[G MONEY]

Originally Posted by geckoRuss

Houston bro. Kinda makes me nervous never had a rwd car with this much power before and I heard things can go real bad real fast if you don’t know what you’re doing. Have spun out in a s2000 before still kind of have PTSD.

Gotcha. I think at the low stock power you will be fine. Sounds like the RWD crowd is happy with the traction of their cars. You definitely need to find an open lot and do a few just to try it out. Let us know

[Vic55]

Kinda of a side bar question but is there any discernable difference between

MDM Sport and DSC OFF 4WD Sport (on the street) for an X drive in regards to shifts and throttle aggression?

Ive been driving my 4 G8X's with MDM Sport and was wondering thoughts on using the above DSC OFF 4WD Sport setup...

[PVC]

Originally Posted by geckoRuss

Houston bro. Kinda makes me nervous never had a rwd car with this much power before and I heard things can go real bad real fast if you don’t know what you’re doing. Have spun out in a s2000 before still kind of have PTSD.

My F80 used to go sideways with or without launch control, but it was manageable.
I don't think the G80 RWD is as bad, but better be safe than sorry. Find an empty road with 2-3 lanes (maybe at night), and you should be fine. You don't have to get to 100mph or 60 to test the LC. You could slam the brakes anytime you feel like you're losing control.

[g82]

Originally Posted by Vic55

Kinda of a side bar question but is there any discernable difference between

MDM Sport and DSC OFF 4WD Sport (on the street) for an X drive in regards to shifts and throttle aggression?

Ive been driving my 4 G8X's with MDM Sport and was wondering thoughts on using the above DSC OFF 4WD Sport setup...

Well the difference is in mdm your traction is off but if it starts to slip, traction control will help and take control. But in dsc fully off traction control is fully off with no help.

[kjx]

Originally Posted by vrships

Explain it to me if you know more. Instead of just saying "A is just A and you know nothing about it!" This 5 year old talk trick doesn't help clarify anything

And I never said "rev hang" =" Slow shift". I said Rev hang is one of the symtpoms of slow shift.

Do you not know the stark difference between these two statements?

Rev hang is a symptom of a slow shift, but not because of transmission mode programming. It is because of transmission aging.

There is neglibible to no rev hang on G8X when brand new. It’s something that happens and gets worse over time. It will eventually get so bad that, in the most aggressive settings, the car will bounce the rev limiter in first due to slow transmission engagement from wear. Not seen that on G8X but it is inevitable as I’ve seen it on every ZF. The G8X is just more robust and ages slower but the progression is similar.

Apples to apples, D3 hangs on to lower gears longer but shifts faster and more abruptly than D2 or D1. Because rev hang is a function of wear, people hitting the drivetrain with launches will probably experience it earlier than others.

[vrships]

Originally Posted by kjx

Rev hang is a symptom of a slow shift, but not because of transmission mode programming. It is because of transmission aging.

There is neglibible to no rev hang on G8X when brand new. It’s something that happens and gets worse over time. It will eventually get so bad that, in the most aggressive settings, the car will bounce the rev limiter in first due to slow transmission engagement from wear. Not seen that on G8X but it is inevitable as I’ve seen it on every ZF. The G8X is just more robust and ages slower but the progression is similar.

Apples to apples, D3 hangs on to lower gears longer but shifts faster and more abruptly than D2 or D1. Because rev hang is a function of wear, people hitting the drivetrain with launches will probably experience it earlier than others.

I would say there is a lot of confusion and misnomers regarding this concepts.

Strictly speaking, rev hang should only refer to that when the drivetrain is DISENGAGED from the crankshaft, the rev does not drop promptly after pedal is fully released, because the electronic throttle body INTENTIONALLY closes up throttle slowly for reasons like emission control. This is mostly only relevant in manual shifting because during each up shift, after gas pedal is released, how fast the engine rev slows down to match the next gear limits the shift speed.

But it's almost irrelavent in modern automatic transmission because you don't and you shouldn't change your throttle pedal input during upshifts. Even at WOT all the way, the ECU does a sequence of complicated things to modulate engine load and RPM which doesn't rely on drivers' intervention at all. And ECU will always cut off ignition/fuel/valves to slow down the engine in a precalculated way to rev-match for the next gear, while simultaneously or subsequently, TCU release a set of clutches and press another set of clutches to engage to the new gear.

During an automatic upshift, if the rev doesn't come down quickly to the next value, there can probably be two reasons:
1) the transmission just does everything slowly and gradually. The ECU doesn't actively slows down the engine but relies more on its internal friction to slow down. And the gearbox clutches disengage and engage slowly, while the new clutches are pressed gradually to allow certain torque transfer, but not too much. It lasts a while until the clutches are fully pressed and engine rev slows down enough to match the gearbox input speed exactly. This way the jerk and wear is minimized, but overall a lot of time is wasted in the transition phase while the overall acceleration is low.

2)The gearbox disengage and engage the clutches as quickly as possible, by pressurizing to the max extent, regardless of what engine is doing. And the ECU only cut off load minimally. The clutches are pressed so hard to the input shaft to allow maximum torque transfer and try to slow down the input shaft to match the speed. But the engine is also loaded heavily so it takes a long time to rev match. And this creates a lot of wear to the clutches, some jerk and maximum acceleration.

I don't think 2) is the case in any OEM BMW cars because it burnouts your gearbox faster than the factory can afford. But it is used in drag race cars with a tuning. If you are familiar with xHP, you will know this setting is called "torque reduction during upshift", and xHP claims minimizing it gives you the most aggressive and fast result, with a feel of "slow shift".

But I am pretty sure D3 is not run in this mode. The "rev hang" in D3 is mostly due to 1) described above. And D3 is certainly not the fastest mode because that's reserved for S3, while S3 doesn't have the so called "rev hang" at all.

[USMC G2]

Greetings,

Wow (video) - now that's a M car with a wee bit of wear and tear on it...sheesh.

Semper Fi