300bhp per tonne

[JonRB]

Poopipe said:

In 1996 you didnt have to hang 15 airbags and a million electric motors off a car in order to be able to sell it and you were allowed to burn a decent amount of fuel in order to make it go.

What about 2005, when the Sagaris was launched?

Or what about 2015 and the £24,000 Caterham 360?

[Poopipe]

JonRB said:

Poopipe said:

In 1996 you didnt have to hang 15 airbags and a million electric motors off a car in order to be able to sell it and you were allowed to burn a decent amount of fuel in order to make it go.

What about 2005, when the Sagaris was launched?

Or what about 2015 and the £24,000 Caterham 360?

arent low volume manufacturers subject to different or less restrictive conditions for type approval etc?

My point is that its more difficult to build a light car now than it was 20years ago if you want to be allowed to sell it - that means if you want 300bhp/ton you have to make more power
power which is difficult if you need an engine that meets emissions requirements and will last 150k miles

Difficult = expensive.
It can all be done but whether its financially viable or not is another questiom

[JonRB]

Poopipe said:

arent low volume manufacturers subject to different or less restrictive conditions for type approval etc?

My point is that its more difficult to build a light car now than it was 20years ago if you want to be allowed to sell it - that means if you want 300bhp/ton you have to make more power
power which is difficult if you need an engine that meets emissions requirements and will last 150k miles

Difficult = expensive.
It can all be done but whether its financially viable or not is another questiom

Ah, I see where you are coming from now. Yes, those are fair points.

[likesachange]

Power to weight is over rated imo, sure mass helps hugely in changing direction and braking etc..

Loads of torque, Mechanical grip and fancy gearboxes that change up in a tenth of a second really are what offer I pressive acceleration times.

Years ago when my cousin had a lotus 7 twin cam with circa 127bhp (240bhp/ton) his pal had a clio 172 (around 155bhp/ton). They were pretty much identical in acceration.

Just 2 week ago I had a play with a remapped Bmw m5 (375bhp/ton) in my atom (545bhp/ton) as soon as I was in 4th (80mph) he comfortably pulled away ! (It probably didn't help that I have to dip the clutch twice while he is still surging through 3rd and then has seemless gearchanges all the way through.

But the atom wasn't just about outright pace it was the sheer event and how you really had to have a tight grip on that steering wheel!

Then there's the latest turbo dsg / stronic cars... (Yes had a stage 1 ttrs s-tronic, 0-100 in just over 7 seconds)

So not really sure what this topic 300bhp/ton is trying to say as there's so many more factors than power and weight for acceleration, grip? well, power is irrelevant ....?!

[likesachange]

Power to weight is over rated imo, sure mass helps hugely in changing direction and braking etc..

Loads of torque, Mechanical grip and fancy gearboxes that change up in a tenth of a second really are what offer I pressive acceleration times.

Years ago when my cousin had a lotus 7 twin cam with circa 127bhp (240bhp/ton) his pal had a clio 172 (around 155bhp/ton). They were pretty much identical in acceration.

Just 2 week ago I had a play with a remapped Bmw m5 (375bhp/ton) in my atom (545bhp/ton) as soon as I was in 4th (80mph) he comfortably pulled away ! (It probably didn't help that I have to dip the clutch twice while he is still surging through 3rd and then has seemless gearchanges all the way through.

But the atom wasn't just about outright pace it was the sheer event and how you really had to have a tight grip on that steering wheel!

Then there's the latest turbo dsg / stronic cars... (Yes had a stage 1 ttrs s-tronic, 0-100 in just over 7 seconds)

So not really sure what this topic 300bhp/ton is trying to say as there's so many more factors than power and weight for acceleration, grip? well, power is irrelevant ....?!

[Welshbeef]

It's relevant within UK speed limits surely? Beyond well if you track a car then you want handling and highest cornering G possible low COG etc not a road car.

[Poopipe]

I can see where 300 Is comimg from. I dont speed much as a rule and doubt ive spent more than fifteen minutes on the wrong side of 100mph in my life but I do enjoy very fast acceleration which is pretty reliant on a good power/weight ratio. You cant predict how fast a car will accelerate by the numbers (a short ratio box knocks half a second off an imprezas quoted 0-60 for example) but more power and less weight will make a car shift faster off the line if everything else is equal.

[GroundEffect]

likesachange said:

Power to weight is over rated imo, sure mass helps hugely in changing direction and braking etc..

Loads of torque, Mechanical grip and fancy gearboxes that change up in a tenth of a second really are what offer I pressive acceleration times.

Years ago when my cousin had a lotus 7 twin cam with circa 127bhp (240bhp/ton) his pal had a clio 172 (around 155bhp/ton). They were pretty much identical in acceration.

Just 2 week ago I had a play with a remapped Bmw m5 (375bhp/ton) in my atom (545bhp/ton) as soon as I was in 4th (80mph) he comfortably pulled away ! (It probably didn't help that I have to dip the clutch twice while he is still surging through 3rd and then has seemless gearchanges all the way through.

But the atom wasn't just about outright pace it was the sheer event and how you really had to have a tight grip on that steering wheel!

Then there's the latest turbo dsg / stronic cars... (Yes had a stage 1 ttrs s-tronic, 0-100 in just over 7 seconds)

So not really sure what this topic 300bhp/ton is trying to say as there's so many more factors than power and weight for acceleration, grip? well, power is irrelevant ....?!

Because BHP/tonne only gives you a low-speed acceleration numbers. As speed increases, drag increases at the square of said speed therefore BHP/tonne is much less important than pure BHP as you start to go over 80-100mph.

That's why Vmax is almost always related to Peak BHP rather than BHP/tonne.

