over reving

Are you saying that if you have it in "manual" mode then it *won't* change up under any circumstances? I haven't explicitly tested this but have never known mine to shift up automatically. But this seems to disagree with Dave's experience?

Reply to
Jeremy
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Must be a different spec to mine. It definitely changes up at the red line, and changes down at about 1000 rpm.

Reply to
Dave Plowman (News)

In normal auto mode, kickdown will take you into the red area.

Reply to
Dave Plowman (News)

Perhaps it does upshift at redline. It was not my car so I did not test it at that high an rpm. But who cares, no sane person waits until redline to shift up. You are past peak horsepower so there really is no point...

Reply to
Fred W

Peak horsepower matters not a jot, really.;-) And my 528 doesn't run out of puff at the maximum auto change up point. What you ideally need is to get near peak torque on the next higher gear. Hence the demise of 2 speed autos...

Reply to
Dave Plowman (News)

Interesting experiment

Select say 2nd and rev to red line, and then keep pressing the options are: -

  1. Car changes to 3rd and keeps accelerating. Unlucky if on steep descent, but might not change if accelerator not pressed.

  1. Car stays in gear and EMU limits rev's to red line - no change in speed. Shame if you are overtaking a truck with something coming towards you.

  2. Engine over rev's. Expensive trip to the repair shop.

Does it make any difference in a diesel?

Reply to
R. Mark Clayton

Option 2 is in my opinion how it should behave if you're in manual mode

- otherwise it is not manual IYSWIM.

Only a complete pillock would fail to register that it might be a good idea to engage a higher gear....

No idea.

Reply to
Jeremy

Not sure about the 2.8, but the 220hp 3.0 litre develops maximum torque at

3,500. So with the exception of the 1~2 shift, upshifts should be well below the 6,500 redline (ca. 4,500~5,000) to hit the torque peak in the next gear in a 6 speed manual.

Tom K.

Reply to
Tom K.

Which it's not. It changes up or down regardless of the gear you've selected once outside the pre-determined rev limits. No true manual I've ever driven does this. ;-)

True - but then the engine has a rev limiter to keep it safe.

Reply to
Dave Plowman (News)

Well, I think that pulling it into the S mode does the trick, in general that takes it down on gear which normally produces quite sufficient torque to overtake the most...

** Lars / 2002 - 530dA touring
Reply to
Lars Knudsen

Then the driver is doing something wrong. If a downshift carries the motor into Red Line, the downshift was poorly timed. Period.

Reply to
Jeff Strickland

The rev limiter kicks in @ 6500RPM on the M54 engine. 7000 on the newer (magnesium block) six. 4500 RPM is just getting into the power band.

There's this red area on your tachometer (that's the big round dial next to the speedometer). Keep the needle from getting too far into that zone and you won't hurt the engine. BTW, the auto trans and ECU will prevent you from goving too far into that zone and over-revving the engine. If a step downshift would result in an over-rev, it won't downshift. Now if you had a manual transmission, you CAN goon it up.

R / John

Reply to
John Carrier

Not necessarily. Acceleration is proportional to horsepower, not torque (I'll show you from F=ma, if you want) so what you want to do is maintain the highest value of hp that you can. Pretty sure this means that you want to go far enough past the peak that when you shift to the next gear, and drop down on the other side of the peak, you haven't gone significantly lower in hp than where you just were in the previous gear.

If that point matches peak torque, it's just a coincidence.

Frank

Reply to
Raybender

Excellent example, Tom, of why shifting for peak torque in the next gear is usually shifting too early when you want maximum acceleration.

Frank

Reply to
Raybender

Quite possibly because of what you drive

I think dropping down 2 is required more often though in mine :)

Reply to
Jeremy

That's alright, I'm not buying it. I don't believe the transmission control module is stupid enough to down shift into redline, which BTW would then invalidate the engine warranty. Unless you see some real evidence to the contrary, I would not believe Mr Plowman's assertion.

Reply to
Fred W

It's unlikely you have driven a 528 with the ZF auto.

Reply to
Dave Plowman (News)

Ok I tested this at the weekend. Switched into manual mode, popped it into 2nd and took it up to 6000rpm - no automatic upchange. I didn't feel inclined ot keep it at those revs for any longer but, certainly on mine, selecting a gear manually keeps it in that gear *unless8 the speed drops to a crawl. If it had changed up automatically at over 6000 revs it would be academic anyway - therefore I think that, with reference to your previous statement:

"On a fun twisty road it's often the case where you'd do that with a manual in say second gear then back off slightly before the next bend - but the Steptronic changes up."

In my experience you can do exactly as you describe above without the system automatically changing up.

cheers

Reply to
Jeremy

Have you observed the RPM at the gearbox changes up when using kickdown? That is exactly the same maximum as it will when using the Steptronic selection. That you choose to rely on some arbitrary figure on your rev counter for the sake of your argument makes no difference.

You've not been trying hard enough. ;-)

Reply to
Dave Plowman (News)

OK I'll go and do some more testing and report back :)

Reply to
Jeremy

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