Forced Throttling at speed

Knifeedge2k1 · 10-04-2020, 02:37 AM

Hi Guys,

Firstly I apologize for the wall of text but it's just how I write.

I've just noticed something strange throttle action while logging pulls done into higher gears (4th and higher).

Background:
Car: G30 5 Series
Year: 2019
Trim: 20i MSport
Engine: B48B20B (identical to 30i engine hardware-wise, difference in software)
Fuel: 98 RON (93 AKI), no E85 or any form of Ethanol where I live
Mods: Only JB4, stock everything else

Originally I was intending to increase my boost via the JB4 given the artificially low limits set in the stock ECU tune from the factory. Given the gains available from a proper flash tune on the 20i engines I didn't feel Map 3 on the JB4 was "enough" so I was just getting some data to see how much more additive boost I could command safely.

While gathering data however, I noticed that my engine was experiencing extreme amount of forced throttling at speeds greater than 90mph in 4th and 5th gear (I presume it would be true in 6th-8th as well but given I don't have the space nor power to pull in those gears so it's a bit of a moot point).

All my prior logs/pulls in 2nd & 3rd gear from 2200rpm-redline have had throttle progressively ramp up to 100% and stay there. Once in 4th or 5th however at ~5000rpm I can see the throttle cut back extremely abruptly and the throttle oscillating/feathering in a strange manner (while on JB4 maps 1 thru 3) and all of this is accompanied by a drop in DME BT (comparing the DME BT at the same RPM in 4th vs 3rd for example always yields a lower DME BT in 4th vs 3rd).

Its worth nothing that as far as I can tell, this throttling is NOT accompanied by a drop in timing or AFR straying too lean so is not obviously "safety" related behavior in my view.

At first I thought the throttling was caused by something that happened "around" the gearshift which I couldn't see in the logs.

So I proceeded to do a single gear pull in 4th and 5th to see if the same problem occurred .... and it did.

Curious

I then proceeded to see if maybe the JB4 was doing something strange so I tried to do a few runs in Map0 (JB4 is "off") ... and STILL I see this forced throttling.

With the data from the Map 0 log though it seems "obvious" to me that this behavior is hardcoded into the 20i ECU (or atleast ... it's hardcoded into MY 20i ECU).

My only guess is that as part of the detuning tricks used to downspec the 30i engine to what we have in the 20i. It seems there's a combination of forced throttling & DME BT reduction triggered by high speed (90+MPH and or a combination of RPM & gear trigger .... i.e Gears 4 to 8 and RPMs in excess of 4500 to 5000rpm or something).

I have NOT seen this throttling action happen on any B58 or B48 (30i) logs I've seen, but to be fair, there aren't THAT many logs which have useful data beyond 90MPH as most people log on their draggy runs where they don't really push beyond the 1/4 mile or on the street where it will be difficult to push up to 120+mph safely.

It would be interesting to see if other 20i owners that are still on stock ECU (not flashed) can corroborate my results above. If a few users experience the same thing then unfortunately the conclusion would be that the JB4 is basically useless at 90mph+ on a stock tune 20i engine as the throttling action seems to be hard wired into the ECU. A flash tune like MHD or BM3 should get rid of this behavior (but again I'm not certain as I have not seen many BM3 or MHD logs myself with significant data above 90 MPH). With that said I am still glad I got the JB4 as it's "undetectability" during warranty period means it's the only thing I can do at the moment plus it still has good logging features and even out of warrant when I will eventually get a BM3 or MGF tune or something the JB4 can still act as an effective boost controller and/or WMI controller down the line.

I'll try to get these logs into a chart form in the next couple days so I can explain the above visually but I really wanted to get this out there first since I've been racking my head around this throttling thing for a few days now.

Photos uploaded

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.

Knifeedge2k1 · 10-06-2020, 07:46 AM

Would be great to see if there are other 20i engine owners that are still on factory tune who can chime in on this

Fully understand it's difficult to find enough open road to get a 4th or 5th gear pull

VipinLJ · 10-06-2020, 02:03 PM

Quote:

Originally Posted by Knifeedge2k1

Would be great to see if there are other 20i engine owners that are still on factory tune who can chime in on this

Fully understand it's difficult to find enough open road to get a 4th or 5th gear pull

Plus in America, it'll be hard to get a 5th gear pull since our cars are limited to 130mph. I can't get a 5th gear log because of that. And for 4th gear, you'll need a really long stretch.

