Can VEMS control a variable geometry turbo?

[BimmerDread]

Has anyone messed about with using VEMS output to control a variable geometry turbo such as the Holset 351VGT? These vary the turbine housing volume from 3mm² to 25mm².

I am looking at using this set up to achieve fast spool using TPS and RPM to activate it on an BMW s38b36 engine. My idea is that for:

TPS<50% all RPM range to set the housing to 25mm² which I have calculated to to spool 1 bar from ~4500rpm.

TPS >50, RPM 1000 to 2500 to set the housing to say 10mm² for spool at 1800 RPM,

TPS > 50%, RPM 2501 to 4500 housing 18mm²

TPS > 50%, RPM 4501 to Redline (Set to 7000) housing at 25mm²

The concept is to control spool. The built in boost control will monitor boost. 

People have been messing about with controlling this turbo. See here http://www.homemadeturbo.com/f7/holset-vgt-he351ve-controller-117261/
It is a long read but with good info.

[GintsK]

PWM - yes
CAN - no.

[gunni]

I thought about this 2 years ago and at that time was going to use a mechanical linkage to the turbo to control the movement.
But with a pressure actuated one a boost solenoid would work the same.

You can use the alternative pwm table to do this based on manifold pressure against rpm.

Which should provide you with the control ability . If needed then you should be able to get a TPS/RPM pwm table from the developers.

[BimmerDread]

Its CAN

So I think I have 3 options:
1) A PWM solenoid and lever and not the stock actuator.
2) A on/off solenoid activated on TPS and RPM
3) The mechanical route (Boost activated).

Thanks guys.

[GintsK]

Some drives for VNT was just PWM. May be it is possible to find some..

[gunni]

Its CAN

So I think I have 3 options:
1) A PWM solenoid and lever and not the stock actuator.
2) A on/off solenoid activated on TPS and RPM
3) The mechanical route (Boost activated).

Thanks guys.

What is the actuation process ? is it pressure based or mechanical linkage within the adjustment unit?

[BimmerDread]

The turbo uses a mechanical linkage operated by a motor.

[gunni]

then just replace the motor?

my idea was to use a servo motor to handle the mechanical movement.

[GintsK]

Servomotor from what?
There is harsh environment!

[andreNL]

Maybe the steppermotor driver can be used

[gunni]

Servomotor from what?
There is harsh environment!

the servo doesn´t have to be directly close to the turbo, it can be mounted elsewhere and rotate a arm.

[GintsK]

Ok. What servo?
===
Stepper isn't best idea. It require firmware modificatons. Servo usually use pulse width. So PWM with right frequency could be used. VEMS can control VNT + control W-gate using two independent PWMs.
SI engine require w-gate too.

[gunni]

I can´t remember which, but it has to have a bit of torque available

[BimmerDread]

So... after some thought I decided to modify my parameters. This is what I came up with:
At 12mm² spool comes on at 2000 rpm and back pressure effect begins at 4100 rpm.
At 23mm² spool comes on at 4000 rpm and back pressure effect begins at 8000 rpm.

I want to have a two state (on/off) solenoid that when off keeps the volume at 23mm² and at
12mm² when on.

A function table would look like this:

TPS            RPM           State      Volume
<50%         Varies         Off          23mm²   
>50%         0 - 4k         On          12mm²
>50%         4k - 8k        Off          23mm²
 
The waste gate would manage any boost ripples on transition.

I needed a mechanical system that would have pressure at all rpms so I am opting for an oil pressure based system (like vanos )

I want to feed the oil to the waste gate port that would operate the system.

What do you think?

[gunni]

Most wastegates would leak.