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KnifeEdge87 KnifeEdge87 is offline
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Default Weird throttling action in 4th & 5th gears - 10-02-2020, 06:33 PM

Did a 3rd to 5th pull today and got really weird throttling action after the 3rd to 4th upshift which seems entirely unprovoked.

Timing remain advanced so it didn't seem to be knock related. The ecu just suddenly decided to start closing the throttle for what to me seems to be no reason.

I have a 520i G30 with a B48B20B. Ambient temperature was about 28 degrees celcius.

I'm running 98 Ron (~93AKI) pump gas, bone stock car other than the JB4. No E85 or E30 or E anything where I am.
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File Type: csv P58_M0_R1_201003_081655.csv (31.6 KB, 8 views)
File Type: csv P58_M3_R1_201003_075218.csv (22.5 KB, 7 views)
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KnifeEdge87 KnifeEdge87 is offline
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Default 10-02-2020, 09:42 PM

Tin foil hat time

I went out and did a single 4th gear pull thinking that the original throttle issues were somehow related to the 3rd to 4th shift or something. I did two pulls from 4th gear, both experienced the same throttling issues in map 3 (likely in conjuction or precipitated from the dme pulling boost target)

But isn't it just a huge coincidence that it happens pretty much exactly at 100mph. Almost like the stock tune is deliberately making high speed acceleration poor in the 20i model...
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KnifeEdge87 KnifeEdge87 is offline
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Default 10-02-2020, 09:42 PM

Logs of 4th gear pulls
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File Type: csv P58_M3_R1_B48D_G30_520i_201003_123014.csv (21.4 KB, 6 views)
File Type: csv P58_M3_R1_B48D_G30_520i_201003_1227.csv (17.1 KB, 6 views)
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Terry @ BMS's Avatar
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Default 10-03-2020, 09:20 AM

Looks like an issue at higher RPM where DME BT is dropping. For comparison sake update to v18 firmware and grab a similar log. If it continues we can always setup a map6 for you with more top end boost taper.
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Default 10-03-2020, 02:14 PM

Yea not sure why the dmebt is coming off there because in 3rd gear it doesn't really come off in the same way

The 3rd gear throttle increases progressively to 100 and stays there until redline for the most part

Will try the firmware upgrade as recommended
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Default 10-03-2020, 02:26 PM

V18 is beta right?

I'm upgrade to stable v17 first?
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Default 10-03-2020, 02:46 PM

Quote:
Originally Posted by Terry @ BMS
Looks like an issue at higher RPM where DME BT is dropping. For comparison sake update to v18 firmware and grab a similar log. If it continues we can always setup a map6 for you with more top end boost taper.
In map 0 it does the same throttle pullback, it doesn't feather like it did in map 3 because the spoofed signal + throttle activity seems to be exasperating the situation. The core issue still "feels" like it is throttling related given the map 0 data. The throttle is closed abruptly in 4th and 5th gear for what appears to be no reason, and the dmebt curve is still relatively smooth with no abrupt drop. In map 0 log the ecupsi doesn't exceed the dmebt until will after throttle closure has already occurred
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Default 10-03-2020, 04:33 PM

My tin foil hat just became a tin foil crown

I just made a couple runs more after updating v17, no difference

I did the runs in map 0 to try and pinpoint the issue

Did a run in 4th gear single gear pull, did two in 5th (again single gear pulls, although I had to cut one short due to traffic so really it's only one run in 5th gear)

My conclusion is that for 20i engines, in 4th gear and above you're going to see the ecu throttle no matter what. There's nothing you can do about it. This unfortunately also means that the jb4 provides very little if any benefit for 20i B48 engine above 100mph (roughly when this throttling begins in 4th gear).

It seems that this throttling behavior is done because the boost limit (remember the 20i engine is a handicapped 30i engine with artificially low boost target) is SO low that the ecu HAS to use the throttle plate to reduce manifold pressure to the target level. We can see the actual boost (Chargepipe) in both 4th and 5th gear exceed dmebt significantly but the manifold boost (boost 2) tracks (though undershooting) the ecu boost target.

Because this throttling seems to be hardwired into the stock 20i dme (normal boost regulation is performed via the waste gate, the fact this swordfish use case is NOT done like this strongly suggests that the throttle behavior was put in deliberately, especially because 30i B48s nor B58s have the same throttling issues at higher gears)

So what does that mean to us? Since the jb4 spoofs the Chargepipe boost signal and this high speed throttling effect seems to be independent of Chargepipe boost, it appears the jb4 CAN'T overcome the stock boost programming of the 20i engine in this regime (100mph+)

A flash tune can/should probably resolve this as I assume a flash tune would eliminate any hint of this speed dependent (or gear+rpm dependent) throttle mapping.

So under 100mph a jb4 would perform similarly to a car with a comparable flash tune but above 100mph the jb4 equipped car will be severely handicapped as it appears there's no way to combat this throttling effect with the weakness at the jb4's disposal (there's no "throttle wire")

With that said, I still strongly endorse the jb4 given all its other benefits (ability to use as an adhoc boost controller, wmi control, ease of logging, "undetectability" during warranty period, interface, etc)
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Default 10-03-2020, 04:34 PM

4th and 5th pulls in map0
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Default 10-03-2020, 04:44 PM

Fwiw it doesn't seem to be exactly 100mph as the trigger point

Just roughly around 5000rpm in any gear higher than 3rd
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Default 10-03-2020, 04:52 PM

Do the same log on map1, but set 6cyl timing = 5 in the app first.


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Default 10-03-2020, 05:10 PM

Quote:
Originally Posted by Terry @ BMS
Do the same log on map1, but set 6cyl timing = 5 in the app first.
Will try next week given traffic building up now

What does 6cyl timing =5 do?
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Default 10-03-2020, 05:18 PM

Just checked a few old post

My timing is already raw values right, so this setting won't do anything?

Also given I'm experiencing throttle closure with Map 0, surely map 1 won't improve anything right (at least with regards to the boost/throttle issues at high 90mph+ speeds)

Last edited by KnifeEdge87; 10-03-2020 at 05:23 PM..
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Default 10-04-2020, 04:19 AM

Added pics of the logs

You can see the Map3 throttle goes nuts in 4th and 5th gear but in 3rd gear it progressively builds to 100 and stays there.

In Map0 the throttle closes but doesn't feather as much (no doubt because the JB4 spoofing is causing some type of feedback loop which isn't happening on Map0).

In either case the throttle closure occurs BEFORE any overboost condition (defined as ECU PSI > DME BT) takes place so the throttle response in this case cannot be a response to overboost condition. The throttle closure also happens without any drops in timing, AFR deviations, trim deviations, FuelPressure High deviations, or anything else I can think of.
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