22 replies to this topic

[FulcrumF1]

OK, What exactly are they and what do they add to the driving experience?

[DangerMouse]

Torque is the "turning effort" of the engines' crankshaft, Horsepower is simply (torque*revs)/5250 (if my memory serves me right!)

In effect nearly all F1 engines produce a similer peak torque figure as the Volumatic Efficiency of the engines are probably more or less identical as cylinder head design is such a known quantity these days, the more powerful engines are the ones that are able to make the torque further up the rev band.

[Ursus]

Torque is how strongly the engine can twist the crankshaft. Power is a measure of how much work an engine can do. The relation between torque(T/Nm) and power(P/Watts) is P=T*w where w is the angular freq.(radians/second). DM's formula is more convenient as it uses hp/lbs-ft/rpm.

I like to explain the relation between power and torque with two guys carrying sandbags. One is big but slow and can carry 2 bags at the time but can only go one round per minute. The other is small but quick and can only carry one bag but goes 2 rounds per minute. Even though the big guy is stronger(more torque) the small guy makes it up with speed(revs) so they ultimatly do the same work(generate the same power).

Of the two it is the peak power that best represent the performanc of an engine.

One thing I have observed is that engines with the same displacement(no supercharging) often have similar peak torque figures but can have very different peak power outputs because they are tuned for different rev ranges.

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Ursus
Trust me, send money.



[This message has been edited by Ursus (edited 01-26-2000).]

[davo]

One useful way to consider and compare engines is to come up with a measure of engine efficiency.

One often used is HP/1000revs/L/Atm
- horse power per thousand rpm per litre of engine size per atmosphere of boost (Obviously 1 for naturally asirated and >1 for supercharged)

Improving the breathing characteristics of an engine should flow through as an increase in the calculated figure. Increasing the revs (while maintaining air flow) gives more power without an increase in absolute efficiency.

It can be suprising to see how similar various engines actually are and can be used as a "first cut" design tool. What revs would I need for 300hp out of 2L, or what boost etc etc etc.

[Christiaan]

You might wanna check out thislink, there are some interesting perspectives given. You will have to dig around for the info though.

[MattDavis]

OK.
According to someone earler in this thread the HP of an engine is the Torque times the RPM but would it not be better to have more Torque at lower revs which would have a lower HP but it would have more power when you are accelerating not just at top speed.?
I may be completely wrong, as I realy dont have any idear about what I am saying.

[BRG]

Yes, it would of course be preferable to have more torque at lower revs, but current F1 engine design has gone way beyond that. We are looking at 3 litre motors producing 700+bhp, which is more than 230 bhp per litre. Now when I was a lad, 100 bhp per litre was reckoned to be powerful. Be that as it may, to get such high bhp/litre figures with current technology, you have to go up the rev range, hence the astronomical rev limits on the latest motors (15,000+ rpm - in some case 20,000 is being talked about). The more emphasis on bhp, the more you lose out comparatively on torque.

A good example of this is with production motorcycle engines which produce huge bhp figures but low torque. In bikes, as in racing cars, torque is not so important because of the light weight to be moved. As long as you have the bhp power, you are OK. But put such an engine in a heavy car and it would really struggle - for instance put the Ilmor-Mercedes lump into a hefty 2000kg Mercedes saloon, and you would have some trouble getting it moving - the clutch wouldn’t last very long - mind you, it could be fun once you got going!

An interesting example of the values of torque versus bhp was in the 1999 British Rally Championship, where VW entered a Golf turbodiesel. The car was the same spec otherwise as the petrol cars, but it had only some 200bhp agianst their 300+bhp. However, it also had huge amounts of torque. In rallying, torque is very much more valuable than racing because you have hundreds of different corners rather than the average race track’s 10 or so, and you can’t set the car up exactly for all of them. So the ability of an engine to pull from the "wrong" revs is very important.

The results for the VW Golf Tdi were impressive, the best being a 2nd overall on the all-tarmac Manx International Rally. This was down to power delivered pretty evenly from 2,000 to 5,000 rpm.

The ideal would be to have loads of torque and loads of bhp, but at our present level of knowledge, there has to be a trade-off towards the one that is the most useful.


