de_Fre
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« on: March 20, 2015, 05:45:57 AM »
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Hi guys,
I'm looking over boostcontrol on MED17.5 (2.0TSI). as I have a classic problem I guess.
When asking for boost say 1.3bar relative , I do get that boost BUT, at boost onset, I get N75 correction (from 96% down to around 75%) at 0.8bar relative (this is the stock boost level, so it looks like it activates the Proportional part of the PID control, I guess) then it corrects back to 96% and lets me go to 1.3 bar, the boost control is fine once it is close to target. This feels like a hesitation of the car.
Is there anyone who could help identify why this happens, why the N75 doesn't wait till closer to 1.3 to "activate" the PID or is my problem something else ?
I know people use tricks like building boost gradually in order to overcome this or tune the N75 limiter map to around 75-80% in the lower rpm's so you wouldn't feel this, or just kill the P-term in the lower rpm region to reduce the effect, but i'm looking to understand why this happens, which map(s) is (are) responsible.
Thanks for any help.
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Tezotto01
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« Reply #1 on: December 12, 2017, 09:29:19 AM »
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Any solution to this question?
I'm facing the same problem.
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jcsbanks
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« Reply #2 on: December 12, 2017, 11:00:49 AM »
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May not be your reason, but that happens with the D part of PID feedback on many boost control systems.
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vwaudiguy
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« Reply #3 on: December 12, 2017, 11:03:55 AM »
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Not going to be able to help much without decent logs, and/or posting your file... Also, waiting for Nyet to chime in telling you to read up on PID's  |
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« Last Edit: December 12, 2017, 11:05:40 AM by vwaudiguy »
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"If you have a chinese turbo, that you are worried is going to blow up when you floor it, then LOL."
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Tezotto01
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« Reply #4 on: December 13, 2017, 02:21:08 AM »
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I'll post the log.
Basically when you are doing an overdrive and if you ask for a little more load (without wot) the throttle opens 100% and the N75 cycle oscillates between 65% and 100% with this I feel the car oscillating the torque ....
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focalpoint519
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« Reply #5 on: December 13, 2017, 09:02:45 AM »
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any changes in KFVPDKLD or LDRXNLB, KFLDHBN?
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« Last Edit: December 13, 2017, 09:23:16 AM by focalpoint519 »
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NBR
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« Reply #6 on: December 15, 2017, 01:05:10 AM »
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I'm quite interested to know what maps pertain to the boost control on MED17 as it's different to the ME7/MED9.
What maps are you guys using to change the PID, N75 and WG Linearisation? Is it all contained in the LDRREG module or is there another module I should look at?
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panos1975
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« Reply #7 on: December 16, 2017, 10:40:23 AM »
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chck sections ATVLDSTE AWGTV......inside them you will find what are you looking for....
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NBR
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« Reply #8 on: December 18, 2017, 01:34:45 AM »
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Thank you! I will have a look and do some reading/testing
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NBR
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« Reply #9 on: December 20, 2017, 04:16:26 PM »
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Okay, so I've been doing a bit of reading and trying to understand using the FR and google translate...
I'm very far from understanding but i have a few questions and I'd like to know if I'm on the right track.
From what I've gathered KFTVLDST is the feedforward/base duty cycle map. The question I have here is it says that its used in application mode and that the variable B_tvkfldst is the input to the if statement to determine if it's used. Now I can't find any other reference to B_tvkfldst, is it set by a codeword or is it hardcoded so that the ECU always uses KFTVLDST?
The next is i see that KFWGV is used, with the P and I part added to it and then limited by KLWGMX. However the map seems a bit confusing, especially the row of zeros at 5800rpm (see attached pic). Is this because its expected that the PID controller would be in full control of the duty cycle at higher RPM?
I've also noticed that a lot of the time, the input and output variables to a module like AWGTV are not referenced in any other module, so thats where I'm getting stuck, because I don't know where the variable comes from and where the output variable ends up going or what the ECU does with the output of a module. Is this normal or am I missing something?
I still have to read through the entire LDRREG module to get some more understanding, but I would appreciate any help and hints you guys are willing to offer. Thanks once again
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prj
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« Reply #10 on: December 21, 2017, 08:49:07 AM »
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Application mode is set via codeword, disassembly will show you which one and which bit.
Then the entire flow based precontrol can be removed, and replaced with a standard precontrol map, which can be populated from 0-90% wgdc runs.
IIRC though just setting it through the codeword had some consequences, so I patched something in the code. Can't remember what.
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« Last Edit: December 21, 2017, 08:50:51 AM by prj »
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NBR
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« Reply #11 on: December 21, 2017, 09:10:41 AM »
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Thanks prj. I haven't tackled disassembly yet but I will give it a go using the guides here
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woj
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« Reply #12 on: December 21, 2017, 09:14:40 AM »
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(Writing from memory, travelling without my laptop). On ME7.9.10 which supposedly has a very similar boost control, the cw is CWMDAPP, will confirm later. The downside of KFTVLDST is that it is full open loop, at least on ME7.9.10.
While at it, any of you could share the parts of FR that treat boost control? Either for the discussed MED17 or ME7.9.10 or equivalent.
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NBR
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« Reply #13 on: December 21, 2017, 09:32:52 AM »
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Yip the MED17.5 does have CWMDAPP - codeword application without torque function.
Let me see if i can get IDA and try this disassembly thing
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woj
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« Reply #14 on: December 22, 2017, 12:20:52 PM »
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I briefly looked at the description for MED17, unfortunately only the last stage of the control seems similar to ME7.9.10, all previous calculations are different. In particular, in MED17 I do not see HLDSTNGMT and related maps. This probably means that my statement about open/closed loop for KFTVLDST for MED17 does not hold.
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