What determines vehicle power and speed?

cormie

Hi,
Just wondering is there an easy way to know how powerful and fast a vehicle will be without having to go and test drive it?

My own van, even though a 2.4 turbo diesel, is quite slow at getting to top speed, which is around 130kmph on a flat without wind. It can go faster downhill with a full load and the wind behind it of course but on inclines and if there's any wind it's goes to about 120 or lower depending on the incline. For overtaking you really need a good clear road ahead of you as the acceleration has to build momentum.

I'm in possession of a peugeot partner at the moment and I must say it's a lot more responsive, can reach 120 very fast (to me!) and can go beyond if necessary. Hills aren't a problem and overtaking is much easier. Has a lot more kick to it.

I'm in the market for an Astra estate van or mondeo/focus estate if I can find one. Want it to be diesel as it'll be doing 20,000 miles at an average speed of 110kmph. I want it to be as good as the partner or more if possible but how I can I be sure of this without driving it? What do I need to look out for to see how zippy a vehicle is?

Any feedback appreciated

Midnight_EG

Weight, power(Torque mostly), what drives the wheels (FWD, RWD, AWD), overall size, load capacity.

pelisor2000

140km/h 1,7 opel combo 2003...with 2 ladders on top..

Gary ITR

Really comes down to the power to weight ratio (BHP per Tonne) but it would be very hard to judge without driving one.

I drove a Partner a while back and it was far from nippy to your Transit must be really slow

bazz26

Van and truck engines are tuned for pulling power rather than outright speed. A Peugeot Partner is alot smaller and lighter than a Ford Transit too.

mickdw

Onkle wrote: »

I drove a Partner a while back and it was far from nippy to your Transit must be really slow

The 2.0HDI partner is quick for a van. The 1.9 non turbos were about the slowest thing on the road.

peasant

Onkle wrote: »

Really comes down to the power to weight ratio (BHP per Tonne) but it would be very hard to judge without driving one.

Not to forget aerodynamics!

Wind resistance rises exponentially ...something like a Transit with a high roof (and the aerodynamics of a barn) will always struggle, especially once over 100 km/h

Gary ITR

mickdw wrote: »

The 2.0HDI partner is quick for a van. The 1.9 non turbos were about the slowest thing on the road.

I had the 1.9 as a company van. Changed from a mapped TDI caddy. It was some culture shock alright

pelisor2000

Onkle wrote: »

I had the 1.9 as a company van. Changed from a mapped TDI caddy. It was some culture shock alright

are you verry happy with the Caddy? is it fast?

Gary ITR

pelisor2000 wrote: »

are you verry happy with the Caddy? is it fast?

I changed from the Caddy to the Partner. The Caddy was quick for a van. Especially since I used to carry very little in it. It was the older model, an '02. It was a few years ago when I had it, around 2003 I think

Dartz

peasant wrote: »

Not to forget aerodynamics!

Wind resistance rises exponentially ...something like a Transit with a high roof (and the aerodynamics of a barn) will always struggle, especially once over 100 km/h

Aerodynamics Aerodynamics Aerodynamics.

Wind resistance increases with the square of the velocity. Double your speed, quadruple your drag.

And it's not the frontal surfact that determines drag so much as the way the vehicle closes the hole it forces in the air behind it. This is why teardrop shapes are so popular on stuff like solar powered cars and Prius's.

Weight doesn't really make *much* difference. Weight affects the rate of change of velocity. Power/torque affect the final value.

Esel

Dartz wrote: »

And it's not the frontal surfact that determines drag so much as the way the vehicle closes the hole it forces in the air behind it.

Reminded me of an old joke:

Why is a turd tapered at the end?

So your arse doesn't close with a bang!

Midnight_EG

esel wrote: »

Reminded me of an old joke:

Why is a turd tapered at the end?

So your arse doesn't close with a bang!

esel
Adverts Ass Moderator



Anyone else see the connection?

Mr Benevolent

Midnight_EG wrote: »

esel
Adverts Ass Moderator



Anyone else see the connection?

