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 Post subject: boost control
PostPosted: Wed May 15, 2013 6:12 am 
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I've never personally done a turbo install so I'm going to need help with this one to understand what exactly is needed for boost control.

Max Boost set point right?

are all boost controllers created abotu equal so a say a constant 100hz PWM then varies duty cycle to control boost what is needed?

or do you also need a constant Duty cycle option with frequency used for control?

I setup generic optional output control in the tuner.....is what I have ok or is a special boost controler screen needed (which probably means special screens for all the stuff like fan control, etc?)


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 Post subject: Re: boost control
PostPosted: Wed May 15, 2013 3:07 pm 
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Quote:
Max Boost set point right?


Demand value, yes.

Quote:
are all boost controllers created abotu equal so a say a constant 100hz PWM then varies duty cycle to control boost what is needed?


Yes

Quote:
or do you also need a constant Duty cycle option with frequency used for control?


No, but the frequency should be user selectable.

Quote:
I setup generic optional output control in the tuner.....is what I have ok or is a special boost controler screen needed (which probably means special screens for all the stuff like fan control, etc?)


A good boost controller is pretty hard to make and to tune for that matter. A vanilla pid controller will not work all that well. A table with throttle/rpm/duty might be a good start (Open loop). Look at the bosch for a quite good implementation.


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 Post subject: Re: boost control
PostPosted: Wed May 15, 2013 8:03 pm 
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glenn wrote:

A table with throttle/rpm/duty might be a good start (Open loop). Look at the bosch for a quite good implementation.


That seems like a bugger to tune but it's certainly the easiest for me to add so I won't object too loud ;)


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 Post subject: Re: boost control
PostPosted: Thu May 16, 2013 11:34 am 
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That seems like a bugger to tune but it's certainly the easiest for me to add so I won't object too loud ;)


Yes, but what you see is what you get.. Boost will however creep quite a lot.

A proper boost controller is not easier to tune though.. And if this is tuned first it the data can be used as the precontroller then the pid only has the small changes.


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 Post subject: Re: boost control
PostPosted: Thu May 16, 2013 11:36 am 
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mk e wrote:
glenn wrote:

A table with throttle/rpm/duty might be a good start (Open loop). Look at the bosch for a quite good implementation.


That seems like a bugger to tune but it's certainly the easiest for me to add so I won't object too loud ;)



Wait....TPS v RPM?

I was thinking MAP.....but I guess thinking about it more TPS is right because you the turbo sets the MAP. That still seems like a bugger to tune...but I'll put it in.


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 Post subject: Re: boost control
PostPosted: Thu May 16, 2013 11:40 am 
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glenn wrote:

Yes, but what you see is what you get.. Boost will however creep quite a lot.

A proper boost controller is not easier to tune though.. And if this is tuned first it the data can be used as the precontroller then the pid only has the small changes.


The one in haltech just is 3 numbers I think
0% at say 8 psi
100% at say 10 psi
set point say 10 psi

and it does a decent job according to Jack who'll be our guinea pig

I don't know though exactly what they are doing control method wise. I'll have a better look at that and a couple other ecus today I guess.


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 Post subject: Re: boost control
PostPosted: Thu May 16, 2013 12:57 pm 
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Boost is control by map voltage, a 2 bar map will be liner 0-5V so full boost of 14.7psi would be 5V and 7.35 psi would be 3.75V atmospheric would be 2.5V. Correct?


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 Post subject: Re: boost control
PostPosted: Thu May 16, 2013 1:50 pm 
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Wait....TPS v RPM?

I was thinking MAP.....but I guess thinking about it more TPS is right because you the turbo sets the MAP. That still seems like a bugger to tune...but I'll put it in.


It is not that hard to tune but the result is lacking... A closed loop controller is WAY better but this option might be good to have during the development of the controller.

It should have been map vs rpm..

When doing closed loop it is a good idea to scale boost with tps (lower boost with a rpm tps curve) as tps and boost might not have a linear relationship.


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 Post subject: Re: boost control
PostPosted: Fri May 17, 2013 12:47 am 
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Scaling boost against throttle angle means the boost relief valve curve will be have to be less aggressive at lower throttle angles and more aggressive at higher throttle angles.

It might be suggested to move towards increasing boost when the throttle angle is moving towards closed. Theory being that the reduction in throttle angle means the load on the engine is being reduced due to a gear change so take advantage of the situation and increase the turbine spin rate.

Quite complex PID.

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 Post subject: Re: boost control
PostPosted: Fri May 17, 2013 10:41 am 
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p2164 wrote:
Boost is control by map voltage, a 2 bar map will be liner 0-5V so full boost of 14.7psi would be 5V and 7.35 psi would be 3.75V atmospheric would be 2.5V. Correct?


Well...boost is measured by the MAP sensor just as you describe.

But what is the best way to control it is a slightly different question.

Glenn is suggesting a table just like you fuel or spark table but with duty cycle int he cells.

I'm thinking you will probably get about the same result from a simplish PID or maybe just the PD part that looks at MAP and MAPdot

The table version is the easiest so I'll get that working first then move on to a 2nd option of a closed loop solution.


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