F30 330d 8 speed auto question

[Welshbeef]

cerb4.5lee said:

Welshbeef said:

Next gen x35d could be 6k revs... Imagine that a petrol identical rev range

When was that the 1920`s!

My Cerb revved to 7500rpm

My Z4M revved to 8000rpm

My M3 revved to 8400rpm

Surely diesels are about the fact that they pick up very well at 1500rpm which a high rev petrol struggles to match but you cant have it both ways, I love a diesel for its low rev shove for a fact but the noise is the obvious drawback though.

Given the Cerb Z4M and M3 are anything but normal engines you'll find most petrols redline at c5.5-6k revs and revs limits are dropping with the advent of turbo and supercharged petrols.



Also one of the current Rolls Royces has a red line at 4,500 rpm .... - all the big block muscle cars were similar with some even having only 3,500 red line.

[anonymous-user]

Welshbeef said:

cerb4.5lee said:

Welshbeef said:

Next gen x35d could be 6k revs... Imagine that a petrol identical rev range

When was that the 1920`s!

My Cerb revved to 7500rpm

My Z4M revved to 8000rpm

My M3 revved to 8400rpm

Surely diesels are about the fact that they pick up very well at 1500rpm which a high rev petrol struggles to match but you cant have it both ways, I love a diesel for its low rev shove for a fact but the noise is the obvious drawback though.

Given the Cerb Z4M and M3 are anything but normal engines you'll find most petrols redline at c5.5-6k revs and revs limits are dropping with the advent of turbo and supercharged petrols.



Also one of the current Rolls Royces has a red line at 4,500 rpm .... - all the big block muscle cars were similar with some even having only 3,500 red line.

Only your last statement is true and if you understood the reason for that you might realise how so much of your previous posts are utter nonsense.

Work that out, if you can.

[apotts]

To be boring and answer the original question...

You change gear when the torque at the wheels in the next gear will be equal to the torque at the wheels in the current gear.

Points to remember:

• The gearbox ratio changes the torque at the wheels
• As you go up the gears, there is a difference in gear ratio gaps (big gap in low gears, small gap in high gears). So the shift point will gradually get lower for an engine with a long downwardly-sloping torque curve.
• For engines with a flatter torque curve (ie petrol engines) the optimum shift point is normally limited by max mechanical rpm, so you just shift at the red line.

You can find the shift points quite easily in software. I have done in for the 8HP box with 35d engine, and these are the optimum points:



I'd bet the 30d engine was almost identical.

Drive force graph showing optimum shift points:

[JNW1]

apotts said:

To be boring and answer the original question...

You change gear when the torque at the wheels in the next gear will be equal to the torque at the wheels in the current gear.

Points to remember:

• The gearbox ratio changes the torque at the wheels
• As you go up the gears, there is a difference in gear ratio gaps (big gap in low gears, small gap in high gears). So the shift point will gradually get lower for an engine with a long downwardly-sloping torque curve.
• For engines with a flatter torque curve (ie petrol engines) the optimum shift point is normally limited by max mechanical rpm, so you just shift at the red line.

You can find the shift points quite easily in software. I have done in for the 8HP box with 35d engine, and these are the optimum points:



I'd bet the 30d engine was almost identical.

Drive force graph showing optimum shift points:

An interesting post which a) explains why the auto box shifts when it does and b) tends to confirm that revving to the redline is utterly pointless!!

[cerb4.5lee]

Welshbeef said:

Given the Cerb Z4M and M3 are anything but normal engines you'll find most petrols redline at c5.5-6k revs and revs limits are dropping with the advent of turbo and supercharged petrols.



Also one of the current Rolls Royces has a red line at 4,500 rpm .... - all the big block muscle cars were similar with some even having only 3,500 red line.

You don't get much more normal though than the N52 engine in my 330i and that still redlines at around 6800rpm, I hear what you are saying though and modern diesels are far more higher revving than they used to be.

A diesel engine will always be about the torque though and that is the characteristic of that type of engine that many like and what makes them nice and usable with the instant shove you get with them.

[apotts]

I have just asked the software model to measure the effect on 0-60 mph and 0-100 mph times if you change at various fixed rpm rather than at the optimum.

If you change at 3000 rpm, you lose 1.17s on 0-60 and 3.09s on 0-100.
If you change at 4000 rpm, you lose 0.35s on 0-60 and 0.52s on 0-100.
If you change at 5000 rpm, you lose 0.05s on 0-60 and 0.37s on 0-100.
If you change at 5500 rpm, you lose 0.27s on 0-60 and 1.65s on 0-100.

Shows:

• There's not much in it so don't worry about it.
• Short shifting a 35d gives pretty good performance.

