A66 caravan smash

I'd settle for either, frankly, but it will depend on gearing and the journey I suppose. I'd opt for more torque at low revs for towing something heavy, but that's just a personal preference.

BHP /= Torque, but yes, I know power is effectively torque x revs; but it is still the torque of the engine, through the transmission that turns the wheels, not the power. Most drivers drive with the torque of the engine, not it's maximum power; thus generally BHP figures are unimportant when talking about towing especially. How many road drivers keep the revs up at maximum power when driving?

Wrong. No power = zero torque. Masses of power = masses of torque at the wheels even if the engine makes very little because its a high reving unit. EG a 200 bhp bike engine will propel your car/trailer at exactly the same rate and rate of acceleration as a 200 bhp truck engine.

In other words - a diesel!!

Uno-Hoo!

Personally, being now on my second (a diesel auto), I can truthfully say that I will never go back to petrol. The power delivery characteristics of a modern turbo-diesel make it far more suitable for everyday driving than a peaky multi-valve petrol engine that only delivers max power at high revs.

My 2.0 litre auto diesel is revving at around 2,200 rpm at 70 on the motorway and is extremely quiet and relaxed at that speed. My son's Passat

2.0 litre auto petrol is revving far higher at that speed and sounds fussy and far less relaxed. Added to which I average over 10 mpg more than his car!

Uno-Hoo!

Of course it will if you keep it in the powerband.

Wrong, power is derived from torque, not the other way round. And a 200bhp bike engine will not accelerate a car at the same speed as a

200 bhp truck engine unless they have the same torque figure. Torque accelerates cars, not BHP. Gearboxes transfer torque (a pair of gears is actually just a load of levers), not BHP.

Another misnomer - You're actually keeping it in the torque band (the portion of the rev range where the torque curve is flat and at its highest). As the revs climb, so does the power, but then you change up and the gears have been selected to drop you right where you're getting most torque.

Still wrong. You cannot have either without the other! And as a manufacturer of rolling roads I do actually understand torque and power!

Wrong yet again. Power (like KW or any measure of power) is DIRECTLY comparable. In fact the opposite is true. The bike engine and box is actually both lighter AND more efficient in regards power losses in the respective transmissions. So it would actually go better with the lighter more efficient bike engine.

Wrong again. At 50 mph ROADSPEED the engine that gives 200 bhp at 10,000 rpm gives the same torque at the wheels as the 5000 rpm "bigger" lower reving motor. It does this precicely because it needs exactly half the gearing. The 2x extra reduction ratio doubles the torque available at the output shaft. So there isnt any difference! 200 bhp is always 200 bhp. The wheels or road dont care if it came from a tiny electric motor doing godzillions of revs or a big heavy diesel engine. Just like length, weight, voltage, etc POWER is DIRECTLY comparable. Torque isnt because you do not know the "rate" that the torque is produced and hence have no idea what gearing needs to be employed. Its only half the story. If you DO know the rate (or RPM) you can use the torque x rpm formula to give you a POWER figure. This can be compared directly!

"Martin" wrote in news:edh4as$6gq$2$ snipped-for-privacy@news.demon.co.uk:

Soon to be followed by anti-funnel web spidering, and, because of recent developments, anti-sting raying.

Almost. But the best power is available at the point where the torque curve is falling away because while the torque is less there is more revolutions! So best power is almost always at higher rpms than best torque. What you really need is an engine that has a flat or fairly level torque curve that stretches across the graph. Then you have good usable torque over a wide rpm band. But diesels are bad here because they are rpm range limited by the very "small" turbo that makes them able pull away. If it was big enough to allow decent high rpm power then it would be too big to give the much needed assistance from just above idle that a deisel needs. Without it (small turbo) they are useless and cant get out of there own way. Consequently because they are more economical they are used in trucks (with dozens of gears) cars (7?) and so on. A turbo petrol engine of the same capacity will murder a turbo deisel for power and makes about the same torque but at a slightly higher rpm. And has a wider rev band.

Uno-Hoo! wrote in snipped-for-privacy@pipex.net:

I'm just the same: I'm on my second Peugeot 306 HDi and this one has done

110,000 miles and still achieves over 50 mpg as it did almost from new (once the engine had lost its initial tightness). On a long motorway journey I've sometimes got 55 out of it and when I'm on holiday in Yorkshire, driving at a maxmum of about 50 mph most of the time but with very little town driving stopping at lights or roundabouts, I've sometimes got just under 60 mpg from it. My 1.8 Golf did about 35 mpg. And it still has pretty good acceleration in the crucial 50-70 mph range that you need when overtaking cars on a motorway. If I let it (and Mr Plod wasn't watching) it would get up to 90 or 100 without any problem. I drove a 16V 1.8 petrol version of the car while mine was in for a service and it was a tiring experience. It had great acceleration providing you were willing to let the engine rev to silly speeds, but it ran out of puff on the motorway: in either 4th or 5th gear, it had very little 50-70 acceleration and the engine was screaming away at about 4000 rpm at 70, whereas my car runs at about 2500 and is quieter - so much for diesels always being noisy. OK, so it clatters a bit when the engine is cold, but that soon goes once the engine gets up to temp.

