Sprint Chief

With regard to power at wheels / power at flywheel.

Power at wheels is incredibly difficult to measure accurately, or in a meaningful way. Most rolling roads attempt to measure transmission losses, but in truth these bear only a distant relation to the actual losses seen on the road. The main reason for this is the loss through the tyre deformation, which counts for a significant wedge of the power loss. On a 2WD rolling road, only the tyre deformation through one set of wheels is measured; yet in practice the other set of wheels still deform and still sap power. In addition to this, the rollers contact the tyres in twice as many places as the road, leading to a doubling of lost power through this mechanism. As if this isn't enough, the radius of the rollers is quite small compared to that of a flat road (!), which again increases the tyre deformation, and making the apparent loss worse than it really is.

Basically, the upshot of this, the difference in the transmission loss of AWD and 2WD will be much less significant on the road than it will be on the rolling road; whilst the difference will be less, the AWD car *will* ultimately have the greater transmission loss.

Plus having pushed all manner of cars into position on sprint startlines, I can personally vouch for the fact that M3s are much easier to push than imprezas

Vate

2 pence worth..........
They handle very differently. On normal roads in dry conditions neither would particularly 'outhandle' the other. A driver who could push the M3 along quickly would probably not have much trouble doing the same with a P1. If a P1 driver has little RWD experience then he may find it a lot harder to repeat the handling levels of his/her P1. Both of these cars are very fast across country but the P1 probably could cover the twisty bits easier at speed at the hands of almost any driver. In wet conditions nobody could really argue the virtues of the extra traction of the P1's AWD. This is about traction though not specifically handling. Even cars much less powerful than an M3 find life easier in the wet. I have heard that a Legacy 2.5GX Auto can change direction at silly speeds in wet weather (The auto has some extra electronic gizmos than the manual). If the thread is falling into which car is more desirable then I have to say goodbye P1. Whatever your opinions of BMW ownership image are the car is just one of the most sublime pieces of everyday travel money can buy. I may be tempted when the novelty of my MY00 + mods wears off but that wouldn't be anytime soon :-)

Blow Dog

In answer to the question:

M3 any day of the week

Cem

CraigH

Adam,

You don't understand why manufacturers don't quote power at wheel figures rather than power at flywheel if it's important?

You really that naive? (everyone shouts YEEEEEEEEEEEES )

Err, marketing for one thing........

New M3 - 338ish hp, or 270-300 @ wheels? Quite simple really.
Plus I believe for TUV approval all the engines have to be dynoed and produce a figure within a couple of percent of output claimed.

Also, re mass and accelertaion whilst moving.....

Lets look at it this way.....

You (Mr Heavyweight )line up for a 200metre race alongside me (Mr Slim "cough" )

I get off the line much quicker than you and your bulk allow - but if we decide to accelerate whilst running, it will be about the same even if you do weigh a lot more.

Geddit?

CraigH

Steve,

Forgot to say.

BITE ME

PS - why don't you just set up a race team? After all, whenever you buy a car the only time it ever gets driven in anger is when you let Birdy drive it

elondan

Wrong!! the added weight will always hold you back!
and one more thing there is no way the Impreza loses 90hp because of the AWD!!

if thats true how come an Impreza GT is so much faster than an Accord Type-R??
they weight almost the same, has the same power (215hp and 209hp).
but according to your theory the Impreza shopuld be really around 140hp and the Accord around 190hp-180hp??

elondan

BTW
according to all the dyno the Impreza really loses around 30% of it power but guess what the B.M.W loses 25% of its power and not 10% like you said...
and the scoob still has better torque than the M3...

Adam M

Craig,

shut up.

Your argument is still invalid purely because I think it is, and more importantly because

Sprint Chief makes it clear why.

Sprint Chief makes a vlaid point which I find valid and acceptable.

Everyone here keeps making reference to power at the wheels but this is simply nonsense, there is no question that a 4wd drive car will suffer greater transmission losses, I dont doubt that for a second. But I dont believe the difference is as significant as you make out for the reasons stated in Sprint Chief's post.

manufacturers dont quote wheel horse power figures for several reasons. Mostly because they arent accurate and can vary wildly between dynos, whereas engine dynos can be much more easily regualted and calibrated and do not suffer from the error input created by the interaction between the drivetrain components and the dyno.

