Exaggerated top speeds?

[sjn2004]

Do manufacturers exaggerate the top speed of their repmobiles these days? For instance, Mercedes Benz claim for the C180K (156 BHP) ----> 143 mph but 0-60 in 9.5 , Audi claim for the A4 1.8TFsi (120BHP) ---->130mph but 0-60 in 10.5.

Who do they think they are kidding?

[Chris_w666]

Well I drove a new 1.4 Turbo astra a few weeks back, its theoretical top speed was around 200mph because 6th was such a long gear and 3000rpm = an indicated 100mph.

Power and aerodynamics were the cars enemies in reaching 200, but with that gearing and 150hp it meant that the top speed was probably more than would be expected.

[maniac0796]

A 1.9 Diesel Peugeot 309 will go up to 140 on the speedo, but at about 4k RPM in 5th gear , you're doing 80mph, and you've only got about 750rpm left to play with. Hmmmmmmmm

[plfrench]

Chris_w666 said:

Well I drove a new 1.4 Turbo astra a few weeks back, its theoretical top speed was around 200mph because 6th was such a long gear and 3000rpm = an indicated 100mph.

Power and aerodynamics were the cars enemies in reaching 200, but with that gearing and 150hp it meant that the top speed was probably more than would be expected.

Vauxhall seem particularly bad for having stupidly long gearing. I had a Insignia CDti 160 demo car for a week, and it was doing 2k rpm at 85mph. The problem was that it was simply under-engined for this length of gearing, and to get any meaningful acceleration at this speed you had to drop to 4th. Bit of a pain if you want to just nip out past something on the motorway.

[sjn2004]

brickwall said:

At the other end of the spectrum look at the caterhams or mk1 elise - 0-60 pretty low but topping out at c.120mph.

Maybe but they are the models with 150bhp or so. They do have a higher drag coefficient(Cd), however for total drag you need to look at drag area which is the Cd x frontal area of the car. As these cars are small, they will have a similar drag area to a larger car with a lower Cd.

[KieronGSi]

plfrench said:

Chris_w666 said:

Well I drove a new 1.4 Turbo astra a few weeks back, its theoretical top speed was around 200mph because 6th was such a long gear and 3000rpm = an indicated 100mph.

Power and aerodynamics were the cars enemies in reaching 200, but with that gearing and 150hp it meant that the top speed was probably more than would be expected.

Vauxhall seem particularly bad for having stupidly long gearing. I had a Insignia CDti 160 demo car for a week, and it was doing 2k rpm at 85mph. The problem was that it was simply under-engined for this length of gearing, and to get any meaningful acceleration at this speed you had to drop to 4th. Bit of a pain if you want to just nip out past something on the motorway.

True, my old Vec C GSi 3.2 could have done with an extra gear as third topped out at 110mph and you always felt like changing up well before you needed to.

I'll just add this was track driving.

[otolith]

Adding weight to a car will have a negligible effect on top speed, but will decrease acceleration in proportion to mass added.