Power falls sharply from 5,000 rpm to the top. Possible causes?

ajm55 · 01-24-2021, 08:49 PM

Some context-

This is a 2013 comp pack M5. Prior to the current issue, this car was really strong. With downpipes only, it was comfortably making over 800nm and around 590 whp

Last year, I bought a stage 1 tune from Evolve. Great service and decent gains. The dyno sheet is attached. My only discontent was with the huge torque gains low down. Over 1000 nm at 3,500 rpm is surplus to my requirements. I don't track the car and I don't run semi-slicks. The bucket-load of added low-down torque simple exacerbates the low down traction issues and adds virtually nothing to straight line performance where revs will always be beyond 5,000 from 2nd gear up.

I decided therefore to explore an alternative and opted for a BPM tune late last year. Mike from BPM has been very helpful and clearly knows this platform well. Car feels good enough on the road and my data logs look dialed in but I have unfortunately not been able to properly assess the gains because of the issue with the car described below.

The issue:

On the dyno (with the BPM stage 2 tune loaded), the car would fall of its face from about 5,000 rpm - as though the throttle was closing to protect the motor. This is curious because the data logs of the dyno runs show healthy timing, boost and AFRs while the power is falling off. The data logs and the dyno sheet just don't match up. The dyno operator said it felt as though the throttle was closing from about 5,000 rpm up. I wasn't logging throttle position so can't verify or refute this suspicion

On the road, the car feels strong and the data logs look fine. There is no indication of timing being pulled, while AFRs and boost look good and the throttle remains fully open. However, my best 100-200 kph dragy run with the Stage 2 (7.5 s) was slightly slower than my best 100-200 kph run on the stock file (7.3 s), but this is no doubt influenced by the fact that the stock run (done about 8 months ago) was done in much cooler whether. Stock runs previously done in similar conditions to the Stage 2 run were in the 7.6 - 7.8 s range. I would expect the Stage 2 to yield better gains than 0.2 s. This prompted me to reload the Evolve tune and re-dyno. This confirmed that there is definitely an issue. Power also fell off sharply from about 5,000 rpm and the car made less power from 6,000 rpm up than my stock file had made on the same dyno about 8 months ago

The only hardware change made between my healthy dyno runs about 8 months back and the recent runs was to change out the rear O2 sensors with new ones. In so doing I did use Bosch sensors rather than OE sensors. This prompted me to explore whether the new rear O2 sensors might be at play. I gather from an article I read that with catless downpipes on this platform, the extra heat detected by the rear O2 sensors might result in the car limiting power to protect the cats (with the ECU thinking the cats are still present).

This got me wondering the heat generated on the dyno from 5,000 rpm up, would prompt the rear O2s to tell the ECU to limit the power to protect the cats. However, I must assume that the BPM and Evolve tunes would render this theory implausible (because they presumably account for catless dps) and in any event, I don’t understand why the fall in power from 5.000 rpm up would not be apparent from the data logs (i.e. in the boost and/or timing and/or fueling data).

Any ideas? Anyone here experience similar symptoms?

Noggie · 01-26-2021, 03:34 AM

Not sure this is relatable, but I have a -14 Comp pack and tuned mine last year.
My tuner said that my car had a different software than later comp packs they had seen and they did struggle to find the parameters to tune (BMW shifts them around in different versions to confuse tuners), so there was no tune to just upload.

My car had serious issues with the first tune, torque was insane down low and it had several flat spots in the power curve. Initially I thought it might be the traction control, even in MDM mode it kept blinking past 150kph.

Turned out I was hitting a torque limiter, so once they dialed back the power, things became much smoother.
I'm now on tune number #3, when winter storage is over, I planned to take it on a dyno and perhaps we need to do some minor tweeks. I still have som minor issues around 2800-3200rpm, where there is a sudden spike in power, I see the revs increasing smooth and when it gets to 2800 it just jumps to 3200.

Could be that you hit some sort of limiter around 5000rpm and that it why the power is dialed back.

Also the car sends a max torque to the Gearbox in different rpm's, so that could also be something.

ajm55 · 01-26-2021, 04:37 AM

Quote:

Originally Posted by Noggie

Not sure this is relatable, but I have a -14 Comp pack and tuned mine last year.
My tuner said that my car had a different software than later comp packs they had seen and they did struggle to find the parameters to tune (BMW shifts them around in different versions to confuse tuners), so there was no tune to just upload.