Engine dynos can give consistent figures which can be verifiable and accurately tested by the manufacturers. they will also quote the figures within an accepted error level, otherwise they would be subject to the trade desrciptions act.

I also fail to understand why a quoted number is so important.

Regardless of whp or fwhp, performance on the road is what counts, and you cant argue with figures from timing gear.

The P1 is without question quicker to 60, significantly, remember anders' car (albeit 22B) getting 3.8 to 62 with just a back box change and that was with datron timing gear.

It has already been stated that higher speed acceleration comes mostly from slipperyness. The impreza has the aerodynamics of a brick and although the BMW probably isnt much better, I think it is that factor which accounts for its higher speed capability.
Remember aerodynamic drag is proprtioanl to the square of velocity.


if drivetrain losses were as significant as you believe them to be then why do a diablo VT and porsche 911 turbo perform almost identically in a straight line to their 2wd brothers?

CraigH

The current 911 turbo doesn't have a 2wd version you plum.

So your argument is flawed already as usual

If we put aside the money issue (not insignificant I know) - but if someone is looking at both these one would assume they can afford both...

The M3 is a better car - handling (if driven well) is arguably better, build is better, quality of engineering is better, performance is better (apart from a pub talk 0-60 - only just off the pace tho).

Looks? - pumped up 3 series or Rice Boy spoilers.....personal choice....

As to whether it's worth £20k more - you've got to say no. It's a mass produced hotted up saloon car variant. Albeit it the best one on sale.
But in the end it's a 3 series.

So buy the P1 and get a 320D as well

Adam M

once again craig, you are so stupid you cant see beyond your own chin!

I would go for the M3 over a P1 for the same reasons you state, but that is not my argument.

I was merely talking about the transmission losses between any 2wd and any 4wd car. So I am afraid it is your argument that is flawed baby puppy.

The 911 GT2 has is a 911 turbo but with even more power and less weight, yet its figures are not very different from the 911 turbo.

and if you are going to be pedantic, then how about answering the same question with regard to the diablo because I dont believe you addressed that one, you just brought price into the equation which is completely irrelevant in a theortetical argument about drivetrain losses.

droid42

[i]BTW
according to all the dyno the Impreza really loses around 30% of it power but guess what the B.M.W loses 25% of its power and not 10% like you said...

<sigh> ... you didn't get the point that IT DOESN'T MATTER WHAT THE DYNO. THINKS ABOUT FLYWHEEL POWER ... the only one that matters is power at the wheels. I have seen RR results that give 190'ish bhp at the wheels for a P1 and I have seen RR results that give 300'ish bhp at the wheels for an M3. It's completely irrelevant what the transmission losses are because they can never be accurately calculated by rolling roads.


and the scoob still has better torque than the M3...

<sigh> ... your point being?

Ian.

Fat Boy

I've fought against getting involved in this and lost the battle .

Last month at Brands GP track day (hot and sunny), I was in the same group as an E46 M3. We came along Bottom Bend me right behind and turned left to head out into the country nose to tail, both having had to slow to wait for a caterham and a Honda something to get out of the way just before Surtees. It was then a straight drag race up the hill and down to the right hander at the end of the straight. Passed the M3 and put about 60 feet on him by the bottom of the hill.

At lunch in the Kentagon I happened to be standing behind someone in a BMW shirt who was going to his mate " That can't be a standard Subaru, there's no way he should be able to go away from me like that...". I felt obliged to inform him that my car is absolutely standard in th engine dept only mods being full SS exhaust and ITG filter.

The point is that we had a straight drag race from a rolling start (probably about 50mph to 110mph)and he was overtaken and left behind. Weight does matter, but the losses can't be as big as people say either or that wouldn't have happened. By the time we went under the bridge to Clearways he was about the length of the straight behind.

All on video for any doubting thomases.

But I'd still have one, as well as the Scooby, and 5 other cars as well if money was no object. Frankly the M3 is a better car but I like the fun nature/image of the scooby. I might get an E46 when I mature a little more.

elondan

you say the Impreza loses 30% of its power on the way to the wheels while the M3 loses only 10%??
then why is it that a B.M.W 328i loses 25% (look at http://dyno.scoobynet.co.uk/PEindex/other.htm)

I don't know what you saw but an M3 should lose more power...

