Using PLX KIWI MPG to reduse fuel consumption

I bought a KIWI MPG trip calculator to be able to measure the fuel consumption in my Citroen Berlingo 2004. My hope was that it would help me learn how to drive the most fuel efficient, and I will give it credit for teaching me a few things. It does, however, have some bugs. Here is my short test and review.

It all started out after reading the tips on Ecomodder.com. Reading, understanding and then following these tips will most likely have the biggest impact on saving you fuel. But I like statistics and to compete with myself using the least fuel. That is why I bought the KIWI MPG.



I plugged the unit into the OBDII port in my car. The KIWI MPG indicated that my car had a "CALP" sensor, which is the one that needs to be calibrated. After some days of driving, I changed the 1.00 value to 0.27 to get fuel consumption close to actual use. Then I have tested it for several months.

It is interesting to see the fuel consumption when driving. Sometimes a try to push the clutch pedal to the floor and just coast, and then compare it to having the enging engaged and running. But can the display be trusted? When going downhill with the gear engaged and no throttle, I have been told that the car should be using no fuel. The KIWI MPG should be showing 0, but it is showing something like 2.4 (liter/100km). Another bug is that the unit does not always start when starting the car. Perhaps as often as 1 out of 3 times it does not start. Then I have to use the on/off switch. When I stop the car, the KIWI MPG does not always stop. It thinks the car is running and the average fuel consumption keeps rising, which ruins the average function. Twice it has gotten some kind of hick-up, showing much too low fuel consumption. Turning it on-off-on brings it back.

The best I can say is that it is an educational toy. After all it is fun, and I have managed to lower my fuel consumption with 5-10% after using it, or is it just because I am using the techniques from ecomodder.com ?

Update: This winter I was not using my car for a week, and after that I could not start it. Flat battery. Then I recalled how I had noticed one morning that the entire windscreen had been covered by a thin layer of ice, except for one small spot. This spot was about a foot above the location of the KIWI MPG. You can feel that the unit is warm even when it is in standby. I have now disconnected the unit, and have had no problems starting the car later this freezing cold winter in Norway. So make sure you unplug this unit if you are not going to use your car for a week or so.

Summary in Norwegian: Har din bil ikke en forbruksmåler? KIWI MPG er en bensinmåler du kan ettermontere i de fleste biler. Imidlertid er jeg noe usikker på hvor godt den egentlig måler forbruket. Det er en morsom dings. Kan kappe kjøre med meg selv til jobben for å se om jeg kan forbedre forbruket fra dagen før. Men jeg er ganske sikker på at det er teknikkene fra ecomodder.com som er det som virkelig monner. Enheten bruker mye strøm i standby, så den bør frakobles hvis du parkere bilen over lenger tid.

DIY heat exchanger for your shower

Update December 2011: You may now buy the new affordable DWHR unit for stand alone shower cabinets at the HeatSnagger Shop  (Norwegian link: Varmegjenvinner for dusj )
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Update April 2011: Arthur and I have joined forces and are now working on a commercial, low cost DWHR unit based on this blog post. You may follow our progress at Meander Heat Recovery
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Nov 2009:
I got an E-mail from Arthur Kimmels. He has come up with a DIY concept for a small shower heat exchanger, a drain water heat recovery (DWHR) unit. I really like the simplicity of this design. His mail speaks well for itself, so here it is:

Hei Svein,

With interest I read your blog about miljødusj http://urge4lessenergy.blogspot.com/2008_11_01_archive.html. I had been walking around with a similar idea of building a heat exchanger for the shower (before I read about miljodusj, but inspired by some products on the Dutch market), and after some months of thinking and building I installed it today. Attached you will find some pictures of the unit. It is built of wood, coated with fiber glass and polyester. It measures 85x32x12cm. The water channels have an inclination of approximately 1cm/m. The heat exchanger is built of ca. 4m copper, 12mm diameter and soldered together. It works as 'counterflow'. A disadvantage of this setup is the pressure drop/flow reduction due to the long PEX/copper/PEX length (ca. 8m), but I measured this to be within acceptable limits for my setup. The measured temperature increase at a flowrate of ca. 10liter/min was 23.3(out) -8.8 (in) or 14.5degC. Total material cost was ca. NOK 1500, including PEX tubes to and from the unit. (The thermometer in the picture measures at the in and outlet, I removed the 'indoor' sensor from the housing and soldered it to some wire.)

