Hey guys,

Can we get a how-to on calibrating the LDRPID from scratch? I mean from a clean slate.

First discovering duty <=> boost open loop
then duty linearization
and only then P I D components

?

i.e.
What needs to be set to get into the mode for open loop discovery of duty <=> boost relationship and duty linearization.

And then what are the steps of setting a specified duty, run car, and record boost maintained by that duty @ RPMs and then set another specified duty, repeat.

I'm finding the stock PID maps are way off when different wastegates (actuators) and more open exhausts are used. And just tweaking the PID maps are getting me no where fast.

Thanks,
Rey

...previous post continued because of truncation:

I did a quick Google search and there is a very short summary of the Ziegler-Nichols tuning rules on Wikipedia which references the original source here:

http://www.mstarlabs.com/control/znrule.html

The Ziegler-Nichols method apparently results in aggressive gain and overshoot which probably explains why we all see overshoot of boost on the stock maps! The table gives parameters for different states including 'no overshoot'. Worth a look but I've never used it myself in any context even though I'm surrounded by PID controllers at work.

I agree

To make matters even more difficult, tuning a BRAND new PID is going to be difficult if you are trying to tune near max MAP readings ....

I'd probably put the wastegate + n75 on a bench, apply cracking pressure + a few psi to the n75, and see how far the gate opens for a given duty.

Maybe get a stock wg and compare.

nice  work... I'm in to see some data.

You can see I had to make several runs in different gears to cover the whole RPM range.
then trace (yellow) the boost curve that emerges from the compiled runs.


logged runs from KFLDRAPP = 0
traced at same RPM points as KFLDRL in yellow (table below)



logged runs from KFLDRAPP = 10 (leaving lower 3 PED% rows =0)
traced at same RPM points as KFLDRL in yellow (table below)



logged runs from KFLDRAPP = 20 (leaving lower 3 PED% rows =0)
traced at same RPM points as KFLDRL in yellow (table below)



logged runs from KFLDRAPP = 30 (leaving lower 3 PED% rows =0)
traced at same RPM points as KFLDRL in yellow (table below)



logged runs from KFLDRAPP = 40 (leaving lower 3 PED% rows =0)
traced at same RPM points as KFLDRL in yellow (table below)



logged runs from KFLDRAPP = 50 (leaving lower 3 PED% rows =0)
traced at same RPM points as KFLDRL in yellow (table below)



logged runs from KFLDRAPP = 60 (leaving lower 3 PED% rows =0)
traced at same RPM points as KFLDRL in yellow (table below)



logged runs from KFLDRAPP = 70 (leaving lower 3 PED% rows =0)
traced at same RPM points as KFLDRL in yellow (table below)



logged runs from KFLDRAPP = 80 (leaving lower 3 PED% rows =0)
traced at same RPM points as KFLDRL in yellow (table below)

Now I use the values for the linear boost table and look up/interpolate  where it would fall on the non-linear table to duty.



But this is really done by an excel formula:



Once I do this lookup/interpolation for all nodes I get the final KFLDRL values:




vs stock:




Granted this is not 100% accurate because the true boost response is not a straight line between each duty node, but I doing the lookup/interpolation against it as if it were straight. You could build the first table with more duty nodes for a more accurate calibration, but that requires more KFLDRAPP change/run log sessions.

Simple K04 replace for a B5 passat 1.8T. Internal wastegate with actuator.

But stock PID maps could not hold boost steady at all. Since I was going to rework PID maps I thought it wise to make sure KFLDRL was calibrated correctly. I'll see if  I can post some before and after request boost vs actual boost graphs.