Mercedes Benz Forums


Go Back   Mercedes Forum - Mercedes Benz Enthusiast Forums > Mercedes Benz Models > Diesel Performance
Sign in using an external account
Register Forgot Password?
Search

Welcome to Mercedes Forum!
Welcome to Mercedes Forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to start new topics, reply to conversations, privately message other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join Mercedes Forum today!

Reply
 
 
 
 
LinkBack Thread Tools Search this Thread
  #1  
Old 10-10-2011, 03:13 PM
ForcedInduction's Avatar
Super Moderator
 
Join Date: May 2006
Location: Federal Heights, Colorado
Posts: 4,620
Default VNT/VGT turbo control based on engine load

This system regulates boost pressure directly based on engine load (throttle position). It is independent of engine RPM, turbo speed, vane position, air filter restriction, exhaust restriction and any engine modifications. No electricity or electronics are involved, though switches and vacuum solenoids instead of valves on the throttle will work exactly the same.

Click the image to open in full size.


Boost side
3 stages; 4psi, 10psi and 14.5psi
two roller switches on EGR cam plate (The stock 3-2 valves could be retained with altered positioning)
Manual Air Control Valves- 4LB50, Grainger Industrial Supply
low boost- valves open, not contacting cam plate
med boost- egr cam closes low valve
high boost- egr cam keeps low valve closed, closes medium valve

Click the image to open in full size.



Vacuum side
Small reservoir (vacuum sphere from a chevy) to buffer vacuum pulses from the pump and provide storage volume. (Consistent turbo operation in all conditions.)
A manual on/off switch valve (commonly used on most semi trucks) is used on the dash to "turn off" the turbo during low speed conditions (low loads under 40mph) to maximize economy.
A white 0.8mm orifice is between the switch and vacuum side of the controller to limit return flow to the vacuum system.
Three boost controller valves from Grainger, commonly called a "Dawes device" by the VW crowd. Modified with a copper tube soldered to the outlet for the vacuum hose to connect.
The high pressure regulator has a stronger spring to increase its adjustable range up to 18psi.
Grainger 5Z763

Click the image to open in full size.

A boost pressure signal is supplied from the intake manifold to the underside of the valves.
Vacuum from the supply switch is given directly to the VNT turbo's actuator, closing the vanes.
As boost rises to the set pressure the regulators bleed boost air into the actuator's vacuum hose, causing the actuator to extend and open the vanes so that manifold pressure is equalized with the airflow through the regulator.

The turbo's actuator starts pulling the vane lever at 3inHg, vanes are all the way closed at 11inHg and the vacuum system maxes out at 15inHg.
My controller lives in the cruise actuator's old location, secured by longer bracket bolts, but any location is suitable since its not hard tied to anything on the engine.
The hardware is very durable. As of this writing I have two years of use on the system with no faults. (Update 1/2014, still zero issues)

Quote:
The last thing I will try is to link the vanes directly to the pedal in an adjustable way regarding movement, then push back the vane lever with up coming boost. The pedal linkage is spring loaded to the vane lever so the boost actuator can push the lever back although the pedal is depressed.
That method has been popular in the VW world. It is obsolete though, it doesn't have any way to limit/vary boost pressure with engine load. Throttle movement only changes how quickly the turbo spools up to maximum boost. Boost will rise and fall significantly with RPM and as a result fuel economy is very poor and turbo response is slow.
Here is an example of that outdated system:


Quote:
Its only going to be 6CM for about 10-15PSI to get it to light fast, then it will jump to 9CM for 25 - 30PSI then jump to 12CM for 40PSI.
Ramp allows for micro adjustments, PSI is measured in 0.01Vdc increments. When voltage increases with pressure, the controller will make small proportional adjustments to turbo
position.
Jump holds one position until a predetermined PSI is achieved, at that time the controller will move to the next predetermined position. This programming is great for staged turbos.
That is another example of a somewhat recent "solution" by steed. Being set to "steps" causes large jumps in VGT position to fixed points. The result is its little better than a fixed geometry turbine. As soon as it reaches 15psi, the turbo's response is drastically reduced. It is changing position based only on boost output. Boost output in VGT turbos is not based on load, an engine at constant RPM and load can have drastically different boost pressure based solely on vane position. VGTs require load/throttle input to work properly. Without it you end up like steed's system with laggy/jerky response.


Click the image to open in full size. Click the image to open in full size.
Register today for free or log in if already registered to remove this ad!

Last edited by ForcedInduction; 12-29-2013 at 10:40 PM.
Reply With Quote
Old 10-10-2011, 03:13 PM
 
 
 
Reply

Tags
air, controller, custom, diesel, electric, enjin, grainger, limit, list, mercedes, open, operation, switch, turbo, turbos, valve, vgt, vnt


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
Trackbacks are On
Pingbacks are On
Refbacks are On


LinkBacks (?)
LinkBack to this Thread: http://mercedesforum.com/forum/diesel-performance-49/vnt-vgt-turbo-control-based-engine-load-49672/
Posted By For Type Date
vnt 15 actuation without computer - Page 2 - TDIClub Forums This thread Refback 02-21-2013 10:40 AM
HomemadeTurbo - DIY Turbo Forum - Holset VGT HE351VE Controller This thread Refback 02-14-2013 04:29 PM
Ideal boost at cruising speed - Australian Land Rover Owners This thread Refback 02-09-2013 08:36 PM
Holset VGT HE351VE Controller - Page 15 - HomemadeTurbo - DIY Turbo Forum This thread Refback 09-25-2012 02:57 PM

Advertising
Featured Sponsors
Vendor Directory
Our Sponsors
GetCoolParts.com
Monroe, WA 98272
360.863.0557
All times are GMT -5. The time now is 10:16 AM.

Internet Brands, Inc.



SEO by vBSEO ©2010, Crawlability, Inc.