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BRG

[MattC]

Davo:
Something I have always wondered about (mainly in connection with road cars) is efficiency of 'power vs fuel used'.
e.g. BHP/(Litres per second) (and possibly lbft/l-per-sec)
This would seem much more interesting than the 'Urban Cycle mpg' type figures, as it would tell you how well an _engine_ was converting petrol into performance.
Know anything about these sort of numbers?

[Ursus]

BRG, I think you are separating hp and torque too much, because they are very much connected. Also you are confusing 'torque' with 'low end torque'. Substitute the 'torque' with 'low end torque' then I will agree with you.

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Ursus
Trust me, send money.

[BRG]

Ursus, you are of course right. Torque and HP are really two aspects of the same thing. I was trying to draw a distinction to show that you tune engine characteristics to suit the use that you are going to put it to.

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BRG

[f1speed]

We may have a friendly discusion here, actually BRG is right. To keep this as short as possible the encyclopedia is a good reference. Horsepower is the rate of doing work,33,000 lbs one foot in one minute or one pound 33,000 ft in one minute. Torque is a meausment of force that can be stationary. Normaly torque drops off rapidly as rpms increase, and high hp high reving engines have less torque (at low rpm) than slower running engines.

[davo]

MattC:
You are quite right with your comments.


The previous "efficiency" (BHP/L/1000rpm/atm) is focused on speed around a race track as opposed to low running costs, and is somewhat like cardiovascular fitness of a human - how well does it breath.

Brake specific fuel consumption is probably the best measure of actual thermal efficiency of an engine. That is how well does it translate the energy in the fuel into thrust Various units used but I belive (?) often quoted in BHP per hour per pound of fuel - happy to be corrected on units? anyone?

Typically if you are looking at a naturally aspirated engine improving its actual horsepower will coincide with an improvement in BSFC. A happy coincidence

There is a great tech motorsport site at
http://www.performan....com/index.html

which is worth some time over several visits.

In Australian 5L touring car racing Gibson Motorsport have proved highly effective at optimising engines to performance and fuel efficiency. They dyno develop with O2 probes in each cylinder outlet and (I believe - that word again) have the computer set up to give them instantaneous BSFC figures. They typically get more laps out of a fuel limited tank than anyone else, without being short on oomph.

The qualification to all of this discussion is that we are talking N/A on petrol. Turbos can be made to make more HP by uping boost (no suprise there) but can then be made to accept yet more boost by retarding spark and running rich (it cools the combustion chamber) and keeps pistons and turbos alive.

Methanol and various nitro blends are not my field but I do know that methanol can (and often is) made to run quite rich which I presume is done for similar reasons.

[MikeA]

davo:

>Brake specific fuel consumption is probably the best measure of actual thermal efficiency of an engine.

Indeed.
And I suggest this would probably be the most clever way of limiting performance.
Via a limit on allowed fuelflow we'd have a very close and welldefined tool for lowering "speed" (for safety reasons or whatever reasons) instead of limiting rpm's (F2 or BTCC) or volume (F1...) or air-flow (WRC) or boost (Cart/IRL), etc


>In Australian 5L touring car racing Gibson Motorsport have proved highly effective at optimising engines to performance and fuel efficiency. They dyno develop with O2 probes in each cylinder outlet and (I believe - that word again) have the computer set up to give them instantaneous BSFC figures. They typically get more laps out of a fuel limited tank than anyone else, without being short on oomph.

An other alternative could have been monitoring the EGT (& of each cylinder).

>Turbos can be made to make more HP by uping boost (no suprise there) but can then be made to accept yet more boost by retarding spark and running rich (it cools the combustion chamber) and keeps pistons and turbos alive.

What might happen with the BFSC when running overrich in boostapplications...

BR

M.Aaro

[Nathan]

Incase you wanted the formula for calculating horsepower it is as follows:

torque (ft. lbs) x RPM / 5252 = Horsepower

so 200ft./lbs of torque at 5252rpm would make 200-hp

[tak]

For people who want to observe the difference between torque and horsepower, pay attention to this years World Superbike Championship. In the high torque camp is the Ducati (1 liter v-twins). In the high horsepower camp is the Suzuki GSXR (750 cc fours). In the middle will be the Honda RC-51 (also a 1 liter V-twin) The Honda is tuned for more horsepower than the Ducati, but will be 20 HP down to the four cylinder bikes. The V-twins make more torque, the fours have more HP. Should be an interesting season!