Knifeedge2k1 · 10-06-2020, 06:44 PM

Quote:

Originally Posted by VipinLJ

Plus in America, it'll be hard to get a 5th gear pull since our cars are limited to 130mph. I can't get a 5th gear log because of that. And for 4th gear, you'll need a really long stretch.

Thryre 130limited in the us ?!?!

VipinLJ · 10-06-2020, 10:07 PM

Quote:

Originally Posted by Knifeedge2k1

Thryre 130limited in the us ?!?!

Yup. 128mph according to dragy. All my cars are. Because of all season tyres.

Knifeedge2k1 · 10-06-2020, 10:21 PM

Quote:

Originally Posted by VipinLJ

Yup. 128mph according to dragy. All my cars are. Because of all season tyres.

Wow

I didn't know that

I remember bombing down the highway like 15 years ago in my friend's A4 at 240kph on stock all seasons...

Changing times I guess

Another reason to get a tune =D

Unlocked to speed

VipinLJ · 10-06-2020, 11:49 PM

Quote:

Originally Posted by Knifeedge2k1

Wow

I didn't know that

I remember bombing down the highway like 15 years ago in my friend's A4 at 240kph on stock all seasons...

Changing times I guess

Another reason to get a tune =D

Unlocked to speed

Yup. But then where I live, I hardly get to do 90MPH. Forget 130. Plus I did try tuning my G20 and it got bricked temporarily. BMW and their DME security!

Avaley · 10-06-2020, 11:56 PM

Quote:

Originally Posted by VipinLJ

Yup. 128mph according to dragy. All my cars are. Because of all season tyres.

I have bm3 and limiter removed I've hit 150 mph on the stock all seasons. Its electronically limited from the factory.

Knifeedge2k1 · 10-07-2020, 12:30 AM

Quote:

Originally Posted by Avaley

I have bm3 and limiter removed I've hit 150 mph on the stock all seasons. Its electronically limited from the factory.

Would you happen to have logs from before you flashed BM3 to help diagnose the throttle issue above?

VipinLJ · 10-07-2020, 02:20 PM

Quote:

Originally Posted by Avaley

I have bm3 and limiter removed I've hit 150 mph on the stock all seasons. Its electronically limited from the factory.

Yup. Unfortunately with the new G20, I need to send in my ECU for it to be bench unlocked. Which is why I went with JB4 instead.

Avaley · 10-07-2020, 05:45 PM

Quote:

Originally Posted by Knifeedge2k1

Would you happen to have logs from before you flashed BM3 to help diagnose the throttle issue above?

i don't but your issue is probably due to JB4 not unlocking your ECU and that the stock restrictions for emissions / flow are what is causing your issue at higher speeds.

fwiw, bm3 has a unflash and relock DME option and for ~4 standard service visits for my car i didn't bother unflashing and my service agent said nothing, however, i do have a very good relationship with my local dealer.

Knifeedge2k1 · 10-07-2020, 11:33 PM

Quote:

Originally Posted by Avaley

i don't but your issue is probably due to JB4 not unlocking your ECU and that the stock restrictions for emissions / flow are what is causing your issue at higher speeds.

fwiw, bm3 has a unflash and relock DME option and for ~4 standard service visits for my car i didn't bother unflashing and my service agent said nothing, however, i do have a very good relationship with my local dealer.

Not trying to fear monger but if I were the dealer I wouldn't ever mention this stuff until the user decides to claim something under warranty

I would just keep a record

Unless you have a direct relationship with the actual service rep who just neglects to mail down these changes on the record...

With that said there's another user on the n54 forum who bought a certified pre-owned used g20 330i which is apparently tuned (dme BT was up to 19+psi) and he didn't know it.only found out after installing his jb4, running map 3 and seeing massive throttle and ignition issues. So maybe the dealers really really don't check...

Knifeedge2k1 · 10-14-2020, 11:40 PM

Bumping this thread for anyone that is running stock ECU on JB4 that could provide some JB4 logs on 4th gear (or higher) single gear pulls.