[Welshbeef]

apotts said:

I have just asked the software model to measure the effect on 0-60 mph and 0-100 mph times if you change at various fixed rpm rather than at the optimum.

If you change at 3000 rpm, you lose 1.17s on 0-60 and 3.09s on 0-100.
If you change at 4000 rpm, you lose 0.35s on 0-60 and 0.52s on 0-100.
If you change at 5000 rpm, you lose 0.05s on 0-60 and 0.37s on 0-100.
If you change at 5500 rpm, you lose 0.27s on 0-60 and 1.65s on 0-100.

Shows:

• There's not much in it so don't worry about it.
• Short shifting a 35d gives pretty good performance.

So 5k shifts appear to be fine - all those posts of utterly pointless in doing so/you'll be watching the car pass you who changed up earlier all tosh.

[JNW1]

apotts said:

I have just asked the software model to measure the effect on 0-60 mph and 0-100 mph times if you change at various fixed rpm rather than at the optimum.

If you change at 3000 rpm, you lose 1.17s on 0-60 and 3.09s on 0-100.
If you change at 4000 rpm, you lose 0.35s on 0-60 and 0.52s on 0-100.
If you change at 5000 rpm, you lose 0.05s on 0-60 and 0.37s on 0-100.
If you change at 5500 rpm, you lose 0.27s on 0-60 and 1.65s on 0-100.

Shows:

• There's not much in it so don't worry about it.
• Short shifting a 35d gives pretty good performance.

Probably a daft question but presumably in Sport mode the gearbox shifts at the optimum point for acceleration if left to its own devices? The figures above also show that to get to 100mph you're better short-shifting slightly (at 4k revs) rather than taking it to the 5.5k redline; I trust Drmark is feeling vindicated!

[converted lurker]

DrMark wins. Welshbeef loses.

[JNW1]

Welshbeef said:

So 5k shifts appear to be fine - all those posts of utterly pointless in doing so/you'll be watching the car pass you who changed up earlier all tosh.

What an unbelievable interpretation of the numbers that is! You've been a consistent advocate of going to the 5.5k redline and the figures suggest that's both slower than leaving the gearbox to do its own thing and, to 100mph at least, slower than short-shifting at 4k. That would suggest that revving to 5.5k is indeed pointless (you're gaining nothing and actually accelerating less quickly by doing so) yet you have the cheek to claim you've been proved right and that others have been talking tosh - priceless!

[Welshbeef]

JNW1 said:

Welshbeef said:

So 5k shifts appear to be fine - all those posts of utterly pointless in doing so/you'll be watching the car pass you who changed up earlier all tosh.

What an unbelievable interpretation of the numbers that is! You've been a consistent advocate of going to the 5.5k redline and the figures suggest that's both slower than leaving the gearbox to do its own thing and, to 100mph at least, slower than short-shifting at 4k. That would suggest that revving to 5.5k is indeed pointless (you're gaining nothing and actually accelerating less quickly by doing so) yet you have the cheek to claim you've been proved right and that others have been talking tosh - priceless!

?

Changing at 4k costs 0.37 seconds to 62mph while changing at 5k 0.05 seconds loss.

Do you struggle with basic pre school maths ie 0.05<0.37

[JNW1]

Welshbeef said:

?

Changing at 4k costs 0.37 seconds to 62mph while changing at 5k 0.05 seconds loss.

Do you struggle with basic pre school maths ie 0.05<0.37

Come off it Welshy, are you now trying to tell us you meant 5k when you've been banging-on about revving Le Mans-style round to the 5.5k redline? I can see why you're playing that card (your idea of revving to 5.5k has been discredited) but I really think you should just have the decency to admit when you're wrong. It appears that over-riding the gearbox and holding the revs manually is counter-productive regardless of whether you shift at 5k or 5.5k; either way it's slower than letting the gearbox do its own thing so using the paddles in that way is surely pointless?

Edited by JNW1 on Thursday 18th December 14:02

[Welshbeef]

JNW1 said:

Come off it Welshy, are you now trying to tell us you meant 5k when you've been banging-on about revving Le Mans-style round to the 5.5k redline? I can see why you're playing that card (your idea of revving to 5.5k has been discredited) but I really think you should just have the decency to admit when you're wrong. It appears that over-riding the gearbox and holding the revs manually is counter-productive regardless of whether you shift at 5k or 5.5k; either way it's slower than letting the gearbox do its own thing so using the paddles in that way is surely pointless?

Edited by JNW1 on Thursday 18th December 14:02

Not really as my F10 535d pre LCI has a 5k red line not the LCI 5.5k so there you go .

