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Author Topic: MED9 - limp on extended overboost  (Read 15976 times)
gman86
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« on: January 23, 2017, 09:08:42 AM »

Starting to run out of options. Mk6 Golf R, MED9.1. Hybrid turbocharger that loves boost, doesn't like flow as much. 1K8907115F. / 510589.

From 4k -> 7k my boost profile tapers from 3000mbar to 2800mbar. Extended runs in 6th gear (around ~150mph) will cause the ECU to throw an overboost code and go into limp. Key cycle fixes it.

All the boost limiters are 2550mbar so they can't be raised. I'm driving duty cycle manually to achieve the required boost.

Short of rescaling the MAP sensor, is there anyway to disable the overboost protection? I've got a full A2L for the software and hunted high and low for the error class and can't see anything obvious.
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nyet
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« Reply #1 on: January 23, 2017, 11:23:19 AM »

Short of rescaling the MAP sensor

You mean every single pressure variable and calculation in the system?

No.
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gman86
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« Reply #2 on: January 23, 2017, 11:40:01 AM »

You mean every single pressure variable and calculation in the system?

No.

Hence why I said "short of". As in I absolutely don't want to do it, but I don't know of any other way - yet.
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littco
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« Reply #3 on: January 23, 2017, 03:26:35 PM »

Hence why I said "short of". As in I absolutely don't want to do it, but I don't know of any other way - yet.

Have you adjusted ELDOB?
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gman86
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« Reply #4 on: January 23, 2017, 05:20:07 PM »

Have you adjusted ELDOB?

Yep, it's at 1270hPa - max Sad
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gman86
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« Reply #5 on: January 23, 2017, 06:04:06 PM »

Found something. CLALDR and FFTLDR. Will disabling these prevent limp? Obviously I'd rather not if there's a threshold somewhere else that will be happy with more boost.
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nyet
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« Reply #6 on: January 23, 2017, 06:10:09 PM »

You're going to be chasing your tail forever.

Properly scale your pressure variables or GTFO.

Stop looking for shortcuts, they're only going to make things worse.
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gman86
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« Reply #7 on: January 24, 2017, 05:58:31 AM »

You're going to be chasing your tail forever.

Properly scale your pressure variables or GTFO.

Stop looking for shortcuts, they're only going to make things worse.

Scale my pressure variables? This is the problem - the car is hitting an "overboost" condition because of the boost pressure. My only solutions are a) run lower boost b) rescale MAP so it reads lower or c) remove the fault class.

If there is another way, I'm posting to find out what that is. I can't make that more obvious. I don't want to do the shortcut ways, I just don't know what I'm missing to do it "correctly". If you don't know, that's fine - not everybody knows everything. But coming in and selectively reading what I've wrote isn't useful in the slightest. I've made it perfectly clear I don't want to kill fault codes or bodge pressure readings.
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vwaudiguy
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« Reply #8 on: January 24, 2017, 08:25:03 AM »

When you say controlling duty manually, do you mean using a manual/electronic boost controller? Could you possibly adjust your request to match what you're seeing during those long runs? Does it seem like a time, or deviation thing? Do you have any logs when this happens? Ran into this type of thing a lot with a few BT 2.7T's that weren't using a 5120 a while back on mbc's.
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littco
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« Reply #9 on: January 24, 2017, 09:30:00 AM »

When you say controlling duty manually, do you mean using a manual/electronic boost controller? Could you possibly adjust your request to match what you're seeing during those long runs? Does it seem like a time, or deviation thing? Do you have any logs when this happens? Ran into this type of thing a lot with a few BT 2.7T's that weren't using a 5120 a while back on mbc's.

Id imagine he's controlling it via KFLDRL and a fixed duty cycle.

The only way its going to know its over boosting is by load variations, so are you sure the load limiters like LDRXn are high enough?

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gman86
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« Reply #10 on: January 24, 2017, 12:48:07 PM »

When you say controlling duty manually, do you mean using a manual/electronic boost controller? Could you possibly adjust your request to match what you're seeing during those long runs? Does it seem like a time, or deviation thing? Do you have any logs when this happens? Ran into this type of thing a lot with a few BT 2.7T's that weren't using a 5120 a while back on mbc's.

As above, driving via the ECUs PID. It's definitely a time. I've plotted boost in 4th, 5th and 6th and they're pretty much identical profiles. 6th gear seems to trigger it as it's held out for longer.
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nyet
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« Reply #11 on: January 24, 2017, 12:52:02 PM »

Scale my pressure variables? This is the problem - the car is hitting an "overboost" condition because of the boost pressure. My only solutions are a) run lower boost b) rescale MAP so it reads lower or c) remove the fault class.

If there is another way, I'm posting to find out what that is. I can't make that more obvious. I don't want to do the shortcut ways, I just don't know what I'm missing to do it "correctly". If you don't know, that's fine - not everybody knows everything. But coming in and selectively reading what I've wrote isn't useful in the slightest. I've made it perfectly clear I don't want to kill fault codes or bodge pressure readings.

5120 changes plus a boost pressure sensor that can read the boost levels you are running, or run under 2500 mbar. Those are your only two choices.

http://nefariousmotorsports.com/forum/index.php?topic=3027.0title=
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gman86
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« Reply #12 on: January 24, 2017, 12:52:13 PM »

Id imagine he's controlling it via KFLDRL and a fixed duty cycle.

The only way its going to know its over boosting is by load variations, so are you sure the load limiters like LDRXn are high enough?



Yep. The problem is the requested boost, no matter how high, is always 2550mbar absolute. Without ASM changes, I don't know of any way to request more pressure.
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gman86
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« Reply #13 on: January 24, 2017, 12:54:26 PM »

5120 changes plus a boost pressure sensor that can read the boost levels you are running, or run under 2500 mbar. Those are your only two choices.

5120 changes on MED9?
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nyet
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« Reply #14 on: January 24, 2017, 01:05:30 PM »

Yes.

Good luck.
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ME7.1 tuning guide
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Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your ex
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