Z4 Coupe to Z4M Coupe Questions?

[Jembo]

It's only more top speed that comes from more power.

I'm afraid that is incorrect.
Hence for example why a diesel car with more torque but less power, then the petrol version, is indeed slower 0-60mph.
Of course, with the S54 narrow powerband you have to "shoot straight" and match it to use it.

I believe the OP was referring to top speed, not acceleration.

Power & drag are the two primary factors to top speed

[buzyg]

That's interesting, but after my drive in an MC on Tuesday to me it felt more keen to get moving well before 5,000 rpm.

Assuming similar gearing, the 'seat of the pants' acceleration force comes down to the torque to weight ratio. I did a few stats on this in another thread which showed very interesting results:

Peak torque to weight ratio (higher is better)

3.0Si - 0.181 lbft/kg
Z4M - 0.186 lbft/kg
E46 M3 - 0.167 lbft/kg

You can see how close the N52 and S54 are. But perhaps also as important is at what rpm peak torque is:

S54 - 4900 rpm
N52 - 2750 rpm

What really stands out here is how low down in the rev range the N52 makes peak torque, in fact that is truly exceptional for a normally aspirated engine and I doubt there is another na engine in the world that makes peak torque so low down. Looking specifically at that point in the rev range:

S54 @ 2750rpm = 220lbft / 115bhp
N52 @ 2750rpm = 232lbft / 121bhp

...but also remember that M is at least 50Kg heavier and the difference becomes even more pronounced - the N52 is the clear winner.

As mentioned above, all the S54 gains are after the second vanos changeover point around 4500rpm. Fundamentally it only really makes more power because it revs higher, but I agree it's all the more exciting for it!

Though it is always nice to read the figures and do the math, it misses the very real world point. As soon as you want to have a bit of fun on a good road, you natrualy head straight for the engines sweet stop and try and keep it there as you change cogs. Point being no body drives at 2750 rpm when they are having fun. Handy on the commute to work. Worth noubt once your on it, then it's all about power.

[mmm-five]

As a 'bit of fun' at the Ring, we have a challenge to see whether we can do the whole lap in a single gear (once under the gantry of course).

1st/2nd/3rd are useless as you can't get above 105mph, 6th is useless as it won't pull up the long hills, 5th is almost perfect except for one or two corners where you drop to below 50mph.

4th is the winner if you really had to drive the whole circuit in one gear.


The other 'fun' exercise we do is to artificially set ourselves a specific RPM limit - so no more than 3000/4000/5000/6000/7000rpm.

7000/6000 is easy and is like driving a 3.0 or an e34 M5, with plenty of torque/power over a few 000rpm, 5000/4000 means forever changing gear to use the bit of extra power. 3000 is doable, but you lose the 'rocket' effect out of corners as you never get into peak power curve.


The upside of all of these 'fun exercises' is that it shows how much difference the right gear makes to the performance and the fuel economy (as low as 6mpg, or as high as 14mpg)

It also shows you don't have to drive at 10/10ths on track to have 'fun'.

[Argenta]

Also its sometimes more fun in a less powerful car on any track, you're bound to use all the power available.
I'm having great fun in my Fiat Argenta (145hp) even on Nurburgring

[MrPT]

The throttle pick up on the S54 is very good. It does make it seem a lot pokier than it actually is, especially if you’re up in the rev range and already holding a bit of lateral G (terrible idea on a wet day, I know...).

[buzyg]

The throttle pick up on the S54 is very good. It does make it seem a lot pokier than it actually is, especially if you’re up in the rev range and already holding a bit of lateral G (terrible idea on a wet day, I know...).

Sounds like you may already have tried that Idea out in the wet.

[Jembo]

The throttle pick up on the S54 is very good. It does make it seem a lot pokier than it actually is, especially if you’re up in the rev range and already holding a bit of lateral G (terrible idea on a wet day, I know...).

Sounds like you may already have tried that Idea out in the wet.

I don’t think there’s a MR or MC owner that hasn’t

[MrPT]

Yeah, maybe not mid-roundabout but certainly coming off them with no TC in the rain!

[Argenta]

I'm afraid that is incorrect.
Hence for example why a diesel car with more torque but less power, then the petrol version, is indeed slower 0-60mph.

You are being over-simplistic. The only reason diesel cars tend to be slower to 60 is that they cannot maintain the high torque over a very wide rev range. In terms of acceleration force (or G-force if you like) from 2000 - 4000 rpm they tend to wipe the floor compared to na petrol engines. Like I said earlier, you have to look at the whole power curve to determine which will be quicker to a particular speed.

You are actually defining what ”power” is: torque x revs.

[TomK]

It's only more top speed that comes from more power.

I'm afraid that is incorrect.
Hence for example why a diesel car with more torque but less power, then the petrol version, is indeed slower 0-60mph.
Of course, with the S54 narrow powerband you have to "shoot straight" and match it to use it.

That is a really bad analogy of the point I think you are trying to get across. ph001 is quite correct in what he says.
Lost in translation

[RedUn]

And back to topic...

Good luck in your search OP, drive as many as you can and don't buy the first one you come across...

Make sure the engine is cold when you go to look at one, there's loads of info on here about the s54 have a good read

[mr wilks]

And back to topic...

Good luck in your search OP, drive as many as you can and don't buy the first one you come across...

Make sure the engine is cold when you go to look at one, there's loads of info on here about the s54 have a good read

Good advice , a listen to the S54 start from cold & ticking over can often tell a good one from bad.
One that needs valve clearance doing compared to one that doesn't sounds massively different.
Similar with the vanos , if it's needing therapy you should be able to hear