20 replies to this topic

[Nuno]

We all know that current F-1 engine specifications are highly secret. Nobody knows them but half a dozen engineers at each of the engine manufacturers - although many people in the magazines use to make a lot of guessing.
Just for fun I've taken the time to try and determine some of the parameter of a typical contemporary F-1 engine . Using a computer program and projecting the data of 1787 internal combustion , Otto , motorcycle and car engines ( including some racing engines from the 60's , 70's and 80s ) , I found the following data and parameters :
( Configuration = 10 cylinders "V" - everybody knows )
Bore = 92.00 mm
Stroke = 45.00 mm ( average piston speed = 24,75 m/s - OK, it's pretty high )
Displacement = 2,991cc
Compression rate = 13.8 : 1
Power output = 780 HP at 16,500 RPM
Max.torque = 332,6 Nm at 14,800 RPM

Does anyone knows how far from reality I am ?

[Christiaan]

I'd say your guess is pretty good. Now make variations to the bore and stroke and also allow a variations on fuel effieceincy and spark. You will probable be able to vary that number by about 75hp each way. Arrows - Maclaren.

[Keith Sawatsky]

Nuno...


Do it with the 12 cylinder configuration and let's see what the program tells us.

Can you map HP and Torque peaks as well or is more detailed input not accessible to mere mortals like us required?

[Nuno]

The program is quite simple , based on curve adjustment :
a)First you establish a desired peak power,and you assume certain value for the average working pressure and compression ratio , and you have yet the engine capacity ( 3000 cc , for F-1 ).
b)So, the program tells you at which RPM that power will appear.
c) Given the number of cylinders, the capacity and the data of item a), the program tells you then which the optimum bore and stroke, and what will probably be the value of peak torque and at which RPM it will occur .
On our case, for a 12 cylinder engine, we have:

B = 89,3 mm
S = 39,9 mm ( 23.94 m/s )
Vh = 2999 cc
Power = 860 HP ( PS ) at 18,000 RPM
Mt = 336,6 Nm at 16,400 RPM

In both cases ( for the 10 V and for the 12 V configurations ) we assumed a quite conservative value for the average working pressure .

[Nuno]

The program is quite simple , based on curve adjustment :
a)First you establish a desired peak power,and you assume certain value for the average working pressure and compression ratio , and you have yet the engine capacity ( 3000 cc , for F-1 ).
b)So, the program tells you at which RPM that power will appear.
c) Given the number of cylinders, the capacity and the data of item a), the program tells you then which the optimum bore and stroke, and what will probably be the value of peak torque and at which RPM it will occur .
On our case, for a 12 cylinder engine, we have:

B = 89,3 mm
S = 39,9 mm ( 23.94 m/s )
Vh = 2999 cc
Power = 860 HP ( PS ) at 18,000 RPM
Mt = 336,6 Nm at 16,400 RPM

In both cases ( for the 10 V and for the 12 V configurations ) we assumed a quite conservative value for the average working pressure .

[Keith Sawatsky]

An exceptional gain in horsepower...10%+ considering the same displacement is used.

Is the reliability factor or the driveability
factor the main inhibitor in the teams reluctance to go back to V12's though?

[PDA]

I was under the impression that the main arguments against V12s were weight, length and additional fuel consumpion. V12s have been a reliable race configuration since the 1930's.

[DangerMouse]

With todays casting technologies a V12 needent be much longer or heavier than a equivilantly displaced V10, Fuel efficiency depends on the Volumatic Efficiency of the engine and there's no reason why a V12 shouldn't have a better VE than a V10.

[PDA]

DM - if you have six holes in line rather than 5, it is inevitable that the engine will be longer and therefore heavier.

Fuel efficiency: The V12 puts out more power than a V10 essentially because it burns more fuel. For the same thermal efficiency, to get 10% more power, you have to burn 10% more fuel.

this always used to be the argument in the 70s betweeen the Ferrari 12s and the Cosworth V8, where the differences would be even more pronounced. I have no doubt that Honda, or Ferrari , could make a good V12 and win races with it. I hope they do, because the sound is glorious.

[Nuno]

A greater number of cylinder for the same capacity , means smaller unitary volume ( cylinder volume ) and therefore potentially more RPM ( and thus more power ) .
The smaller the cylinder capacity , the higher the speed it can work at ( for example a model plane engine runs at 50,000 RPM , whereas a ship engine runs at some 200 RPM ).
The problem is that with more cylinders you have more complexity ( and possibility of failure ) , more size, more weight. etc.

[DangerMouse]

PDA,
A V12 doesn't necessarily have to be longer than a V10 if the designer does something interesting like staggering the cylinders, which would make a V12 as short as a current V10.

You do not need to burn 10% more fuel to make 10% more power, if engine A) has a higher VE than engine B) then it will make more power for the same fuel burned. Currently F1 V10s are rev limited by the amount of time it takes to fill the (Relatively) large cylinders, this means at high RPM the VE will dramatically drop off, a V12 having smaller cylinders at the same capacity will not suffer this fate until higher up the rev range, Better VE = better fuel consumption and more power.