My car had serious issues with the first tune, torque was insane down low and it had several flat spots in the power curve. Initially I thought it might be the traction control, even in MDM mode it kept blinking past 150kph.

Turned out I was hitting a torque limiter, so once they dialed back the power, things became much smoother.
I'm now on tune number #3, when winter storage is over, I planned to take it on a dyno and perhaps we need to do some minor tweeks. I still have som minor issues around 2800-3200rpm, where there is a sudden spike in power, I see the revs increasing smooth and when it gets to 2800 it just jumps to 3200.

Could be that you hit some sort of limiter around 5000rpm and that it why the power is dialed back.

Also the car sends a max torque to the Gearbox in different rpm's, so that could also be something.

Thanks Noggie. Your situation is perhaps similar to mine with regard to the torque spike at or at about 3,000 rpm (which serves no useful purpose) but it unfortunately doesn't explain the issue I am now experiencing.

By way of clarification, the 1st of the two dyno sheets published in my originating post, depicts runs done on the Evolve tune and on my stock tune on the same day (in about May 2020). You will see that on the Evolve dyno run, there is no drop-off in power.

The 2nd dyno sheet depicts the run done earlier this month on the Evolve tune and the run on my stock tune done on the same dyno but in about May 2020.

It seems clear to me that subsequent to the runs depicted on my 1st dyno sheet (done in about May 2020) and the stock run depicted on the 2nd dyno sheet (also done in about May 2020), a problem has intervened and that is borne out by the run on the Evolve tune depicted on the 2nd dyno sheet (done earlier this month). I did not run my stock file on the same day, but have little doubt that if I had done so, it would've revealed a similar drop-off in power from about 5,000 rpm and looked nothing like the stock run depicted in the 2nd dyno sheet.

Whatever issue is now causing the power drop-off was not present when I did the Evolve run in May 2020.

I hope that clarifies the confusion created by my first post.

Who has tuned / is tuning your M5?

Noggie · 01-26-2021, 09:39 AM

Dont think I can be of much help unfortunately.
My tune is being done by a local shop, so not a straight up job like Evolve or ESS.

They have tuned many M5's, but not that many comp pack ones, and the file they had on a -15 was completely different from my April 14 model.

I looked at your graps (focused on red lines only as I believe they are the stock tune) but I cant make much of them.
For one the units are different, one is KW/NM the other is HP/NM, and the scaling is different, also it is not scaled so that you can see the power and torque curves cross at 5252rpm.
I do notice that on your top chart your Torque and HP curves start to level out at 3400rpm, while on your lower chart it does the same at 2700rpm.
Also there seems to be a loss of around 50NM at that area on the lower one.
On the top graph you have 464KW = 622HP
On the bottom you have 588HP, a loss of 34hp

Were these runs done on the same dyno and in the same gear?

If both top and bottom red graphs is the stock tune, the only explanation I have to the curves behaving different at different RPM's and loss of HP and torque is that they were not done in the same gear.

I see the same in the black Evolve graps.
1028nm vs 943nm
529KW=709hp vs 586HP
Further strengthening the suspicion that the pull was done in different gears

Given that the engine and gearbox exchange a "max available torque", this is different in the different gears the power difference after 5000rpm could be caused by that.

Boosted M5 · 01-26-2021, 11:36 PM

Just wanted to chime in, as I'm interested to know what the solution or reason might be to your dilemma, but I asked my tuner what that spike at around 3k meant on my dyno sheet and he said it's an indication of clutch slippage due to the high torque demand. Not sure how true that is but I am on stock clutch still.

ajm55 · 01-27-2021, 07:30 AM

Noggie, I'm sure the inadequate context provided by me about the dyno sheets is confusing. To clarify:

- the black graph (Evolve) and the red graph (stock) on the first dyno sheet are in respect of dyno runs done on the same dyno ("the first dyno") and on the same day in May 2020.

- the red graph (stock) on the second dyno sheet is in respect of a dyno run also done in May 2020 but on a different dyno ("the second dyno").

On those 3 runs (i.e. one with the Evolve file loaded and the other two with the stock file loaded), the issue about which I am now seeking advice was not present. Don't read anything into the slightly different the graph shapes and power output between the stock run on the first dyno and the stock run done on the second dyno. That's attributable to the different dynos and not to any issue with the car.

The black graph (Evolve) on the second dyno sheet is in respect of a dyno run done on the second dyno in January 2020. You will note from the black graph how the power falls off from about 5,000 rpm to the top. That is symptomatic of the issue I am trying to resolve. It seems clear that at some point between the 3 dyno runs done in May 2020 and the Evolve dyno run done in January 2021, the issue reared its head.

I also ran the BPM stage 2 tune on the first dyno in January 2021 and the power also fell off sharply from about 5,000 rpm up.

This is not an issue with the tune. If it was, I would presumably have had the same problem when doing the Evolve run on the first dyno in May 2020. It is also not an issue with the dyno because the issue was present with the Evolve run on the second dyno in January 2021 and with the BPM run on the first dyno in January 2021. It has to be an issue with the car. I'm trying to figure out what issue with the car might cause the power to fall off. What makes all of this more curious is that the boost, timing and AFRs on the January 2021 Evolve and BPM dyno runs all look healthy - even from 5,000 rpm to the top (while on the dyno, the power is rapidly falling)

ajm55 · 01-27-2021, 07:47 AM

Quote:

Originally Posted by Boosted M5

Just wanted to chime in, as I'm interested to know what the solution or reason might be to your dilemma, but I asked my tuner what that spike at around 3k meant on my dyno sheet and he said it's an indication of clutch slippage due to the high torque demand. Not sure how true that is but I am on stock clutch still.

Peak torque on the Evolve tune seems to be at around 4,000 rpm. I doubt that this is from the clutches slipping. The data logs show a significant increase in boost over stock between about 3,500 rpm and 4,500 rpm which, I am sure, will account for the high torque in that area. I'm sure there are guys who like the added torque in that range. I would prefer the gains to only feature from 5,000 rpm up because that's all the car will see once you've kicked into 2nd on a WOT run and the added torque low down serves only to exacerbate the already-present traction issues. But that's a story for another day. The Evolve and BPM tunes are good and I have no hesitation recommending both

czornaldo89 · 08-19-2021, 02:58 AM

Hi guys
have simmilar problem. After 5k rpms the power increase drops drastically... Now I have pure stage 2 turbos and SSP clutch for upgrades. Catless DP as well ofcourse. Do you have any clue what could be causing that? The same issue took place with stock turbos onboard...

czornaldo89 · 08-19-2021, 03:01 AM

Hi guys
have simmilar problem. After 5k rpms the power increase drops drastically... Now I have pure stage 2 turbos and SSP clutch for upgrades. Catless DP as well ofcourse. Do you have any clue what could be causing that? the same problem with stock turbos

M5Rick · 08-19-2021, 05:26 AM

^ It would probably have been easier to sort the power drop with the standard set up, now that you have put on st 2 turbos and ssp could make it trickier. Have the clutches been fully adapted in?
Try cleaning the MAF's with CRC cleaner and leave to dry before re installing, be careful not to drop them.

czornaldo89 · 08-19-2021, 07:30 AM

Quote:

Originally Posted by M5Rick

^ It would probably have been easier to sort the power drop with the standard set up, now that you have put on st 2 turbos and ssp could make it trickier. Have the clutches been fully adapted in?
Try cleaning the MAF's with CRC cleaner and leave to dry before re installing, be careful not to drop them.

Thank you for your advice. We will try to change MAF's and see what happens. If it won't help we will try to go back to stock turbos and try to tune it to be sure if it's not hybrid's fault. I've already send them for repair once before (wastegate got stuck...)
The clutch is addapted...

