What Makes the Overhead Console Tick? - Hemi Truck Club
 
Go Back   Hemi Truck Club > HEMI | Trucks and Special Editions > 3rd Generation Ram | 2003 - 2008

Reply
 
Thread Tools Display Modes
 
Old 04-15-2015, 12:06 PM   #1
Jim-CO Chapter Dictator
 
RockyMtnXpress's Avatar
 
Join Date: Jan 2010
Location: Salida, Colorado
Posts: 2,290
Question What Makes the Overhead Console Tick?

A couple of days ago, I applied a custom "Mileage" tune to my truck via the SC tuner. This was the second time I used this particular tune, coming off from using it the first time by not being very "Impressed". However, yesterday, we were driving from Colorado to Arizona and I will admit that I was pulling some happy numbers via the overhead console. That is --- 'happy numbers' in Colorado! Once we drove by the Four Corners turn-off, the wind really begin to blow and like the old rock song it was "Against the Wind" every linear inch to Phoenix.

Now I am religious fanatic when it comes to going through the motions of fill-ups and resetting the overhead console. Such is the case when we stopped in Tuba City (AZ) for a fill-up. Remember headwind! Driving the 215 miles to my doorstep, resulted in using just over a half of tank of 87 octane. Roughly calculate, will show it at 15 and a half mile per gallon. I am not complaining considering what we had to go through. My problem is the overhead console? My readout shows 11.4 miles per gallon. Now, usually, my overhead is not that far off.

My question is this...I thought at one time I read the sensor, for the overhead console, was buried behind the headlight assembly and in part determined mpg by wind speed. Is this right? Can a headwind apply a different outcome of display and all the numbers it will show (mpg, dte)? I tried to Google for this answer, but came up with nill. Might be a 'silly question', but I am determined to know what makes this thing tick. It's just something I always took for granted...Until now!

__________________
RockyMtnXpress is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 04-15-2015, 03:49 PM   #2
Greg
 
Redtruck-VA's Avatar
 
Join Date: Jan 2011
Location: Virginia
Posts: 18,823
Garage
Don't have an answer, but interesting question.
__________________
2003 RCSB, 2wd, "Pro-Street"
6.4L/cog driven V7-Ysi/46rh trans/HTH Truckarm coilover suspension. HP Tuning...

1# 2017 HTC FASTEST HEMI List....
Current 1/4 mile [email protected] (2018)
Current 60' PB 1.351 (2019) mechanical issue for 1/4m

HTC 2018 TOTY

Support vehicle- 2007 QC G56 4x4 diesel
Redtruck-VA is offline   Reply With Quote
Old 04-15-2015, 04:02 PM   #3
2012 Truck of the Year
Engine Specialist
 
charged392's Avatar
 
Join Date: May 2011
Location: Fort pierce, FL
Posts: 17,168
Garage
The readout is done by a soeed sensor on the front wheels. Should that sensor fail for any reason it will use the rear wheel sensor for the calculation. It is strictly done of tires on the ground distance. Why it is so far off is sometimes hard to figure out. I do know that the overhead is the avg mpg not the current. So maybe it has calculated you avg 11 but this trip you got 15 doing math yourself.
__________________
"CMR TUNER" [email protected] 1/4 with a 7.32 1/8 custom long/short bars by "Me" Turbocharged 392 on 9psi S475/96/1.32 . Running thru an A518! [email protected]
charged392 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 04-15-2015, 04:39 PM   #4
Senior Member
 
MikeHTally's Avatar
 
Join Date: Aug 2007
Location: Tallahassee, FL
Posts: 5,447
Garage
Hope you're not relying on that to determine your mileage. There is only one way to get accurate mileage information, an' the computer ain't it.
__________________
MikeHTally is offline   Reply With Quote
Old 04-15-2015, 05:43 PM   #5
Matt
 
MANual_puller's Avatar
 
Join Date: Mar 2014
Location: Vinton
Posts: 2,651
Garage
That's interesting. I know mine is usually off by a couple and rarely closer than 1 off. Mine usually reads better than actual though I'd take bets the variance is in the fuel metering. Distance traveled is pretty easy. Fuel metering though, because it uses such low quantities, is tough to meter accurately. You're talking about the computer adding up a couple CC's a billion times to get a gallon. How exactly is that done on a dodge? Does it just use injector firing events and assumes they are all actually calibrated identically?
__________________
2011 Ram 2500 ST 4x4, 5.7L Hemi, crew cab, short box, 4:10 gear ratio with rear LSD, 180 amp alternator, tow mirrors w/ puddle and signal lamps, popular options group, carpet deleted, Ranch Hand front bumper, 9500# winch, pair of 100w KC lights, Magnum RT steps, Line-x sprayed bedliner, stampede o/e style fender flares, Ram branded oversize rubber mud flaps, stampede smoked bug deflector, Dee Zee toolbox

