SMG - Does yours blip the throttle on upshifts?

[R1pilot]

Like the title says. I’ve had my car for 6 years and 60k miles and either I am nuts or it never did it before.

It does it almost all the time when driving slow from 2nd to third and third to fourth.

I have been driving a lot with the windows open and really notice it. I think I would have noticed it before with the windows closed as you can feel it, but not sure.

Car has a CSL SMG tune.

[r4dr]

No. Only on downshifts, after the car's warmed up. My SMG also has the CSL stuff.

[m3nt0s]

Mine only blips on downshifts after the CSL coding, and is significantly more audible and enjoyable after installing an airbox.

[Thoglan]

I don't know anything about the smg software so it could be that this is unusual. But it makes sense to me, same as in a manual car if you are shifting slowly or double clutching. The revs will drop off faster than the gear change and fall below the matched rpm of the wheel speed for the next gear. A blip on the throttle is required to change smoothly, that or slip the clutch sightly but the former is probably easier for the smg software to execute.

Whether or not it's normal for the smg to take long enough to change to warrant a blip while driving normally, I have no idea. You wouldn't think so.

[eacmen]

Mine does not do that.

What drive mode?

[erickhoyos]

Are you letting go of throttle with every shift? It’ll do that, like thoglan said it’s as if you’re double clutching.

[sapote]

But it makes sense to me, same as in a manual car if you are shifting slowly or double clutching. The revs will drop off faster than the gear change and fall below the matched rpm of the wheel speed for the next gear.

Unless the clutch is disengaged for too long, there is no way the input shaft dropped off faster than the next higher gear selected. There is no reason to double clutching when up shift unless the clutch pedal was pressed for too long and the input speed had dropped too low.

[Thoglan]

sapote A lot of the time yes, there is no reason to double clutch up the gear box. But these are picky gearboxes and it pays to move slow when they are cold for instance. In this case, there are times pulling away while the fluids are cold, you're changing low rpm, it's very easy for the input shaft speed to fall below the matched rpm for your second gear.

Whether or not this is what is happening to OP I have no idea. Seems unlikely that the SMG would take as long to shift as a delicate person might in the morning but it's not inconceivable.

[sapote]

[USER="1470"] But these are picky gearboxes and it pays to move slow when they are cold for instance. In this case, there are times pulling away while the fluids are cold, you're changing low rpm, it's very easy for the input shaft speed to fall below the matched rpm for your second gear.
.

Assuming for this we are talking about manual box. When it's cold, move the shifter faster and when it's hot, move it a little slower to match the rpm. No reason to do slow shifting when cold regard less of rpm range.

[Thoglan]

sapote That's just not really true. The 1-2 shift below 2500rpm has to be relatively quick and getting that change in time means putting a bit more unnecessary force on the second gear synchro with cold fluid. Double clutching allows you to be far more gentle with the selector while still matching the synchro speed. These are pretty stout boxes, but it doesn't change that things like synchos are just wear items. They will last a long time if treated correctly. Is it necessary for every M3 driver to double clutch while the car is warming up? No. Will it extend the life of the gearbox? Absolutely. Every M3 owner I know has experience a crunch in second or third gear in their car, and it's because people are too quick with them when it's not appropriate. I have seen these gearboxes stripped down and have seen how they wear. I have talked with one of the few people in the southern hemisphere who is able to service these boxes about this exact topic and the advice is take your time, which sometimes means double clutching up the box.

[TexaZ3]

SMG does not rev match on upshifts.

[R1pilot]

Mine does not do that.

What drive mode?

S4

[sapote]

S4

Do you feel a delay from shifter to when the rpm blipping? 2 sec? If the next gear didn’t happen quick enough then the input speed could drop off too low and blipping is needed.

[Will ZCPM3]

Only downshift for me.

[R1pilot]

Do you feel a delay from shifter to when the rpm blipping? 2 sec? If the next gear didn’t happen quick enough then the input speed could drop off too low and blipping is needed.

Its difficult to describe, its shifting more and more lazy if that makes sense.

I am not new to SMGs and had an '05 before that I bought new, I never remember this happening. I hope its not a sign of bad things to come.

I made a small video on the way home, it happened on the 1-2 and 2-3 shifts: