Vauxhall Zafira

[mlj26]

Hi there,
I am considering buyng a Zafira 2009 or 2010 1.9 diesel but I have only ever towed my 'van with a Hyundai Tucson 4wd 2.0 diesel and wondered if the Zafira will magage just as well?
My 'van is an Ace Award Transtar 2004 with an MPTLM of 1435kg.
I realise I will need the 150ps Zafira which is actually more bhp than the Tucson but a much lighter kerb weight than the Tucson.

Does anyone else tow a similar weight 'van with a Zafira that could help me decide?
Thanks,
Marie

 

[ProfJohnL]

A car will tow exactly what its manufacture claim it will tow, so provided the trailers MTPLM is within the braked towing capacity of the car it will be legally able to tow it.

Whether it tows it well, is an entirely differnt question, and that depends on a vast range of factors. But in essence if you are used to towing witha car with 300bhp available, then a car with only 150bhp will feel very different and you might consider it to be a poor tow compared to your prevous one. ON the other hand someone who used only 100bhp car woudl find the 150bhp model brisker and may consider it to be a better tow.

In your case unless you are particularly unusual most of your driving will be on normal roads where there is no real benefit to 4 wheel drive. In fact most 4x4s have worse handling characteristsics than cars, so you may actually feel the Zafira is better behaved. You could also look at the VW turan or Ford/VW/Seat MPVs

 

[JonnyG]

Lets remember one thing here, the absolute BHP figurer is very miss leading when we actually need the torque, and the lower down the torque is, the better for towing it is.
Another thing to remember is turbo and non turbo, so if you have say a zaffire 1.9 tdi with 150 bhp, it maywell have 230 plus ft/lb of torque available from 1500 rpm on wards.
You could compare that to say a non turbo petrol engine of say 3 litres with 100 bhp more, but it might not have the same high torque figurers, or have them from such a low Rpm. Which might make it inferior in the pulling power area compared to the Zafira.

 

[Lutz]

A nice flat torque curve from relatively low rpm of course makes the car more relaxing to tow with, but that does not necessarily mean that a car with a peaky torque curve is a poor towcar. It just means that you need to change gear more often.

 

[JonnyG]

A nice flat torque curve from relatively low rpm of course makes the car more relaxing to tow with, but that does not necessarily mean that a car with a peaky torque curve is a poor towcar. It just means that you need to change gear more often.

that is only correct if one assumes we are talking of similar torque/ figurers.My point was using a cars max bhp for a comparison of how well it will pull a caravan isn't the real answer,

 

[Lutz]

Horsepower is basically torque times rpm. Therefore, if the torque is low one can make up for it by increasing the rpm. This, of course, means that you need to change gear more often to keep the the engine revvving, but that doesn't make it a poor towcar, just a less relaxing one to drive.
A car with lots of horsepower but low on bottom end torque will therefore need to be revved a lot more than its flat-torqued counterpart.

 

[JonnyG]

hi lutz from your responses then, i would have to assume then,that you are in agreement with The profs observation which are based solely on BHP! To discribe how "well" or not a car will tow. That is entirely miss leading .
And also you can use as many gear changes as you like if you only have 200 ft/lb of torque high up but 230bhp, you will struggle in comparison to a 300 ft/lb of low down torque but only 155 bhp car .

 

[Lutz]

hi lutz from your responses then, i would have to assume then,that you are in agreement with The profs observation which are based solely on BHP! To discribe how "well" or not a car will tow. That is entirely miss leading .
And also you can use as many gear changes as you like if you only have 200 ft/lb of torque high up but 230bhp, you will struggle in comparison to a 300 ft/lb of low down torque but only 155 bhp car .

An engine producing 200ft/lb of torque will be just as capable of towing as one with 300ft/lb if it is revving 50% faster. It will only be at a disadvantage if it cannot rev that fast.
The only issue is whether one feels comfortable with an engine that may be screaming away to achieve the desired performance.

 

[JonnyG]

hi lutz from your responses then, i would have to assume then,that you are in agreement with The profs observation which are based solely on BHP! To discribe how "well" or not a car will tow. That is entirely miss leading .
And also you can use as many gear changes as you like if you only have 200 ft/lb of torque high up but 230bhp, you will struggle in comparison to a 300 ft/lb of low down torque but only 155 bhp car .

An engine producing 200ft/lb of torque will be just as capable of towing as one with 300ft/lb if it is revving 50% faster. It will only be at a disadvantage if it cannot rev that fast.
The only issue is whether one feels comfortable with an engine that may be screaming away to achieve the desired performance.

