KFDPLGU and KFPLGUB in MED17.5?

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ThomasHH

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	KFDPLGU and KFPLGUB in MED17.5? « on: September 07, 2022, 05:50:54 AM »

Hello,

Could someone please explain the difference in plgru_w (result from KFDPLGU and KFPLGUB maps) handling between MED9.1 and MED17.5?

In MED9.1 according to the scheme, plgru_w is used to calculate relative pressure: plsol_w - plgru_w = plsolr_w, which is the x-axis of KFLDIMX.

With MED17.5, I quite often see a rise in the values in the KFDPLGU and KFPLGUB maps, but I can't understand from the scheme, what exactly plgru_w is messing with boost pressure control.


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quattro85

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	Re: KFDPLGU and KFPLGUB in MED17.5? « Reply #1 on: September 07, 2022, 09:11:21 AM »

My understanding (not pretending it is right) - it is used only for enabling wastegate control.
If plsol < plgru + histeresis curve than pressure can't be controlled with N75 duty cycle => no output to N75.


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ThomasHH

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	Re: KFDPLGU and KFPLGUB in MED17.5? « Reply #2 on: September 08, 2022, 09:13:03 AM »

Thanks, that seems like a logical explanation.

This might also confirm that plgru_w indicates the maximum achievable charging pressure with the throttle valve fully open and removed vacuum to the actuator.


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quattro85

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	Re: KFDPLGU and KFPLGUB in MED17.5? « Reply #3 on: September 08, 2022, 01:09:56 PM »

Quote from: ThomasHH on September 08, 2022, 09:13:03 AM

... and removed vacuum to the actuator.

Not exactly - more like if "vacuum" (more exactly boost) pipe connected directly between compressor outlet and actuator. Which is equal to disconnecting N75 eclectically or outputting 0% dc to N75.

With disconnected actuator the only force counteracting spring in actuator is Exhaust manifold pressure applied to the flap of wastegate.
When it is connected without N75 (0% DC), then full boost pressure is applied to diaphragm and this force is added to the force mentioned above.

Most Variable Geometry Turbochargers are controlled trough vacuum, while wastegate turbochargers are controlled trough boost.

Lately all of them are controlled directly with electrical actuators. Grin


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ThomasHH

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	Re: KFDPLGU and KFPLGUB in MED17.5? « Reply #4 on: September 09, 2022, 12:44:54 AM »

Thank you again. Very good explanation.

Now I remember how on my previous car with ME7.5 when I get an overboost error then WDC goes to 0, so I've been checking what the turbo is capable of with the direct pressure to the actuator.

So, rising the plgru_w in MED17.5 leads to raising the pressure when the Westgate control is enabled.


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