163 bhp performance any good ?

[wimorrison]

Originally Posted by darbs

i think the compression ratio would be the same now as the bore and stroke are the same - at least they are on the volvo web site.

With the same bore and stroke you get the same swept volume. The compression ratio depends on the total volume that is compressed and a different head design can increase/decrease the unswept volume thus changing the total volume and consequently compression ratio.

I understand that the efficiency gain that appeared on the 2011 engine over the 2010 was due to a head design change also which in that case resulted in more efficient combustion therefore better fuel consumption figures, yet retaining the same power output.

[darbs]

Originally Posted by volvorocks

the same performance stats could in reality be possibly achieved by 2 totally "different" engines.

i don't doubt that but would your theory apply to the D3 vs the D5? the presence of only a single turbo must make a difference to the torque the engine produces.

Originally Posted by volvorocks

performance stats for example on D5 pre Polestar were virtually the same as D3

could you clarify what you mean? a pre-polestar D5 is either 205 or 215ps. a D3 is 163ps. the torque drops off much quicker in the D3 too. i guess this might suggest that the single turbo the D3 has is the small one, not the big one.

[darbs]

Originally Posted by wimorrison

With the same bore and stroke you get the same swept volume. The compression ratio depends on the total volume that is compressed and a different head design can increase/decrease the unswept volume thus changing the total volume and consequently compression ratio.

I understand that the efficiency gain that appeared on the 2011 engine over the 2010 was due to a head design change also which in that case resulted in more efficient combustion therefore better fuel consumption figures, yet retaining the same power output.

yes, i overlooked your mention of heads! this indeed is an important part of the compression ratio.

[crossedover]

Originally Posted by darbs

you sure that's not a mistake? polestar.se shows the torque and power curves as 100% identical to the D5. since the D3 has only got a single turbo, but same displacement, it's got to be practically impossible to achieve exactly the same performance curves.

Well no, if you wind up the boost on the D3 turbo to the same level of the D5 you'll get the same performance at the engine speeds at which it is performant.

Where I was dubious about the polestar graphs were that the graphs were identical at all engine speeds and of course the point of bi-turb is increased power at engine speeds where a larger turbo is not optimal.

If a D3 is tuned to the same level as a D5 you won't get the same drive because the D3 will always feel more "laggy" than the D5. Which is not to say if I had the D3 and a 215 polestar were available I would not go for it - of course I would

[darbs]

Originally Posted by darbs

polestar.se shows the torque and power curves as 100% identical to the D5

is meant to mean:

Originally Posted by crossedover

the polestar graphs were that the graphs were identical at all engine speeds and of course the point of bi-turb is increased power at engine speeds where a larger turbo is not optimal.

and i didn't say it couldn't achieve the same performance. i said performance curves.

[volvorocks]

Originally Posted by darbs

i don't doubt that but would your theory apply to the D3 vs the D5? the presence of only a single turbo must make a difference to the torque the engine produces.



could you clarify what you mean? a pre-polestar D5 is either 205 or 215ps. a D3 is 163ps. the torque drops off much quicker in the D3 too. i guess this might suggest that the single turbo the D3 has is the small one, not the big one.

Hi Darbs

The torque figures as standard for D3 and D5 (215) are similar.

New D3 AWD is 420 as is D5 .
D5 torque is 1500-3250 whereas D3 is 1500-2500 so drops off sooner as you say.

2wd D3 torque is 1400-2850

Regards pre-polestar I refer to a standard D5 MY12 215

I find that I can rev my D5 to over 4000 revs with no noticable drop in surge.
(not that I do and of course you have to change up)

I think the D3 confuses matters as we have the D3 2.0 Litre and the D3 2.4 Litre with the same bhp output.

Regards

[crossedover]

Originally Posted by darbs

and i didn't say it couldn't achieve the same performance. i said performance curves.

Good point well made, in which case we agree entirely

[volvorocks]

Originally Posted by volvorocks

Hi Darbs

The torque figures as standard for D3 and D5 (215) are similar.

D5 torque is 1500-3250

2wd D3 torque is 1400-2850

Regards

Hi Darbs

As per my above shortened quote I do believe the figures demonstrate why I found standard D3 163 AND D5 215 to have similar performance as per my post in this thread previous due to the D3 torque coming in that slight bit earlier and peaking only a bit earlier at 2850.

Overall in perhaps a drag race or extended distance at speed I feel the D5 will conquer although in real life driving believe this will not be apparent.

Had D3 163 AWD been available I may have chosen this over D5 awd.

Regards

[crossedover]

As we're on the sticky issue of torque vs power, remember three things:

Power and torque are linearly related via rpm, which is why low torque engines that rev a lot e.g. S2000 make lots of power.

What matters is torque at the wheels not torque at flywheel. The gearing multiplies the engine torque i.e gear ratio times final drive ratio times torque = torque at wheels. A gearbox is a torque amplifier.

Two vehicles that have the same weight, aerodynamics and power will be near enough identical in performance assuming sensible gearing irrespective of the max torque output of either. Equally, if everything is the same but one vehicles power is less than the other the lower power car will always be slower even if its max torque is higher than its counterpart.

[crossedover]

Originally Posted by volvorocks

Hi Darbs

As per my above shortened quote I do believe the figures demonstrate why I found standard D3 163 AND D5 215 to have similar performance as per my post in this thread previous due to the D3 torque coming in that slight bit earlier and peaking only a bit earlier at 2850.

Overall in perhaps a drag race or extended distance at speed I feel the D5 will conquer although in real life driving believe this will not be apparent.

Had D3 163 AWD been available I may have chosen this over D5 awd.

Regards

VR, with all due respect you cannot compare your figures with three adults, a bag of cement, a load of fuel and eyeballed speed/time date with What Car's figures where the car is driven by a jockey on fumes using electronic timing and speed measurement!

I have driven the d3 and d5 back-to-back on test drives albeit I don't know what particular incarnation of the D3 and they are poles apart performance-wise.