Throttle response issue - interesting log

[works]

I'm at a bit of a loss here, so I'm reaching out to the community to see if anyone has ever seen similar behavior. If you search for "N54 throttle response" you will get a ton of people complaining about it, but I've yet to see anyone with a similar issue as mine.

The problem that I'm trying to solve is a massive throttle lag that makes the car feel extremely slow to react to accelerator pedal input. The following data shows that the car CAN, when software/sensors allow, react blazingly fast to accelerator pedal position. But it doesn't.

Car is E82 135i, 2007, MT, with MSD80 running I8A0S (not sure what the native version was).

In short:

No load to the engine, this behavior is logged with the car coasting on neutral and the only difference is clutch pedal either being up or down. This behavior does not exhibit itself when the car is at standstill. Throttle response is immediate at standstill regardless of clutch pedal position.

The delayed throttle response is present always when driving the car, the only way to get the throttle to respond quickly is to press down the clutch pedal and then work the accelerator pedal. Therefore, as this is MT, rev-matching downshifts accurately is possible.

So, the following behavior can and has been logged:

• clutch pedal pressed, gear neutral
  • gear reads correctly in logs
  • throttle response with accelerator pedal press is immediate
  • rpms respond immediately
  • boost target is raised
  • wdgc can react upwards, up to 100
• clutch pedal raised, gear neutral
  • gear reads incorrectly in logs
  • throttle response with accelerator pedal press is delayed
  • rpms respond sluggishly
  • boost target is 0
  • wdgc reacts downwards or minimally upwards

And here is a log of the behavior: https://datazap.me/u/works/throttle-debug-normal-adaptations?log=0&data=2-25

First three rev ups are with clutch pedal raised, the next three clutch pedal pressed. You can clearly see that with a similar accelerator pedal position the throttle opens either super fast and RPM's climb quick which leads to me releasing the accelerator pedal, or when the clutch pedal is raised the throttle opens slowly + only a little and the RPMs raise slower which leads me to keep the accelerator pedal pressed for longer.

I've replaced both MAP sensors and the throttle body assembly. The car is stage 1 turbo +fbo +flexfuel. Clutch delay valve has been deleted and the clutch is from 550i, not sure if either of those are somehow involved in this. To me this looks like a sensor or software issue as the throttle response can be amazingly fast when the clutch is disengaged and pedal is down or the car is stationary.

Do note that resetting adaptations does nothing to alleviate this. I've tried several different software versions from two tuners and the problem persists. So that puts more weight on this being a sensor issue. But which one?

I sincerely hope that some of you brainy people can shed some light on this and come up with solutions for me to try out.

 

[nahor]

My car does the same thing. I believe this is designed behavior by BMW to smooth out throttle inputs and make the car feel more "luxurious."

I know on E46s, the same feature was called anti-jerk, and could be disabled through tuning. I haven't been able to find any tables to do so within MSD8X, but there's a chance they exist somewhere.

As you observed, the throttle smoothing only activates while the car is moving and the ECU sees the clutch pedal up. I wired in a switch that interrupts the clutch switch wire to the ECU to get around this. When I interrupt the signal, the ECU defaults to seeing the clutch pedal as down, and does not activate the throttle smoothing in any scenario. Downside is, you lose gear detection, and therefore boost by gear won't work. Also, cruise control won't work, but since I have a switch, I can just flip it back on if I need either of those. Beyond that, I have noticed no negative effects. The car just feels much more responsive, and in my opinion, a lot more fun to drive.

 

[works]

That sounds quite plausible and would explain why so many people complain about this and why this behavior is present with different tunes. Thanks, I'll give it a go!

Can you draw a simple wire diagram on what clutch wire to cut and install the switch to?

If anyone can pipe in with knowledge of this "anti-jerk" table and how to disable/null it, the entire N54 world would thank you.

 

[works]

I wired in a switch that interrupts the clutch switch wire to the ECU to get around this. When I interrupt the signal, the ECU defaults to seeing the clutch pedal as down, and does not activate the throttle smoothing in any scenario.

Google served me up this: https://www.m3post.com/forums/showthread.php?t=1099239

So on the connector we have:

Signal 1 (brown/black): Ground
Signal 2 (blue/brown): This signal is triggered when the clutch pedal is depressed just slightly--it goes to DME for cruise control, idle-up such as when you push in the clutch to prepare for take-off, etc.
Signal 3 (purple/yellow): This is +12V supply for the clutch switch
Signal 4 (blue/black): This signal is triggered and goes to +12V only when the clutch pedal is fully depressed--it goes to CAS for clutch interlock.

Did you nahor put a switch to the Signal 2, 4 or both? As you stated "wire to the ECU" I'd think it would be signal 2.

 

[MoreBoost]

Have you tried flashing the car with a map where throttle position targets higher loads?

 

[works]

I know on E46s, the same feature was called anti-jerk, and could be disabled through tuning. I haven't been able to find any tables to do so within MSD8X, but there's a chance they exist somewhere.

An user posted to another forum where I discuss this issue: "The tables exist and have apparently been found. Better values need to be copied in from the 1M which apparently doesn't have this "feature". Its still unknown if the DCT cars have the same table and if so, activating sport mode in those cars does the same thing to an extent. "

That would indicate that the tables are starting to be out there, I just don't yet know who to bug in order to get definitions for those and the data from 1M to patch my car. Story develops

Have you tried flashing the car with a map where throttle position targets higher loads?

I tried with my tuner quite some time last year several different ways to get around this, to no avail. If we can't turn this off in software, I'll just bruteforce the problem like nahor above and wire a switch to the proper sensor(s) to get at least a chose to turn it off when I want to do some spirited or track driving.

