How to Tune the MPG estimate in the DIC.

**lightfoot__** · 01-17-2008

I have heard that the dic uses the IFR table, so since mine was off 5-10% I added 5% to the ifr table and then fixed my maf table for fuel trims. My dic showed 26.7mpg I got 23mpg. It is not any closer. How do you tune the dic estimate to be right?

(ps I search clubgp and pt forums and didn't find anything to help, at club gp someone asked and they just got reffered to pt forums, I went there, searched, nothing on the term "dic".)

Can a mod change the heading to quesiton please?

**DuBob** · 01-17-2008

Can a mod change the heading to quesiton please?

Done

Good question BTW, I've wondered this myself.

**SyntheticShield** · 01-17-2008

I recall Jerry or someone addressing this issue and I remember it being said that they had tuned it to where it was maybe a tenth or two off at worst. Now ask me where I saw that or where it was posted and I'll just stare off into yonder. I know that isnt much help other than to reinforce that it can be done.

I thought Jerrys Tuning Notebook dealt with this, might want to check there.

**Toasty** · 01-17-2008

Originally Posted by SyntheticShield

I recall Jerry or someone addressing this issue and I remember it being said that they had tuned it to where it was maybe a tenth or two off at worst. Now ask me where I saw that or where it was posted and I'll just stare off into yonder. I know that isnt much help other than to reinforce that it can be done.

I thought Jerrys Tuning Notebook dealt with this, might want to check there.

yep, it's in the wiki

- Make sure your IFR is the correct one for your car. This does 2 things. First is that
your DIC indicated mileage indicated will be pretty accurate, and second is that it

will be better able to meter the fuel out more accurately. Stock injectors = stock IFR.

**IndeedSS** · 01-17-2008

If you want more infomation from Jerry, register at HPTuners as this is his new tuning forum hang out.

**Trannyman95** · 01-18-2008

The fuel trims have to be as close to 0 as possible as if the pcm has to add or remove fuel in the fuel trims the result will show up on the DIC. Example.... if you added 42lb/hr injectors to a stock pcm tune then your DIC generally will tell you you are getting 36-39mpg on the highway. If you look at the LTFT while driving as it says this it will probably be in the -16.4 to -22 range so the pcm is pulling out a lot of fuel from its base fueling to compensate for the injectors, but unfortunately throws off everything when the trims are off that much. All the cars I have tuned with good fuel trims have pretty accurated DIC mpg readings and I found it best to reset the average right after a fillup at the gas station and AFTER you leave and reset it immediately while rolling down the road so it doesnt start at 0 from sitting still and have to work its way back up.

**IndeedSS** · 01-18-2008

Originally Posted by Trannyman95

The fuel trims have to be as close to 0 as possible as if the pcm has to add or remove fuel in the fuel trims the result will show up on the DIC. Example.... if you added 42lb/hr injectors to a stock pcm tune then your DIC generally will tell you you are getting 36-39mpg on the highway. If you look at the LTFT while driving as it says this it will probably be in the -16.4 to -22 range so the pcm is pulling out a lot of fuel from its base fueling to compensate for the injectors, but unfortunately throws off everything when the trims are off that much. All the cars I have tuned with good fuel trims have pretty accurated DIC mpg readings and I found it best to reset the average right after a fillup at the gas station and AFTER you leave and reset it immediately while rolling down the road so it doesnt start at 0 from sitting still and have to work its way back up.

Dave tuned mine and iirc actual mpg is within 1 mpg of the DIC reading.