bhp or torque?

[Henry]

the thing seems to be the more bhp the better (some poeple seem to get very upset/defensive on the subject when it's about the 200+ mark 😬)

 

so...in simple terms for a road going 7.....is a higher value of torque low down the revs better for say, touring and big bhp high up the revs for track days?

 

i think i understand myself!

 

Henry.

[Normans_Ghost]

Henry, I think I understand you as well. The torque figure is directly linked to the BHP. It's the engine charateristics that make the difference. Gear ratio's and final drive ratio makes a big difference as well.

 

High torque, produced low down in the engine rev range, as large V8's do will allow you to pull away in top gear at a low road speed. As you're not really interested in doing this in a 7 (as you may in a limo) I would say the high outputs of BHP, which will also produce a relevant value of torque, is what you want for both.

 

So the question is, in my opinion, not the difference between touring and track, but how flexible you want the engine to be.

 

For example, my BDR as it came, was flexible in so much it had power from about 1500 rpm, when the power was increased from 160 (more like 15) to 220 the power comes in at 4500 rpm but as the figures sho there's lots more of it.

 

I'm sure someone will be along in a minute to give a different opinion.

 

edited to correct bad typing and to add: A friend of mine has a 100 bhp xflow. It's lovely to drive, smooth, easy, gentle etc. Mine's a handfull, not made easier by having a comp clutch, and sometimes, in traffic, I wish I had something easier to drive. However when I get on the open, traffic free roads in Yorkshire & Derbyshire, I know I've got the right car.

 

Norman Verona, 1989 BDR 220bhp, Mem No 2166, the full story here

 

Edited by - nverona on 14 Oct 2004 11:35:21

[Shaun_E]

Have a read of this as it explains the relevance of torque, power and gearing in a car application in an easily understandable way.

 

Yellow SL #32

[tjm]

put it this way:

1) torque is the thing that accelerates you. power is just a measure of work done.

2) power is torque * revs * constant. ie if you have one curve you know the other.

 

So in theory you only need the torque curve, power curve gives you nothing new.

So why does power get quoted so much? The trouble is that torque at the engine is not the same as torque at the wheel. It is the torque at the wheel that accelerates you but that is the torque at the engine / gearing. The advantage of power (as a single figure) is that it is a simple measure that shows the capability of the engine without having to consider gearing etc (ie assuming ideal gearing for the engine and use). When you consider that a bike engine with 70lbft at 8000rpm will give the same acceleration as a car engine with 140lbft at 4000rpm if the final drive is 2:1 then you can see why people get confused by torque figures.

However, max power is as useless as a max torque figure for telling you how fast you will accelerate in reality as you still need to know revs and gearing.

 

So what I am trying to say is. Initially think of everying as torque. A high power/revs engine is just one that can maintain high torque at high revs so your ideal engine is high torque over as large a rev range as possible. It doesn't matter if that rev range starts low and ends low or starts high and ends high, the result is the same if the gearing is adjusted to compensate. Unfortunately, to get low down torque you need smaller inlets, injectors close in etc. To get high end torque you need larger inlets, injectors way out etc. So it is all a compromise ☹️

 

To answer your question, which is better, low end or high end torque, you need to consider the practicalities. Do you like listening to your engine revving away? Are you restricted in the gearing you can select? Is it easier to get decent torque over a wide rev range at the bottom or top of the rev range etc.

 

To answer your question simply though is more difficult. You don't want huge amounts of torque at low revs but no rev range (ever driven a diesel?!) or a peaking engine (no torque low down). You want that ideal compromise between the two which is very personal to you and doesn't really exist However, from you description you do indeed what something biased towards lower end torque at the expense of high end.

[Dunk]

Still confused...... Can anyone apply these arguments to the differences between the K series and the Duratec based on the quoted figures for both. Is it possible to say which is the better engine based at the current levels of tune available from CC?

 

 

[Wahey]

I would say it is down to personaly preference.

 

My 7 is a K supersport and its power delivered high in the rev range which is ideal for track use.

 

My road car has been tuned for loads of torque to save changing gear as much and makes for effortless overtaking.

 

That's the way I like it.

 

I think the duratec is naturally quite torquey, for a start it has a bigger capacity. I know of someone who had a Duratec mated to the CC 6 speed but was too busy chaging gears because of torque etc so had a 5 speed made for better driveability.

 

horses for courses

 

bear in mind, if you are not used to going sideways a peaky high BHP engine will probably suit better than a torquey one as lots of torque means lots of wheelspin.