26 replies to this topic

[Jhope]

I just thought i'd ask this:

We get rough estimates of what the horsepower figures of an F1 racer is.

Why is it that the engine manufacturers are not willing to release the torque figures?

Can torque figures give out way more info about an engines capabilities that bhp figures? (stupid question)

Can power bands be figures out by rivals if the torque of a cetain engine was known?

Am I asking stupid questions?;)

[slipstream]

A couple months ago Road & Track had a very interesting article about last years Jaguar Formula One car. They listed the Cosworth V-10 as having 800 HP and 270 lb-ft of Torque. It is interesting because todays F1 engines have alot less Torque than F1 engines 10 or even 15 years ago. The Honda V-12 used by Mclaren had 300 lb-ft of Torque and the Turbo engines of the 1980`s had over 500 lb-ft of Torque:)

[Nathan]

Torque seems to have a maximum of roughly 90 ft./lbs per liter. I have yet to find a engine that exceeds that. My guesses would be they make between 255 and 270-ft.lbs.

[desmo]

True, Nathan. At least for non-supercharged engines.

[Jhope]

thanks guys.

the new Hennessy Viper 825 bhp, and 725 lbs of torque.

[Pioneer]

And the Viper is an 8 liter engine IIRC.

[Jhope]

uhmm forgot about the displacement.

[slipstream]

But even with all that Torque a F1 car can still out Accelerate the Hennessy Viper:)

[IndyIan]

Here's a question:
Would the Hennessy Viper accelerate faster or slower with an F1 engine and the appropriate gearing.
Assuming that the Viper would weigh the same with the F1 engine.

Another question:
How would an F1 car do with the hennessay viper engine acceleration wise?
Assuming the Hennessay F1 car could be made to weigh the same as normal F1 car.

[SennaVsProst]

I was just thinking about the old 1911 Fiat GP with 14 1/2 Liter engine, making 150 some odd HP and 750 lb./ft. of torque!! thats something else... kinda like a diesel big rig, but this was 1911....

[Jhope]

Originally posted by IndyIan
Here's a question:
Would the Hennessy Viper accelerate faster or slower with an F1 engine and the appropriate gearing.
Assuming that the Viper would weigh the same with the F1 engine.

Another question:
How would an F1 car do with the hennessay viper engine acceleration wise?
Assuming the Hennessay F1 car could be made to weigh the same as normal F1 car.

Would we be using the F1 gear box? If so, the gear ratio is tighter than those of regular street cars, but i still can't see why they would accelerate quicker than a car that has over 700lbs of torque, even with the same weight?

But the Viper would have turbo lag due to the twin turbo's. I read that they did all they could to reduce the amount of lag, but they are still ways off. Let's say the lag is resolved, would an F1 car be quicker?

[Pioneer]

Since when are Vipers turbo?

[Jhope]

There ya go.

[Pioneer]

But thats just wrong!

Thats like buying a naturally aspirated Impreza WRX!

Blasphemy!

[desmo]

I have a customer who owns a Viper among other interesting cars and after a ride I would have to say in Rolls-Royce fashion that the torque of the stock motor surely is "adequate."

[imaginesix]

Originally posted by Jhope
But i still can't see why they would accelerate quicker than a car that has over 700lbs of torque, even with the same weight?

You're right Jhope, it is all about engine torque...
...and RPM!

The reason why RPM is so important is because torque can be multiplied by gearing down the engine speed.
For the sake of illustration, an F1 car that produces 250 lb-ft of torque will produce 500 lb-ft at the rear wheels if driven down by a 2:1 gear ratio. So the higher RPM an engine has to spin, the more it has to be geared down to match the wheel speeds, so the more it's torque is multiplied.

You may also prefer to look at it from the point of view of rear-wheel torque. The more torque that is present at the rear wheels, the greater the acceleration is for a given mass.

Another way to illustrate it is that an engine that produces 250 lb-ft @ 6000 rpm is better than an engine that produces 250 lb-ft @5000 rpm, (because it can be geared down more). And that's where horsepower comes in. Horsepower is nothing other than an indicator of power that considers both torque AND rpm.

Torque x RPM = hp x 5252

The more torque that is produced, and the higher the rpm, the more power you get. 5252 is just a constant that converts the torque figure from lb-ft into the commonly used units of 'horsepower'.
If you go from Newton-meters to Watts, you need a different constant.

In fact, looking at torque values is very misleading. An engine that produces 255 lb-ft @ 17500rpm will provide better acceleration than an engine that produces 725 lb-ft @ 6000 rpm.

So the long and the short of it is: An F1 engine with 850 hp should out-accelerate a twin-turbo Viper engine with 830 hp, all else being equal.

Rear-wheel torque rules, but horsepower gets you there.

[Zoe]

Originally posted by imaginesix

Rear-wheel torque rules, but horsepower gets you there.

Really? I remember the old saying (from the US): Torque is for racing, horsepower is for selling

Zoe

[colejk]

imaginesix, wow! That was cool. Never ever thought of it that way.
Question I have is, why all the fuss to make peak torque at lower revs then? For as long as I've been around cars, sports car makers are always stressing flat torque curves and low rev torque peaks.
So this seems to contradict what I've always heard and read.

I've always thought of torque as how much weight can be moved, and horsepower determining how fast it gets moved. Is this wrong?
Explain more, I'm very interested.