It's funny how all of you prefer the M3 (I don't) while TG and "evo" prefer the Impreza.

droid42

It was then a straight drag race up the hill and down to the right hander at the end of the straight. Passed the M3 and put about 60 feet on him by the bottom of the hill.

As I've said to a previous poster, this is NOT proof of anything. You don't know any of the following information:

- who put their foot on the pedal first
- what your speed differential really was
- what gear each of you was really in

etc. etc.

It's worthless information.

I came across a P1 at Castle Combe in my (standard) M3 and outdragged it. What does that prove? Like your story, it proves nothing and this is why we need to resort to objective performance results in magazines to decide which is really quickest in a straight line in most situations.

Ian.

droid42

you say the Impreza loses 30% of its power on the way to the wheels while the M3 loses only 10%??
then why is it that a B.M.W 328i loses 25%

A couple of points:

1. 328 is a completely different car (different transmission etc.)
2. I have never claimed specific power losses for any cars
3. You should completely ignore rolling road estimates for flywheel power because they can never be correct

You're either a little slow or you've not been reading my posts.

The very same part of the site you refer to shows a P1 producing around 190bhp at the wheels. You can draw whatever conclusions you want from that (maybe it does lose 30% in the transmission or maybe it doesn't really produce 276bhp) but it's irrelevant.

An M3 owner in Sweden put his standard M3 on a rolling road and it showed in excess of 300bhp at the wheels. A number of US owners have seen around 295bhp at the wheels (US cars develop slightly less power than Euro cars). Again, draw whatever conclusions you like but they don't matter.

How much flywheel torque does a P1 have as a matter of interest?

Ian.

CraigH

To put 60ft on an M3 on a racetrack, you need a LOT of extra power - assuming flooring it at same time.

Adam,

Test figures for a Lambo VT (4wd)- 0-60 in 5.1, 0-100 in 10.8
Test figures for a Diablo SE - 0-60 in 4.1, 0-100 in 9.3.

I think the phrase is, "Sit and swivel lard4ss"

A GT2 Porsche is not simply a slightly more power 2wd Turbo......get it right boy

Adam M

a gt2 is,

and chin man, look at the power and torque figures of the SE and you will you arent comapring like with like, the SE was a light weight and more powerful diablo.

ps. you are a tart!

CraigH

OK - Diablo SV then.

0-60 in 4.2, 0-100 in 9.5.

Still swivel Stumpy

A GT2 is more like an RS, lighter weight etc.

so guess what?

Hope you're still swivelling

LG John

I also question the 'starting from behind and putting 60 foot on' an M3 thing! That is a massive performance difference and you'd stuggle to have done that to my VTS. If the M3 was being properly floored it would not have happened.

These arguments are all pointless as so much of it comes down to the driver. I once had a nutcase on my tail in the VTS and I would thump him in the striaghts and knew I could carry more speed through the corners but I couldn't loose him because he was using both sides of the road on the corners and showed no regard to his life, his passengers lives or other road users. I promptly pulled over and stopped before he killed someone! Nevertheless the VTS was by far a faster and better car but he was willing to take more risks and kept up.

The M3 and P1 are both brilliant cars but I think if I could afford it I'd have the M3, they really are the 'complete' package

chrisp

If you had the money to buy an M3 would you though ?. People say they would have an M3 over a P1, sure yes I can understand that, sell the M3 buy a P1 and keep 15K good result . Or buy a mint STI6 and keep 20K.

For 40K that would get you a TVR which would wipe the floor with an M3 in terms of performance and handling and it RWD and they are all quicker than an M3. As for the reliability question well a mate has a Tamora with the speed 6 engine and yes he delighted with it and it has been a reliable everyday motor. The sound is simply stunning and the interior trim is superb. All for a few thousand cheaper than an M3 . Must admit an M3 has the attraction of blending with other cars where as the TVR is right in your face and everyone notices it.

So my 40K would go on either a 2nd hand 911 or TVR or a 22B .

Cheers

ChrisP

Adam M

there is no way any tvr handles better than an m3 and can even be compared in terms of quality and reliability.

The only one that comes close in the handling department is said to be the tuscan R but that is £75k and not out yet.