*sigh*

Dartz is right, top speed is mainly limited by aerodynamics (and power/torque). Aerodynamics is a truly horribly bitch, doubling the drag if you increase your speed by 50%. That's why the Prius is the lowest drag car on the road (0.27Cd). Incidentally, the second-lowest drag standard production car was the Opel/Vauxhall/GM Calibra. The other things (besides the obvious) that affect top speed are rolling resistance and drivetrain friction.

Cars really are horribly inefficient in terms of aerodynamics. An airliner has a Cd of around 0.04!

cormie

Jaysus, didn't think it would be such a complicated question :P So there's no real way to tell from a vehicle spec how nippy it'll be until you actually get in and drive it?

The Peugeot Partner I'm driving at the moment is a 08 so I'm not sure if it's changed much in the last few years, first time I've driven one anyway.

My 02 transit is A LOT faster than my old 99 (old shape) and than my 00 Luton body one. I think it may be a bit worse since I put the roof rack on it. The luton body one is quite slow and my mechanic said it wasn't restricted or anything that it's just not aerodynamic at all (it's got a flat front, not curved or anything to aid with the wind).

Would anyone have any idea how nippy a 01/02 Opel Astra van would be? I'd hate to arrange to buy one and turn up and have another non responsive vehicle

AugustusMaximus

Things Affecting Top Speed: Power, gear ratios, aerodynamics, rolling resistance, power drain from engine to wheels. Weight does not affect top speed

Things Affecting Acceleration: Power, gear ratios, aerodynamics, rolling resistance, power drain from engine to wheels, weight, grip, centre of gravity of car, amount of powered wheels

Things Affecting Deceleration: Grip, type of braking disks, aerodynamics, centre of gravity of car, usage of brakes by driver

Things Affecting Cornering: Weight, grip, aerodynamics, centre of gravity

stevenmu

Easiest thing would be to look up 0-60 times and top speeds?

cormie

Thanks for the suggestion. Would it not be a bit hard to pinpoint the model though for that I wonder?

I looked up the reg of the partner on mywheels.ie and see it's a 1.6 (diesel that is) and looked up an Astra van from donedeal which is a 1.7. The astra definitely looks more aerodynamic and probably is a little bit lighter too. Are older models likely to be less powerful though? Is a test drive the only way to find out? I'd definitely be happy if it was as nippy as the partner I have is

Redisle

Give this site a go. Very very good for car info.
http://www.parkers.co.uk/cars/specs/

Eg: 01-08 Partner

Here's the Astra
There seems to be 2 very different 1.7 Diesils there so be careful not to get the crappy one (67Bhp 1.7 TD)

cormie

That looks like a good site, thanks!

The other Astra is 73bhp, only a difference of 6. Looking at the partner, it appears to have 90bhp, which is quite a leap from 73 if 73 is a leap from 67?

The site doesn't seem to have any info on Ford Transits which is a pity as it'd be good to compare to that.

So if BHP is anything to go by, maybe the Astra wont be near as nippy, although it does have a higher top speed and 0-60 is only 2 seconds slower.

irisheddie85

the astra will drive like a car, because it is one, The 1.7 engine should be fine for normal driving. The only reason to pick between the partner and the astra is how much load space you need. both will be fine on motorways.

Neither are really comparable with a transit which is much bigger. Anything that much smaller will be much nippier to drive

cormie

The only "cars" I owned before the transit were a 1l micra and a 1.1l fiesta, the transit is faster than both Can I be confident that the astra will be faster than the transit and on par with the partner I wonder?

irisheddie85

my first transport was a transit so i know what they are like (I had alot of fun in it) your top speed may not improve much in either but when you drop a gear to overtake they should be much quicker to respond.
Unless you have a lot of weight in the back. this will affect the smaller vehicles much more than the transit.
If I was you i would get a test drive in whatever you are interested in. But if you are going to be carrying heavy loads, like a lot of tools or machinery all the time bring them on the test drive with you and see how it feels then.
You would be amazed the difference a boot full of stuff makes in driving a normal car.

demag

I had an 01 astravan for a couple of years, make sure it's the 1.7 DTI with the 8v isuzu engine, NOT the 16v opel engine, grand van, drove like a car, topped out at about 102-105 mph (on private roads of course)

voxpop

That astra looks pretty slow to me. Even at 73bhp, the car weighs over a ton. It will be slow - I drove a 90bhp golf which is similar weight to that astra and it was slow, you end up putting the foot down and doing that shaking thing at the wheel trying to make it go faster

I suppose it depends on what your after and what you are use to, but Id be looking for something with about ~100bhp+ and a 0-60 time of around 10secs. Something with figures like that wont be fast, but should have a bit of go.

