Not sure that we can. I would agree if you said "feels more responsive" but my BX sounds more powerful at the moment as it has developed an exhaust blow.mat_fenwick wrote: Anyway, a more powerful engine sounds better, we can agree on that can't we?
![Wink :wink:](./images/smilies/icon_wink.gif)
Sadly Mat, it's Newton's 2nd Law of Motionmat_fenwick wrote:Oooh, now you've got me thinking - will it? I was told that it was related to the square of the mass, but not so sure now!I don't see why the lighter car would be quicker accelerating, they would both accelerate side-by-side until drag starts to dominate, when the heavier car starts to leave the lighter car behind
I'm not (now) disagreeing with you on the other point, if I'd actually thought about it a bit more I'd have come to the same conclusion. Wish I'd remembered Newton's laws when I was told (wrongly) about the square relationship.BX Meteor wrote:Here is what we both agree on though
I agree, IMO a 2cv sounds really good and my BX14 I had sounded similar to this (a bit), all throaty and growly like. Comparing the 2CV & BX14 to a ZX 1.6 (same engine as BX16 but injection, sounds like sewing machine) very clear winner of noise to the 14/2CV.Way2go wrote:Not sure that we can. I would agree if you said "feels more responsive" but my BX sounds more powerful at the moment as it has developed an exhaust blow.mat_fenwick wrote: Anyway, a more powerful engine sounds better, we can agree on that can't we?
errrr .... hang on a minutemat_fenwick wrote:I'm not (now) disagreeing with you on the other point, if I'd actually thought about it a bit more I'd have come to the same conclusion. Wish I'd remembered Newton's laws when I was told (wrongly) about the square relationship.BX Meteor wrote:Here is what we both agree on though![]()
(I think) I'm right in saying though, that bhp has no direct influence on acceleration. The force available is simply a product of the torque at the wheels and the wheel radius.
Where bhp comes into play is at higher engine speeds, as it's a measure of how fast the engine can produce that torque to provide a force acting against wind resistance.
So a (wheel) torque to weight ratio is probably more representative of a car's acceleration. But then if a car had the same torque as another but lower bhp, it must have a smaller rev range and therefore the 0-60 time would be slower due to more gear changes.
What was the question again?![]()
And next post by magic (I've been slaving away in a spreadsheet for a couple of hours)I wrote:Hold on, that's torque from the engine, it depends on gearing and wheel size to give torque at the tyre surface on the tarmac (wheel radius).
Force = Mass x Acceleration, and the Force is that torque at the wheel radius.
A superior BHP/tonne figure is an indication that the car's gearing will give more "longevity" in lower gears, over an inferior BHP/tonne i.e. in the car with the inferior BHP/tonne, one will be changing gear sooner, and that is the key.
I don't agree with Mat's analysis saying that where BHP/tonne is equal, the lighter car will be quicker, it depends purely on the torque curves and gearing. If the engine torque curves are the same, I would expect the gearing to give equal torque at the wheel radius, so neither will be quicker.
However, as the cars go past 60mph, then wind resistance starts to dominate, and the car with the higher BHP, assuming its drag (drag-ratio x cross-section) is not much bigger than the car with lower BHP, will start to dominate, because it is BHP to drag which determines top speed, and if you have more BHP than a car with identical BHP/tonnne but lighter, there is more power still available to overcome the drag, and if the drag is not significantly more on the heavier car, it wins.
That is what I find in my Honda Accord, 190 BHP, there is a dual carriageway near me, and smaller cars that are obviously trying to outrun me, lose out once we get past zzz mph (Plod might read this, at least one of the z's is a zero eg Plod 055).
Here is how the gearing affects the acceleration.Philip Chidlow wrote:I guess the question is, how do you compare a BX with a 'modern' car like the Mondeo in terms of potential. Factors like economy/efficiency and aerodynamics/gearing are critical, so maybe there could be a formula taking a number of factors into account to give a 'score'? I bet something like this exists already.
They have,BX Meteor wrote:
Note however that the Book of Lies seems to have the wrong max Torques for the 1.9 engine.
Oh yeah, so I haveBX Meteor wrote:errrr .... hang on a minute, you've read what I said earlier and then made it out as if you're saying it
And there was me about to say I only understand about 50% of this thread (mainly the conjunctions and prepositions). While nosing around for translation, I found this, which kinda seems logical, can't vouch for it's correctitude though!Grenman wrote:Can you explain all this in simple English so that dummies like me can understand please?