E90Post
 


TNT Racewerks
 
BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Technical Question



Reply
 
Thread Tools Search this Thread
      07-11-2009, 01:37 PM   #1
Presidio335xi
Lieutenant
21
Rep
414
Posts

Drives: 335xi coupe
Join Date: Oct 2007
Location: San Francisco

iTrader: (0)

Technical Question

I understand the BMW has tapered the psi at the top of the RPM range to save turbo life.

My question is, is that standard for all turbos or just in this case?

Why do they do it if that isn't standard?

thanks
__________________
2017 F82
Appreciate 0
      07-11-2009, 01:44 PM   #2
Zeph
Major
United_States
27
Rep
1,410
Posts

Drives: 2008 E92 335i 6MT SGM CR/BD
Join Date: Jul 2008
Location: Southeast USA

iTrader: (0)

I am curious to this as well, why is 9psi "harder on the turbos" @ 6k RPM as opposed to 4K RPM? I mean unless they are just saying by the time you go from 3K to 6K you have been maxing the turbos for a few seconds already, thus building up too much heat? It almost seems like it would be easier to hit high boost at higher RPM's due to increased exhaust pressure/heat/speed? That plus wouldn't the engine be "wanting" more air at higher RPM?
Appreciate 0
      07-11-2009, 02:16 PM   #3
bimmerboy
Captain
bimmerboy's Avatar
23
Rep
601
Posts

Drives: 135i
Join Date: Jan 2009
Location: Bay Area

iTrader: (0)

boost tapering is pretty common on all cars with factory turbos.... my wrx had the same taper. It's usually more of a problem with the stock turbos being too small, therefore tapering in psi as the rpms increase towards redline.

If you upgraded to a larger turbo along with supporting modifications(intake/exhaust/fuel/ecu) you can eliminate this by keeping the psi constant once spooled...

Maybe someone can explain in more detail? i'm no expert.
__________________
--2009 BSM 135i--
-Manual, Sport Package, BMW Assist
Appreciate 0
      07-11-2009, 02:22 PM   #4
Ilma
Colonel
Canada
181
Rep
2,840
Posts

Drives: 2008 135i
Join Date: Nov 2008
Location: Mississauga

iTrader: (0)

Quote:
Originally Posted by Zeph View Post
I am curious to this as well, why is 9psi "harder on the turbos" @ 6k RPM as opposed to 4K RPM? I mean unless they are just saying by the time you go from 3K to 6K you have been maxing the turbos for a few seconds already, thus building up too much heat? It almost seems like it would be easier to hit high boost at higher RPM's due to increased exhaust pressure/heat/speed? That plus wouldn't the engine be "wanting" more air at higher RPM?
Yes...the engine wants more air at higher rpms.

The pistons are moving much faster and sucking in more air as a result.

Therefore, the turbos have to compress the air much faster just to keep the boost at a constant pressure.

Seems to me the only way they can do that is by spinning faster and faster as rpms climb.

Same boost = higher turbine speeds as rpms climb.

Pretty soon you max out the turbos ability to move air efficiently and they create friction which heats up the intake charge.......not to mention that shaft speeds go through the roof.
Appreciate 0
      07-11-2009, 02:25 PM   #5
Zeph
Major
United_States
27
Rep
1,410
Posts

Drives: 2008 E92 335i 6MT SGM CR/BD
Join Date: Jul 2008
Location: Southeast USA

iTrader: (0)

^ awesome, that really does make sense. Thanks!

So where is this GT35R kit we have been waiting for?
Appreciate 0
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 02:44 PM.




e90post
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, 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