01-24-2021, 08:49 PM	#1
ajm55 Private First Class 56 Rep 179 Posts Drives: f10 m5 Join Date: Dec 2019 Location: south africa iTrader: (0)	Power falls sharply from 5,000 rpm to the top. Possible causes? Some context- This is a 2013 comp pack M5. Prior to the current issue, this car was really strong. With downpipes only, it was comfortably making over 800nm and around 590 whp Last year, I bought a stage 1 tune from Evolve. Great service and decent gains. The dyno sheet is attached. My only discontent was with the huge torque gains low down. Over 1000 nm at 3,500 rpm is surplus to my requirements. I don't track the car and I don't run semi-slicks. The bucket-load of added low-down torque simple exacerbates the low down traction issues and adds virtually nothing to straight line performance where revs will always be beyond 5,000 from 2nd gear up. I decided therefore to explore an alternative and opted for a BPM tune late last year. Mike from BPM has been very helpful and clearly knows this platform well. Car feels good enough on the road and my data logs look dialed in but I have unfortunately not been able to properly assess the gains because of the issue with the car described below. The issue: On the dyno (with the BPM stage 2 tune loaded), the car would fall of its face from about 5,000 rpm - as though the throttle was closing to protect the motor. This is curious because the data logs of the dyno runs show healthy timing, boost and AFRs while the power is falling off. The data logs and the dyno sheet just don't match up. The dyno operator said it felt as though the throttle was closing from about 5,000 rpm up. I wasn't logging throttle position so can't verify or refute this suspicion On the road, the car feels strong and the data logs look fine. There is no indication of timing being pulled, while AFRs and boost look good and the throttle remains fully open. However, my best 100-200 kph dragy run with the Stage 2 (7.5 s) was slightly slower than my best 100-200 kph run on the stock file (7.3 s), but this is no doubt influenced by the fact that the stock run (done about 8 months ago) was done in much cooler whether. Stock runs previously done in similar conditions to the Stage 2 run were in the 7.6 - 7.8 s range. I would expect the Stage 2 to yield better gains than 0.2 s. This prompted me to reload the Evolve tune and re-dyno. This confirmed that there is definitely an issue. Power also fell off sharply from about 5,000 rpm and the car made less power from 6,000 rpm up than my stock file had made on the same dyno about 8 months ago The only hardware change made between my healthy dyno runs about 8 months back and the recent runs was to change out the rear O2 sensors with new ones. In so doing I did use Bosch sensors rather than OE sensors. This prompted me to explore whether the new rear O2 sensors might be at play. I gather from an article I read that with catless downpipes on this platform, the extra heat detected by the rear O2 sensors might result in the car limiting power to protect the cats (with the ECU thinking the cats are still present). This got me wondering the heat generated on the dyno from 5,000 rpm up, would prompt the rear O2s to tell the ECU to limit the power to protect the cats. However, I must assume that the BPM and Evolve tunes would render this theory implausible (because they presumably account for catless dps) and in any event, I don’t understand why the fall in power from 5.000 rpm up would not be apparent from the data logs (i.e. in the boost and/or timing and/or fueling data). Any ideas? Anyone here experience similar symptoms? Attached Images
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01-26-2021, 03:34 AM	#2
Noggie Captain 292 Rep 634 Posts Drives: E31 850i,i3s Join Date: May 2014 Location: Norway iTrader: (0)	Not sure this is relatable, but I have a -14 Comp pack and tuned mine last year. My tuner said that my car had a different software than later comp packs they had seen and they did struggle to find the parameters to tune (BMW shifts them around in different versions to confuse tuners), so there was no tune to just upload. My car had serious issues with the first tune, torque was insane down low and it had several flat spots in the power curve. Initially I thought it might be the traction control, even in MDM mode it kept blinking past 150kph. Turned out I was hitting a torque limiter, so once they dialed back the power, things became much smoother. I'm now on tune number #3, when winter storage is over, I planned to take it on a dyno and perhaps we need to do some minor tweeks. I still have som minor issues around 2800-3200rpm, where there is a sudden spike in power, I see the revs increasing smooth and when it gets to 2800 it just jumps to 3200. Could be that you hit some sort of limiter around 5000rpm and that it why the power is dialed back. Also the car sends a max torque to the Gearbox in different rpm's, so that could also be something. __________________ _____________________________ -14 Imola Red M5 Competition Pack (sold) -90 BMW 850i Supercharged -20 i3s -20 Ducati Diavel 1260s
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01-26-2021, 09:39 AM	#4
