BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read




 

Post Reply
 
Thread Tools Search this Thread
      12-19-2018, 06:13 AM   #1
Piets94
Second Lieutenant
71
Rep
299
Posts

Drives: 94 M3, AW 1M
Join Date: Jun 2013
Location: Australia

iTrader: (0)

'Rev hang'

Just looking for some head starts into what I should be troubleshooting here.

I've noticed only recently that when coming off throttle, that the revs seem to hang a little more than normal. No surging, but just not dropping as quickly as I'm used to. Happens both in gear or when changing gears. So much so that the car will continue creeping at low speed at say 1500rpm. Probably a bit laggier as well? Can't confirm that one though.

66k kms, custom tuned for 40k and hitting boost targets, coils/plugs have done 6k, metal chargepipe, stock clutch/fly. No ecu codes.

Thanks all.
Appreciate 0
      12-20-2018, 10:01 AM   #2
nachob
Brigadier General
United_States
1527
Rep
3,838
Posts

Drives: 2011 1M, 2003 330i ZHP
Join Date: Apr 2008
Location: California

iTrader: (5)

I wonder if you have a slow wastegate? Tunes can be hard on wastegates as the extra boost overheats them. If they are slow to open, they can keep the boost on instead of quickly releasing and vice versa when you need boost they are slow to close and you get laggy. My OBD scanner can test individual components but I don't recall if it can test the wastegate.

That is where I would look first based on the three things you mentioned....revs hanging, slightly laggier and a tune which raises boost pressures and heat on the wastegates which are already not the sturdiest parts in our cars.

I'm an IT guy by career and I think the best move would be to return the car to stock flash and see if that helps because it could be a software issue also. Is that an option for you?

Also anyone out there know how to test wastegate performance?
Appreciate 0
      12-20-2018, 05:28 PM   #3
Piets94
Second Lieutenant
71
Rep
299
Posts

Drives: 94 M3, AW 1M
Join Date: Jun 2013
Location: Australia

iTrader: (0)

Thanks Nachob. It's an interesting theory and makes sense.
I can certainly flash back to stock and check if the anomaly remains.
When I get more time I'll also get some logs as they should (?) show how the boost is coming on/off, which might shed some light on the wastegate idea.
Appreciate 0
      12-20-2018, 07:50 PM   #4
nachob
Brigadier General
United_States
1527
Rep
3,838
Posts

Drives: 2011 1M, 2003 330i ZHP
Join Date: Apr 2008
Location: California

iTrader: (5)

Quote:
Originally Posted by Piets94 View Post
Thanks Nachob. It's an interesting theory and makes sense.
I can certainly flash back to stock and check if the anomaly remains.
When I get more time I'll also get some logs as they should (?) show how the boost is coming on/off, which might shed some light on the wastegate idea.
That would be cool if it would show throttle position and boost side by side!
Appreciate 0
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 08:09 AM.




1addicts
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST