EVIC accuracy?

Reidsjeep · **Joined:** Tue Nov 13, 2018 10:40 am **Posts:** 18

Just made my second careful mileage calculation. First one was around town tank at 24.6 mph. Second test was 500 mile all freeway at 63 mph with cruise control, 28.2 mph. Although I was hoping for a little better freeway results from what I read here on the forum this isn't bad. My big question concerns my EVIC readouts. They were 29 and 36 respectively. I did not expect great accuracy but they were WAY off.
I have no manual for the car and I am wondering if I am not correctly using the EVIC?
Thanks

Mountainman · **Posted:** Wed Dec 26, 2018 1:19 pm

You could enter a different tire size with a starscan, but that would throw your mph off. How far off was the EVIC?

Reidsjeep · **Joined:** Tue Nov 13, 2018 10:40 am **Posts:** 18

The EVIC was 8 mph higher on my 500 mile freeway test.

TURBO-DIESEL-FREAK · **Joined:** Sat Apr 17, 2010 3:29 pm **Posts:** 1167

Reidsjeep wrote:

The EVIC was 8 mph higher on my 500 mile freeway test.

You mean MPG; yes?

Mountainman · **Posted:** Fri Dec 28, 2018 12:54 am

Reidsjeep wrote:

The EVIC was 8 mph higher on my 500 mile freeway test.

Gotta love chrysler :furious:

Reidsjeep · **Joined:** Tue Nov 13, 2018 10:40 am **Posts:** 18

Yes. 8 mpg higher. I would hope I can correct this some how. Suggestions welcomed. I am stumped.

TURBO-DIESEL-FREAK · **Joined:** Sat Apr 17, 2010 3:29 pm **Posts:** 1167

Reidsjeep wrote:

Yes. 8 mpg higher. I would hope I can correct this some how. Suggestions welcomed. I am stumped.

There are a lot more important upgrades to perform than worrying about the EVIC. It probably was deliberately designed by Daimler-Chrysler to be optimistic, just like I suspect that the engine temperature gauge to be deliberately inaccurate and non-linear.

However, if it really is that important to you, try checking with the people at Green Diesel Engineering. Perhaps in their tunes they have found a way to make the EVIC more accurate.

GordnadoCRD · **Posted:** Fri Dec 28, 2018 3:57 am

My experience with EVIC with both Mopar and Ford models, is they tend to be universally optimistic.

Most I have dealt with to any extent, adjusting them will either throw the MPH off or the MPG off. Especially with the diesel. The stock CRD knows precisely the volume of fuel that's injected into each cylinder, every time, so unless they are modified with a tune, they have the "Fuel used" part accurate. It's the tire and gearing changes that get them all mixed up.

Mountainman · **Posted:** Fri Dec 28, 2018 2:26 pm

I think the average difference of those two calculations are about 18.6%. You could multiply the evic reading by .814 and have a ballpark number.
Or .78 for mostly freeway trips (at 63mph)
Or .848 for mostly town.
FWIW :juggle:

GordnadoCRD · **Posted:** Sat Dec 29, 2018 3:21 am

It's probably different for each one, but yeah, it's consistent enough that there will be a conversion factor until something is changed.

Reidsjeep · **Joined:** Tue Nov 13, 2018 10:40 am **Posts:** 18

Thanks for the replies. I can live with it. It is so far off I wondered I was overlooking some trick to using it. Dont know yet if it is consistent. If it is it will still be of interest.

geordi · **Posted:** Wed Jan 02, 2019 5:40 pm

Wow yours is way out... I've seen them in a bunch of CRDs and they tend to be universally about 3mpg high against the hand-calculated.

One thing to be aware of for your hand calculations: Your odometer may ALSO be incorrect, reading low by anywhere up to about 15%. Use a GPS or a known-route and always fill up the entire fuel system right to having wet fuel not-draining from the filler neck. It is hard to do this, but that is the only way to eliminate as many variables as possible.

Non-standard size tires will also alter the mileage reading, heavy tires will lower economy but not change the readouts. Rotations-per-mile is an important factor in correcting the tire mileage for the odometer, this is why you just use a known-route or GPS.

TURBO-DIESEL-FREAK · **Joined:** Sat Apr 17, 2010 3:29 pm **Posts:** 1167

geordi wrote:

Wow yours is way out... I've seen them in a bunch of CRDs and they tend to be universally about 3mpg high against the hand-calculated.

One thing to be aware of for your hand calculations: Your odometer may ALSO be incorrect, reading low by anywhere up to about 15%. Use a GPS or a known-route and always fill up the entire fuel system right to having wet fuel not-draining from the filler neck. It is hard to do this, but that is the only way to eliminate as many variables as possible.

Non-standard size tires will also alter the mileage reading, heavy tires will lower economy but not change the readouts. Rotations-per-mile is an important factor in correcting the tire mileage for the odometer, this is why you just use a known-route or GPS.

I agree with this exact procedure.

I am only pointing this out because miracles CAN happen from time-to-time.

In this case I am actually agreeing with geordi.... :shock:

Ludi Neethling · **Joined:** Sat Feb 02, 2013 11:04 am **Posts:** 87

I had a leaking fuel injector. Before the leak the EVIC showed 8.7Lt/100Km. During the time the injector was faulty the EVIC showed 11.1Lt/100Km. After the fault has been rectified the reading was back to 8.7Lt/100Km. I keep record of my fuel and my average over the entire time was actually 10Lt/100Km.

TKB4 · **Posted:** Wed Jan 09, 2019 6:53 am

I agree first get a gps speed reading at say an indicated constant 50 mph ( there are many apps for phones that will do this the one I use is speedometer) Then you can just multiply the difference in gps speed and indicated speed on speedometer by 2 and you get the percent your speedometer is off. This can be used to correct the actual miles you drove . The tires that came on CRD from factory are about 29 inches in diameter so you can see that if you have 31 inch diameter tires that alone would throw speedometer off almost 7 %.

Problem is any current tires would likely be original size or larger not smaller and if they are larger it will have the effect of making speedometer show lower than actual speed and EVIC closer to actual mileage.

My CRD EVICS are off about 12 to 15 percent and with 32 inch tires they end up pretty close to correct mileage indicated but of course speedometer is now off.

I someone replaced differential gears ratio that would also change things but is fairly unlikely.

EVIC accuracy?

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