[Jiffy]

Well, I think the Dukes should win 'cos they look the best, and surely that must be worth a second a lap?

[desmo]

With this username, guess who I'm pulling for!

[Yelnats]

Without specific knowledge of these bikes I would assume the twins carry less weight to make them competative. This is done in many classes in the States and in racing, power almost always wins over raw tourque. Gearing can turns this extra power into more tourque at the rear wheel at a given speed.

On the road we may not bother shifting down as often so tourque is much more important to driveing feel and thrust.

[DangerMouse]

Yelnats, the twins used to run lighter, these days they all run a 162KG minimum, the difference is Twins are allowed to be up to 1000CC, triples 900CC and fours 750CC.
Why no one has bothered building a decent triple beats me, they should slaughter the opposition!

Tak, there isn't a huge difference in peak torque between the 996 Dukes and the best 750 fours (RC45 last year) but the best fours make *much* more horsepower (by nature of making the torque further up the rev range.)
it's an old wives tale than twins produce more torque, they don't (per given capacity) it's simply that they do not rev (limited by heavy reciprocating mass), so the engine is obviously optimised to run strongly at lower revs and the lack of top end rush exaggerates the midrange punch.
A good example is compare a Ducati 996 SPS to a Yamaha R1, the Yamaha kills the duke in terms of torque and horsepower from tick over to the redline.

[desmo]

In motorcycles the contact patch which must transmit that torque to the pavement is so tiny that drive out of a corner is often a function of having a smooth controlable powerband as much as raw torque. The drive is largely traction rather than power limited. This is partly why the Ducatis with their seemingly uncompetitive power outputs can lap so fast against the more powerful fours.

[This message has been edited by desmo (edited 02-22-2000).]

[DangerMouse]

Desmo - sort of! the advantage the Duke twins have is there's 270 degrees gap between the power strokes (they fire only twice with a 90 degree interval) therefore the tyre gets a much longer time to recover traction from the power stokes than on a four which fires every 90 degrees, I'm surprised Honda too went for a 270 degree twin rather than experiment on "big bang" four cylinder units, (ie build a fancy crank which makes the four fire as a twin.) you'd have almost twin traction and four cylinder horsepower, it would be less of a risk and more of a known quantity for Honda, especially as they led the way for "big bang" two strokes in GP 500s.

The Ducati's carry their weight better then most of the fours, Dukes handling advantage is more significant than it's traction advantage. I expect the RC51s will fly and the press will say "see the Ducati had an engine advantage" - wrong. Honda had an engine disadvantage, the RC45s (V4) engine was large and compromised the wheelbase of the bike as well as the steering geometry and centre of gravity, Honda should have gone for a across the frame four like the other Japs and the bike would have been very competitive.

Ducati are lucky in that Honda screwed up with the design on the RC45, and Yamaha/Suzuki and Kawasaki haven't had the resources to compete and have only recently pulled their finger out. Expect a strong season from Yamaha and Suzuki, Plus Kawasaki will end the year by pensioning of the fast but bad handling ZX7 and start on a rebuilding exercise.
I think the ZX7 will be the fastest (speed) but slowest (laptimes) works effort in 2000.

That said, I agree with Ducati's design principal, the Jap manufacturers are obsessed with bigger and stronger two spar aluminium chassis, this is a blind ally, the Dukes steel trellis frame is lighter and stronger and carries it's weight lower - that's Ducati's real advantage, but the big four Japs are too proud to admit they've been wrong all these years with something as fundamental as frame design. Of course having Foggy pilot the thing could be considered quite an advantage for Ducati! The smoothest rider in the world with the highest corner speed allied with the bike that needs the smoothest riding to use it's only real advantage - corner speed!

[desmo]

DM, Thank you for the clarification. I always find your posts interesting and informative.

[DangerMouse]

Desmo, no prob, nice to see another "bike nut" on the board!