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RIGHT CLICK IS BACK! (09 May 2021)

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Desired vs measured readings

  • Takeeon
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02 May 2021 09:48 #48575 by Takeeon
Replied by Takeeon on topic Desired vs measured readings
Yeah. I did a deep dive into diagnosing the map a while ago. By all accounts, it appears to be working and registering proper values and temps. There are ways to log, but it's super complicated. Torque has a nice graph function in real time tho. It doesn't seem to pickup the PID for the "boost pressure upstream valve", so I can't use that to check it. Somewhere there is an update to that crappy chinese scanner I have, but it's nearly impossible to navigate the web of crummy websites you need to find it. I have been using the settings for a 2017 1.6t Elantra, which I didn't think would be very different, but apparently, they are or that thing just sucks. Either way, I will probably take it to an exhaust shop and have it checked out. Regardless of weather it's doing the proper calculations, it seems to not match the "desired" values.
If *900hpa* is atmospheric pressure, then maybe *1200hpa* by the scanner is a normal pressure while idling.
What doesn't seem to make sense is the "desired" value would actually be below atmospheric pressure. I'm not sure if that makes any sense

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02 May 2021 09:56 #48576 by Takeeon
Replied by Takeeon on topic Desired vs measured readings
Wait no. The conversion app uncle Google supplies is wrong, actually. 900hpa is equal to 90kpa. So 980hpa is close to atmospheric pressure. It would seem the sensors are correct. I've got too much back pressure during normal operation and it evens out at full load. I'm not sure this indicates a clog in the exhaust

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02 May 2021 09:58 #48577 by RimmersTechSWE
Replied by RimmersTechSWE on topic Desired vs measured readings
Yeah the anomaly is almost exactly 1 atmosphere of pressure so it looks like there is some calculation error. That upstream throttle sensor might be a dead end. Do you know wether the turbo is variable vane or fixed? The exhaust side sensor could be for the control of varible vanes and if those are gummed up with sut that might be the problem. I have seen it happen on VW buses with variable vane turbos they use a normal map sensor and a separate vacuum actuator on the turbo housing though and quite often crack the turbo/exhaust manifold housing aswell.

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02 May 2021 10:10 #48579 by Takeeon
Replied by Takeeon on topic Desired vs measured readings
I believe it's a variable twin scroll borgwerner

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02 May 2021 10:42 #48580 by RimmersTechSWE
Replied by RimmersTechSWE on topic Desired vs measured readings
"Back pressure" would be a negative value though. Unless they compensate a car with the key on and engine off should be a 1 atmosphere unless it's compensated to 0. Any positive exhaust pressure should push exhaust gases out of the exhaust and any negative pressure should suck them back in again. The more throttle the more positive pressure. "Back pressure" should only be posible in a 4 stroke exhaust if it had a leak to the intake through a permanently open open EGR. That would also explain the exhaust pressure being lower with the engine running. Strange if it didnt set a code though. That's unless there is any other path for exhaust gasses to get into the intake.

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03 May 2021 10:07 - 03 May 2021 10:13 #48598 by Takeeon
Replied by Takeeon on topic Desired vs measured readings
Crap. I've got to look into this further
Last edit: 03 May 2021 10:13 by Takeeon.

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03 May 2021 13:28 #48601 by Matt T
Replied by Matt T on topic Desired vs measured readings

RimmersTechSWE wrote: Yeah the anomaly is almost exactly 1 atmosphere of pressure so it looks like there is some calculation error. That upstream throttle sensor might be a dead end.


Actual is definitely absolute pressure because it's ~ BARO KOEO. The desired is less than BARO so it might be gauge pressure??

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03 May 2021 13:50 #48603 by Takeeon
Replied by Takeeon on topic Desired vs measured readings
What exactly to do you mean by "guage pressure"?

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03 May 2021 13:57 #48604 by Takeeon
Replied by Takeeon on topic Desired vs measured readings
Oh, I see what you mean. That wouldn't add up either. The odd thing is that it smooths out when both numbers even out. That makes me think the desired is absolute as well

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03 May 2021 14:21 #48605 by Takeeon
Replied by Takeeon on topic Desired vs measured readings
Seen here at about 3.5k. This is usually when the car feels like it flips a switch and starts to pull normally. It runs like garbage mostly when I see the numbers out of alignment. This is the only quantitative thing I've found that shows when it runs well and when it doesn't.
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07 May 2021 10:16 #48699 by Takeeon
Replied by Takeeon on topic Desired vs measured readings
It looks like the readings for "desired" are mirroring absolute intake manifold pressure. So what the hell is it measuring?!
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