Which is faster - 170ps or 163ps?

[CraigyMc]

Hello all,
I found an odd piece of data from my research on a new car:
2013 BMW 320i (F30) EfficientDynamics (1.6 turbo petrol, manual 'box) - 170ps, 250Nm. 0-62 7.6s, 130mph.
2013 BMW 320d (F30) EfficientDynamics (2.0 turbo diesel, manual 'box) - 163ps, 380Nm. 0-62 8.0s, 143mph.

Why does the more powerful car have a slower top speed (and a hell of a lot slower, from the looks of it!)

Other than gearing, I can't think of a reason why. Any ideas?

C

Edited by CraigyMc on Tuesday 4th December 17:14

[blueg33]

Weight? followed by drag coefficient (one may have a sports body kit). Bigger wheels and tyres = more weight and more drag.

[thinfourth2]

Gearing?

[Cyder]

Don't forget gearing.

ETA, it seems he didn't having re-read the post!

[CraigyMc]

Both models are identical in terms of aero, and the weight is 30Kg in the petrol cars' favour.

Unless all the reviews I've been reading are wrong, I can't figure it out.

C

[CraigyMc]

blueg33 said:

Weight? followed by drag coefficient (one may have a sports body kit). Bigger wheels and tyres = more weight and more drag.

They have the same body, wheels and tyres.

C

[Cyder]

Almost certainly gearing then I would suggest.

[Ari]

The diesel has way more torque.

[Caulkhead]

CraigyMc said:

Other than gearing, I can't think of a reason why. Any ideas?

Marketing.

[CraigyMc]

Cyder said:

Almost certainly gearing then I would suggest.

Gearing loses you 13mph when you start with about 6bhp more: this smells very fishy to me but that's the only difference I can think of.

[CraigyMc]

Ari said:

The diesel has way more torque.

True, but top speed is just power versus drag.

[CraigyMc]

Caulkhead said:

Marketing.

Do you mean the petrol car is made slower by marketing? How much marketing is it delivered with?

[John145]

Torque output at the top end. Although one has more power as an absolute figure, the actual torque generated at 130mph vs whatever rpm might not be enough to push the car on to the higher speeds. (aka bogging down)

[wooooody]

ummmm, maybe the extra 100lbft of torque may have an influence?

As in,the it'll allow the car to be geared higher.

[mattnunn]

Is it something to do with gearing?

[Sam.F]

OP, are you sure those numbers are lb/ft or are they NM?

[mikecassie]

The gearing will be selected to suit the torque of the engine, so probably the diesel has longer gearing to allow greater fuel efficiency. With it's larger torque figures it can accelarate at an adequate rate and longer gearing. That's probably why it's 0-60 times are longer too.

[CraigyMc]

doogz said:

Also, isn't the petrol a 2.0L as well? Not the 1.6 quoted in the OP? The 1.6 is 134bhp, no?

The 320i EfficientDynamics isn't the same as the other, normal 320i's.
The ED model uses a 1.6 instead of a 2.0, and has 170ps instead of the 2.0's 184ps.

C

[CraigyMc]

Sam.F said:

OP, are you sure those numbers are lb/ft or are they NM?

They are nm, my apologies!

C

Edited to add: I've changed my original post. The torque for the petrol car is actually 250Nm, not 280.

Edited by CraigyMc on Tuesday 4th December 17:20

[GC8]

CraigyMc said:

Ari said:

The diesel has way more torque.

True, but top speed is just power versus drag.

Not so simple. Gearing and power/torque characteristics play their part too.