Hi lutz. and indeed it is for that reason and that reason alone that many consider a high low down torque engine to be the better tow car.
Now how about explaining why the 300 bhp car would be considered better than the 150 BHP using the same reasoning, as you used for the torque scenario. I assume you consider that to be true, as you make no mention of that statement being incorrect !

 

[seth1]

Sorry Lutz i dont thing that statement is quite right.Even if the said car could maintain twice or even three times the engine speed its still only developing 200 lbs ft of torque as agaist 300lbs ft.It will always be at a disadvantage.

 

[Lutz]

In all my posts on this subject I have never denied that plenty of low end torque makes for more relaxed driving which is something that everyone appreciates of a good towcar, but in the end it's horsepower that determines whether the outfit struggles uphill or not, not torque.
I recall that for several years back in the 90's I towed a 1300kg caravan behind a Vectra 1.8 with only 145Nm (107ft/lb) max. torque at 3000rpm, but I was still able to keep up with the flow of traffic even though it sometimes needed changing down to second year with the engine revving at 5400rpm where maximum horsepower was achieved in order to get the performance needed.

 

[seth1]

Different school of thought here,with a decent bit of low end torque there is no need for high hp,the proof is in the pudding take a look at a modern truck engine,400 hp,1500 lbs ft of torque.I understand by reving the engine to near its max you will make progress but even so this belief is misleading.

 

[Lutz]

Different school of thought here,with a decent bit of low end torque there is no need for high hp,the proof is in the pudding take a look at a modern truck engine,400 hp,1500 lbs ft of torque.I understand by reving the engine to near its max you will make progress but even so this belief is misleading.

There's no contradiction in what you are saying, Seth. The modern truck engines that you are referring to have relatively flat torque curves and maximum horsepower is developed at an engine speed not much higher than where maximum torque is encountered. Certainly the engine speed at max. horsepower is nowhere near double that for max. torque, which is the case for some petrol engines with particularly peaky power curves.

 

[ProfAlGoogle]

I can remember the trucks of yesteryear, the old Gardener 150 / 180 BHP, low revving, piston would go up and down at every other lamp post, and look at it now, we have Volvo and Scania both pushing over 600 BHP in a bid to out do each other.

 

[ProfJohnL]

The point of my post was not to differentaite between diesels and petrol, but in blunt terms a more powerfull engine will give a brisker performance than a less powerful one.

Is brisker better? not necesearily as good towing is down to a lot more than just BHP figures.

 

[Lutz]

Even looking at both horsepower and torque figures doesn't enable one to judge whether a car is a good towcar or not. The way in which the various gear ratios are set up is equally important. In an attempt to reduce emissions, a manufacturer may place more emphasis on gear ratios that keep the engine revs as low as possible, even at motorway speeds, but this doesn't help towing ability.
Quite apart from performance there is also the issue of stability. It has often been mentioned in various threads in this forum that cars with a big rear overhang or with laterally very compliant suspensions do not make particularly good towcars.

 

[seth1]

Lutz,the point i was trying to make was modern truck engines or the example i gave have a lot lower hp than torque,yet they seem to climb well enough.This to me would be a clear indicator that torque is the main feature required.Flat torque curves are extremly useful but i know off plenty of power units with progressive torque curves which perfom satisfactory too.

 

[Lutz]

.... modern truck engines ........ have a lot lower hp than torque.....

I don't understand what you are trying to say here because you cannot compare maximum hp with torque figures. They are defined using completely different physical units. All one can say about a numerically low horsepower figure and a numerically high torque figure is that the torque curve must be very flat. Maximum horsepower is always developed at a higher engine speed than maximum torque.
For example, the most powerful MAN truck engine, the D2676LF, develops 397kW (540PS) max. power at 1900rpm and 2500Nm (1850 ftlb) of torque at 1100 to 1400rpm.
It's the power not the torque that determines whether an oufit can start on a hill or not. However, if the power required is developed at a very high rpm, then this requires a lot of clutch slip to do so. Obviously this is more an issue with manual transmissions than automatics. This is where low end torque helps. It allows you to move off with less clutch slip.

 

[seth1]

Ok Lutz what im getting at is the fact torque has a far greater impact on an engines pulling capabilitys than as you stated hp.Here we have the latest breed of MAN Diesel,s D26 12.5 litre straight six engine.Rated at 540hp which incedently is the top rating at Euro 3 but with something like 1800 lbs ft of torque.At the european weight limit of 40 ton that works out at roughly 13.5 hp per ton ,on your belief of hp is what matters the vehicle wouldnt move due to reletively the low hp for wieght.So therefore torque must be an important factor and more so than hp.