Noggie Captain 292 Rep 634 Posts Drives: E31 850i,i3s Join Date: May 2014 Location: Norway iTrader: (0)	Dont think I can be of much help unfortunately. My tune is being done by a local shop, so not a straight up job like Evolve or ESS. They have tuned many M5's, but not that many comp pack ones, and the file they had on a -15 was completely different from my April 14 model. I looked at your graps (focused on red lines only as I believe they are the stock tune) but I cant make much of them. For one the units are different, one is KW/NM the other is HP/NM, and the scaling is different, also it is not scaled so that you can see the power and torque curves cross at 5252rpm. I do notice that on your top chart your Torque and HP curves start to level out at 3400rpm, while on your lower chart it does the same at 2700rpm. Also there seems to be a loss of around 50NM at that area on the lower one. On the top graph you have 464KW = 622HP On the bottom you have 588HP, a loss of 34hp Were these runs done on the same dyno and in the same gear? If both top and bottom red graphs is the stock tune, the only explanation I have to the curves behaving different at different RPM's and loss of HP and torque is that they were not done in the same gear. I see the same in the black Evolve graps. 1028nm vs 943nm 529KW=709hp vs 586HP Further strengthening the suspicion that the pull was done in different gears Given that the engine and gearbox exchange a "max available torque", this is different in the different gears the power difference after 5000rpm could be caused by that. __________________ _____________________________ -14 Imola Red M5 Competition Pack (sold) -90 BMW 850i Supercharged -20 i3s -20 Ducati Diavel 1260s
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01-26-2021, 11:36 PM	#5
Boosted M5 Private First Class 73 Rep 196 Posts Drives: F10 m5 Join Date: Dec 2018 Location: Sf bay area iTrader: (0)	Just wanted to chime in, as I'm interested to know what the solution or reason might be to your dilemma, but I asked my tuner what that spike at around 3k meant on my dyno sheet and he said it's an indication of clutch slippage due to the high torque demand. Not sure how true that is but I am on stock clutch still.
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01-27-2021, 07:30 AM	#6
ajm55 Private First Class 56 Rep 179 Posts Drives: f10 m5 Join Date: Dec 2019 Location: south africa iTrader: (0)	Noggie, I'm sure the inadequate context provided by me about the dyno sheets is confusing. To clarify: - the black graph (Evolve) and the red graph (stock) on the first dyno sheet are in respect of dyno runs done on the same dyno ("the first dyno") and on the same day in May 2020. - the red graph (stock) on the second dyno sheet is in respect of a dyno run also done in May 2020 but on a different dyno ("the second dyno"). On those 3 runs (i.e. one with the Evolve file loaded and the other two with the stock file loaded), the issue about which I am now seeking advice was not present. Don't read anything into the slightly different the graph shapes and power output between the stock run on the first dyno and the stock run done on the second dyno. That's attributable to the different dynos and not to any issue with the car. The black graph (Evolve) on the second dyno sheet is in respect of a dyno run done on the second dyno in January 2020. You will note from the black graph how the power falls off from about 5,000 rpm to the top. That is symptomatic of the issue I am trying to resolve. It seems clear that at some point between the 3 dyno runs done in May 2020 and the Evolve dyno run done in January 2021, the issue reared its head. I also ran the BPM stage 2 tune on the first dyno in January 2021 and the power also fell off sharply from about 5,000 rpm up. This is not an issue with the tune. If it was, I would presumably have had the same problem when doing the Evolve run on the first dyno in May 2020. It is also not an issue with the dyno because the issue was present with the Evolve run on the second dyno in January 2021 and with the BPM run on the first dyno in January 2021. It has to be an issue with the car. I'm trying to figure out what issue with the car might cause the power to fall off. What makes all of this more curious is that the boost, timing and AFRs on the January 2021 Evolve and BPM dyno runs all look healthy - even from 5,000 rpm to the top (while on the dyno, the power is rapidly falling)
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08-19-2021, 02:58 AM	#8
czornaldo89 New Member -1 Rep 7 Posts Drives: 2015 BMW M6 f13, 2006 BMW M5 Join Date: Nov 2020 Location: Cracow, Poland iTrader: (0)	Hi guys have simmilar problem. After 5k rpms the power increase drops drastically... Now I have pure stage 2 turbos and SSP clutch for upgrades. Catless DP as well ofcourse. Do you have any clue what could be causing that? The same issue took place with stock turbos onboard...
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08-19-2021, 03:01 AM	#9
czornaldo89 New Member -1 Rep 7 Posts Drives: 2015 BMW M6 f13, 2006 BMW M5 Join Date: Nov 2020 Location: Cracow, Poland iTrader: (0)	Hi guys have simmilar problem. After 5k rpms the power increase drops drastically... Now I have pure stage 2 turbos and SSP clutch for upgrades. Catless DP as well ofcourse. Do you have any clue what could be causing that? the same problem with stock turbos
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08-19-2021, 05:26 AM	#10
M5Rick General 66295 Rep 21,449 Posts Drives: M5 F10 DCT Gunmetal Join Date: Aug 2018 Location: GB iTrader: (0)	^ It would probably have been easier to sort the power drop with the standard set up, now that you have put on st 2 turbos and ssp could make it trickier. Have the clutches been fully adapted in? Try cleaning the MAF's with CRC cleaner and leave to dry before re installing, be careful not to drop them.
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