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  #1  
Old 07-17-2016, 01:22 PM
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MPG drop after recall?

It's been a while since I've been on here. Glad to see some of the same folks still on here. It seems like just yesterday we were playing guessing games trying to figure out what the latest reason was for our SFUs being delayed. DEF tanks? Ohhhh..... we were supposed to install those?

Anyway, I took mine in for an oil change ahead of a planned roadtrip and they said I also had to get the recalls done, so those were done too. They did the S27 shifter recall and the R69 SCR recall (edit in case it's relevant, they also did a flash of the ELSD). And then I took it on a road trip up the CA coast to Oregon.

I noticed right away that the MPG being reported on the EVIC was noticeably lower. At first I thought it was just going through the regen cycle. Normally I'd know for sure because I normally have a Scan Gauge plugged in and monitoring the temps so I can see when it's regen'ing, but I didn't have it for this trip. After a while, the MPG was still low and there was no way it was still regen'ing.

I kept monitoring and it remained noticeably lower. The overall average for the entire 700 miles was 22MPG. :-( Normally on a trip like that, nearly all freeway, I'd be up closer to 27-28MPG (I'm a little heavy on the pedal so I rarely get the 30+ I often see others get). That's a pretty dramatic difference.

I'm curious if anyone else has noticed this after the recall or whether the dealer may have screwed something up. He did say that they were unable to remove the O2 sensors when doing the SCR recall, so had to order and install new ones.

It seemed like maybe the MPG was getting better at the very end of the trip, but there wasn't enough distance left to really be sure.

Any thoughts/ideas?

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  #2  
Old 07-17-2016, 07:17 PM
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Just an fyi, there is an actual regen pid that will tell you whether you're in active or passive regen--no need to guess through use of egt or cat temp.
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Old 07-17-2016, 09:25 PM
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Re: MPG drop after recall?

I had no idea about the regen pid - learn something new everyday. Now I just need to find it. I too saw the mileage plunge after the SCR recall. Something to the tune of 3-4 mpg. After 3000 miles I have seen it come back up, but it's still about 1/2mpg less an before the recall was applied. That being said however, I did do one extended drive at a steady 55mph and easily saw 31.8mpg - and that is with a 50mm lift and 32.1" tires fitted.
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Old 07-17-2016, 10:44 PM
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Quote:
Originally Posted by Nordic1 View Post
I had no idea about the regen pid - learn something new everyday. Now I just need to find it.
Here you go; lots of good stuff in that thread. Users running stock EcoDiesels will very rarely see a passive regen (ie. value 2) it will be active regen (value = 3) or nothing. GDE tune users apparently see much more passive regen that pops on for about half a minute or so after pushing the engine hard.

Quote:
I too saw the mileage plunge after the SCR recall. Something to the tune of 3-4 mpg. After 3000 miles I have seen it come back up, but it's still about 1/2mpg less an before the recall was applied.
BTW, if you're intending to discuss fuel economy then simply giving a delta in mpg is essentially meaningless without the actual values. For example, if you travel 100 miles, the fuel economy difference of changing from 6 mpg to 3 mpg is substantially different from dropping from 150 mpg to 147 mpg. Both represent a difference of 3 mpg, but the former example would imply a difference of ~17 gallons burned, while the latter would be a difference of ~0.01 gallons.

Conversely, you can give a fuel economy delta value in L/100 km (or gallons/100 miles, if you insist) that is always comparable without needing the absolute reference. You could also give a percentage difference.
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Old 07-18-2016, 12:29 PM
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Quote:
Originally Posted by Roadkill View Post
Here you go; lots of good stuff in that thread. Users running stock EcoDiesels will very rarely see a passive regen (ie. value 2) it will be active regen (value = 3) or nothing. GDE tune users apparently see much more passive regen that pops on for about half a minute or so after pushing the engine hard.

BTW, if you're intending to discuss fuel economy then simply giving a delta in mpg is essentially meaningless without the actual values. For example, if you travel 100 miles, the fuel economy difference of changing from 6 mpg to 3 mpg is substantially different from dropping from 150 mpg to 147 mpg. Both represent a difference of 3 mpg, but the former example would imply a difference of ~17 gallons burned, while the latter would be a difference of ~0.01 gallons.

