What does 600bhp feel like?

[Clarkey]

No there's no difference in measurement. HP does follow torque. That much is surely obvious, torque is a force, power is a measure of work done by that force. There is a formula, HP = (torque x rpm) / 5252.

It's easy to determine the character of an engine by the numbers. Something with high torque and low hp is a low revving unit with 'grunt', something with high HP but low torque is a high revving unit which will feel relatively gutless down low.

 

[Mercenary Keyboard Warrior]

Sorry to sound stupid here, but when looking at specs of different cars, is torque worked out differently? The reason i ask is that if you said it was linked that much, wouldn't torque follow hp, and then wouldn't all cars have exactly the same torque curve with they have the same hp? I know in my car the torque is quite linear whereas power goes up, but my last car they were much closer. Again sorry if this sounds stupid but i can't get my head around it.

This is quite a decent starter, ignore the fact about "Every engine designer has to bear in mind the balance between power and torque. He might even move the balance a little away from power and towards torque if enough drivers understood the importance of torque and the generalization that power versus aerodynamic drag determines maximum speed, but torque versus weight determines acceleration." as clearly the author doesn't know hes wrong

https://www.howacarworks.com/technology/torque-and-bhp-explained

Following on from Clarkey most diesels for example would be grunty type engines, low down shifting ability but top end seems to be weak, where as the opposite would be something like a Honda VTEC which can be really weak below 5k or so, but once they go high lif they are transformed into fast revving more powerful engines
Turbo engines in most cars tend to be more tuned for across the rev range ease of driving.

 

[DRZ]

My car is 414bhp, there are supercharged M3s out there on 625ish bhp and they just walk away from the standard cars. The difference is enormous.

My car is about 260bhp/tonne whereas my old supercharged MX-5 was about 210/220ish and the cars aren't that far apart at lower speeds - the MX-5 might have even been quicker A to B on twisty roads due to the lower weight meaning I could carry more speed through bends.

 

[Dominic-Toretto]

Thank you for the input everyone, the general consensus I am getting is that is a big difference, provided the other factors mentioned are also inline

 

[theone8181]

I think i understand my confusion, my previous car did this

My current car does this

(Pictures shamelessly stolen from google). I was looking at the 2 graphs and trying to work out why torque is not related, but these will be post gearbox so am i right in thinking that unless you work backwards using the gearbox ratios, you can't work out engine torque from power?

 

[Mercenary Keyboard Warrior]

You can, you were given the formula above. BHP is a function of torque so its always possible to go from one to the other.

Your first car is interesting, looks like it was torque limited, auto box? CVT?
Some cars do limit torque in certain gears for example. (BMW boxes had a limit on 3rd and 6th which was to do with the clutches, although not all the other gears were the same those gears were lower)

Actually the first one is really wierd, what was it?
The second is the normal one with the expected cross over at 5252RPM

 

[SonicSW20]

too many variables in that to really comment but recently changed from 200 bhp/1500kg to 300bhp/1900kg on paper not a huge increase at around 20% power to weight increase but everything else about the car also changed FWD to RWD manual to 8 speed auto and a huge jump in torque of about 60% means in the real world its much much quicker.

would certainly echo some of the sentiments above though, anything north of 200bhp/ton on the road is pretty much a quick point and squirt at best.

Well yeah, you've gained ~20% on the power to weight ratio, of course its going to be quicker.

 

[SonicSW20]

I think i understand my confusion, my previous car did this

My current car does this

(Pictures shamelessly stolen from google). I was looking at the 2 graphs and trying to work out why torque is not related, but these will be post gearbox so am i right in thinking that unless you work backwards using the gearbox ratios, you can't work out engine torque from power?

One of those graphs is in kW and Nm, the other is in bhp and ft-lb.

 

[theone8181]

You can, you were given the formula above. BHP is a function of torque so its always possible to go from one to the other.

Your first car is interesting, looks like it was torque limited, auto box? CVT?
Some cars do limit torque in certain gears for example. (BMW boxes had a limit on 3rd and 6th which was to do with the clutches, although not all the other gears were the same those gears were lower)

Actually the first one is really wierd, what was it?
The second is the normal one with the expected cross over at 5252RPM

911 turbo, it was pretty nippy. But I still don't understand, power is going up but there's a massive flat in the torque curve. I get the maths but that doesn't add up (although I'm guessing limiting torque would possibly do that, but not sure if that happens on all Turboed cars). Again sorry to sound stupid.

