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TDIwyse

Joined: 01/10/2009 06:58:20
Messages: 54
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It was warming up a little last week and into the weekend. But after Monday it started getting cold again. My mileage was really going up and I had removed the mechanical fan (following GDE's lead) to try and improve mpg's.

Filled up and started tracking mileage again. The truck stop I fill up at says they sell straight #2 (they say that's what the truckers want since it doesn't impact their mpg's as much as blended fuel) that is only guaranteed to not gel down to 0F and strongly recommends antigel additive, which I use. I've done some test on their fuel and without additive it did gel at about -5F.

Using the EVIC for mpg data on my 14 mile commute shows some interesting data on mpg vs temp. This data is for the exact same fuel/vehicle configuration (it was plugged in for 1.5 hrs before starting both times) and identical wind conditions (verified from www.wunderground.com archived data). The only real difference is ambient temp.

Monday morning commute the temp was ~15F and there was an 8mph NW tailwind. EVIC recorded 29.5 for the entire trip into work (from garage to parking spot). This wouldn't be much different than hand calc results from last Fall when things were much warmer, but many aspects of the vehicle are different. Today the outside temp was ~ -4F and there was an 8 mph NW tailwind. EVIC recorded 27.1.

Since getting the HOT tune with the recalibrated EVIC tweak from GDE the EVIC has been consistently accurate to within ~4-7% of hand calculated results (consistently optimistic, but consistent nonetheless) when I leave the EVIC alone between fillups. So it appears there is steep drop off in efficiency (roughly a 9% reduction) on my vehicle due solely to ambient temps when they approach 0F.

Does it make sense that there's that sharp of a drop off due to temp?


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

Joined: 01/10/2009 06:58:20
Messages: 54
Offline
Weather is providing some good variable control. This morning 0F and 8 mph NW winds. Same procedure/configuration as above yielded 27.2 mpg on EVIC. Seems like my cliff happens somewhere between 0 and +15F.

Could my air intake sensor be getting saturated below ~15F so it doesn't continue to provide correct data to the ECM for use in making timing of injection calculations correctly? I assume the ECM advances the timing as air temps go down . . .

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: 348
Location: Southeast Michigan
The sensor is designed to read temps down to -40 F. The tune continually adjusts the timing advance based on temp and reaches full correction at -15 F. Antoher way to boost intake manifold air temps in the winter is to remove the snorkel attached to the airbox. In this manner the engine will pull warmer air from inside the engine compartment. We do not have fuel economy data for this change, but it is directionally correct. During the summer months the snorkel helps efficiency by reducing intake air temps and is recommended in warmer climates.
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TDIwyse

Joined: 01/10/2009 06:58:20
Messages: 54
Offline
Blocking the air intake so it draws warmer air seems to have had a more dramatic impact on mpg than removing the rad fan. Last fill up was 27.8 mpg hand calculated which is by far the best its been for a long time. Although road conditions are better and the afternoon post-work temps are getting warmer so there are some variables I'm not controlling properly.

I've got the V6 airbox mod so to block the "cold air" I removed the snorkle section that goes up to the space by the hood and blocked that area with some foam water pipe insulation. Also used the insulation to block a section by the side of the radiator in that area that allowed air to enter. Morning commute mpg's shown below are not significantly higher than previously recorded for these types of temps, but the return home mpgs and overall mpgs are much better. What is encouraging is the last two readings that had less optimum wind conditions for the commute but still held on to good #'s.

I also did some more playing with the viscous heater relay in place (all data below has the relay in) and with GDE's new algorithm for shutting it off sooner I am not seeing much of a difference in mpgs . . . which is a good thing so I'll keep it in place from now on.


Date Air Temp Wind spd Wind dir EVIC mpg* Vehicle Condition

3/1/2010 25 F 8 mph NW 29.7mpg No fan, VH relay, blocked intake, coolant heater plugged in 2 hrs before commute.
3/2/2010 14 F 10 mph NW 29.5mpg No fan, VH relay, blocked intake, coolant heater plugged in for 2 hrs before commute.
3/3/2010 11 F 10 mph NW 29.5mpg No fan, VH relay, blocked intake, coolant heater plugged in for 2 hrs before commute.
3/4/2010 11 F 5 mph NW 29.7mpg Re-fuel, No fan, VH relay, blocked intake, coolant heater plugged in for 2 hrs.
3/5/2010 17 F 5 mph NE 29.6mpg No fan, VH relay, blocked intake, coolant heater plugged in for 2 hrs before commute.



* Morning commute direction is primarily SE

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: 348
Location: Southeast Michigan
Great data! The warmer intake air can become significant especially with the cold temps you experience everyday. Almost 28 mpg in the winter is very good, our vehicles do not fair as well due to mainly city driving with several 2 hour soaks throughout the day. Removing the snorkel is an easy way to gain back some fuel economy during the winter.
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TDIwyse

Joined: 01/10/2009 06:58:20
Messages: 54
Offline
I used my "outdoor" thermometer to measure the temp of the air going into the air box by putting the probe down in side there. Around town it showed a fairly descent increase above ambient, but at 55-60 it really was only about 4-5 F above ambient. I was a little surprised at that.

Since I recently got a set of Samco's I had the old CAC hoses sitting around. I just used the old CAC hose from the driver side to redneck up a snorkel that draws air for the intake over by the engine cover/radiator fan shroud. According to a test run tonight this has increased the intake temp above ambient to about 17-20 F at 55-60 after the radiator heats up. It was kind of neat to see this temp jump from ~4F to ~20F above ambient when the engine got up to temp. I've also added a block off to the lower radiator grill opening (along with the upper radiator opening I've been running). The weather isn't cooperating due to a low pressure system bringing in rain and S/SE winds so I'm not sure if I'll get a good controlled comparison of whether or not this does anything. Warmer temps are coming as well so this experiment might get put on hold until next winter. . .

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

Joined: 01/10/2009 06:58:20
Messages: 54
Offline
This morning the temp was 41, SE wind at 6mph (head wind), wet roads but still pulled down a 29.7 according to the EVIC. Yesterday without some of this new grill/intake blocking stuff the temp was 35, SE wind at 10mph (headwind), wet roads gave a 28.2 according to the EVIC.

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

Joined: 10/07/2009 07:25:47
Messages: 348
Location: Southeast Michigan
You have the makings of a good way to improve the KJs' fuel economy next winter. The mechanical fan helps throw the heat toward the airbox and with your "winter" snorkel it should have a significant effect.

Low speed was the main reason to have the snorkel routed in front of the radiator due to high levels of heat soak and recirculation, at higher speeds flow through the engine bay is fairly high and some spots are hotter than others.
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