It's great being able to crawl along in a traffic jam controlling the speed only with the clutch and with my foot off the throttle - can't do that in a petrol engine. And it's got lots of useful torque in 3rd gear for negotiating roundabouts without having to change right down into second gear. Climbing steep hills (eg Sutton Bank or Park Rash in Yorkshire) is a doddle because of all that lovely low-end torque.

The only downside is that the engine is so efficient that it takes a while for the heater to warm up in very cold weather because less energy is being wasted as heat than in a petrol engined car!

And apart from the time that the fuel pump failed, it's always started first time every time, something that my petrol engined cars were reluctant to do in damp weather. And it doesn't have that annoying chugging engine and fading of power when accelerating that a petrol engine has when it's cold.

I'd get another 306 if they still made them. Sadly the 307 isn't a patch on the 306: it's got this modern design of a steeply sloping bonnet so you can't see anything of the front of the car beyond the bottom of the windscreen, which I found very scary when I test-drove one. It also felt inclined to roll on corners, presumably because it's a taller car. I'm 5'10" but I could ahve done with the seat being about six inches higher to have proper visibility out of the front and back windows instad of feeling as if I was driving blind. The new Golf is a lovely car - I test-drove a TDI one with traction control a few months ago which was very sure-footed. But VW are *still* fitting these stupid toy spare wheels (the spacesaver ones) and the rear seat bases don't fold down or remove, so I wouldn't be able to carry my bicycle inside. These spacesaver wheels are a liability: of the three punctures that I've had over the 7 years I've had with my 306, every single one has been at night near the beginning of a long journey, so I'd have been stranded if I'd had a toy spare with its distance restriction. "Just take the flat tyre to the nearest garage" isn't practical on a Sunday or at 8PM when I've got a 200 mile journey ahead of me :-(

In message , Jerry writes

Given power, torque at the wheels is a function of gearing. You are stuck with the power you have at the crankshaft, you cannot increase it through gearing.

Look at these graphs for the Japanese market versions of our 192ps and

231ps RX8s. As with the UK cars, the less powerful version produces more torque at low revs, but has lower peak power and does not rev as high. The two cars have different gearing, however, which means that the more powerful car with less torque at low revs actually has more torque at the wheels all the time.

That's what gears are for.

In message , Jerry writes

Here is a box containing an engine. Coming out of it is a driveshaft. The shaft produces 200bhp @ 5000rpm. Why does it matter whether the engine inside the box is directly turning the shaft at 5000rpm, or whether it is turning an input shaft into a gearbox at 10,000rpm? You know how much power the engine is producing, but you have no way of knowing (or reason for caring) what rpm the engine is running at or how much torque it is producing. Both are academic, all that matters is the output.

My 528 BMW auto is reving at under 2,000 at 70 on the m/way.

2,200 revs takes it to about 80 mph, so I don't think high revs is necessarily a characteristic of multi-valve engines at cruising speeds. . My son's Passat

My BM doesn't sound fussy at all. Even under hard acceleration engine noise isn't particularly intrusive, and at 70-80 mph on the m/way, it quietly does over 30mpg. . The main advantage of a diesel car, as I see it, is it's better fuel consumption, but if you don't do high miles, much of that advantage could be offset by a diesels higher purchase price. It also appears that with diesels that have a comparable performance to their petrol fuelled equivelents, their fuel consumption is not significantly better.

Personally I don't think the choice between petrol and diesel is as clear cut as your post would suggest. Mike.

But your engine is a ~200Hp straight six, and has rather taller gearing than a more equivalently powerful unit would have - 2000rpm/10mph is fairly normal.

Which is nothing special. A typical mondeo/passat diesel will average very close to 50mpg at those speeds.

Not really. The net depreciation is typically lower diesel models, so you get your purchase price differential back at sale. You do lose interest on the capital over that period, but that is negligible.

A similarly powerful diesel is typically around 30% more economical

Audi A4 2.0 FSI 4d: 130BHp, 0-60=9.9s, 35mpg(comb) Audi A4 2.0 TDI 4d: 140BHp, 0-60=9.7s, 49mpg(comb)

mondeo 2.0 16v : 145bhp, 0-60=9.9s, 36mpg(comb) mondeo 2.2tdci : 153BHp, 0-60=8.7s, 46mpg(comb)

Accord 2.0 i-vtec: 153BHp, 0-60=9.3, 35mpg(comb) Accord 2.2 i-cdti: 140BHp, 0-60=9.3, 51mpg(comb) etc..

It's very subjective - some people simply don't like the power delivery and non-flat torque curve of the diesel engine, which is fair enough, but it is unarguably the case that for equivalent power outputs diesels are quicker, they are generally quieter on the motorway, they are more fuel efficient and, particularly as a 2nd-hand purchase, do make economical sense.

The figures for the A4 TDI are pure fiction.

Although, the figures for the FSI are probably iffy, too.

In normal use my Passat 2.0TDI averages high 30s / very low 40s.

Actually, it can be offset for all drivers. According to book prices, my car (2.5 years old at purchase) cost 1200 extra for the diesel compared to the petrol. A quick look at the list price showed that it only cost 500 quid extra when new. So even if you drove no miles at all, you'd still be 700 quid to good when selling it after a few years. Obviously, it will be different for different types of car.

Christian.

In message , Burgerman writes

Someone needs to go back to school, what a load of rubbish I've just tipped from the above.