Conversely, you can give a fuel economy delta value in L/100 km (or gallons/100 miles, if you insist) that is always comparable without needing the absolute reference. You could also give a percentage difference.
I've noticed the phantom passive regens. Has anyone said why this is?
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Old 07-18-2016, 01:09 PM
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Originally Posted by Floridaman View Post
I've noticed the phantom passive regens. Has anyone said why this is?
What do you mean by "phantom"? The context that's described seems reasonable for a brief, incomplete passive regen--viz. the gases briefly got hot enough to burn a bit of soot. I presumed people were describing a GDE efficiency tweak that helps to stretch the interval between active regens.
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Old 07-18-2016, 01:13 PM
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Quote:
Originally Posted by Roadkill View Post
What do you mean by "phantom"? The context that's described seems reasonable for a brief, incomplete passive regen--viz. the gases briefly got hot enough to burn a bit of soot. I presumed people were describing a GDE efficiency tweak that helps to stretch the interval between active regens.
Phantom as in it pops up briefly and goes away. As in my soot % hasn't reached 80%. But I get what you're saying and it makes sense. I noticed it a few weeks back when I had quick accelerations and the EGTs spiked over 650.
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Old 08-12-2016, 01:01 AM
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MPG drop after recall?

I had the catalytic converter replaced back in December. Then two new heads on the engine in February. My mpg has dropped at least 3mpg since then. I'm struggling to keep it at 27mpg when usually this time of year I'm at 30 mpg or more.

Is it time for a trade in?


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Old 08-12-2016, 01:58 AM
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Quote:
Originally Posted by Mtn Hkr View Post
I'm struggling to keep it at 27mpg when usually this time of year I'm at 30 mpg or more. Is it time for a trade in?
Presuming you want to do a cost analysis, it's much more convenient to calculate fuel efficiency costs using the reciprocal measurement of fuel per distance (e.g. L/100 km or gallons/100 miles) rather than distance per fuel (e.g. mpg).

27 mpg is roughly 8.7 L/100 km
30 mpg is roughly 7.8 L/100 km

The difference is about 1 L/100 km, which is about 0.4 gallons/100 miles. Let's call it half a gallon per 100 miles, or 5 gallons of fuel per 1000 miles. How far do you typically drive a vehicle before it gets replaced? Even at 100,000 miles and $4/gallon for diesel, that's only roughly $2000 more in fuel over the entire ownership duration—certainly less than the first year depreciation on these Jeeps. If you really want to geek out with the numbers, you can use Google Calculator.

Of course, YMMV (haha) and only you can determine how much the intangible benefits associated with a brand new vehicle are worth to you. Thinking outside the box, you might recover some fuel economy if you were to obtain a GDE Hot Tune, which should definitely be on your list of options to consider anyway if you are planning to retain this vehicle long-term. You'd have to weigh the potential risks to warranty coverage vs. the expected engine lifetime improvement, etc.
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Old 08-12-2016, 10:27 AM
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Re: MPG drop after recall?

I am getting the S27 done today, but noticed a drop in mileage with the previous TCM software install I got about 5k miles ago. Also was re-gifted the rough 2-1 downshift, lucky me!

Getting the thread back on topic...anyone else seeing reduced mileage with the recent software packages?
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Old 08-12-2016, 09:04 PM
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Re: MPG drop after recall?

Roadkill,

Good point. But put aside the financial aspect...if the engine can't maintain the same mpg due to software updates and/or recalls, is it really a reliable product?

I'm disappointed in how this Jeep turned out. If there were more options out there, I'd probably switch. Now I just feel stuck with what I have or getting a '17 seems to be the only alternative.


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Old 08-14-2016, 07:12 AM
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Re: MPG drop after recall?

I have never gotten the 30+ MPG that I got when the vehicle was new... Ever since the 1st flashes, RRT's, new cat's and updates I can barely crack 27-28 on 200+ mile highway trips any more. 38K miles now. Still like the vehicle very much, but would like to tell every one it is still 30+ MPG...but it's not.....
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