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I have lurking around for a quite a while now.

I’ve been a M5 fan for a very long time now because I consider it to be the consummate all-rounder.

Unfortunately admiration at a distance is all I can muster at the moment.

I have a 530d (e39) which will remain my steed for the foreseeable future.

I am buying a house so cannot indulge.

To pass the time I thought I would stir things up a bit by trying to compare the characteristics of B5 and M5.

I have made a few assumptions in the absence of information.

I conclude without actually driving either vehicle as follows that:
  1. the M5’s optimal cruising speed is around 6-6,500 rpm from 1st to 5th gears, 4,000 rpm in 6th gear and 3,000 rpm in 7th gear
  2. the B5’s optimal cruising speed is around 4,500 rpm from 1st to 4th gears and 3,500 rpm in 5th and 6th gears.
I enclose my spreadsheet – please modify and correct where necessary. I used Greg Neumann’s spreadsheet as the template and made my own amendments.

On another note I have to say that the UK has some fantastic “driver’s” roads. I have compiled a long list which I hope to experience some time.

I have videoed my first foray.

I will try and upload it if anyone is interested.

Sheikh
 

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vndkshn said:
Holy small font Batman!!
hiha hiha First good belly laugh of the 21st hour of this day. Had a good one last hour, but I try for one really good laugh an hour. Keeps me looking young. Oh wait, I am young.
:cheers:
 

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vndkshn said:
Holy small font Batman!!

Why cruise at 6k rpm? Don't really follow the logic. Optimal how?
I could see it as optimal if you were about to floor the car, :M5launch:

all the best
adam
 

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Welcome aboard Sheikh :byebye:

I've not driven the B5 yet but comparing the E39 M5 (which is a V8) with the new V10 powered M5 which I have driven, I think that the Alpina will ride around on that torque a lot "easier" than the M5 which just loves to be revved. That said, the V10 is so powerful even at low revs that one never feels that it is lacking any torque.

It's more a matter of taste. The Alpina has some gorgeous interiors which will satisfy some buyers like no other car can. Of course, until the M5 touring is launched, the B5 is also the only option if you want a load lugger.
 

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Discussion Starter #7
Adam

Yes, that's my idea.

The table shows the force for acceleration is greatest at the rpms mentioned.

I arrived at the rpms in the accelerate to column by comparing the force in the given gear with range of values in the next.

If you achieve more force by revving more rather than shifting up then you continue revving.



Sheikh
 

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When I previewed the post it came out fine at 1.

See my reply to Adam which is at 4.

What's the best font for viewing?

This font is at 2.



Sheikh
 

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Nice and interesting analysis!

Also, please show us some videos, but I am afraid you have it at your server or some other server, since we cannot host it.


The post below was in perfect normal font.

sheikh said:
When I previewed the post it came out fine at 1.

See my reply to Adam which is at 4.

What's the best font for viewing?

This font is at 2.



Sheikh
 

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Discussion Starter #10
Thanks Gustav.

I am looking at neptune.com for the video uploads.

Will let you know if it works out.


Sheikh
 

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Adam said:
I could see it as optimal if you were about to floor the car,
But, by definition, that wouldn't be cruising...

But, I will say it might come in handy when determining what gear to flip to to dust that AMG...

sheikh, how did you come up with the hp/tq levels, from looking at the charts?
 

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vndkshn said:
But, by definition, that wouldn't be cruising...
In the UK the highest form of driver training for the public road is based on RoadCraft which is the basically that taught by the Police instructors to their own.

This involves driving at the limit of vision and road conditions, not the limit of grip. Public roads are not race tracks.

That is you must at any time be able to stop well within the distance you see to be clear on your side of the road.

But this also means that you continue accelerating until and unless there is a reason not to.

UK B-roads and country roads are very good for testing driving ability - I especially like the downhill decreasing radius corner which is camouflaged by hedges and trees.

Given that M5 drivers are driving high performance cars I wanted to compare the power/drivetrain of the M5 and B5 by reference to high performance road driving.

So cruising does not mean shifting to the highest gear at the steady state.

This does not mean that you would not do this at any time. If there is no opportunity to make progress then you cruise in the traditional sense of the word. For example when you are stuck in traffic or as is usual in British B-roads these days behind a snake of traffic - no one car in front leaving you enough space for an overtake and at the same time not willing to overtake themselves.

Under better circumstances you find yourself making efficient progress and you see in the far distance say an Impreza.

You catch the Impreza, match his speed, move over to the other side of the road to confirm there is no oncoming traffic and then despatch him.

