Flatspot at low revs help.

Coops395 · 05-10-2017, 05:12 AM

I'm hoping I can get some feedback here from any 2016/17 640d owners.

I have a 2017 640d M sport with 1500 miles on the clock.

I have a huge flatspot/turbo lag at low revs, when the car settles at whatever speed and the revs drop just below 2000 and it's changed into 7/8th gear when I apply the throttle gently... nothing. It seems to strain then you have to push the accelerator deep so it kicks down before the turbo wakes up.. all very jolty. (Not sure that's a word)

It catches out sport mode when the revs are around 2000 and I want to accelerate but not as often as it holds the revs, comfort mode is really laggy at the same revs and just under.. eco mode.. well, apply the throttle slightly and nothing.. nothing at all in fact it exaggerates the who lag issue x 100!

I appreciate eco mode is not suppose to react in the same way and I never use it but it's showing in a big way what the other modes are doing in a smaller but still significant way.

I took the car into the dealership and they found nothing wrong on all the checks, I took the top technician out and let him drive to see the issue and he was shocked and we booked the car in for a deeper look into what's wrong but they came back with nothing and couldn't explain it.

They asked me to drive another 6 (their new demo) and it has the same issue! My previous 2 640d's never had this so I need either advice or feedback from anyone who has or is experiencing the same issue.

Any help would be appreciated.

325_bucks · 05-10-2017, 05:35 AM

There's certainly some lag when the revs are low, a bit of hesitation at motorway speeds occasionally where you might have to press harder, but I just press harder!

In sport mode I don't think I experience the issue though.

NINJA59 · 05-10-2017, 06:44 AM

How many weeks have you driven it for? (talking with my dealer it records the previous 8 weeks of driving - mileages etc.)

It is possible if you do a vast amount of different driving or a concentrated portion of one driving and then change it again the driving behaviour can be odd as the gearbox relearns.

Coops395 · 05-10-2017, 07:03 AM

I've driven it for 6 weeks with a mixture of motorway/country and city as I have in my previous 6ers.

Even the bmw technician thought it wasn't right, talked about the hand off from the smaller turbo to the large one but couldn't find a single fault when they went over it thoroughly.

Maybe a future software update may cure this? Who knows.

05-10-2017, 05:12 AM	#1
Coops395 Private First Class 213 Rep 116 Posts Drives: 2020 840d Msport/ 2018 M2 Join Date: Sep 2016 Location: Norwich UK iTrader: (0)	Flatspot at low revs help. I'm hoping I can get some feedback here from any 2016/17 640d owners. I have a 2017 640d M sport with 1500 miles on the clock. I have a huge flatspot/turbo lag at low revs, when the car settles at whatever speed and the revs drop just below 2000 and it's changed into 7/8th gear when I apply the throttle gently... nothing. It seems to strain then you have to push the accelerator deep so it kicks down before the turbo wakes up.. all very jolty. (Not sure that's a word) It catches out sport mode when the revs are around 2000 and I want to accelerate but not as often as it holds the revs, comfort mode is really laggy at the same revs and just under.. eco mode.. well, apply the throttle slightly and nothing.. nothing at all in fact it exaggerates the who lag issue x 100! I appreciate eco mode is not suppose to react in the same way and I never use it but it's showing in a big way what the other modes are doing in a smaller but still significant way. I took the car into the dealership and they found nothing wrong on all the checks, I took the top technician out and let him drive to see the issue and he was shocked and we booked the car in for a deeper look into what's wrong but they came back with nothing and couldn't explain it. They asked me to drive another 6 (their new demo) and it has the same issue! My previous 2 640d's never had this so I need either advice or feedback from anyone who has or is experiencing the same issue. Any help would be appreciated.
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05-10-2017, 05:35 AM	#2
325_bucks Captain 115 Rep 835 Posts Drives: F90 M5 Competition Join Date: Jan 2013 Location: High Wycombe iTrader: (1)	There's certainly some lag when the revs are low, a bit of hesitation at motorway speeds occasionally where you might have to press harder, but I just press harder! In sport mode I don't think I experience the issue though.
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05-10-2017, 06:44 AM	#3
NINJA59 Second Lieutenant 63 Rep 222 Posts Drives: 640D GC and MX5 NC PRHT Join Date: Jan 2016 Location: UK iTrader: (0)	How many weeks have you driven it for? (talking with my dealer it records the previous 8 weeks of driving - mileages etc.) It is possible if you do a vast amount of different driving or a concentrated portion of one driving and then change it again the driving behaviour can be odd as the gearbox relearns.
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05-10-2017, 07:03 AM	#4
Coops395 Private First Class 213 Rep 116 Posts Drives: 2020 840d Msport/ 2018 M2 Join Date: Sep 2016 Location: Norwich UK iTrader: (0)	I've driven it for 6 weeks with a mixture of motorway/country and city as I have in my previous 6ers. Even the bmw technician thought it wasn't right, talked about the hand off from the smaller turbo to the large one but couldn't find a single fault when they went over it thoroughly. Maybe a future software update may cure this? Who knows.
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