From: Nick Finnigan on
Conor wrote:
>> Bollocks not again, here comes your Physics primer.
>>
> I have a 2L Capri. It has 130BHP, weighs 1098kg. It has roughly 100lb/ft
> torque.
>
> I have a 2L Mondeo TDCi. It has 130BHP, weighs approx 1500kg. It has
> roughly 244lb/ft.
>
> The Mondeo absolutely thrashes the Capri on 30-70MPH acceleration
> despite weighing nearly 50% more.
>
> Explain.

The Capri 2l doesn't have 130bhp.
From: Silk on
Nick Finnigan wrote:
> Conor wrote:
>>> Bollocks not again, here comes your Physics primer.
>>>
>> I have a 2L Capri. It has 130BHP, weighs 1098kg. It has roughly
>> 100lb/ft torque.
>>
>> I have a 2L Mondeo TDCi. It has 130BHP, weighs approx 1500kg. It has
>> roughly 244lb/ft.
>>
>> The Mondeo absolutely thrashes the Capri on 30-70MPH acceleration
>> despite weighing nearly 50% more.
>>
>> Explain.
>
> The Capri 2l doesn't have 130bhp.

I was thinking that. I doubt even the 3L has that, even when it was new.
From: Mark on

"Peter Hill" <peter.usenet1(a)nospam.demon.co.uk> wrote in message
news:bl12c59opbj8nhjp1egdipukm2gr3p7f2d(a)4ax.com...
> On Mon, 28 Sep 2009 17:36:25 +0100, "Mark" <mark(a)nowhere.com> wrote:
>
>>
>>>"fishman" <spammeifyoulikebutiwontreadit(a)gmail.com> wrote in message
>>>news:54241104-8b30-4df1->aba4-f022c54796b2(a)r36g2000vbn.googlegroups.com...
>>>On 28 Sep, 16:23, The Debacler <jameswoolford2...(a)yahoo.co.uk> wrote:
>>>> Trying to top the poll of the most boring or stupid question..
>>>>
>>>> How powerful does a car need to be to 'push you back in your seat' I
>>>> seem to remember the acceleration from a friends Vauxhall cavalier 2.0
>>>> 16v was when I first noticed it(which was about 130bhp). I guess
>>>> higher torque causes the sensation more than higher revving lower
>>>> torque cars? Or is it more about delivery Turbo instead of NA?
>>
>>>Power to weight ratio is the most important factor.
>>
>>Torque to weight really
>
> Bollocks not again, here comes your Physics primer.

SNIP lots of calcs

> [2] There's more bad news.
> In a given gear the peak acceleration will be at about peak torque.
> But unless peak torque rpm is very close to peak power there's always
> a lower gear that will give better acceleration for a given road
> speed. Torque = power / speed. So the peak torque quoted is quite
> useless for performance. What it does do is make the car nice to drive
> in everyday use on public roads where you accept a less than startling
> performance for quietness and smoothness.
>
> [2] It's really more complex than just power as it's engine power -
> drag power. That's because the Force right up there at the start in
> Newton's law was really Traction force - drag force. But unless very
> underpowered drag isn't a major player in 0-60mph or even 1/4 mile
> times for most production cars.
> --

This NG is really funny.

One slight post to show that in most situations, torque is more important
than power to actual acceleration and I get an insult while we all get a
basic Physics lecture :-)

I did do A level Physics, got an A grade, and understand perfectly well that
gear ratios and wheel sizes are also important to figure actual forces
but.....

Who cares? When we are comparing normal mid-sized road going cars going at a
set speed and the same gears, there's not a whole heap of difference between
ratios and wheel sizes. Certainly any difference in the maximum
*instantanious* feel of the acceleration would be mainly down to the
respective torque of the engines.

Calculating the actual acceleration to 16 decimal places seems rather anal
when you look at the title of the original post.

& then you go on to mention drag while pointing out that it's largely
irrelevant for the speeds we are talking about! Why bloody mention it then?!

& you forgot to mention the coefficient of friction between the road and the
tyres. And the tyre pressures. and the tyre widths.........





From: Nick Finnigan on
Silk wrote:
> Nick Finnigan wrote:
>> Conor wrote:
>>>> Bollocks not again, here comes your Physics primer.
>>>>
>>> I have a 2L Capri. It has 130BHP, weighs 1098kg. It has roughly
>>> 100lb/ft torque.
>>>
>>> I have a 2L Mondeo TDCi. It has 130BHP, weighs approx 1500kg. It has
>>> roughly 244lb/ft.
>>>
>>> The Mondeo absolutely thrashes the Capri on 30-70MPH acceleration
>>> despite weighing nearly 50% more.
>>>
>>> Explain.
>>
>> The Capri 2l doesn't have 130bhp.
>
> I was thinking that. I doubt even the 3L has that, even when it was new.

130 from the 3l, a bit more from the 2.8i.
From: Silk on
Conor wrote:
> In article <h9tdp2$8el$1(a)news.eternal-september.org>, Nick Finnigan
> says...
>
>> The Capri 2l doesn't have 130bhp.
>
> Correct. However one with a Kent FR31 camshaft, 4-2-1 exhaust manifold,
> K&N air filter and a rejetted carb does.
>

I doubt it. Unless you could put a turbo on it, none of the above chav
tat is going to help.