n57 sizeable power loss

Ghilou · 12-29-2021, 04:24 AM

Hey there, I'd love to have insights on my issue.

- I run a stock n57d30 on my e91, with about 190kkm or 120kmiles
- It used to run good enough, with only detected issue regarding injectors
- I had all injector replaced along with the EGR and the turbo pressure sensor which apparently did not survive the whole operation
- My car now runs fine (no stutter, good idle, nice low end when driving around town) EXCEPT it lacks power in the high RPM band. It's like someone took my perfectly fine 330d and gave me a perfectly fine 318d instead. 0-60 in the vicinity of 9s where it should be sub 7.

I first suspected an issue with the VGT. But ProTools reports that the "boost" value totally matches the "boost target" set by the ECU when driving, even under load where the power seems lacking.

I have a handful of ECU error code related to swirl faps (which were never removed on this car) that pops back whenever the engine is started. The intake probably needs a thorough cleaning, but I don't think it would cause such drastic change in power, especially this quickly (went from OK to Meh in the time it stayed in the shop).

I have an ok relationship with my shop, and I could try to make it his problem since it started after he changed my injectors/EGR, but it will be a long, tedious troubleshooting which will very likely involve cleaning/replacing the intake... which I'm not ready to do just yet. I'm an average enthusiast at best but maybe it's time I take the maintenance of this car in my own hands.

Any thoughts on what I should do?

Andy198712 · 12-29-2021, 08:36 AM

was it mapped before?
what codes are showing exactly?
does it sound the same?

Ghilou · 12-29-2021, 08:55 AM

Afaik it was never mapped. I have no reasons to believe otherwise because it was a family car (but remapping Diesels is very popular here so who knows). It does absolutely feels like it was "downmapped" if that makes sense.

The codes I have are 4DFF (swirl flaps actuator, position regulation) and 4E09 (swirl flaps, plausibility). I am translating here because Protool output was in French for some reason.

Interesting question! It sounds the same, except that under full load it doesn't sound fully loaded. Typically when the engine is under load the "diesel rattle" is kinda muffled. In my case, it sound like it would if you were to slowly let the engine rev-up with the throttle open at 20% or less. Matter of factly, this is how I realised there was something wrong, maybe even more so than the perceived loss in power.

12-29-2021, 04:24 AM	#1
Ghilou New Member 1 Rep 5 Posts Drives: 330xd e91 Join Date: Dec 2021 Location: France iTrader: (0)	n57 sizeable power loss Hey there, I'd love to have insights on my issue. - I run a stock n57d30 on my e91, with about 190kkm or 120kmiles - It used to run good enough, with only detected issue regarding injectors - I had all injector replaced along with the EGR and the turbo pressure sensor which apparently did not survive the whole operation - My car now runs fine (no stutter, good idle, nice low end when driving around town) EXCEPT it lacks power in the high RPM band. It's like someone took my perfectly fine 330d and gave me a perfectly fine 318d instead. 0-60 in the vicinity of 9s where it should be sub 7. I first suspected an issue with the VGT. But ProTools reports that the "boost" value totally matches the "boost target" set by the ECU when driving, even under load where the power seems lacking. I have a handful of ECU error code related to swirl faps (which were never removed on this car) that pops back whenever the engine is started. The intake probably needs a thorough cleaning, but I don't think it would cause such drastic change in power, especially this quickly (went from OK to Meh in the time it stayed in the shop). I have an ok relationship with my shop, and I could try to make it his problem since it started after he changed my injectors/EGR, but it will be a long, tedious troubleshooting which will very likely involve cleaning/replacing the intake... which I'm not ready to do just yet. I'm an average enthusiast at best but maybe it's time I take the maintenance of this car in my own hands. Any thoughts on what I should do?
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12-29-2021, 08:36 AM	#2
Andy198712 Major 145 Rep 1,006 Posts Drives: 2010 E91 325d Join Date: Mar 2017 Location: Cornwall iTrader: (0)	was it mapped before? what codes are showing exactly? does it sound the same?
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12-29-2021, 08:55 AM	#3
Ghilou New Member 1 Rep 5 Posts Drives: 330xd e91 Join Date: Dec 2021 Location: France iTrader: (0)	Afaik it was never mapped. I have no reasons to believe otherwise because it was a family car (but remapping Diesels is very popular here so who knows). It does absolutely feels like it was "downmapped" if that makes sense. The codes I have are 4DFF (swirl flaps actuator, position regulation) and 4E09 (swirl flaps, plausibility). I am translating here because Protool output was in French for some reason. Interesting question! It sounds the same, except that under full load it doesn't sound fully loaded. Typically when the engine is under load the "diesel rattle" is kinda muffled. In my case, it sound like it would if you were to slowly let the engine rev-up with the throttle open at 20% or less. Matter of factly, this is how I realised there was something wrong, maybe even more so than the perceived loss in power.
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