Feel free to add to your 'blog'.

Kind regards, Arthur Kimmels

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Summary in Norwegian: Arthur har laget en enkel varmeveksler for dusj. Avløpsvannet fra dusjen brukes til å forvarme kaldtvannet som kommer inn i dusjen. Temperatur økningen på kaldtvannet er målt til 14.5 C. Det medfører at man bruker mindre varmtvann og dermed sparer energi. Spillvarme gjenvinning i praksis.

The most efficient way to boil water

This is a follow up of a great article by Pablo at the Treehugger http://www.treehugger.com/files/2009/11/electric-kettle-stove-or-microwave.php where he tested the efficiency of different ways of boiling water. By bringing 350ml of 17°C water to a boil and measuring the energi used, he found the efficiency of using a pot on the stove to be 30.5%, a microwave 47%, and an electric kettle 81%.

I have been thinking of how to make coffee in the morning. I can use the drip brewer or the Frensh press pot. So I first repetead the Pablo test with our 2000W electric kettle. It took 77 seconds to bring the water the 83 C° up to a boil. Actually slightly shorter, but I timed it to the point where the kettle turned it self off. The specific heat of water is 4.180 kJ/kgK, which means that it takes 4,180 kWs to heat one liter one C°. Needed energy transfered to the water is then 0.350 l * 83C°*4.180 kWs which is 121.4kWs. The kettle averaged 2000 W and used 77 seconds, which is 154 kWs. From this I get the efficiency of my electric kettle to be 78%, which is close to what Pable got. Then I tried the drip brewer. It averaged 950 W and after 153 seconds it was done, but the next 15 minutes it turned it self on again four times for 6 seonds each time. So at the time of automatic shut off it had been running for 177 seconds. 168.2 kWs turns out to be an efficiency of 72%. I did this test with 350 ml so it could compare to Pablos test.
For us, a more realistic water use is typical 700ml, so after waiting for an hour, I redid the tests with twice as much water. The result from this was that the drip brewer was 95% efficient and the electric kettle 88% efficient. So for our family, the drip brewer is the most efficient way boiling water for coffee.

Summary in Norwegian: Det kreves store mengder energi for å varme opp vann. Derfor er det lønnsomt å være bevisst på hvordan man varmer opp vann. Konklusjonen fra denne testen er at en kaffe trakter er den minst energikrevende måten å lage kaffe på.

Moving hot air from ceiling to floor

I have been contacted by a lady, Kari, that has a vertical pipe that she uses during the winter to move hot air from underneith the ceiling to the floor in her small house. It is about 8 ft tall, 4 inch wide and has a 7W fan inside the pipe. In her first year in the house she was often cold on her feet, but after installing the vertical air transporter her feet were much warmer. Before starting the fan in the morning she measured 18C (64F) three feet off the floor, and 13C (55F) at the floor. After running the vertical air transporter for 3-4 minutes the heat was distrubeted more evenly such that the temperature at the floor also was 18C (64F). She claims to have saved a lot on her heating bill by using this for one winter, comparing it to the heating bill from the previous winter. She has been trying to get Enova interested in the consept and get them to promote the consept as a general energy saver in Norway, but without much luck. So is this a working consept for saving energy?

I think it can be compared to using a celing fan. During the summer it blows cold air down at you and you feel cooler because of the wind chill factor. During the winter it can be reversed to slowly rotatet the air up and then down the sides of the walls. It must be done slowly so it does not create any noticeable wind chill factor, as it will make the air feel cooler. Slowly mixing the air evenly is known to save energy during the heating season. Energy Star: Using the Ceiling Fan Year Round It should not matter how you mix the air as long as it is done slowly. Kari measured as much as 5 C difference between floor and 3 feet up. I would think that in particulare a house with cold floor will benefit from mixing the air, as this will probably be where the highest difference is in vertical temperature. If mixing the air will help you lower the average temperature in the room with 5 C then the saving would be as if you turned down your thermosate with 5 C, which should give a noticeable difference on your heating bill.

