a lower gear to increase rpm and warm up the trans fluid faster, at a certain temp the shift strategy reverts to normal mode. This also holds true for the engine warm-up, uses more fuel to increase heat output, two pilot injection events and longer combustion heat release aid in transferring more heat to the head and block. The warm-up cycle is off when coolant temps reach the 140's.

The short trips with intervals of 3+ hours will have a negative impact on fuel economy. The severity increases with the length of soak, lower ambient temps, snow, 4x4, etc.

Low coolant temps (160-176 F) in the winter are not directionally good and a 195 F thermostat would provide significant benefit. Increased oil temps and liner temps will help make the combustion more efficient and further reduce HC emissions, all leading to better fuel economy.

The CRD is best suited for longer periods of highway driving and this becomes more evident during the winter months. City driving has no TC lock-up in the trans and the repeated warm-ups are just not helping. Blocking part of the radiator fresh air flow should help somewhat, but we have not tested it to validate the impact.

The confidence behind the wheel during snowy winter driving is still the primary motivator for the KJ, especially the ESP on the 2006 models. We tend to get to throttle happy and the ESP keeps everything in line. Our 2005 with turbo kit is for the fun factor...however, without snow tires it is mainly used on clear roads.

Thanks for the feedback.
GDE

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TDIwyse

Joined: 01/10/2009 06:58:20
Messages: 54
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flman wrote:Make sure the card board is not blocking air flow to the CAC?


It's three sections of black painted (so you can't see it's there unless you look real close) cardboard that slip in behind the grill when the hood is opened. They do block most of the CAC. The bottom air inlet under the bumper is still all open. Don't all the winter covers block most of the CAC on diesel trucks? My Ram and YJ Cummins also get the black cardboard in the winters unless they're towing. The TDI has never been cardboarded.


2006 Liberty Limited CRD
2004 Ram Quad Cab 4x4 Cummins
2001 VW Jetta TDI
1990 YJ with 2006 Cummins B3.3T
 
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