Desired Boost & VGT Tables

2012dually

New member
Joined
Sep 28, 2015
Messages
24
Reaction score
0
Location
Canada
Hi everyone!

I am a new member but long time viewer and am thrilled to have a 6.7 tuning section and is why I joined!

I recently ******d my 2012 and have been playing with mcc but am having a hard time with a few things. The first thing I would like to tackle is the desired boost and vgt tables. I am sure all of us would benefit greatly on understanding how the ecm goes through the tables.

So off to tuning! How does the ecm decide on boost? As in which table is the limiting one, vane position or desired boost?

Say i am commanding 10 psi of boost at low rpm but desired vane position is 30%. Would the ecm limit vane position to 30% even though say boost was only at 5 psi?

I am really excited about this and hope we can all help eachother tune our trucks just the way we want!
 

CoreyMS

New member
Joined
May 5, 2014
Messages
108
Reaction score
0
I've just gotten into those tables and doing some experimenting. Seems like other than vgt most of them are the same as stock. I've never seen over 24lbs on the mini on their file. Too much will kill the turbo as we found in the early days when they were pushing the mid 30s but I figure a couple pounds wont hurt. Worst case we can do a swap lol.
 

2012dually

New member
Joined
Sep 28, 2015
Messages
24
Reaction score
0
Location
Canada
Desired boost seems relatively the same as stock yes. So say I set the vane position table all to 30%. Do you know what would happen? Thats what I am trying to figure out if the vane position limits or desired boost.

Say does the ecm do this accel pedal input -> vane position -> desired boost

or

accel pedal input -> desired boost -> vane position
 

CoreyMS

New member
Joined
May 5, 2014
Messages
108
Reaction score
0
IMO based on the table Max boost variation from desired set at 29...vgt > desired boost

I'm raising my desired to test.
 
Last edited:

2012dually

New member
Joined
Sep 28, 2015
Messages
24
Reaction score
0
Location
Canada
I am actually changing all the vane position tables to 30% and leaving desired boost alone right now! I will post what I find!
 

2012dually

New member
Joined
Sep 28, 2015
Messages
24
Reaction score
0
Location
Canada
Well I just got back from a quick test drive with all vane position tables set to 30%.

Only thing it changed was vane position at idle. Boost was as if nothing was changed so from this I think it is safe to say that the vane positions are more of a guidline and at the end of the day the desired boost tables govern both how much boost and vane position.
 

ckrueg

Member
Joined
Sep 18, 2013
Messages
859
Reaction score
1
Location
Belding MI
Well I just got back from a quick test drive with all vane position tables set to 30%.

Only thing it changed was vane position at idle. Boost was as if nothing was changed so from this I think it is safe to say that the vane positions are more of a guidline and at the end of the day the desired boost tables govern both how much boost and vane position.
I know on 6.4s the desired back pressure tables seem to be the ones that matter. Vgt tables don't change a whole lot.
 

SpartanDieselTech

New member
Joined
Jul 14, 2015
Messages
524
Reaction score
0
I am actually changing all the vane position tables to 30% and leaving desired boost alone right now! I will post what I find!

Changing vane position (feedforward) will not actually change your boost levels, only the response rate.

These turbos are a feed-forward, closed loop system. The desired pressure is the pressure the system is looking for, and the PID controller will alter the feed-forward to find the setpoint at a given RPM and Torque setpoint.

https://en.wikipedia.org/wiki/Feed_forward_(control)
https://en.wikipedia.org/wiki/Control_theory#Classical_control_theory

Changes to the feedforward tables need to accompany a similar change to the desired pressure tables.

More desired pressure without extra feedforward duty cycle will get you an increase in manifold pressure, but the response will be slow. Too much feedforward duty cycle will not get an overall increase in manifold pressure, but will make the turbo overreact (and surge/fluctuate or overshoot the setpoint).

There are a LOT of tricks that can be played with this for performance purposes, including getting more boost out of the truck in lower gears (lower overall load) without overboosting the truck at high load/higher gears.
 
Last edited:

20136.7

New member
Joined
Oct 28, 2015
Messages
18
Reaction score
0
Does anyone know what the boost pressure as a function of torque and engine speed does? Do we ever need to change it? It doesn't look as though h&s has changed it.
 

Attachments

  • Capture.JPG
    Capture.JPG
    141.8 KB · Views: 61

Dzchey21

Active member
Joined
May 18, 2011
Messages
11,784
Reaction score
0
Location
wyoming
from what I have seen that table helps the ecm determine the "torque" that is used in other tables. I have changed them some but not much Mostly matching the 2015 turbo tables to the 2012 ecm with the turbo swap.
 

Dzchey21

Active member
Joined
May 18, 2011
Messages
11,784
Reaction score
0
Location
wyoming
Changing vane position (feedforward) will not actually change your boost levels, only the response rate.

These turbos are a feed-forward, closed loop system. The desired pressure is the pressure the system is looking for, and the PID controller will alter the feed-forward to find the setpoint at a given RPM and Torque setpoint.

https://en.wikipedia.org/wiki/Feed_forward_(control)
https://en.wikipedia.org/wiki/Control_theory#Classical_control_theory

Changes to the feedforward tables need to accompany a similar change to the desired pressure tables.

More desired pressure without extra feedforward duty cycle will get you an increase in manifold pressure, but the response will be slow. Too much feedforward duty cycle will not get an overall increase in manifold pressure, but will make the turbo overreact (and surge/fluctuate or overshoot the setpoint).

There are a LOT of tricks that can be played with this for performance purposes, including getting more boost out of the truck in lower gears (lower overall load) without overboosting the truck at high load/higher gears.



I have a surge in the higher settings and I figured that's probably where it was coming from. Tracing which two tables is causing it seems to be the hard part.

Anyone have any idea the typical EOM/Temp/configuration that the truck runs in during most "normal" conditions?
 

20136.7

New member
Joined
Oct 28, 2015
Messages
18
Reaction score
0
EOM 0 and Temp 1 is normal operating conditions from what I have gathered.

Dzchey21, did you self tune your 64mm streetmax? I am thinking about going with that turbo and would like to tune it myself.
 

Dzchey21

Active member
Joined
May 18, 2011
Messages
11,784
Reaction score
0
Location
wyoming
yeah, wasn't too bad, if you decide to go that route I will send you some base files to try that should get you close.
 

Latest posts

Members online

Top