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Roland@pcmtec

HOWTO: Open Loop Boost Control (FG)

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When tuning with a different wastegate actuator or boost control solenoid it is best to tune the vehicle in open loop first to get your initial open loop duty cycle correct. Once this is correct you would enable closed loop again

There are 4 modes the boost control works in in the FG.

  • Idle/Cruising mode (0% duty cycle)
  • Overboost (0% duty cyle)
  • Underboost (100% duty cycle)
  • Closed Loop (Variable %)

In closed loop the wastegate duty cycle is determined via the following (this ignores the boost adder functionality at WOT and assumes you have zero'd them out)

duty_cycle = auF16463 (predicted open loop duty cycle) * auF0318 (injector duty cycle) * auF16634 (boost multiplier ECT) * auF0315 (Barometric multipler) * auF16475 (desired boost multiplier TPS) + KP + KI

Where KP and KI are the PID outputs (closed loop control).

So knowing the above we can force permanent open loop control by the following:

Setting the PID constants to all zero.

We can then set the underboost value to a very high number so that we never get true underboost (100% duty cycle)

Set the overboost value to a very low number so we never get true overboost (0% duty cycle)

Set the "cruising mode" TP Count to a low number so you never get 0% duty cycle unless you really are at cruise or idle.

 

If you would like a dummys guide change the following items:

auF2645 P1228 Timer - Set this to 1000 for the entire table

auF2150 P1228 - Wastegate Failed Open (Under Pressure) - Set to "No Error"

auF2279 P1227 - Wastegate Failed Closed (Over Pressure) - Set to "No Error"

auF16459 Desired Boost (inHG) set this out of range to a high number like 35

auF16475 TPS Boost multipler - Set this all to 1 other than idle/cruise.

auF3184 Underboost Required For Open Loop - Set this to a high number like 40-100

auF3204 Intake Cam Adder for boost error - Set the degree adder to 0. This is important otherwise your VCT system will command incorrect angles.

auF3264 Exhaust Cam Adder for boost error - set the degree adder to 0. This is important otherwise your VCT system will command incorrect angles.

auF3002 Spark Adder/Delta Change in Wastegate - set to 0

auF0286 Integral gain - Set to 0

auF0287 Proportional gain - Set to 0 (try 1 as well, however most likely will be ignored in open loop)

auF0296 Overboost to trigger open loop - set to -50 to -100

auF16555 Integral Gain - Set to 0

auF16519 Integral max - Set to 0

auF16453 Integral min - Set to 0

auF0289 Proportional Max - Set to 0

auF0288 Proportional Min - Set to 0

auF1193 P1227 Fault Filter - Recommended to leave unchanged.

auF1328 P1227 Fault Filter - Recommended to leave unchanged.

auF1898 - Open loop duty cycle for underboost - set to 40-50%

auF1098 - P1227 overboost error - Recommended to leave unchanged.

auF2625 - Slope due to pre turbing temperature - This function accounts for heat soak into the wastegate actuator. It will modify the final wastegate duty cycle to try and keep a more consistent boost pressure when the exhaust is hot or cold. If you want a completely open loop boost control, set the unitless column to 0. If you leave it as stock, the wastegate duty cycle will change with exhaust temp, however it should give you a flatter boost curve when then exhaust is extremely hot vs cold.

auF16680 Boost Clip based on Inferred Turbo Temp - This is not in all FGs, only the later model vehicles. This will clip the desired boost. If you are using proper closed loop boost control, or you are utilising this table, make sure you raise this table to be higher than what you are requesting in your desired boost table.

auF0286 - Integral Clip (this is the "cruising mode" table which sets duty cycle to 0% below these TPS values. Set the TPS column to ~150 counts at higher rpm to ensure you always get the commanded duty cycle.

image.png.00fd30fe9156cef1b4321d8789922dc2.png

 

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Will I notice from your uploaded file you have auF2776 set to -100, this may be causing you issues as well. You also have P1228 and P1227 set to "No MIL" which will still trigger them I believe, auF1098 (boost error) is set to 18 as well which may not be high enough.

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I will have a look at your file and see if any of the other workshops would be willing to give advice as I've never personally done an FG, though I know lots of people do what you are trying to do.

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Can you try setting auF0287 to 1.0 instead of 0.0 ? It may use this as a multiplier still.

Everything else looks good.

edit: Can you use a scanner to see if P1228 or P1227 are being set?

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I don't know whats going on now I just tried 0 desired boost and still commands 100% dc and it's all ways at the 4000rpm

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Corrupted file? Does that happen with these cars?

I've had that happen with an aftermarket unit and it wouldn't change the fuelling no matter what I did. I reloaded the file and it fixed it.

Just a thought.

