F30 330d 8 speed auto question

F30 330d 8 speed auto question

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Discussion

Welshbeef

49,633 posts

197 months

Thursday 11th December 2014
quotequote all
Wills2 said:
Welshbeef said:
The car it giving more power at 5k revs than say 3k revs so you are accelerating at a faster rate. Well worth it if your in the mood.
Launch control changes up at 4.5k so I reckon BMW have figured that is the change up point to give maximum acceleration.

After 4.5k the torque drops off a cliff therefore so does the power despite the extra revs everything tails off.



Graph shows otherwise - sure torque falls but the power drop is not that much from peak power. Infact unless the next gear changes up to 3.900 revs then you should continue right up to the limiter then bang into the next gear given this graph.


http://www.superchips.co.uk/curves/BMWF13640dEPC.p...

Wills2

22,666 posts

174 months

Thursday 11th December 2014
quotequote all
Welshbeef said:
Wills2 said:
Welshbeef said:
The car it giving more power at 5k revs than say 3k revs so you are accelerating at a faster rate. Well worth it if your in the mood.
Launch control changes up at 4.5k so I reckon BMW have figured that is the change up point to give maximum acceleration.

After 4.5k the torque drops off a cliff therefore so does the power despite the extra revs everything tails off.



Graph shows otherwise - sure torque falls but the power drop is not that much from peak power. Infact unless the next gear changes up to 3.900 revs then you should continue right up to the limiter then bang into the next gear given this graph.


http://www.superchips.co.uk/curves/BMWF13640dEPC.p...
That's right welshy superchips know more than BMW, I'll take the engine dyno from BMW every time over the wheel HP calc of a rolling road.


Welshbeef

49,633 posts

197 months

Thursday 11th December 2014
quotequote all
Wills2 said:
That's right welshy superchips know more than BMW, I'll take the engine dyno from BMW every time over the wheel HP calc of a rolling road.

Have BMW published a full dyno readout for the standard car? I'd like to see the difference - also I'd expect Super-chips to play down the OEM output not show it in its strongest light which is what that dyno shows.



Unless that info exists this dyno is the best info we have the rest is pure speculation

knitware

1,473 posts

192 months

Friday 12th December 2014
quotequote all
Don’t worry about the revs, the gearbox will do the work. Looking at the rev counter is so 1970’s…

cerb4.5lee

30,176 posts

179 months

Friday 12th December 2014
quotequote all
knitware said:
Looking at the rev counter is so 1970’s…
I liked the 70`s and anyway back then cars were mostly fuelled by petrol...so even better lol!

I always enjoyed watching the rev counter as a kid and its something I still enjoy doing now for some daft reason...

drmark

4,793 posts

185 months

Friday 12th December 2014
quotequote all
Welshbeef said:
Graph shows otherwise - sure torque falls but the power drop is not that much from peak power. Infact unless the next gear changes up to 3.900 revs then you should continue right up to the limiter then bang into the next gear given this graph.


http://www.superchips.co.uk/curves/BMWF13640dEPC.p...
This graph confirms the point I was trying to make - peak power is 4250 -4500. Peak torque way below that. Ergo change at 4500 max for best progress. Or am I missing something. No point in bouncing off redline in these cars.
At least the 8 speed gearbox understands wink

Shezbo

594 posts

129 months

Friday 12th December 2014
quotequote all
The key here is that there are two points:
1. Max performance from a diesel engine.
2. Max engine rev's.

1. BMW have designed the autobox so once max power has been achieved - it changes up. There is no point in going past 4,500 rev's, as the vehicle will increase speed - if a gear change is made (the revs drop) and the engine is back in the power band and doing good work.

If you have a manual diesel - it is very easy to over rev a diesel i.e. stray past 4,500 rpm. You think you are accelerating faster as the revs are still increasing (this is our "petrol brain"!)but once past 4,500 revs you are actually accelerating more slowly.

2. Max rev's of a diesel engine is the limit of safe rpm.

JNW1

7,707 posts

193 months

Friday 12th December 2014
quotequote all
drmark said:
This graph confirms the point I was trying to make - peak power is 4250 -4500. Peak torque way below that. Ergo change at 4500 max for best progress. Or am I missing something. No point in bouncing off redline in these cars.
At least the 8 speed gearbox understands wink
No, you're not missing the point, you're spot on! Perhaps others enjoy hitting the red line in their diesel because like the noise it makes at high revs but each to their own if that's the case.....

anonymous-user

53 months

Friday 12th December 2014
quotequote all
drmark said:
Welshbeef said:
Graph shows otherwise - sure torque falls but the power drop is not that much from peak power. Infact unless the next gear changes up to 3.900 revs then you should continue right up to the limiter then bang into the next gear given this graph.


http://www.superchips.co.uk/curves/BMWF13640dEPC.p...
This graph confirms the point I was trying to make - peak power is 4250 -4500. Peak torque way below that. Ergo change at 4500 max for best progress. Or am I missing something. No point in bouncing off redline in these cars.
At least the 8 speed gearbox understands wink
....which is why the 8 speed was developed.

