The dreaded 4K RPM power dip - 5 minute fix?

[KevinC]

Just stumbled on this post in a 7-yr-old thread at e46fanatics, just posted yesterday...

Hi all,

May I please share my experience?

After 3 years of owning my 2005 ZHP (150k miles), endless DIY, Vanos, & not a single trip to the dealership yet (thanks to my fellow fanatics), I have come across my most impactful fix... and it is the 4k Dip... which I couldn't even get a dealership to help me with.

As we all know, and can be seen in the service bulletin... the 4k dip is due to a "knock adaptation", that is stored until deleted (even if the battery is unplugged for X hours).

Rather than mail away my DME for a week, I was able to use INPA and a VagCom cable ($35) to go in and clear ALL adaptations. It seemed too good to be true.... but it wasn't. After a few hours of tinkering with the software and hardware I was in, cleared the adaptations... and it is 100% gone.

That was only yesterday so I will keep all posted. Please let me know any questions.

AGAIN: TO FIX THE ZHP 4K DIP JUST GET INPA AND THE $35 CABLE (Google It) TO CLEAR THE KNOCK ADAPTATION YOURSELF. IT TAKES 5 MINUTES AND IT IS THE MOST HP YOU CAN POSSIBLY ADD BACK IN FOR THE MONEY.

My concern is the "few hours of tinkering" to get to the final result. Could this truly be a 5-minute fix? INPA is available from Amazon and elsewhere.. before I buy, I want to be sure the process is simple enough to carry out without "hours" of frustration.

[Crickett]

I didn't think that the 4k dip was a "learned" adaptation, but a DME-programmed adjustment. That said, I haven't tried clearing out my adaptations, nor have I heard of anyone with the dip trying to clear adaptations as a fix. Has anyone given it a shot?

As for INPA, I'd be willing to bet that the "hours of tinkering" was just his initial setup & getting familiar with the program; actually using INPA is very simple, straightforward, & not terribly time-consuming.

[UdubBadger]

Hmmm


- Goin' H.A.M. Mobile

[nike001]

AFAIK, the 4K dip was fixed by a software update, no?

[KevinC]

AFAIK, the 4K dip was fixed by a software update, no?

It would seem that the original fix of sending in the DME was both for new programming, and to clear the otherwise-unclearable adaptations that were stored from the false knock readings caused by the original DISA valve. Part of the permanent fix was to replace the DISA with the later version that would apparently not cause the noises in the first place. But apparently the full reprogram was a "must" as it was the only way to clear the otherwise-permanent adaptations.

I'm going to give this a shot. There are all kinds of options to buy cable + sw on Ebay for ~$30 delivered. Then I'll have to borrow a Windoze laptop from somebody to actually use it.

[az3579]

I'll try this when I get a chance. I have the equipment so we'll see.


Sent from my iPhone 4S from Tapatalk

[Nivo]

If the DISA 4k rpm dip is really pronounced then it probably has something to do with knock adaptations after several drive cycles if the DISA is loose or something is wrong with the solenoid at the DISA.

BMW purposely makes it open slow (slow in micro seconds) to reduce any instant "slap" noise, in this case harmonics that can make its way to one of the Knock sensors. This slow opening is why there isn't a smooth transition much like the transition of the V-Tec cam profile change over isn't smooth on V-Tec Honda engines.

Make the DISA open faster and you might see a larger dip. But because of the volume changes I guess the dip will always be there just not as pronounced as if you also had the knock sensor hear the DISA open. Mine had a huge dip which I could feel right at that area, using BMW Logger I cleared the adaptations and drove the car for a week. The transition "feels" smoother now but because the nature on how the intake manifold is designed the 4k rpm dip will still be there just not 25lb ft of torque loss which translates to a momentary rpm slow down at that rpm. Now I hear the switch over with less rpm slow down.

I have been studying this intake manifold for months now and looking over log data with BMW schematics. on my manifold (DISA) the valve opens sometimes at 3860 rpms or so, most of the times at 4100 rpms. (Opening does vary with temps).

My 4th gear dyno run showing detail of the dip.
7067

V-Tec switch over point (Non iVtec)
7068

[BRGcoopahS]

it kind of amazes me that BMW cant fix such a simple problem just because they added slightly larger cams for the ZHP.

Actually, I think its more of a "These cams should work fine" from BMW, and then they realized they didnt and they said "Hardly anyone bought this option, so lets just fix it with a DME tune even though its not really a fix". I think they could fix it, but they dont care since its a 7-10 yr old car now.

[zhpnsnv]

Clearing adaptations is temporary until the ecu adapts again I believe.

[UdubBadger]

right but if the disa is fixed isn't it essentially learning something different than before?

[ELCID86]

Has anyone else tried this? Outcome?

[az3579]

I forgot to post my outcome. lol
I cleared the adaptations entirely a month or so ago. It helped some, but the dip is still ever so slightly there. It doesn't bother me much as I'm used to it; it's not as bad as it once was. I've done the DISA rebuild as well and the issue was almost entirely resolved after doing the DISA. The reason I ended up doing the adaptations was due to very jerky throttle actuation at low RPM and low speed and throttle input. Clearing the adaptations helped quite a bit with that, but I still have issues with it. The dip is still slightly present.


I can't iterate this enough: I hate drive by wire.

[SoCalZman]

would this cable and disc work in order to get to this clear adaptations task?
http://www.ebay.com/itm/For-BMW-INPAEdiabas-KDCAN-USB-Interface-OBD2-OBDII-Car-Diagnostic-Tool-Cable-/190970602608

[BumpinAlpine]

Has anybody else tried this method? Results?
Thanks

[UdubBadger]

I forgot to post my outcome. lol
I cleared the adaptations entirely a month or so ago. It helped some, but the dip is still ever so slightly there. It doesn't bother me much as I'm used to it; it's not as bad as it once was. I've done the DISA rebuild as well and the issue was almost entirely resolved after doing the DISA. The reason I ended up doing the adaptations was due to very jerky throttle actuation at low RPM and low speed and throttle input. Clearing the adaptations helped quite a bit with that, but I still have issues with it. The dip is still slightly present.


I can't iterate this enough: I hate drive by wire.

If it's ALMOST gone why not try tuning it out?


GoingHAM mobile

[ryankokesh]

Yeah, clearing adaptations get's really close to getting rid of the dip. It comes back, though.

[UdubBadger]

Yeah, clearing adaptations get's really close to getting rid of the dip. It comes back, though.

kinda like you.


;)

[rkneeshaw]

If the DISA is the source of the false knock detection, then it would seem logical that you would need to replace the DISA with the newer version (if there is a newer version) and THEN clear the knock adaptations.

Otherwise I would expect it just to come back.