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Just now, Puffwagon said:

Corrupted file? Does that happen with these cars?

I've had that happen with an aftermarket unit and it wouldn't change the fuelling no matter what I did. I reloaded the file and it fixed it.

Just a thought.

Unlikely. You would get a checksum error, and if any of the code gets corrupted the car wouldn't even start as it would crash and just constant restart the CPU.

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Will it looks like you have whole number in the duty cycle. Eg 42 will cause 100% duty cycle. 1.00 is 100% duty so scale these numbers back by a factor of 100

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  • I totally over looked that, thanks man that's fixed it. you guys are doing a awesome job thanks for the quick replies.
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I didn't even think to look either!

Glad to see it is working now. We will make up some parameter files (a file with presets) for enabling/disabling open loop at some point soon.

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Hi Guys,

Sorry bit of a newbie question. With applying all the above settings, how do you then set your targeted boost setting??

Say i want to run 15 psi?

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Depends.

If you are running everything open loop you need to adjust your wastegate duty cycle until you reach your desired boost. If you are running closed loop you need to adjust your desired boost (uses inHG units) and also adjust your open loop wastegate duty cycle otherwise you will get oscillations when going in and out of closed loop/open loop.

The recommended procedure is to force open loop. Get your 15psi via the duty cycle table, then set your desired boost table to match what you are measuring boost wise. Then if you run your car on a freezing cold night it won't over boost.

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In an FG the wastegate duty cycle is "auF16463 Predicted Open Loop Wastegate Duty Cycle" and Desired Boost is auF16459 "Base Desired Boost Pressure for Turbo Control"

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The closed loop fueling controls the afr to 1.0 lambda, it has nothing to do with closed loop boost control which controls boost pressure to that which is in the desired boost table. 

There are probably 20 closed loop PID controllers in the PCM. 

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Hi, need some help.

Followed the guide to enable open loop.

I'm finding that something is not set right, Initially i'm getting full boost like 15-18psi on 1 run then after only 3 psi.

Any help would be appreciated. Looking to have a valet and low boost profile

Also not sure which parameter is to set boost by gear.

Using HAER1UB sprint as base with custom OS

 

F6 Sprint_CustomOS-boost open loop.tec

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Sprint is complicated as it has overboost and boost by gear from factory. You are best off disabling all of the temporary overboost multiplier tables and boost by gear tables then enabling our custom os boost by gear tables.

The factory ones work off timers and will only run for a few seconds.

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Ok thanks, I will try that.

Already had all WOT waste gate and boost adders set to 0

Set all WOT boost multipliers to 0 now as well

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1 hour ago, Superb said:

Initially i'm getting full boost like 15-18psi on 1 run then after only 3 psi.

Is the throttle blade staying completely open while this is happening? The only way I can think of making 3 pounds at WOT via the tune is for the throttle to be closed for torque reduction.

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1 minute ago, Puffwagon said:

Is the throttle blade staying completely open while this is happening? The only way I can think of making 3 pounds at WOT via the tune is for the throttle to be closed for torque reduction.

Unsure? I will log that tomorrow and see if that is happening.

Thanks

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Always log torque source. It is the most important thing to log. 

Also log map pressure you could have an intake pipe sucking shut. 

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19 hours ago, Roland@pcmtec said:

Always log torque source. It is the most important thing to log. 

Also log map pressure you could have an intake pipe sucking shut. 

Is that TQ_ETC_SRC ?

No its not a intake pipe problems, too wet today to test much but I think the car is going into limp mode after a WOT run.

As @Puffwagon said I noticed when this happens I'm only getting 20% throttle. 

If I don't push it, I have boost but i'm still not getting boost control to where I set it. 

Need to spend more time seeing whats going on

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As an example of torque reduction, I tried loading the car up on the brake in 3rd gear at low rpm, before logging the run. The car felt very sluggish compared to just planting it with no brake boosting.

When I reviewed the log, the throttle wasn't fully open until just after 4000rpm, which showed as a massive dip in the virtual dyno graph I made.

I haven't gotten around to removing any torque reductions yet and I'm ok with that, as it rarely affects how the car drives, but in your case 20% throttle clearly needs sorting out.

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I know this sounds like a dumb question but just for confirmation

0% duty cycle is the wastegate 100% open & 100% dc fully closed ?

which would be in auF16463 0 for 100% open & 1 for fully closed?

 

 

 

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It's the bleed valve that is open /closed and indirectly the waste gate. 

1.0 is 100% duty and hence maximum bypass or keeping the wastegate as closed as possible. 

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1 minute ago, Roland@pcmtec said:

It's the bleed valve that is open /closed and indirectly the waste gate. 

1.0 is 100% duty and hence maximum bypass or keeping the wastegate as closed as possible. 

Perfect, thanks

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