I wouldn't take much notice of welsh, wouldn't be the first time he has guessed wrong.

Wills2

22,666 posts

174 months

Friday 12th December 2014
quotequote all
drmark said:
Welshbeef said:
Graph shows otherwise - sure torque falls but the power drop is not that much from peak power. Infact unless the next gear changes up to 3.900 revs then you should continue right up to the limiter then bang into the next gear given this graph.


http://www.superchips.co.uk/curves/BMWF13640dEPC.p...
This graph confirms the point I was trying to make - peak power is 4250 -4500. Peak torque way below that. Ergo change at 4500 max for best progress. Or am I missing something. No point in bouncing off redline in these cars.
At least the 8 speed gearbox understands wink
Indeed, the fact that launch control changes up at 4.5k tells you everything you need to know..

Wills2

22,666 posts

174 months

Friday 12th December 2014
quotequote all
Welshbeef said:
Have BMW published a full dyno readout for the standard car? I'd like to see the difference - also I'd expect Super-chips to play down the OEM output not show it in its strongest light which is what that dyno shows.



Unless that info exists this dyno is the best info we have the rest is pure speculation
Jesus wept.....

Welshbeef

49,633 posts

197 months

Saturday 13th December 2014
quotequote all
REALIST123 said:
drmark said:
Welshbeef said:
Graph shows otherwise - sure torque falls but the power drop is not that much from peak power. Infact unless the next gear changes up to 3.900 revs then you should continue right up to the limiter then bang into the next gear given this graph.


http://www.superchips.co.uk/curves/BMWF13640dEPC.p...
This graph confirms the point I was trying to make - peak power is 4250 -4500. Peak torque way below that. Ergo change at 4500 max for best progress. Or am I missing something. No point in bouncing off redline in these cars.
At least the 8 speed gearbox understands wink
....which is why the 8 speed was developed.

I wouldn't take much notice of welsh, wouldn't be the first time he has guessed wrong.
What?
Its clearly producing well over 95% of power at 5k revs while when it changed up it drops revs into the 3k rev range this is much much less that 95%

The 8 speed box was certainly not developed for BMW Diesel engines shame you are wrong on this and certainly not the first time try harder.

drmark

4,793 posts

185 months

Saturday 13th December 2014
quotequote all
Welshy, BMW and I bow to your superior experience. I have driven these cars for 170,000 miles (E61 and 70k in my F11) and BMW have spent a small fortune getting the best out of one of the best drive trains in the business.
Not our fault you don't understand the proper use of peak power and torque.
I bow out.
All yours sir. Enjoy playing with your tyre pressures and redlining the car. getmecoat

Welshbeef

49,633 posts

197 months

Saturday 13th December 2014
quotequote all
drmark said:
Welshy, BMW and I bow to your superior experience. I have driven these cars for 170,000 miles (E61 and 70k in my F11) and BMW have spent a small fortune getting the best out of one of the best drive trains in the business.
Not our fault you don't understand the proper use of peak power and torque.
I bow out.
All yours sir. Enjoy playing with your tyre pressures and redlining the car. getmecoat
Dmark you have seen the power graph it holds 95% of peak power up to 5k however under 4k revs its producing less than 5%.

I'm struggling here is your sight impared or have you simply ignored the graph? If another one exists official BMW great lets post a link up (I cannot find one) so until that comes to light lets take this as the best info we have.


BMW do not make the gearboxes the gearbox is available in other cars (non BMW) totally indifferent they did not design the gearbox for a diesel BMW.



Anyway back on topic why can the OP not hit max revs? Is it a fault?

drmark

4,793 posts

185 months

Saturday 13th December 2014
quotequote all
Ok. One more try.

At 4250 revs - max power (320 in graph) and 520 NM

At redline 290 bhp and 440 NM

If box changes at 4250 - 4500 output drops to 275 - 290 but torque is much higher at 550 and car entering run to peak power - just want you want to pull a higher gear.

If you change at redline, power is higher in next gear but torque much lower and both reduce as you accelerate beyond the sweet spot again, compounding the inefficiency.

Think area under both curves and direction of travel (graph not car), rather than point references.

And if you think BMW just plucked the ZF box off the shelf and fitted it with nary a thought about ratios, software etc then you are misguided.

Now let's leave it there.