[palmas]

Imagesix, that is only partly correct. In order to coment on acceleration skills, you should consider the torque line between min and max rpm you use to accelerate.
rear weel torque will give you stantaneous acceleration, but average acceleration you should integrate the rear weel torque line.

"An engine that produces 255 lb-ft @ 17500rpm will provide better acceleration than an engine that produces 725 lb-ft @ 6000 rpm." that is correct if torque lines are proportional, and it is wrong if the 725 torque engine has a flat torque line and the 255 torque engine has a narow peak at 17500rpm.

[imaginesix]

Originally posted by palmas
Imagesix, that is only partly correct. In order to coment on acceleration skills, you should consider the torque line between min and max rpm you use to accelerate.
rear weel torque will give you stantaneous acceleration, but average acceleration you should integrate the rear weel torque line.

"An engine that produces 255 lb-ft @ 17500rpm will provide better acceleration than an engine that produces 725 lb-ft @ 6000 rpm." that is correct if torque lines are proportional, and it is wrong if the 725 torque engine has a flat torque line and the 255 torque engine has a narow peak at 17500rpm.

That is true palmas, I should have included that.
Since the car must accelerate through a range of rpm in one gear, then shift back to lower rpm and accelerate again, acceleration will depend on the total power within that useable rpm range.

However, additional gearing can be used to offset any peakiness in hp curve:
Since hp curve within the applicable rpm range IS the truest indicator of accelerative performance, then it stands to reason that if the power curve cannot be modified, then changing the rpm range is the only way to improve performance. That is accomplished by adding gears to narrow the powerband and reduce the 'low point' on either side of the power peak.

There is a limit to how many gears can be added, as gains become negated by the incresed number of shifts, which is time spent not accelerating, and by the additional weight. As an aside, this explains the potential value of an infinitely variable transmission, as it allows the engine to spend the vast majority of it's time right on it's peak power point, so the power can be made very peaky without the tradeoff of increasing shift time or transmission weight.

So in sum, the difference in performance of an F1 car or a Viper with drivetrain exchanged, but at their usual weight, is not as clear-cut as I made it out to be. With 830 hp in the Viper engine and 850 in the F1 engine, they are close enough in performance that the power curve factor mentionned by palmas could have a deciding impact on any improvement or worsening of performance.

In fact, I would argue that the Viper engine/gearbox car would out-accelerate the F1 engine/gearbox car initally, because it's gearing is lower for street use, but then the F1 engine/gearbox car would overtake it, as it's gearing is optimised for higher speeds.

Though you will note, palmas, that I did cover my bee-hind by saying 'all else being equal' when referring to lower torque providing better acceleration.

[palmas]

You're correct imaginesix (a little knoledge is more dangerous than a huge one);)

[imaginesix]

Originally posted by colejk
Question I have is, why all the fuss to make peak torque at lower revs then?

That's a good question.

So far, our discussion has focussed solely on optimum acceleration, to which I have indicated that high torque and high rpm are essential. There are benefits to be had from improving an engine's low-rpm torque too though.

Lowering the operating powerband of a motor has several benefits:
- Improving driveability;
- Reduced need for shifting;
- Reducing noise and vibrations;
- Reducing engine manufacturing costs;
- Improving fuel economy.
There may be other gains, too.

As you can see, all these benfits are prime considerations in road car design, so are most likely to be found reported in road-car tests. The first item also carries some weight in race car engine design. I'm assuming that the reports you've heard and read about were referring to road cars, not race cars?

If you ever read of a sport-car manufacturer reporting that a lower, wider torque curve directly translates into improved performance in speed contests, rest assured that that is complete marketing bull***t.

Unless the peak torque speed is not much lower, the torque curve is much much wider, and depending on gearbox attributes as discussed above.

[slipstream]

What about the reduced intertia and mass of a F1 engine ? A F1 car whould rev through it's powerband much quicker than the 800 HP Turbo Viper .

[jsadie]

So, According to My calculations :

The BMW engine (reported spinning to 18000 rpm)

18000 rpm with 250 ft-lb torque=856 Hp
17500 rpm with 250 ft-lb torque=833 Hp
18000 rpm with 270 ft-lb torque=925 Hp
17500 rpm with 270 ft-lb torque=899 Hp

These figures assume max torque@max revs,and that rarely happens. So,these engines will make max 925 hp for normally aspirated engines,unless the rpm's increase.

Suggested max torque for 3.0l = 270 ft-lb.

[palmas]

Originally posted by slipstream
What about the reduced intertia and mass of a F1 engine ? A F1 car whould rev through it's powerband much quicker than the 800 HP Turbo Viper .

You mean with the clutch open? if not the enertia would come from the car mass itself.

[palmas]

Originally posted by jsadie
So, According to My calculations :

The BMW engine (reported spinning to 18000 rpm)

18000 rpm with 250 ft-lb torque=856 Hp
17500 rpm with 250 ft-lb torque=833 Hp
18000 rpm with 270 ft-lb torque=925 Hp
17500 rpm with 270 ft-lb torque=899 Hp

These figures assume max torque@max revs,and that rarely happens. So,these engines will make max 925 hp for normally aspirated engines,unless the rpm's increase.

Suggested max torque for 3.0l = 270 ft-lb.

That is correct for those figures of rpm' and torque. But please never state this the best we can do (torquewise or otherwise).

[Jhope]

great stuff guys. I'm learning a few things here and there, but it will all soon come and gel as one!