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  #1  
Old 07-16-2019, 07:32 PM
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Power loss on hot day (x5d)

Last week I was towing at max load (6300lbs, tall enclosed trailer).
My mileage was down (12 instead of the usual 13), and more importantly I couldn’t get it up over about 82mph going up some long hills. It was about a 160 mile tow. Normally I have no problems cruising at 85 up and down these hills. Ambient Temp was 91F.

After I arrive and unhitched, the X5 ran great. Plenty of power and i noticed much better than normal mileage (28 rather than 26mpg) around our rural town.

Do you think the hot weather is the main reason I was down on power?
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Old 07-16-2019, 08:56 PM
ard ard is offline
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that, or the tranny is shot.



What was the trans temperature? Exhaust gas temps got how high?


I cannot speak from X5 D experience, but ambient temps (and higher operating temps) can lead to reduced power to protect the driveline


(also, shall we assume that the 'normals' you refer to are 'normally with this same trailer'?)
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Old 07-16-2019, 10:42 PM
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I sympathize with Bfang Unfortunately BMW doesn't think we need temperature information. I have a code reader plugged into the obd2 and an app on my cellphone. I can get coolant temperature but no transmission temperature. You need to look into getting a Bluetooth or WiFi obd2 code reader and download an app to your cellphone. Then add to the set up a code string allowing access to BMW specific PID's. I have gotten this far but still cannot add the transmission temp to the reader. Sorry I cannot be of more help but hopefully an internet search will help.
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Old 07-16-2019, 10:55 PM
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I forgot to add that my 2011 X5D goes into reduced power mode when pulling my trailer at high altitude. Did not seem to be related to outside air temperature but climbing only at high altitude. I asked on another forum and was told it because BMW seems to have gotten the programming wrong for high altitude. at first I cleared the engine fault code and it never came back until high altitude again. Since then I found the fault code clears itself after normal shut down. I got no transmission code or any other warning except "possible imminent engine failure and car is in reduced power mode. It is okay to keep driving and take it to a BMW dealer at next opportunity".
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Old 07-17-2019, 12:09 AM
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Quote:
Originally Posted by ard View Post
that, or the tranny is shot.
What was the trans temperature? Exhaust gas temps got how high?
I cannot speak from X5 D experience, but ambient temps (and higher operating temps) can lead to reduced power to protect the driveline
(also, shall we assume that the 'normals' you refer to are 'normally with this same trailer'?)
Transmission seemed to be operating fine. Car just lacked power. But-o-meter says it was down 50hp. I was wondering if this was a combo of the ambient heat and not big enough intercooler. I’d forgotten my OBD2 WiFi interface so no data monitoring. Even in winter weather the coolant temp creeps up over 90C on this particular drive when I’m pulling the trailer.
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Old 07-17-2019, 01:06 AM
ard ard is offline
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i was kidding about the trans being shot. Hence the




I'll be interested to see if others chime in with real info from thior towing experience....kanar & bluedragon come to mind.
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Old 07-17-2019, 03:15 AM
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I've noticed something similar on a recent long trip in 85F+ bright sunny conditions in my X5d.

Wasn't towing, but had about 800 pounds of gear in the back. After about an hour & a half of driving on long backroads w/ moderate rolling hills going a steady 60 MPH with no stopping, power was noticeably reduced but I was getting AWESOME fuel mileage (31.5 MPG avg over about 90 miles according to the trip computer).

Pulled out the Foxwell NT520: Trans temp was 193-196F, engine oil & coolant temps were between 187-191F, boost requested vs actual only deviated by less than a PSI w/ actual boost often reading very slightly higher than requested (normal). EGT was around 600F, intake air temp was around 90F, charge air temp was around 115-120F if I remember right. Exhaust manifold pressure was nothing out of the ordinary & DPF diff pressure was around 75 mBar (normal).

Nothing I saw indicated an issue w/ any of the engine operating parameters, everything was where it should be; however, power was noticeably reduced when floored albeit w/ the absolute best fuel mileage I've experienced thus far...

Considering how perfect, smooth, & powerful the engine runs in every other scenario, & how many sensors / parts / etc have been preemptively replaced over the past few months to ensure continued performance over the next 50K miles, my best speculative guess is that the DDE is programmed to throttle power for some unknown reason under the specific conditions and / or duration I was driving. My guess would be charge air temp has a lot to do with the significant change in engine mapping.

I've driven a few 300 mile long trips on the highway w/ the cruise set to 95MPH w/ pulls to 135MPH (when safe & in Mexico of course). Zero throttling of power, engine felt as strong as it ever has; however, the ambient temps were only around 70-75F. Going normal highway speeds (75-85 MPH), engine coolant & charge air temps are measurably lower in my X5d, vs loafing around backroads going 60 MPH.
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Old 07-17-2019, 06:31 AM
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Quote:
Originally Posted by ard View Post
i was kidding about the trans being shot. Hence the




I'll be interested to see if others chime in with real info from thior towing experience....kanar & bluedragon come to mind.
I don’t know how I missed the humor. Duh
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Old 07-17-2019, 06:38 AM
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Sounds like I should get a better monitoring app than the generic one I currently use.

I guess the silver lining is that the car always seems to run really well after towing for an hour or so. Most of my driving is a 15 min commute to the office, and I know this is too short to get everything nice and hot.
I wonder if towing (long periods of heavy throttle) initiates a DPF cleaning cycle or somehow helps offset all those short trips.
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Old 07-17-2019, 09:47 AM
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DPF regeneration can make the engine feel different. I know a regeneration is taking place when I see engine coolant temperature get up to about 92 or 93C during normal driving with a higher than expected fuel delivery rate and the throttle valve moving from the 94% position. I first notice it, however, because of a feeling and different engine noise.

They take place a lot more often than I expected. I drive about 80 miles round trip every day. I think there's differing levels of regeneration also.
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