 

[nahor]

I referenced this diagram from the JB4 shift box fix thread. As you can see, same color wire as #2 in the picture you posted:

I used this DIY for getting to the clutch switch itself (from the M3post one you linked). In the picture you posted, all you'll need to cut is wire 2. I cut that wire in the footwell, extended it on both ends, and connected the ends to a cheap switch I bought from Fry's (which I mounted right under the headlight switch). Unfortunately I don't have any pictures from when I did it, but once you find the correct wire it's pretty simple from there on out.

An user posted to another forum where I discuss this issue: "The tables exist and have apparently been found. Better values need to be copied in from the 1M which apparently doesn't have this "feature". Its still unknown if the DCT cars have the same table and if so, activating sport mode in those cars does the same thing to an extent. "

This is interesting. Is it confirmed that 1Ms have it completely disabled? It's also possible that the more aggressive throttle mapping in sport mode could be masking the smoothing effect, as sharper changes in pedal position seem to decrease its severity. Do you think you could get whoever you were talking to to post a log similar to yours?

 

[works]

This is interesting. Is it confirmed that 1Ms have it completely disabled? It's also possible that the more aggressive throttle mapping in sport mode could be masking the smoothing effect, as sharper changes in pedal position seem to decrease its severity. Do you think you could get whoever you were talking to to post a log similar to yours?

The software/table information is second hand and the person relaying that might not have access to the info nor have the software on their car.

I did reach out to my tuner as well as MHD directly to see if this can be patched out in my tune or added as a feature, like linear throttle map in flash options, to MHD itself. Getting this feature added to MHD would be by far the best option as the entire community would benefit from having the option at hand. Perhaps the people here that are in close collaboration with MHD could help in raising awareness. Of course, as they are full on with B58, this might take awhile even if they agreed to research and add it in.

But, I now at least have the hardware route to try. Will need to shop for connectors, wire and a switch to try this out.

I’m SO happy to finally have potentially a way out of this issue as it has been bugging me HARD for over a year.

 

[works]

Got a response from MHD and they are not interested. I did ask if they could fill me in with details on how to fix it in software as they seem to know, but apparently most of their users lean on the ”smooth” throttle. I’m waiting for a follow-up reply.

I understand why this smooth application works for some, but not for all. And definitely it does not work for me.

Hardware is always a solution unless my tuner can come through.

 

[works]

And in the near future this can be fixed in software: https://www.e90post.com/forums/showpost.php?p=24705921

 

[nahor]

This is awesome. I had all but given up on a software solution, can’t wait to have gear detection and boost by gear back. I’m no table discoverer, but I searched for and tested tables in the DAMOS for a while with no real luck. Impressive work, well done to those involved.

 

[EthanolTurbo]

@V8bait I know you're going to want to see this. I knew something was weird about the throttle on these cars.

 

[aus335iguy]

IVe since had confirmation that the DCT cars dont have zero’d figures in the table. Once released this will be huge.

 

[SJ_1989]

This is awesome. Always hated the ramp rates they applied to the throttle

 

[works]

@nahor Do you have a RPM limit of 6800 with the switch activated and signal 2 cable disconnected?

 

[nahor]

@nahor Do you have a RPM limit of 6800 with the switch activated and signal 2 cable disconnected?

I did at first, you just have to change the rev limit for gear 0, as with the cable disconnected, the car will always think that’s the gear it’s in. I’d also recommend you equal out your load target for all gears. I haven’t tested which section of that table the car follows with the clutch switch disconnected, but obviously without gear detection it won’t use them all.

 

[RSL]

IVe since had confirmation that the DCT cars dont have zero’d figures in the table. Once released this will be huge.

If it's the pedal correction tables I'm thinking about, DCT/AT will not want to blatantly zero them out. IKM0S has very slightly lower values in the DCT table than 135/335 roms, but barely any different. Using 50% of the stock 335is DCT correction values (nowhere near the 0 of the 1M MT values) and the 1M torque requests (about as linear as you can get), 1st gear is already jumpy. Crawling traffic/starting from dead stop would get annoying quickly on a daily and you'd look like a first time driver learning stick lol

Zeroing the corrections out completely like 1M MT and retaining the stock 135/335 torque request tables would probably be pretty rough for AT/DCT, if it could even be driven. Low RPM/low pedal corrections should probably stay reasonably close to stock values and the rest could possibly be zeroed out, with some torque request changes to suit for all of it.

 

[aus335iguy]

So I assume the tables you know are the same as the ones that were recently found. Have you tried changing them ? It sounds like it might fix the lag issue from standstill on DCTs? I’ve never been a fan of throttle adaptation.

 

[RSL]

If it's the same ones, but judging by the description in his thread, it sounds like them. An initial dead spot should be able to be overcome with just torque request really. Pedal is the input request, torque request is what you want from it at the wheels. A ridiculous amount of torque management goes on in between.

Yes, I cut the stock DCT pedal correction values in half to test while using the 1M torque request tables, which are much more tame than 335is. Loosen up the input side while keeping the stock output matrix and you're asking for/getting more torque more quickly. 1st gear is so tall on DCT, can go from dull response to hold on for your life in a small margin lol

The main benefit with freeing up the input side (pedal) is if the motor itself does respond more directly and MTs will probably have the biggest benefit from that. It's just one very small piece of the puzzle though.

 

[V8bait]

I'd be interested to see what new table address they're talking about here. There's a handful of throttle tables already available and one in particular, I forget the name but it's a single value and does numb down response if you set it too low (I think cobb used to do this). I'll have to log my car when I get a chance and see if this is present.