Probably the best thing to do is drive 1 or 2 so you have a bench mark - then you know roughly what the performance will be like from figures on the web.

Theanswers

I drive a 05 Caddy Van 1.9 Turbo the majority of the time.... It's fast for a van, will out do alot of saloon cars. I believe due to it's light weight and powerfull engine.
I also drive a 06 range rover and both have the exactly the same speed and accleration. The range rover will however out do the caddy in the higher speed range e.g. 140kph up.... As it is geared more towards this....

cormie

Thanks again for the replies everyone

voxpop wrote: »

That astra looks pretty slow to me. Even at 73bhp, the car weighs over a ton. It will be slow - I drove a 90bhp golf which is similar weight to that astra and it was slow, you end up putting the foot down and doing that shaking thing at the wheel trying to make it go faster

I suppose it depends on what your after and what you are use to, but Id be looking for something with about ~100bhp+ and a 0-60 time of around 10secs. Something with figures like that wont be fast, but should have a bit of go.

Probably the best thing to do is drive 1 or 2 so you have a bench mark - then you know roughly what the performance will be like from figures on the web.

Hmmm, fast and slow may have a different meaning to you and me :P When I mean fast and nippy. I just mean fast enough so it will build up enough speed to be able to overtake somebody who's doing 95 kmph with oncoming traffic 300m away. In the transit I couldn't.

Fast to me also means that I'd be able to overtake the line of cars I've been slowly trailing behind for the past age when I get to a "slow lane" (yes, a slow lane is what most are called) which in most cases are up hill to allow cars to overtake slow trucks, but because of the weight of the transit I can't get fast enough on the uphill to overtake the rest who are still plodding along at their normal pace.

Fast to me also means that I'll be able to maintain a steady speed and not be hindered by wind or inclines.

With the transit I pretty much have my foot to the floor on a Motorway. There's no more dept to go to. I want that little bit extra so I can do all the above.

So you don't think the Astra is capable?

voxpop

cormie wrote: »

So you don't think the Astra is capable?

Its hard to know - I would guess it has decent mid-range grunt (ie going from 30 to 60 sort of thing) as all diesels (turbo'd) generally have that. So it might suit.
If it were me I would try to get something with a bit more power - it will make driving alot more relaxed.


Btw the panther looks very slow - the 1.9 (71bhp) is slower than a 1.0L corsa and the corsa is sllllooooooww.

Ber

cormie wrote: »

Hmmm, fast and slow may have a different meaning to you and me :P When I mean fast and nippy. I just mean fast enough so it will build up enough speed to be able to overtake somebody who's doing 95 kmph with oncoming traffic 300m away. In the transit I couldn't.

:eek:

You would need a fairly fast van to complete that manoeuvre in that distance. At that speed, and given the length of your Van you would have approx 3.5-4 seconds to overtake and would need to top 270km/h (approx), I'm not even sure a Veyron would complete that manoeuvre in that distance, but I'm open to correction..! :eek:

cormie

Haha, I was going to sit and calculate it out that if 2 vehicles approaching eachother at 100kmph, how long a gap would be left if they were 300m apart. But it got too complicated. So say 500m then, or whatever distance I see other cars overtake safely at while I'm left waiting for a huge clearance

voxpop, did you mean the partner at 1.9 looks slow? The partner I had was 1.6 and was well within my needs for speed

voxpop

cormie wrote: »

voxpop, did you mean the partner at 1.9 looks slow? The partner I had was 1.6 and was well within my needs for speed

Yeah - the 1.9 has actually less power than the 1.6 - 71hbp vs 90bhp. The astra(1.7,73bhp) is comparable to the 1.6 partner (when you take weight into consideration) - a bit slower though. So if you were well happy with the partner, the astra should be grand.