MANual_puller is offline   Reply With Quote
Old 04-15-2015, 06:07 PM   #6
The Original Bee
 
HemiSuperBee's Avatar
 
Join Date: Jul 2005
Location: DFW, Texas
Posts: 2,071
The sensor by the headlight is for outside temp reading.
MPG is determined by the pcm/ecm.
__________________
********AWARDS********

9 Best of Show
21 First Place
3 Class Awards
2 Truck of the Month
HTC Best Dressed Engine

**********************
HemiSuperBee is offline   Reply With Quote
Old 04-15-2015, 07:06 PM   #7
Senior Member
 
MikeHTally's Avatar
 
Join Date: Aug 2007
Location: Tallahassee, FL
Posts: 5,447
Garage
Quote:
Originally Posted by HemiSuperBee View Post
The sensor by the headlight is for outside temp reading.
MPG is determined by the pcm/ecm.
That's strange. Mine is determined by my right foot.
MikeHTally is offline   Reply With Quote
Old 04-16-2015, 10:50 AM   #8
Senior Member
 
HemiFun05's Avatar
 
Join Date: Jul 2007
Location: College Station, Texas
Posts: 13,172
Talking

Quote:
Originally Posted by MikeHTally View Post
That's strange. Mine is determined by my right foot.
-----------------------------------

YEP - It sure gives the most variable outcomes .


__________________
HemiFun05
'Doc'
"Christians Aren't Perfect - We Are Forgiven"
HemiFun05 is offline   Reply With Quote
Old 04-16-2015, 11:13 AM   #9
Jim-CO Chapter Dictator
 
RockyMtnXpress's Avatar
 
Join Date: Jan 2010
Location: Salida, Colorado
Posts: 2,290
Quote:
Originally Posted by charged392 View Post
The readout is done by a soeed sensor on the front wheels. Should that sensor fail for any reason it will use the rear wheel sensor for the calculation. It is strictly done of tires on the ground distance. Why it is so far off is sometimes hard to figure out. I do know that the overhead is the avg mpg not the current. So maybe it has calculated you avg 11 but this trip you got 15 doing math yourself.

(begin sheepish reply) Well --- Ok? That's what I get for reading rumored untruths about how this thing works by "Wind speed(?)". Pffffttttt! (/end sheepish reply)

With that behind us and considering (assuming) the whole thing is calculated, via on-board processor, fuel metering (?) and most importantly soceed sensor in the wheel, another question. Can road conditions throw the reading off? The reason I ask, somewhere between the 160/89 junction and Cameron Trading post it becomes a 'rollercoaster ride'. Not the type where you're going up one ridge and down another. The type where it dang nears maxes out your suspension both directions in the matter of a split second (roads here are something else). It is extreme and a real challenge on a semi full bladder (more-so when there is a headwind with gust 50-60 mph). Also as a bonus question, SC tire size selection works when the user selects 31.5" tire diameter (stock selection and with a load on the tire). This particular selections calibrates the speedometer as close to true as one can achieve as I found out with a little experimenting. The true size of the P275/60R20 tire is 33". Can this difference and road conditions cause the on-board processor mistake mpg?

The reason I am asking all the questions is this...While I do go through all the motions of fill-ups, re-setting the console and occasionally break out a calculator for spot checking, I rely on it, as a 'platform' idea of mpg. I don't really put a lot of stock in it being accurate, but it has always been close to true. That is until this last tankful and when there is a 'hiccup', I listen and do my best to learn more about the problem...If there is a problem.

Keith - You're a good guy and very knowledgeable about Rams. Appreciate it! I learn a-lot from you and of course from any HTC mems that sets me and my truck glitches straight. Thanks to all!

BTW HSB - Good to know, that sensor hiding out behind the headlight, is for temps. Little wonder, the thing hasn't melted off while driving through AZ. Appreciate it.
__________________
RockyMtnXpress is offline   Reply With Quote
Old 04-16-2015, 12:22 PM   #10
2012 Truck of the Year
Engine Specialist
 
charged392's Avatar
 
Join Date: May 2011
Location: Fort pierce, FL
Posts: 17,168
Garage
The road conditions really play no part in the calculation. The comp does all the math based on wheel speed and injector duty cycle rates. Stock trucks the overhead should be really close to actual mpg. When you mod them up is when things start to get really wacky.
__________________
"CMR TUNER" [email protected] 1/4 with a 7.32 1/8 custom long/short bars by "Me" Turbocharged 392 on 9psi S475/96/1.32 . Running thru an A518! [email protected]
charged392 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Premium Vendor Showcase
n2 Speed Edge InTune Edge OCPerformance Parts

All times are GMT -6. The time now is 02:53 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.