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Author Topic: ME7 part-throttle torque interventions  (Read 16414 times)
prj
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« Reply #30 on: July 08, 2018, 09:21:05 AM »

I have a 90mm MAF housing with a Hitachi sensor. In theory, at 5v the maximum airflow I can measure (without under scaling) is ~560g/sec. When I initially did the fueling, I looked at the few logs I could find and estimated that they were well over 600g/sec based on injector size, idc and afr. So, I under scaled my MAF by ~25% to give me a little bit of breathing room. Based on some of my logs at 32psi in cold weather, it looks like I have hit ~590g/sec. I am at 5,200ft, so I am limited to ~35psi (PR limit is 4) and I could probably reduce the under scaling, but when I go to sea level I don't want to hit any limits, either. I don't like that I have to under scale the MAF, I just don't see an alternative.
Where does this "560g/sec" limit come from?
If you're out of MAF then underscaling doesn't help you in any way, it'll still max out all the same. Explain your reasoning.
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KFDLULS is FF. I'll give it another try, but in the logs I have posted I am fairly sure I am still seeing throttle cut due to pvdk (no codes, however).
Ok, let me say this a third time, so it gets through to you - the ECU will never cut throttle due to pvdk > plsol EVER. Apart from overboost related limp mode.
Which you are hitting because your models are screwed up.
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Or maybe something is just broken. It is all 20 years old and I haven't replaced any of it. It seems like the signal line on the DV's isn't seeing positive pressure (only vacuum/near ambient) and the pressure differential is just pushing the valve open. Not sure if this is by design or if a check-valve is stuck or whatever. I'll take a look. Regardless, I don't really care. As long as I can get actual filling to meet requested filling without the throttle cutting I am happy.
It must see positive pressure, your stuff is plumbed wrong then. The only time it it doesn't is when the N249 is actuated.
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kaleb
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« Reply #31 on: July 08, 2018, 03:22:31 PM »

Where does this "560g/sec" limit come from?
If you're out of MAF then underscaling doesn't help you in any way, it'll still max out all the same. Explain your reasoning.

I was under the impression the MAF/MLHFM should stay under 1738.20kg/hr (~488g/sec) from KFMSNWDK. Is that not the case? Also, is there a hard limit for the MAF g/sec on the ECU? I have never seen a log with numbers anywhere near 600g/sec...

Ok, let me say this a third time, so it gets through to you - the ECU will never cut throttle due to pvdk > plsol EVER. Apart from overboost related limp mode.

I get it now. Nye, this should be made more clear in the wiki, especially since ECUxPlot and the translated FK refer to pvdk as "actual" and it is littered all over the common tuning threads.

"If you don't get all of this just right, and your actual boost goes too far above requested boost (by ~200mBar), you may experience overboost throttle cut due to negative deviation, which is ME attempting to get boost back under control by temporarily closing the throttle plate."

It must see positive pressure, your stuff is plumbed wrong then. The only time it it doesn't is when the N249 is actuated.

One of the few things on the car that is still plumbed from the factory. The N249 might be stuck open (which would explain the increased time to spool with a lighter spring), probably worth replacing.
« Last Edit: July 08, 2018, 03:31:42 PM by kaleb » Logged
prj
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« Reply #32 on: July 08, 2018, 04:24:33 PM »

I was under the impression the MAF/MLHFM should stay under 1738.20kg/hr (~488g/sec) from KFMSNWDK. Is that not the case? Also, is there a hard limit for the MAF g/sec on the ECU? I have never seen a log with numbers anywhere near 600g/sec...
I have no idea where you got that "impression" from, but it couldn't be further removed from the truth. KFMSNWDK gets multiplied by PR, now think about what you said...
The hard limit is ~1800g/s. I don't think that's gonna be a problem for you, now is it?

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I get it now. Nye, this should be made more clear in the wiki, especially since ECUxPlot and the translated FK refer to pvdk as "actual" and it is littered all over the common tuning threads.

"If you don't get all of this just right, and your actual boost goes too far above requested boost (by ~200mBar), you may experience overboost throttle cut due to negative deviation, which is ME attempting to get boost back under control by temporarily closing the throttle plate."
This statement is wrong, read FR not wiki. Negative deviation is limp mode, yes it goes into limp mode, and the reason it cuts throttle then is because you're running on the limp mode limiter for ... drumroll ... load.
Throttle control doesn't care about boost.
« Last Edit: July 08, 2018, 04:26:23 PM by prj » Logged

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nyet
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« Reply #33 on: July 08, 2018, 05:53:28 PM »

Yes, I think there is a ton of wrong "throttle cut" stuff in the s4wiki which was written before I had access to the FR, and it seemed (at the time) that slow path intervention was lde based, not load/torque based. That said, prj, I have a ton of throttle cut logs that show the plate closing WITHOUT throwing a code (I assume because it isn't actually negative deviation, just slow path torque intervention).

Obviously, nobody but me has ever really bothered to correct anything since then. More fail on my part to get anyone interested in documenting anything.
« Last Edit: July 08, 2018, 05:56:06 PM by nyet » Logged

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prj
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« Reply #34 on: July 08, 2018, 11:13:55 PM »

Yes, I think there is a ton of wrong "throttle cut" stuff in the s4wiki which was written before I had access to the FR, and it seemed (at the time) that slow path intervention was lde based, not load/torque based. That said, prj, I have a ton of throttle cut logs that show the plate closing WITHOUT throwing a code (I assume because it isn't actually negative deviation, just slow path torque intervention).

Obviously, nobody but me has ever really bothered to correct anything since then. More fail on my part to get anyone interested in documenting anything.
Yes, slow path intervention due to rl > rlsol
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