[Welshbeef]

JNW1 said:

Come off it Welshy, are you now trying to tell us you meant 5k when you've been banging-on about revving Le Mans-style round to the 5.5k redline? I can see why you're playing that card (your idea of revving to 5.5k has been discredited) but I really think you should just have the decency to admit when you're wrong. It appears that over-riding the gearbox and holding the revs manually is counter-productive regardless of whether you shift at 5k or 5.5k; either way it's slower than letting the gearbox do its own thing so using the paddles in that way is surely pointless?

Edited by JNW1 on Thursday 18th December 14:02

Actually this minting in Sport mode joining the Mway on a verity short slip road foot flat to the floor - I didn't particularly look at the rev counter but it looked like it went close to the full 5k red line no idea which gear as the box did that

[drmark]

apotts said:

To be boring and answer the original question...

You change gear when the torque at the wheels in the next gear will be equal to the torque at the wheels in the current gear.

Points to remember:

• The gearbox ratio changes the torque at the wheels
• As you go up the gears, there is a difference in gear ratio gaps (big gap in low gears, small gap in high gears). So the shift point will gradually get lower for an engine with a long downwardly-sloping torque curve.
• For engines with a flatter torque curve (ie petrol engines) the optimum shift point is normally limited by max mechanical rpm, so you just shift at the red line.

You can find the shift points quite easily in software. I have done in for the 8HP box with 35d engine, and these are the optimum points:



I'd bet the 30d engine was almost identical.

Drive force graph showing optimum shift points:

Thank you. By far the most informative post on here.
Not worth falling out over though Welshbeef.

[Wills2]

apotts said:

To be boring and answer the original question...

You change gear when the torque at the wheels in the next gear will be equal to the torque at the wheels in the current gear.

Points to remember:

• The gearbox ratio changes the torque at the wheels
• As you go up the gears, there is a difference in gear ratio gaps (big gap in low gears, small gap in high gears). So the shift point will gradually get lower for an engine with a long downwardly-sloping torque curve.
• For engines with a flatter torque curve (ie petrol engines) the optimum shift point is normally limited by max mechanical rpm, so you just shift at the red line.

You can find the shift points quite easily in software. I have done in for the 8HP box with 35d engine, and these are the optimum points:



I'd bet the 30d engine was almost identical.

Drive force graph showing optimum shift points:

Good post, I did say that earlier that the launch control on 35d optimises the changes and that they were all under 5k rpm.

Thankfully your post will put an end to this.

[cerb4.5lee]

Wills2 said:

Thankfully your post will put an end to this.

The be careful what you wish for situation has hit me now...I always criticised my V8 M3 for how poor it responded at low revs only to then experience a 640d that picks up at 1500rpm really well yet its not rewarding to open up very much other than it piles speed on effortlessly.

So I can now empathise with you regards the way you feel about the 335d versus the V8 M3...diesels are sadly very boring in reality...effective for sure but ultimately very unrewarding.

[Wills2]

cerb4.5lee said:

Wills2 said:

Thankfully your post will put an end to this.

The be careful what you wish for situation has hit me now...I always criticised my V8 M3 for how poor it responded at low revs only to then experience a 640d that picks up at 1500rpm really well yet its not rewarding to open up very much other than it piles speed on effortlessly.

So I can now empathise with you regards the way you feel about the 335d versus the V8 M3...diesels are sadly very boring in reality...effective for sure but ultimately very unrewarding.

I told you Lee! Amazing that we both have ended up with the same engine! At least you have a good looking car unlike my boring touring.

I really miss that engine this torquey diesel stuff is pants....

I'll add that I'm looking at a few 507 c63's at the moment I can't go on with this car I might as well get a 318d TBH.

Edited by Wills2 on Friday 19th December 23:41

[Welshbeef]

Wills2 said:

I told you Lee! Amazing that we both have ended up with the same engine! At least you have a good looking car unlike my boring touring.

I really miss that engine this torquey diesel stuff is pants....

I'll add that I'm looking at a few 507 c63's at the moment I can't go on with this car I might as well get a 318d TBH.

Edited by Wills2 on Friday 19th December 23:41

Can you afford way under half the economy? If yes do it and don't complain about the big hit ondepteciation you will take for buying new.

If you cannot afford that combination then suck it up - but a 507 C63AMG what a car what a noise but what a thirst.


Nice choice/problem to have.

[Wills2]

Welshbeef said:

Can you afford way under half the economy? If yes do it and don't complain about the big hit ondepteciation you will take for buying new.

If you cannot afford that combination then suck it up - but a 507 C63AMG what a car what a noise but what a thirst.


Nice choice/problem to have.

Hi Welshbeef, I've run a brand new 911, 3 x M3 etc.... I understand about fuel and running costs buddy.


(Please don't feel the need to reply I don't think I have the strength mate, you are quite annoying......)

Edited by Wills2 on Saturday 20th December 00:12