10-04-2020, 02:37 AM	#1
Knifeedge2k1 Second Lieutenant 153 Rep 280 Posts Drives: BMW G30 520i 2019 Join Date: Aug 2020 Location: Hong Kong iTrader: (0)	Forced Throttling at speed Hi Guys, Firstly I apologize for the wall of text but it's just how I write. I've just noticed something strange throttle action while logging pulls done into higher gears (4th and higher). Background: Car: G30 5 Series Year: 2019 Trim: 20i MSport Engine: B48B20B (identical to 30i engine hardware-wise, difference in software) Fuel: 98 RON (93 AKI), no E85 or any form of Ethanol where I live Mods: Only JB4, stock everything else Originally I was intending to increase my boost via the JB4 given the artificially low limits set in the stock ECU tune from the factory. Given the gains available from a proper flash tune on the 20i engines I didn't feel Map 3 on the JB4 was "enough" so I was just getting some data to see how much more additive boost I could command safely. While gathering data however, I noticed that my engine was experiencing extreme amount of forced throttling at speeds greater than 90mph in 4th and 5th gear (I presume it would be true in 6th-8th as well but given I don't have the space nor power to pull in those gears so it's a bit of a moot point). All my prior logs/pulls in 2nd & 3rd gear from 2200rpm-redline have had throttle progressively ramp up to 100% and stay there. Once in 4th or 5th however at ~5000rpm I can see the throttle cut back extremely abruptly and the throttle oscillating/feathering in a strange manner (while on JB4 maps 1 thru 3) and all of this is accompanied by a drop in DME BT (comparing the DME BT at the same RPM in 4th vs 3rd for example always yields a lower DME BT in 4th vs 3rd). Its worth nothing that as far as I can tell, this throttling is NOT accompanied by a drop in timing or AFR straying too lean so is not obviously "safety" related behavior in my view. At first I thought the throttling was caused by something that happened "around" the gearshift which I couldn't see in the logs. So I proceeded to do a single gear pull in 4th and 5th to see if the same problem occurred .... and it did. Curious I then proceeded to see if maybe the JB4 was doing something strange so I tried to do a few runs in Map0 (JB4 is "off") ... and STILL I see this forced throttling. With the data from the Map 0 log though it seems "obvious" to me that this behavior is hardcoded into the 20i ECU (or atleast ... it's hardcoded into MY 20i ECU). My only guess is that as part of the detuning tricks used to downspec the 30i engine to what we have in the 20i. It seems there's a combination of forced throttling & DME BT reduction triggered by high speed (90+MPH and or a combination of RPM & gear trigger .... i.e Gears 4 to 8 and RPMs in excess of 4500 to 5000rpm or something). I have NOT seen this throttling action happen on any B58 or B48 (30i) logs I've seen, but to be fair, there aren't THAT many logs which have useful data beyond 90MPH as most people log on their draggy runs where they don't really push beyond the 1/4 mile or on the street where it will be difficult to push up to 120+mph safely. It would be interesting to see if other 20i owners that are still on stock ECU (not flashed) can corroborate my results above. If a few users experience the same thing then unfortunately the conclusion would be that the JB4 is basically useless at 90mph+ on a stock tune 20i engine as the throttling action seems to be hard wired into the ECU. A flash tune like MHD or BM3 should get rid of this behavior (but again I'm not certain as I have not seen many BM3 or MHD logs myself with significant data above 90 MPH). With that said I am still glad I got the JB4 as it's "undetectability" during warranty period means it's the only thing I can do at the moment plus it still has good logging features and even out of warrant when I will eventually get a BM3 or MGF tune or something the JB4 can still act as an effective boost controller and/or WMI controller down the line. I'll try to get these logs into a chart form in the next couple days so I can explain the above visually but I really wanted to get this out there first since I've been racking my head around this throttling thing for a few days now. Photos uploaded 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. Attached Images Last edited by Knifeedge2k1; 10-04-2020 at 06:15 AM.. Reason: Added pictures
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10-06-2020, 07:46 AM	#2
Knifeedge2k1 Second Lieutenant 153 Rep 280 Posts Drives: BMW G30 520i 2019 Join Date: Aug 2020 Location: Hong Kong iTrader: (0)	Would be great to see if there are other 20i engine owners that are still on factory tune who can chime in on this Fully understand it's difficult to find enough open road to get a 4th or 5th gear pull
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10-14-2020, 11:40 PM	#13
Knifeedge2k1 Second Lieutenant 153 Rep 280 Posts Drives: BMW G30 520i 2019 Join Date: Aug 2020 Location: Hong Kong iTrader: (0)	Bumping this thread for anyone that is running stock ECU on JB4 that could provide some JB4 logs on 4th gear (or higher) single gear pulls.
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