 

[seth1]

Sorry Lutz ive just re-read your post.Yes i do agree with the fact that the hp power curve will generally allways be higher up the engine speed range than the torque curve.

 

[Lutz]

As I have tried to explain, good low end torque allows you to move off with a minimum of clutch slip, but it's the horsepower that determines whether the towing vehicle will pull at all. Horsepower is basically torque times engine speed. Therefore, to get the same performance, a poor torque figure can be made up for by an equivalent high engine speed. Remember the Honda S800 of the 60's, (the first car that Honda exported to these shores)? Its engine needed to rev at 8000rpm in order to get the relatively good performance that it had at the time. With trucks it's the other way round. With their high torque figures, they are capable of developing the necessary power at relatively low engine speeds.

 

[JonnyG]

! Lutz . Torque is power physical power BHP is work rate, you need torque to make bhp and not the other way round, in theory you can have torque at 0 rpm ie in steam train, therefore at 0 rpm there would be no bhp!
I made my piont with regards The prof using BHP in stead of torque, I have no real issue with the fundamentals of revving a low torque engine to pull just as well a high torque low rpm engine. but as the prof used the scenario of BHP figurers to demonstrate what people may well feel the difference in pulling power, that was incorrect and still is you feel the torque end of not the BHP.
Now your physics is slightly floored, Yes you can make an engine work harder [more revs] and change gear much more often to match a vehicle that has superior low down torque, but that only works in the science lab not on the road ie, everything you say assumes that each vehicle is already in the right gear and right revs so that they both make forward movement at the same rate.
Wont happen in the real word the high torque at low revs vehicle will pull better for the want of a term it will be like you said more relaxed and make better progress. from a scientific viewpoint based on how you yourself, stated that that more revs ect ect[words to that effect] but all the time you would be loosing ground and therefore time. changing gear and building up the revs to make the torque figurers equal through a higher work rate all takes time, and time is lost over and over again, so on the road, low down torque for towing a caravan is far far far far more important than over the top BHP and extra work rate.
Surely you understand what i am getting at.?

 

[Parksy]

Hi there,
I am considering buyng a Zafira 2009 or 2010 1.9 diesel but I have only ever towed my 'van with a Hyundai Tucson 4wd 2.0 diesel and wondered if the Zafira will magage just as well?
My 'van is an Ace Award Transtar 2004 with an MPTLM of 1435kg.
I realise I will need the 150ps Zafira which is actually more bhp than the Tucson but a much lighter kerb weight than the Tucson.

Does anyone else tow a similar weight 'van with a Zafira that could help me decide?
Thanks,
Marie

Have you reached any conclusions based on the 'advice' given so far Marie?
....................Thought not!

 

[Lutz]

! Lutz . Torque is power physical power BHP is work rate, you need torque to make bhp and not the other way round, in theory you can have torque at 0 rpm ie in steam train, therefore at 0 rpm there would be no bhp!

Quite true. But without rpm you wouldn't get off the ground either. To be able to move off, you need torque + rpm, i.e. horsepower! This is where electric cars come into their own as they have torque characteristics at low rpm much like a steam engine. However, I have difficulty in imagining electric cars as the ideal towing vehicle for caravans, even once the problem of energy storage is resolved.

Now your physics is slightly floored, Yes you can make an engine work harder [more revs] and change gear much more often to match a vehicle that has superior low down torque, but that only works in the science lab not on the road ie, everything you say assumes that each vehicle is already in the right gear and right revs so that they both make forward movement at the same rate.

I won't deny that it's easier to match suitable gearbox ratios to an engine with a flat torque curve. The peakier the power curve, the more gears you need in order to always stay within a power band that is adequate for the task involved. On the other hand, with ever tighter emissions controls, that will happen anyway. Seven speed automatics are not unusual any more and ZF have just developed a 9 speed automatic for the car industry. I can even foresee the day when it becomes impossible to meet tighter emissions limits with a manual transmission and automatics become a matter of necessity.

 

[Lutz]

Have you reached any conclusions based on the 'advice' given so far Marie?
....................Thought not!

Perhaps, to get back on to the rails, here's the comparative data for the Zafira and Tucson
Zafira
Max. torque 320Nm at 2000 to 2750rpm
Max. power 110kW (150PS) at 4000rpm
Tucson
Max. torque 305Nm at 1800 to 2500rpm
Max. power 103kW (140PS) also at 4000rpm
The Zafira therefore has both more horsepower and more torque. The only point where the Tucson scores is that its max. torque is developed at slightly lower rpm so, at least in theory, it should be a little more relaxing to drive and possibly a little more economical, too. But for performance, even as a towcar, the Zafira is undoubtedly the better alternative.