Go Back   Jeep Garage - Jeep Forum > Jeep Platform Discussion > Grand Cherokee - WK2 - > Engine Performance/Intakes/Exhausts

Join Jeep Garage Today
Reply
 
Thread Tools Display Modes
 
  #1  
Old 08-13-2012, 07:40 AM
benny82's Avatar
Member
My Jeep: 2012 3.6L WK2
 
Join Date: Jul 2012
Location: perth ,western australia
Posts: 18
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 772
benny82 has a reputation beyond reputebenny82 has a reputation beyond repute
fuel economy going crazy with cai!

Hey guys i fitted a k&n cai and a modern muscle ported throttle body a couple of days ago to my pentastar and it went great but yesterday i noticed fuel average went up to 25-35 L/100km and that bar that goes up and down acting strange ,when idol that bar goes right up. Anyone no whats going on?? air leak in the cai ,throttle body not the same or the ecu and air flow sensor not working please help!
__________________

__________________
Reply With Quote
  #2  
Old 08-13-2012, 05:05 PM
armoredsaint's Avatar
Premium Member
My Jeep: 2012 5.7L WK2
 
Join Date: Nov 2011
Location: Ohio
Posts: 1,288
Thanks: 12
Thanked 11 Times in 11 Posts
Rep Power: 234385
armoredsaint has a reputation beyond reputearmoredsaint has a reputation beyond reputearmoredsaint has a reputation beyond reputearmoredsaint has a reputation beyond reputearmoredsaint has a reputation beyond reputearmoredsaint has a reputation beyond reputearmoredsaint has a reputation beyond reputearmoredsaint has a reputation beyond reputearmoredsaint has a reputation beyond reputearmoredsaint has a reputation beyond reputearmoredsaint has a reputation beyond repute
Re: fuel economy going crazy with cai!

did you disconnect your - cable?
__________________

__________________
2012 Jeep Grand Cherokee Overland 4X4 - Hemi V-8
Mineral Grey with Saddle interior / Quadra Lift / ACC / BSW / FCW / Pano-roof /
aFe Pro-Dry S Filter / Borla Cat-Back Exhaust
Reply With Quote
  #3  
Old 08-14-2012, 12:42 AM
benny82's Avatar
Member
My Jeep: 2012 3.6L WK2
 
Join Date: Jul 2012
Location: perth ,western australia
Posts: 18
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 772
benny82 has a reputation beyond reputebenny82 has a reputation beyond repute
Re: fuel economy going crazy with cai!

no i didnt i thought it was just a safety thing like working on a car unisolated ,the k&n instructions didnt say anything about the computer has to reset, i dont want to call the dealer they might say void warrenty!
__________________
Reply With Quote
  #4  
Old 08-17-2012, 09:07 AM
Member
 
Join Date: Apr 2012
Posts: 99
Thanks: 0
Thanked 3 Times in 3 Posts
Rep Power: 1218
Doc_d has a reputation beyond reputeDoc_d has a reputation beyond reputeDoc_d has a reputation beyond reputeDoc_d has a reputation beyond reputeDoc_d has a reputation beyond reputeDoc_d has a reputation beyond reputeDoc_d has a reputation beyond reputeDoc_d has a reputation beyond reputeDoc_d has a reputation beyond reputeDoc_d has a reputation beyond repute
Re: fuel economy going crazy with cai!

V6 or Hemi? I haven't looked at my Hemi yet to see if it's a mass air flow system or a speed density system.

If it's a speed density system it means that it isn't measuring the phsyical amount of air entering the engine like a mass air flow system does with a MAF sensor. Instead it estimates the amount of air entering the system based on known volumentric efficiencies of all the parts involved (including the throttle body).

So if you put on a larger throttle body, the system is completely misjudging the amount of air entering the engine which may lead to miscalculating the fuel economy.

If it is a speed density system then this is what is happening. It thinks X amount of air entered the engine based on estimated volumentric efficiencies of all parts involved (including the throttle body). But your larger throttle body really let 1.2X amount of air in. It calculates that it needs Y amount of fuel for X amount of air to hit it's target air/fuel mixture (probably stoich at idle/light cruise). It injects Y amount of fuel. The O2 sensors read that the mix is too lean. The ECU adjust short and long term fuel trims until it is now injecting 1.2Y amount of fuel. So now the computer thinks that it must inject 20% more fuel than it should normally have to. I wonder if that somehow feeds into the fuel economy calculations and is throwing it off.

This is just a guess. And if your engine is using a mass air system (i.e. if you have a MAF sensor) then this wouldn't apply.
__________________
Reply With Quote
  #5  
Old 08-17-2012, 11:29 AM
ekaz's Avatar
Member
My Jeep: 2009 7.0L SRT8
 
Join Date: Oct 2009
Location: Chicago
Posts: 561
Thanks: 1
Thanked 11 Times in 10 Posts
Rep Power: 2514
ekaz has a reputation beyond reputeekaz has a reputation beyond reputeekaz has a reputation beyond reputeekaz has a reputation beyond reputeekaz has a reputation beyond reputeekaz has a reputation beyond reputeekaz has a reputation beyond reputeekaz has a reputation beyond reputeekaz has a reputation beyond repute
Re: fuel economy going crazy with cai!

Disconnect the negative battery cable for 15-20 minutes, let everything reset and then drive it. It'll need to do some re-learning
__________________
Unlawful Gathering
Click for details!
2012 300 SRT
2011 GC Overland
2009 Modern Blue Pearl (for sale)
Headlights by DC Customs
Powered by PWR
Shifted by SHR
Tooned by Toona
Blinged by Billet Technologies
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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Better fuel economy..? JeremyJamesDec15 Engine Performance/Intakes/Exhausts 28 04-29-2013 08:10 AM
Fuel economy... watchful Audio/Visual/Navigation 21 03-07-2012 02:02 PM
Need better fuel economy qbny94 Engine Performance/Intake/Exhaust 21 09-05-2011 09:32 AM
Fuel economy 5.7 hemi DanD2124 Grand Cherokee - WK 48 05-06-2011 02:00 AM
Another Fuel Economy Threadd jeepgcoman Grand Cherokee - WK 0 01-20-2011 09:31 PM

» Random Garages

Blue

Emshighway

WK

Bogie
Add your Jeep
Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 10:20 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Copyright 2012 - JeepGarage.Org
The Jeep Grand Cherokee Owners Community