Computer MPG - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > ZJ Grand Cherokee Forum > Computer MPG

ROCKRIDGE4WD Introduces a NEW Jeep Wrangler JK *led* tail ANOTHER Rockridge4wd Creation!! Spare Tire Carrier Delete Building a Bumper?

Reply
Unread 12-19-2004, 04:57 AM   #1
gregoryc.
Registered User
 
Join Date: Sep 2004
Posts: 9
Computer MPG

Anyone know what the onboard computer uses to calculate the instant mpg? I would assume it uses engine rpm, throttle position and mph. Also, how accurate is it? I have a 2000 GC Laredo and it tacks about 2000, 2100 around 70 mph. Is that too high.
Thanks

gregoryc. is offline   Reply With Quote
Unread 12-19-2004, 07:47 AM   #2
Texas ZJ1
Jeep Jedi Master
 
Texas ZJ1's Avatar
1994 ZJ 
 
Join Date: Mar 2003
Location: Omaha, NE
Posts: 20,099
Your onboard computer uses the inputs from the ECU that calculates fuel flow based on demand and some other parameters that I get paid not to tell you.

Very top secret.

Hunter
__________________
00 4.7 Laredo...stock

94 5.9 Laredo 6.5 RE lift with 35 Maxxis Bighorns
and 33 Bridgestone Duelers
Detroit and true trac
Red Jeep Club Member
REDNECK JCM
Texas Jeep Owner #6
USN Jeep Club #4
http://www.kevinsoffroad.com/
602.841.3355

For your performance needs:

kolak@kolakperformance.com
480.998.3661
Texas ZJ1 is offline   Reply With Quote
Unread 12-19-2004, 08:41 AM   #3
jeepholic
Registered User
 
Join Date: Aug 2004
Location: Flat South Florida
Posts: 1,221
Can you give us a hint if it has anything to do with wheel rotation?
Does the sliding scale speedometer due to tire size change effect the computer MPG reading?
__________________
I use a Jeep
You drive a car
Big difference.

94 I6 ZJ at 4", 33's and front locker and 4.11 gears. Swampy Bypass.
[B]Black Jeep Club Member Ver. 2 #51[/B]
jeepholic is offline   Reply With Quote
Unread 12-19-2004, 08:46 AM   #4
Stocker
Registered User
 
Join Date: Nov 2002
Location: Jefferson State
Posts: 814
Quote:
Originally Posted by Texas ZJ1
and some other parameters that I get paid not to tell you.

Very top secret.

Hunter
Hah! Very good, Hunter - I'll use that line next time I don't have the exact answer, lol!

Gregory, some have said their computer's mpg reading is inaccurate, but mine been spot-on every time I've checked it. I'd suggest doing the math a few times to see how yours is.

Back to Hunter - I see Nick's email addy in your sig is different from what I've used (Kolak@aol.com) - has he changed it, or will either one work? Thanks...
__________________
1995 5.2 ZJ Sold... but still in the family
Stocker
Stocker is offline   Reply With Quote
Unread 12-20-2004, 01:30 PM   #5
Dacaur
Registered User
2008 MK Patriot 
 
Join Date: Mar 2003
Location: midvale Utah
Posts: 1,138
Quote:
Originally Posted by jeepholic
Can you give us a hint if it has anything to do with wheel rotation?
Does the sliding scale speedometer due to tire size change effect the computer MPG reading?
Yes, it has everything to do with wheel rotation. Basicaly all it does is take the amount of fuel you are using at any given point and calculates your instant MPG based on how fast you are going, thats what your MPG would be if neither of those 2 imputs changed..... Thats why you get 0 instant MPG when you are stopped, and you can get 99 instant MPG when you have it idleing on a steep downhill.....
__________________
Dacaur

99 WJ Laredo
2.5" Budget boost, 265/75/16 tires, K&N air filter
www.dacaur.com/jeep.html

Past Jeeps:
1992 YJ 4.0, 5 speed 6", lift 33's
1992 XJ 4.0, auto, 3" lift, 31's
1999 XJ 4.0, auto, 3" lift, 31's
1985 XJ 2.5, 5 speed, no lift, 255/70/15's
---------------
Dacaur is offline   Reply With Quote
Reply
Thread Tools


Suggested Threads





Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.