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Author Topic: P1555 Charge Pressure exceeded code  (Read 27207 times)
Aragorn
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« on: May 31, 2016, 11:53:11 AM »

Hopefully someone can give me some pointers with this. Maybe it belongs in the n00b zone, but i'm trying to get my head round everything.

I've got a hybrid turbo with a 12psi actuator, on a B5 1.8T, running a TT225 ME7.5 ECU.

I'm supposed to be getting it professionally tuned, but the tuner seems somewhat elusive at the moment. He provided a base map to get it running with the injectors setup and some other tweaks. The axis for KFVPDKSD has been scaled to account for the actuator, but it looks odd to me. In the original tune the axis only goes up to 1.2, which doesnt make any sense? The scaled version goes up to 1.5, but again this seems odd. I'd expect much higher values? The car does seem to manage to control the boost with the throttle upto around 10psi (any more and i get limp mode), but i'm unsure whats going on here. Is it maybe like the RS4 files where 1=wastegate pressure rather than 1=atmospheric pressure? Does simply scaling the axis work in that case? Theres much chat on the forum about hacking files to restore the "normal" version of this function, rather than info about tuning the RS4-style version.

I've been tweaking bits myself to try and get it running a bit better in the interim period, The wife drives the car a lot and it needs to be usable. I've mainly been trying to dial in the injectors a bit better (it was throwing system too lean codes), fixing cruise control, sorting fault codes for missing CAN etc. Getting to grips with the whole tuning thing as i go. The load and boost stuff in the map is all stock.

If i apply more than about 75-80% throttle it drops into a limp mode, limits boost to 5psi and doesnt clear after an ignition cycle remaining like that until i go in and reset the fault codes, leaving the P1555 code behind.

I raised LDRXN slightly, as its default setting was very close to the actuator pressure, lower in some places, and i thaught that might have been the cause of the overboost code but that didnt change anything.

I'm not quite sure whats going on, as engine load in the logs looks sensible, but measured boost pressure (pre throttle) is showing pressure way over requested, 2.2-2.3bar at the point it trips out. Boost guage in the car only shows around 12psi when this happens, The throttle appears to only be 25% open when this occurs. At a guess its related to WGDC, maybe i should just unplug the N75 in the mean time? I have a vague idea i need to fix the boost PID, but its all rather alien, and i'm sort of in at the deep end.

I was out logging nvquot earlier to fix cruise control and happened to catch this happening so i figured i'd post the log and see what you think. The overboost code trips at around 300seconds.

Cheers
« Last Edit: May 31, 2016, 11:56:53 AM by Aragorn » Logged
nyet
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« Reply #1 on: May 31, 2016, 12:10:13 PM »

Need a WOT run to confirm (BEFORE it goes limp) but likely your LDRXN isn't even close to right.
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Aragorn
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« Reply #2 on: May 31, 2016, 12:34:25 PM »

Cant even get WOT, any more than about 80% and its instantly into limp.

Its requesting ~55% WGDC in that log around 300 seconds, despite being way over requested boost? I'm thinking its a boost PID issue? WGDC must have to be a lot lower on the 12psi actuator than whats in the map?

LDRXN tapers up to 170 by 3k, sits flat until 6k then tapers off. Should be easily achievable for the turbo fitted. The logs show requested and actual load was around 140, so well below LDRXN? I cant see why LDRXN could be the issue?
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nyet
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« Reply #3 on: May 31, 2016, 12:35:18 PM »

Because your requested boost is WAY under your actual boost for most of the log.

Could also be IRL related, but w/o a wot log it is hard to tell.

just clear the code, go into 2nd, and floor it from 2k to redline.
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Aragorn
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« Reply #4 on: May 31, 2016, 12:44:02 PM »

I'm not sure i follow.

LDRXN is a limit on requested load. I'm not at the limit, its requesting 140ish, and achieving 140ish according to those logs, yet boost is far too high and the throttle plate is only open 25%. How can it be an LDRXN issue?

55% WGDC seems far too much when it only wants 1800mbar. It'll make 1800mbar with 0 WGDC, you can see it doing exactly that earlier in the log... Yet its requesting 55%, which causes the overboost?