Edited by drmark on Saturday 13th December 12:49


Edited by drmark on Saturday 13th December 12:51

335d

758 posts

117 months

Saturday 13th December 2014
quotequote all
There are official BMW graphs of the 30d engine on page 2 of this document

http://www.matlawrence.com/images/bmw/powerkit.pdf

This suggests that peak power happens at 4000rpm. The graph only goes up to 4500rpm, but by extrapolating you can see that holding on to 5000rpm would not be sensible with a close ratio box. Shifting up at 4500rpm appears to make sense.

budgie smuggler

5,359 posts

158 months

Saturday 13th December 2014
quotequote all
drmark said:
Ok. One more try.

At 4250 revs - max power (320 in graph) and 520 NM

At redline 290 bhp and 440 NM

If box changes at 4250 - 4500 output drops to 275 - 290 but torque is much higher at 550 and car entering run to peak power - just want you want to pull a higher gear.

If you change at redline, power is higher in next gear but torque much lower and both reduce as you accelerate beyond the sweet spot again, compounding the inefficiency.

Think area under both curves and direction of travel (graph not car), rather than point references.

And if you think BMW just plucked the ZF box off the shelf and fitted it with nary a thought about ratios, software etc then you are misguided.

Now let's leave it there.





Edited by drmark on Saturday 13th December 12:49


Edited by drmark on Saturday 13th December 12:51
I'm not arguing with you, but I don't understand what you mean there.

If you change up at 4500 RPM, the next gear comes in at around 3500 RPM. The engine is producing 275 BHP, rising to 309 ish BHP at the point where you change again.

If you changed up at 5000 RPM, the next gear comes in at say 4000ish RPM. The engine is producing 300 BHP at that point. It continues producing over 300 BHP until you change again at 5000 RPM.

Why do you think that the first would be faster? Your average power output between gear changes has been lower.

Edited by budgie smuggler on Saturday 13th December 15:35

drmark

4,793 posts

185 months

Saturday 13th December 2014
quotequote all
Ok. I don't want an argument either - and The example I gave is confusing as it is based on area under torque and power curves, and not specific to the ratios in a 8 speed box.

Let's forget torque for a moment (which is very important but seems to confuse people).

In a F10/11 if you accelerate from 60 - 90 say. Left to its own devices in sport the box changes at 4500 and drops to 4000 for next gear (500 increments not 1000). Look at the graph and compare the power over the 4000 - 4500 range and it beats the power from 4750 - 5250.

Then add in the difference in torque and it is a complete no brainer why the box changes at 4500.

By all means redline your diesel (if you can make it do it) but I will come past you if I leave it sport.

Edited add: this is a common misconception in people used to NA high performance petrol engines where the torque and power curves are much more closely aligned and tend to peak closer together. Wringing their necks has benefits - as any GT3 driver knows. And fab they are too. But very different to an eight speed turbo diesel.




Edited by drmark on Saturday 13th December 16:23

Welshbeef

49,633 posts

197 months

Saturday 13th December 2014
quotequote all
drmark said:
Ok. I don't want an argument either - and The example I gave is confusing as it is based on area under torque and power curves, and not specific to the ratios in a 8 speed box.

Let's forget torque for a moment (which is very important but seems to confuse people).

In a F10/11 if you accelerate from 60 - 90 say. Left to its own devices in sport the box changes at 4500 and drops to 4000 for next gear (500 increments not 1000). Look at the graph and compare the power over the 4000 - 4500 range and it beats the power from 4750 - 5250.

Then add in the difference in torque and it is a complete no brainer why the box changes at 4500.

By all means redline your diesel (if you can make it do it) but I will come past you if I leave it sport.

Edited add: this is a common misconception in people used to NA high performance petrol engines where the torque and power curves are much more closely aligned and tend to peak closer together. Wringing their necks has benefits - as any GT3 driver knows. And fab they are too. But very different to an eight speed turbo diesel.




Edited by drmark on Saturday 13th December 16:23
But given you could hit the same target speed in the lower gear then you are ignoring the zero acceleration time during he gearchange where the still in gear driver is gaining maybe half a car length. This wouldn't be made back in 500rpm 4k to 4.5k



Fact is look at the Derv Le Mans cars how are they driven to extract the maximum performance ? Do they change up at near full revs/just shy of the limiter or as soon as they hit max bhp?

drmark

4,793 posts

185 months

Sunday 14th December 2014
quotequote all
Welshbeef said:
But given you could hit the same target speed in the lower gear then you are ignoring the zero acceleration time during he gearchange where the still in gear driver is gaining maybe half a car length. This wouldn't be made back in 500rpm 4k to 4.5k



Fact is look at the Derv Le Mans cars how are they driven to extract the maximum performance ? Do they change up at near full revs/just shy of the limiter or as soon as they hit max bhp?
Just back from a party and old advice rings true. Never argue with a fool. I tried but failed.
Over and out.