[braddo]

GroundEffect said:

Because BHP/tonne only gives you a low-speed acceleration numbers. As speed increases, drag increases at the square of said speed therefore BHP/tonne is much less important than pure BHP as you start to go over 80-100mph.

That's why Vmax is almost always related to Peak BHP rather than BHP/tonne.

And it's why hp/ton is a good, relevant measure of performance on the road.

[likesachange]

My point still stands... 545bhp/ton atom should be substantially quicker than a 280bhp/ton audi TT ... In reality it is just, if you get a perfect launch and gearchanges ....
Even when you throw in the atom 3.5r with sequential box and over 600bhp/ton 0-100 6s... Still only less than a second quicker than a much lower power to weight than a new 911 turbo s
Obv these are examples at the extreme end of things... But certainly even at the lower end its certainly not a case of higher bhp/ton = a faster car... Maybe in most cases but it's not a certainty..

Bhp wins sales torque wins races .. (Obv not strictly true ). Low down torque is what really counts for 90% of spirited road driving. I'd imagine torque is the big factor fighting drag too? But that's just my theory.

[JockySteer]

likesachange said:

My point still stands... 545bhp/ton atom should be substantially quicker than a 280bhp/ton audi TT ... In reality it is just, if you get a perfect launch and gearchanges ....
Even when you throw in the atom 3.5r with sequential box and over 600bhp/ton 0-100 6s... Still only less than a second quicker than a much lower power to weight than a new 911 turbo s
Obv these are examples at the extreme end of things... But certainly even at the lower end its certainly not a case of higher bhp/ton = a faster car... Maybe in most cases but it's not a certainty..

Bhp wins sales torque wins races .. (Obv not strictly true ). Low down torque is what really counts for 90% of spirited road driving. I'd imagine torque is the big factor fighting drag too? But that's just my theory.

I like it

[ORD]

likesachange said:

Low down torque is what really counts for 90% of spirited road driving.

When on a "spirited" drive, you pootle around at 2,500 revs? Doesnt sound much fun to me. It is how most people drive, I accept, but surely not PHers!

[kambites]

ORD said:

likesachange said:

Low down torque is what really counts for 90% of spirited road driving.

When on a "spirited" drive, you pootle around at 2,500 revs? Doesnt sound much fun to me. It is how most people drive, I accept, but surely not PHers!

If I'm driving "spiritedly" and the revs drop below 5000rpm, I've done something wrong. If anything, I actually quite like a car to be slow(ish) at low revs because it shows up when I've screwed something up.

[300bhp/ton]

likesachange said:

Bhp wins sales torque wins races .. (Obv not strictly true ). Low down torque is what really counts for 90% of spirited road driving. I'd imagine torque is the big factor fighting drag too? But that's just my theory.

I would say your theory seems wrong and rather flawed I'm afraid.

Low down torque is great, if you are low in rev range. But for "spirited driving" in a n/a 2.0 litre would you really spend any time below say 4000rpm? If not, then who cares what torque it makes at 2000rpm. It's all about what power it makes.

I do agree a usable powerband and one that allows you to shift gear before the red line without falling out of it, generally make a car better for road use (although less important for track use).

And lets not forget torque and power are intrinsically linked. You simply can't have power without torque.

HP = torque x rpm /5252


Having said all this, I suspect a good strong mid range punch is probably the most useful for the majority of people for fast road use. As I suspect many people are either to lazy to fully utilise all the gears and all the rev range. Along with the fact that when you do actually do this, you will be giving the car a massive hiding and working it extremely hard.

And the reality is, proper fast cars are likely too fast to utilise on the road in such a manner.

[braddo]

likesachange said:

...Obv these are examples at the extreme end of things...

Indeed, and at the extreme end it's a case of diminishing returns, so the difference between your examples of 280 & 545 hp/ton will feel less extreme than the difference between 120 & 200 hp/ton, or 160 & 300 hp/ton.

To tie back to the original post, anything over 300hp/ton is very quick and there are surprisingly few cars which hit the mark. Hp/ton is a useful measure for comparing cars - especially for road use - but just like the 0-60 sprint, it's imperfect.

[GroundEffect]

Here come the torque vs power posts...

TORQUE IS WHAT THE ENGINE IS DOING.
POWER IS A MEASURE OF TORQUE.

Simple.

The more torque you have at a given rpm, the more power you have and the higher up the rev-range you can produce said torque, the more power you will have.

Think of power as a summary of the torque of an engine - either how big the lump of it is, or where it's produced. It doesn't tell you much else.

It's no surprise then that in my field, we talk in torque, we don't ever mention Power...unless it's homologation time.

[ORD]

300bhp/ton said:

Along with the fact that when you do actually do this, you will be giving the car a massive hiding and working it extremely hard.

I agree with what you say apart from this. High load at low revs is probably more damaging for a lot of cars, and many cars benefit from exploiting the full range.

[kambites]

GroundEffect said:

TORQUE IS WHAT THE ENGINE IS DOING.
POWER IS A MEASURE OF TORQUE.

I'd amend, or possibly extend, that to be:

Torque is what the engine is doing
Power is a modification of that figure to make it have some direct bearing on what's happening at the hubs and tyre contact patch.

[otolith]

I'd suggest that the old canard about torque and power and sales is entirely the wrong way round - cars which make lots of low down torque feel quick to casual test drivers, even if they ultimately aren't. Hence all the people who think their 2.0 TDI is a flying machine.

I think the relevance to racing is that peak power tends to be constrained by technical regulations on capacity, induction, maximum revs, etc, and the difference between a good and bad engine is how much torque and power they make below peak power.

[300bhp/ton]

ORD said:

I agree with what you say apart from this. High load at low revs is probably more damaging for a lot of cars, and many cars benefit from exploiting the full range.

Not sure how running a car at 2000rpm is more damaging than at 7000rpm.