[GenXG87]

I've been testing the JB4 and didn't notice it till later runs but the car will pull throttle out even when pedal is 100%. This isn't traction control it's a consistent amount. For my car it seems to be around 60% throttle when WOT.

After doing some poking around I read that m dynamic mode is designed to keep the turbo spooled so when you are on and off the gas there isn't lag. So based on that I understand the reason for keeping the throttle closed a bit and turbos spinning faster.

However, what may be good on a road course may not be ideal on the drag strip. When I turn MDM and DSC off there is less of this issue but it is still present. However I was running M-Traction at 3.

Anyone else have an explanation, do any testing or know if this is something that can be tuned out with a custom tune?

Do items like the Dinan Throttle Booster override this behavior?

Thanks

[GenXG87]

I should’ve included the link to the thread of my JB4 testing. In that thread there is a spreadsheet with data from JB4 logs.

https://g87.bimmerpost.com/forums/sh....php?t=2030423


When I said it wasn’t traction control that’s what I meant. Not the system but rather the applying of traction control. Conditions aren’t such that there would need to be traction control system intervention. This is throttle being pulled out consistently at speed. Spreadsheet is of 4th gear.

MDM is needed for launch control so I’ve been testing with it on. but in 4th gear not sure what it would need to do in a straight line.

However as I mentioned I did turn off MDM and DSC and had m traction control set at 3 on another test. This improved the situation but still pulls out throttle at speeds. Instead of pull back to 60% it was 70-80. I have yet to log DSC off and M traction at 0. But it is on my to-do.

I have about 9 WOT 4th gear tests ranging from JB4 disabled to map 5. I also tested efficient and sport plus engine settings.

My question is about MDM specifically. Is it designed to keep the turbos spooled up so that on / off throttle conditions don’t result in lag? And does it do this by reducing throttle opening and over spooling the turbos?

[GenXG87]

Originally Posted by M2siast

Thanks for clarifying!
While I understand and agree traction control shouldn’t intervene in higher gears/speeds, it’s best to take it out of the equation first.
Let us know what happens with TC off.

I’ve never heard the claim MDM does anything with engine mapping to spool turbos and not move the car, not sure how it’d do that other than opening the wastegate, which shouldn’t affect “throttle” (understanding these cars don’t use the throttle at all since it’s always 100% open, and valvetronic does the rest). But I’m no expert.
I understand MDM only allows some yaw and wheel spin, nothing more, nothing less.

Tested with DSC off and M-Traction off. Same result.

Understood about the valvetronic. However, there is still something happening. You can see there is a boost differential from sensor 1 and sensor 2 on the spreadsheet. I'm still getting my head around these engines and where everything is at how it works, so I'm not sure where the 2 readings are coming from. But, I have observed and logged the boost difference and it's correlation to the reported throttle.

If the JB4 is targeting 25 psi, sensor 1 will be close to that, while sensor 2 may have a 4-5 psi reduction when the throttle shows 60%.

Is there a blow-off or diverter on the intake stream? I could see that impacting the boost reading in two places on the intake side.

[GenXG87]

Originally Posted by M2siast

Thanks for testing!

I was going to suggest the DME is understanding the deviation from the JB4 and trying to protect the engine.

What does Burger tuning have to say?

We've been chatting. Discussing all the tests. We were focused on AFR and timing with E30. Got that sorted out. But we noticed the throttle issue. No real answer from them either.

I've confirmed that it has the same behavior with the JB4 disabled. I've also tested Map 1 - 5, and it does the same thing pretty consistently.

Waiting to run the tank down and go back to 93 octane only to rule out that there is anything happening there.

[KC87ZB]

What wheel speed are you at in 4th at 6000 rpm?

I really doubt traction control is limiting throttle in those case, makes no sense. I also cannot imagine you are hitting 155 mph limit in 4th

Seems something is limiting boost

I’m not big on piggybacks because they intercept signals to fool the ecu. I’m not sure I’d keep at the same thing without any tuning changes as the ECU is limiting you for some reason

Easy enough to verify not TC, just disable it, M trac at 0

[GenXG87]

Originally Posted by M2siast

Ah is that the way BMW detuned the engine???

Oh man that would be the ultimate conspiracy theory. But would be a great explanation too.

[GenXG87]

Originally Posted by KC87ZB

What wheel speed are you at in 4th at 6000 rpm?

I really doubt traction control is limiting throttle in those case, makes no sense. I also cannot imagine you are hitting 155 mph limit in 4th

Seems something is limiting boost

I’m not big on piggybacks because they intercept signals to fool the ecu. I’m not sure I’d keep at the same thing without any tuning changes as the ECU is limiting you for some reason

Easy enough to verify not TC, just disable it, M trac at 0

Tested DSC off and M traction to 0. Same issue.

Also tested with JB4 disabled.

I’m beginning to believe this is as intended but just not documented. Waiting to see some other G87 6MT logs in the wild.

The car still runs hard but would rather get the boost and not work the turbos as hard.

[DBV]

It's my understanding that only Sport and Sport Plus throttle settings will affect the behavior of the turbos (anticipatory spooling if you will). But that was on F8X, not sure if that's been changed on the G8X series.

[GenXG87]

Originally Posted by DBV

It's my understanding that only Sport and Sport Plus throttle settings will affect the behavior of the turbos (anticipatory spooling if you will). But that was on F8X, not sure if that's been changed on the G8X series.

There is definitely different behavior between efficient and sport/ sport+ with higher boost on the JB4. It actually had a surge effect on efficient and logs showed it bouncing from about 60-100 throttle. On sport it pulls the throttle but car is smooth

[kyrix1st]

Turn that DSC crap off and drive with your right foot.

[RockCrusher]

Originally Posted by GenXG87

Tested DSC off and M traction to 0. Same issue.

Also tested with JB4 disabled.

I’m beginning to believe this is as intended but just not documented. Waiting to see some other G87 6MT logs in the wild.

The car still runs hard but would rather get the boost and not work the turbos as hard.

Can't have boost without the turbos working. And more boost means more work for the turbos.

Really I wouldn't worry about the turbos. Or if you worry then stay out of the throttle.

But even then I suspect there is some boost being made under some conditions. I've not bothered to data log my M2 but with my Porsche Turbo and its in dash boost gauge even encountering a bit of up grade at freeway speed would have the boost climb to 0.2 bar. "Maximum" boost under normal circumstances was 0.7 bar.

Wouldn't surprise me if the M2 engine makes boost some boost even if one isn't hard on the throttle.

[Squidget]

Originally Posted by RockCrusher

Wouldn't surprise me if the M2 engine makes boost some boost even if one isn't hard on the throttle.

It does. I've had the car status app (on ID8) open while on the highway, and it shows a little bit of boost while maintaining 80 MPH.