Great savings with extra water heater insulation

We have under the kitchen bench a 120 liter / 2000W electric water heater from http://www.oso.no/ Several spots outside this was warm to the touch, as indicated on the picture. I called technical support at Oso and they could confirm that it was OK to add extra insulation anywhere, also including the plastic lid that cover the ectrical wiring inside. So I used some spare insulation material and wrapped some plastice aound it all, and taped it up. For the pipes I got special insulation to wrap around the pipes. I have previously measured the standby energi consumption to be 1,8kWh/day. With the added insulation it as dropped to 1,2kWh/day. (You can measure the standby losses by measuring the energy used for a weekend when you are not at home using hot water. Use a plug in meter and just read off how many kWh that has been used to keep the water hot when you where gone).

We have the heater set at 65 C. Our family of five use about 7-8kWh a day for heating water.


I noticed how the power cord to the heater got warm when it was on. I cut off 1,2m of it for an additonal saving og about 4W ( 2,4m wire, 1mm2 copper, and about 8A) when in use :-)

Summary in Norwegian: Kjenn på utsiden av din varmtvannstank. Er den varm kan du med enkle midler spare mye energi. Bruk det du måtte ha av isolasjonsmateriale (Glava e.l.) og pakke det inn i plast til slutt. Alle varmtvannsrør bør også isoleres. Besparelsen hos oss var 0,6kWh/dag. Du kan også spare noe ved å forkorte tilførsledningen til et minimum.

Cleaning and checking the heat pump

We got an offer from Lier Everk to get a service agreement for our Panasonic CS-CE7GK air-to-air heat pump. For NOK 1200,- (about $200) they would come and clean our heat pump every 2nd year. I did some research and it looks like you easy can do this yourself.

The first part is to clean the coils of the unit. Turn off the power of the unit. Remove the filter. Vacuum any dust that can be seen. Use luke varm water and dishwasher liquid (Zalo) and just spray your indoor coils. Use a towel to collect excess water dripping from the unit. The outdoor unit is cleaned the same way. Spray on. Wait for a while for the dish washer liquid to disolve dirt. Then use a garden hose with low pressure and apply water in the opposit direction of the normal airflow. Be careful not to bend any coil fins. Let the unit sit for some hours to dry before turning on power.



The second part is to check that it still delivers the heat (or cold) that it should. According to the Pabasonic service manual the difference should be at least 14 C in heat mode and at least 8 C in cooling mode. I checked ours by setting the temp to 27 C. Inlet temp showed 23C and outlet 42C. A difference of 19C (The unit using 484W). Then for fun I set the additional "Powerful" mode. Inlet temp is then 23 C and out take 48 C. (The unit using 985W). A differance of 25 C. Outdoor temperature was 13 C. If the temperature difference is less than 14C you should check that all coils are clean. If cleaning does not help, it is time to call for service.


Summary in Norwegian:

Du kan enkelt rengjøre din varmepumpe selv. Vask ved å spraye på med lunkent Zalo-vann. Utdelen kan i tillegg spyles med hageslange med lavt trykk, aluminiums finnene må ikke bøyes. Det skal være en temperatur forskjell på minst 14 grader mellom luft som går inn i inndelen og luft som kommer ut av den ved normal drift.

Insulate your unused chimney

Some years ago we had a fireplace, but we never used it that often, and there was always a cold draft from it when it was not in use. So we sold the fireplace (and got space for a home movie theater instead..) and sealed off the chimney. Much of the draft was gone, but last winter I noticed that the chimney was still very cold when touching it. Both on the ground floor, but even more on the first floor. No wonder when all that cold outside air fills the entire chimney.
So in preperation for this winter I made a simple unused chimney insulation. I used a total of seven plastic bags, each filled with some insulation material. After tieing the top of each plasticbag, I connected them all together with a string. Using a long stick a pushed the first one about 4 m ( 12 ft) down the chimney.

Then I pushed the next one a little bit shorter, and the next even shorter, and so on until the last one finshed it off right at the top of the chimney. This should defenitely slow down any cold air trying to go down the chimney this winter. Should we decide to get a fireplace in the future I can easy pull all the insulation bags out of the chimney using the string that interconnect them all.


Summary in Norwegian: En ubrukt pipe er en kald pipe. Du kan isolere pipa ved å trykke plastposer med isolasjon ned i pipa. Hvis du forbinder dem alle med et tau, så går det greit å få dem opp igjen hvis du skal bruke pipa igjen.