I am sorry but I dont think you should even mention m3 and TVR in the same sentence. TVRs are crap pocket rockets, all power, no control, no reliability and no quality, pure bang per buck.

I think they are innovative and stylish, but I really think they are an easy way to get the performance of much more lavish supercars.

I would never take a 40k tvr over an M3.

CraigH

I'd rather chuck £40k into a fire than waste it on a TVR - reckon the trauma of seeing it burn would be akin to TVR ownership

Handling much better than an M3? Didn't do great in the Trackday car test did it (Tamora).

You may have guessed I don't like TVR.

spence7

I dunno. All this is difficult to judge based on a few track manoeuvres as people have mentioned. Something must have been wrong for a scoob to power past an M3 like that, I mean I remember my old man's P REG UK Scoob, he was in a little challenge situation and he left an M3 (not sure of age) behind, not stopped obviously but just basically eeked away from him in a straight line. Having said that my 93WRX keeps up with my dad's scooby and an M3 eeked past me from 90mph onwards. Each individual M3's power must differ just as much the scoobs so it's difficut to tell.

As well as that has anyone read that EVO review with the 11 or so supercars head to head on realworld twisty roads? Basically the 911 Turbo 4X4 was the t1ts, the lambo diablo 4x4 version finished second with the P1 third. The P1 apparently kept with the other two in the twisties which is saying a great deal, but they obviously powered off on the straights so they were better overall. Can't remember if an M3 was in there I'll check tonight, but I think that if you put an M3 against a Scoob it'll generally beat it in a straight line. Introduce a series of difficult twisty roads and the weight HAS to cause problems. You can't just chuck around more weight and keep the nimbleness. Also in wet conditions the P1 would comparitively have far more traction on acceleration out of corners.

So basically if you're talking purely about the time taken between two points on asphalt, then for a straight bit I'd say an M3 would have it based on the power difference. If you're talking a really twisty bit of road then I'd say a P1 would without a doubt be the quicker car.

Luxury levels build quality are a completely different matter though ! Bless the scoobs quality. This is why it doesn't cost an arm and a leg ! It must use cheap bits somehwere !

Cheers,
Alex

BT52b

There is a whole lot of dodgy Physics going on here.

Weight- This only affects acceleration IF (and this is the key point) there is enough power to beat the aerodynamic drag. Clearly to beat an amount of drag X will requre amount of power P, regardless of the weight.

Therefore a 20 tonne Scoob with 300bhp will reach a higher top speed than a 1 tonne Scoob with 280bhp, because drag will stop the lighter car from accelerating first.

Similarly, once moving at a speed where drag becomes a factor then the acceleration will depend more on power than weight the faster you go.

Oh and for the record, if I could afford an M3 to sit alongside the Exige I wouldn't even consider a Scoob of any description, and I'm pretty sure I'd have an M3 over a 911 as well, although I'd need a test to be sure.

Also, F1 cars are not 4WD simply because they are not allowed to be... 4WD was banned ages ago, otherwise I suspect we might see it today.

Mark



[Edited by BT52b - 7/18/2002 1:55:43 PM]

chrisp

LOL @ Craig and Adam drive a tuscan or tamora, blinkered opinions to say the least .

CraigH

My opinion is based on best friend owning 2 over 2 years and the expense and unreliability he endured.

Plus supplying them and knowing what they're like in the factory.

Still less blinkered than the average Scoob owner though

chrisp

Blinkered moi

ProperCharlie

I suppose it would be boring if we all agreed, wouldn't it? I owned a TVR and had a great time with it. At the time it was the only fast(ish) car that I could afford, but it looked great, the handling was always interesting, and I could still get past 90% of anything i might happen to meet on a suitable road. If i was millionaire i would have at least one or two TVRs to play with, cos nothing looks like them, sounds like them or scares your passenger as much as them.

it's like... horses for courses innit?

Charlie

puppypower

Why doesn't someone arranged a race. Enough people on here know people with M3's, in fact some may own one.

I personally have never really relied on phyics. More on sheer physopathic tendencies when it comes to "racing" other cars.:-)

Who will be prepared to go that extra mile per hour?

chuckster

Buy the car you can afford, you like the most, and has the least compromises.
Chuck