Cruising is therefore matching speed to maintain distance until you see the opportunity to despatch the hazard with the throttle.

Based on my analysis I conclude that the "optimal" crusing speeds and shiftpoints are as shown in the spreadsheet for the M5 and B5.

I am sorry that I did not explain this earlier. I had expected that M5 drivers would understand and practice RoadCraft even if they did not know it.

I had expected that only MB E55 and CLS55 drivers would equate cruising with the need to save fuel.

Whenever and wherever possible I avoid motorways and dual carriageways - they require little driving skill, they have multiple lanes. Driving at speed on those roads requires more courage than skill. They are regulated for obvious reasons - most drivers like them because they are easy to drive and the police like them because they can catch more drivers for speeding.

I prefer tight unforgiving B-roads and country lanes, especially in the night. The concentration required is fierce and intense.

I had therefore expected M5 drivers who have in their hands the finest saloon for "proper" road driving to understand this.

vndkshn said:
But, I will say it might come in handy when determining what gear to flip to to dust that AMG...
Exactly.

My questions are:

Do my calculations stack up?

Do you find the steady state cruising speeds mentioned realistic?

Do you find the upshift points realistic?

vndkshn said:
sheikh, how did you come up with the hp/tq levels, from looking at the charts?
Yes, by estimating them from the charts.

I would like to refine the calculations e.g. I have assumed the frontal areas, the Cd for the M5.


Sheikh
 

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I can see we have much different definitions of the word cruising. I don't define cruising as being able to immediately overtake a car without a downshift. I define cruising as true steady state driving, typically with the cruise control on. Situations where you are maintaining a constant speed, typically over a distance. In those situations, I do not want the engine revving at 6k in those situations.

So, it has nothing to do with "saving fuel" or anything of the sort. The type of driving you are describing I would describe as "spirited driving", but certianly not cruising.

In fact, refer to the dictionary.. per Webster's:

cruise ( P ) Pronunciation Key (krz)
v. cruised, cruis·ing, cruis·es
v. intr.
1.)
A. To sail or travel about, as for pleasure or reconnaissance.
B. To go or move along, especially in an unhurried or unconcerned fashion: “A whole cache of babies... cruised imperiously in their strollers, propelled by their mothers or by pairs of grandmothers” (Anne Tyler).
2.) To travel at a constant speed or at a speed providing maximum operating efficiency for a sustained period.

So.. cruising speed? Perhaps refer to the dictionary before correcting someone with statements like you have made.

So, no, I don't find the steady state cruising speeds realistic, using the definition of cruising. Overtaking? Possibly, and even probably. I also bet your shift points are too low, especially at higher speed and higher gears. Several of your shifts occur well below the HP peak.
 

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vndkshn said:
I also bet your shift points are too low, especially at higher speed and higher gears. Several of your shifts occur well below the HP peak.
I don't believe they are.

Force for acceleration = force transmitted through the rear wheels - drag - rolling resistance.

I have ignored rolling resistance.

The first table of speeds at rpms in a given gear shows road speeds in the absence of drag.

The second table shows the force transmitted through the rear wheels by the engine through the transmission.

The third table shows the force for acceleration by subtracting the drag calculated at each rpm in the second table based on the speeds in the first table.

So in the absence of drag the upshift points are always at the rev limit [500 rpm above the power peak].

As Greg Neumann concluded (in the absence of drag) you shift up at the rev limit, not as you say at the power peak.

In the presence of drag at higher speeds I suggest that it pays to upshift earlier because the force for accceleration is greater in a higher gear owing to greater torque at lower rpm.


Sheikh
 

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Oh boy.. here comes the whole torque versus hp debate. My position, the higher speeds will benefit more from shifting above the HP peak.. which would mean shifting near (or at) the rev limit, in order to keep the engine in its power peak.

EDIT: In fact, I'll take it a step further... a high torque car MIGHT be better off shifting before the HP peak in order to help acceleration (although I seriously doubt it), the M5 is not exactly a torque monster.
 

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Sheikh your shift points are wrong!

Its best to hit the full rpm in every gear. Just look at the plot i did of your numbers below. The way to interpret is no matter what speed your are going shifting to a higher gear gives less thrust. Remeber that if you are driving at 100mph in 3rd gear and shift to 4th your still travelling at 100mph. It is also evident that the 7speed and the V10 are made for each other look at the 4,5 & 6th gear graphs.

Also peak torque is at 6500rpm but you coloured the 6000rpm column green :D
 

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