Edit, that second graph should be an e92 m3 but I may have nabbed an e46 by accident. Sorry. Some of the numbers work out, but not all.

 

[PMKeates]

911 turbo, it was pretty nippy. But I still don't understand, power is going up but there's a massive flat in the torque curve. I get the maths but that doesn't add up (although I'm guessing limiting torque would possibly do that, but not sure if that happens on all Turboed cars). Again sorry to sound stupid.

Because the same torque at a higher RPM equals more power.

This is quite a decent starter, ignore the fact about "Every engine designer has to bear in mind the balance between power and torque. He might even move the balance a little away from power and towards torque if enough drivers understood the importance of torque and the generalization that power versus aerodynamic drag determines maximum speed, but torque versus weight determines acceleration." as clearly the author doesn't know hes wrong

He precludes it with "the generalisation". I repeat again, the torque output in Nm or lb-ft of an engine tells you very little about how fast a car is. You can have a 1000 Kg car with a 1000 Nm engine and it can be dog slow, as if that 1000 Nm is at 200 RPM you will not be able to gear it very much. If you have a 1000 Kg car with a 1000 HP engine it will be very fast no matter whether that 1000 HP is at 2 RPM or 20000 RPM, in fact this 20000 RPM engine could produce a peak of 360 Nm and yet be much much more potent than the 1000 Nm engine. In the end an engine is putting a rotation force on the output shaft (torque) to accelerate the car, but the amount of that torque alone is very far from determining how fast a car accelerates.

 

[theone8181]

Because the same torque at a higher RPM equals more power.

I was just going to edit my quote, so the fact that the torque drops off is cancelled out by the increase in rpm. It's just modern turbos 'cap'the torque.

 

[PMKeates]

I was just going to edit my quote, so the fact that the torque drops off is cancelled out by the increase in rpm. It's just modern turbos 'cap'the torque.

It's not really a cap in the sense of some kind of limiter, it's just what it has been designed and calibrated to deliver.

 

[Nasher]

Probably to preserve the turbo.

 

[Frozennova]

Probably to preserve the turbo.

Nope, turbine shaft speed would still be increasing. Torque might be flat, but the airflow demand is still rising.

 

[Mercenary Keyboard Warrior]

Probably to preserve the turbo.

More likely the gearbox/clutch

 

[Django x2]

Title really, what does 600bhp feel like, say compared to a car that has 400bhp, is there a noticeable step in performance, does it push you back in the seat way harder? Is it worth it for a car that will only see road use? Or is it only useful for willy waving and pub talk?

I noticed a massive difference going from 340 to 400bhp, when will the noticeable effects from power increases start to tail off?

I can answer this coming from an M5 to an S6. ( For the sake of argument let's call it 600bhp to about 450bhp)

Although different in their delivery, as the engines are massively different (although both V8) the difference was absolutely night and day. The M5 was completely savage in its acceleration compared to the S6.

 

[Nasher]

The S6 is more like a road boat

 

[theone8181]

The S6 is more like a road boat

Plus it's an Audi so will probably understeer everwhere. Just looking at figures, it's a 50% change in power, but only a 25% increase in speed (comparing my m3 to anything with 600hp), which makes sense with the whole needing double the power to go a little bit faster.

 

[Django x2]

The S6 is more like a road boat

Quoted for truth.

Torque and BHP always seems fairly straightforward until you throw in motorbikes.

If you put an R1 engine into any car, it would barely move, despite generating 180bhp. It's torque is about enough to sneeze through a wet tissue. But, critically, an engine has to generate enough power to overcome it's own weight before it's of any use.
That's where you need plenty of torque, to shift the mass. Bikes don't weigh anything, even with a rider which is why torque output is less of a concern.

 

[Frozennova]

Quoted for truth.

Torque and BHP always seems fairly straightforward until you throw in motorbikes.

If you put an R1 engine into any car, it would barely move, despite generating 180bhp. It's torque is about enough to sneeze through a wet tissue. But, critically, an engine has to generate enough power to overcome it's own weight before it's of any use.
That's where you need plenty of torque, to shift the mass. Bikes don't weigh anything, even with a rider which is why torque output is less of a concern.

That's more of a gearing issue than the lack of torque though.

First gear on most litre sports bikes is ~95mph, reduce that to a more typical 32-34mph and you've got almost 3 times as much torque applied to the road where it matters.

Peak torque for a sports bike isn't any lower than you a typical naturally aspirated 1.2 found in a small hatch