I can try flooring it in 2nd, but i dont want to break it Tongue
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nyet
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« Reply #5 on: May 31, 2016, 12:50:36 PM »

It'll make 1800mbar with 0 WGDC, you can see it doing exactly that earlier in the log...

If that isn't expected, then your WG line is busted or your N75 is malfunctioning.

Start there. I assumed that you were surprised at the overboost code because of something tune related, not hardware related.

In any case, you said in limp you were seeing 5psi, so something is odd if 0wgdc makes 1800 mbar as well.

It is impossible to diagnose anything w/o actually being WOT.

You wont break anything if the car goes insta limp anyway.
« Last Edit: May 31, 2016, 12:52:46 PM by nyet » Logged

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Aragorn
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« Reply #6 on: May 31, 2016, 12:54:05 PM »

Its got a 12psi actuator, 1800mbar with 0 WGDC is expected and normal? A pull on the old ECU with no N75 connected would usually see about 13psi thru the midrange.

The issue is the ECU is wanting 1800mbar and is cranking out 55% WGDC, which clearly results in a lot more than 1800mbar?

edit:
When in limp mode, the ECU is using the throttle to limit boost to 5psi.
« Last Edit: May 31, 2016, 12:56:56 PM by Aragorn » Logged
nyet
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« Reply #7 on: May 31, 2016, 01:16:34 PM »

Something is very very wrong with that file.

ps_w is tiny compared to pvdkds_w because the throttle is almost shut completely.
 
Hard to make head or tail of the log with your throttle part closed though.

Just go WOT. If you're nervous, cut IMX

Also, you'll want to add some of the PID variables to the log. Not sure why you're seeing so much integrator wind up if req is so much higher than actual.
« Last Edit: May 31, 2016, 01:19:22 PM by nyet » Logged

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Lost
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« Reply #8 on: May 31, 2016, 01:22:25 PM »

Problem is in your KFLDRL and IMX not been adjusted for harder WGs
You need to do PID calibration from sctrach or pull n75 before you get it tuned
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nyet
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« Reply #9 on: May 31, 2016, 01:23:00 PM »

Also, if your tuner isn't being helpful, you really should be doing your own file from scratch.


Something is really crazy with the file, the WGDC is not following ldr error properly.

Is this a 5120 file or something?
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« Reply #10 on: May 31, 2016, 01:23:45 PM »

Problem is in your KFLDRL and IMX not been adjusted for harder WGs
You need to do PID calibration from sctrach or pull n75 before you get it tuned

Sort of. Why is he getting 55% WGDC when req boost is BELOW actual?

He needs to log wg before lin and the the rest of the PID variables.

Perhaps something is wrong in DRL, though, like you said. that would explain the 55% dc.
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Aragorn
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« Reply #11 on: May 31, 2016, 01:34:33 PM »

Well went and tried a WOT log. And as expected nearly blew the bloody thing up.  Embarrassed

Boost guage pegged itself at 25psi and massive missfire at about 3100rpm. That sort of shit is what puts holes in the side of 1.8T's...

I've been fairly sensible upto this point, because i cant afford a knackered engine. Mashing full throttle on an engine that clearly has wonky boost control is obviously a shit idea!


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Lost
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« Reply #12 on: May 31, 2016, 01:37:20 PM »

He needs to do a proper log. He is pedaling up and down. I am almost 100% sure that his tuner did not even touch PID maps at this Point.
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« Reply #13 on: May 31, 2016, 01:39:47 PM »

As i said - in this log you can clearly see that PID is not adjusted for your tighter WGs and it overshoots badly. Do not attempt this again.
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nyet
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« Reply #14 on: May 31, 2016, 01:40:47 PM »

I've been fairly sensible upto this point, because i cant afford a knackered engine. Mashing full throttle on an engine that clearly has wonky boost control is obviously a shit idea!

ps_w and pvdkds show well below 25psi.

So whatever you think is happening, either isn't happening or...

Don't mess around with 3rd party tunes you have no clue about.

If the tuner won't help, ditch it and start from scratch. Even if you CAN find the problem, you're wasting your time.

Also, I still don't see wg before lin, or any PID variables in your log.

Bottom line, your tuner screwed you, he gave you a fixed WG file.
« Last Edit: May 31, 2016, 01:44:04 PM by nyet » Logged

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