Traditionally a V12 probably used more fuel because fuelling wasn't the exact science it is today, having 12 cylinders running slightly too rich (usually to err on the side of caution in the interests of reliability) will mean worse fuel consumption than a V10 running in the same trim, with the latest FI systems you do not need to compromise fuelling as it is exact and I'd expect to see V12s compete on even terms with V10 as far a economy is concerned, even the other old V12 bug bears like increased internal friction from more moving parts should be negligible given today’s advances in the knowledge of metallurgy (especially expansion) and advancement of computer controlled milling machines to mean tolerances are always spot on.

In the old days valve gear restricted engine rev limits, piston speed has always been controlled by managing to build engines with shorter and shorter strokes, most top line F1 engines these days can safely rev much higher than they are rated at - they simply do not make any more power at ultra high revs - quite the opposite power drops of drastically due to the reasons outlined above.

I'll say again VE is everything, currently V Twin sports bike engines make less power and have far worse fuel consumption than 4 cylinder sports bikes at the same capacity, why?

[Keith Sawatsky]

Ferrari and Honda...and specifically Honda have said that they intend to bring V12's back.

The weight issue is no longer an issue due to the advances in metallurgy and design...ie: the siamesed bores.

Fuel economy would probably be similiar due to the sophistication of computer engine management systems.

A little added length would spread the weight more along the centerline of the car improving the the yaw characteristics.

The only downside that I see is potential reliability issues because of more parts and higher rpm's due to the power band characteristics.

IMO a worthy trade off for the extra power.

Obrigado Nuno for the V12 scenario.

[This message has been edited by Keith Sawatsky (edited 08-25-1999).]

[PDA]

DM- It is equally true that V10 engines could have staggered bores and make them as short as V8s. Why has nobody done it? Partly because the block will be thicker, and possibly heavier?

It is my contention that the current V10 and proposed V12 WOULD have similar Thermal efficiencies, so the increased fuel consumption in exchange for the increased power is valid. The alternative, as you are suggesting, is that the V12 would have greater Thermal efficiency than the existing V10s. There is no reason to expect this to be so.

[MPH]

DM&PDA - Why would staggering the cylinders make the block shorter? I don't think I am picturing correctly what you are talking about.

[DangerMouse]

300CCs per cylinder used to be the rule of thumb optimum for best VE with normally aspirated engines, the current thinking is more along the lines of 180-200CC per cylinder which is 12-14 cylinder territory! Motorcycle engines are a good indicator of what does and doesn’t work cylinder size wise due to their high state of tune, the highest specific power outputs of four stroke motorcycle engines (and best fuel economy for given power) is in the 600-750CC bracket (for 4 cylinder machines) that give a cylinder size of 150 - 187.5ccs which works out to be the most efficient in terms of power AND economy for road going engines, I’d expect F1 engines to increase in efficiency as cylinder size drops to at least 200CC per cylinder (yes 14 cylinders!) dunno what degree crank you’d have to run for that!

MPH take a V10 and the cylinders look like this.....


O O O O O

O O O O O

Stagger the bores and it will look like...
O O O
.O O

.O O
O O O

Obviously the stagger would be less pronounced than above but you get the general idea!
Staggering the cylinders may actually lead to a lighter block as the shape of the block would add rigidity and mean you could cast it thinner for the same strength.



[This message has been edited by DangerMouse (edited 08-26-1999).]

[PDA]

The staggered bore idea is practically shown in the Volkswagen VR6 engine, in which the cykinders are in a very noarrow v angle within one block. The W 12 that they make for Bugatti and Bentley show cars is two of these blocks on a common crankcase.

What DM is saying about staggered bores is probably true, but it would result in a heavier block. In addition, whoever did it would be breaking new ground, and that is always a risky thing to do. If it works then you are a hero (as Renault were when they introduced V10s to F1. A lot of people said at the time that the vibrations would kill it, but they were wrong.

DM, if you mean by volumetric efficiency the efficiency with which the cylinders are filled with fuel air mixture, then the higher VA would lead to higher fuel consumption, because more fuel is being fed into the cylinder. Anyway, it is a basic law of thermodynamics that, all other things being equal, more power means that more fuel has to be burned. A few years ago they got around this by developing real jungle juice fuels. Now the FIA sets strict rules on fuel composition so that cannot be a factor.

[Keith Sawatsky]

Staggered cylinder bores would not necessarily result in a heavier engine, consider...

The Chevrolet "big block" marine engine with "siamesed" bores has the same weight as the regular block. It has been designed to be bored out to a larger displacement which results in thinner cylinder walls. The net result would be a weight saving in the block equalized by the extra con-rods, pistons, etc. in a V12 versus a V10. The challenge would be for the engineers to create a block with enough heat dissipation capability, stress bearing capability and weight saving to make it feasible for a 2 hour race. We're not talking about LeMans durability here.

Quite frankly, it doesn't seem like a tall order to me.

[This message has been edited by Keith Sawatsky (edited 08-26-1999).]

[PDA]

KS - I agree that it is feasible. However, if all of your database concerns V10 engines, you are taking a big risk going to an unknown format. That is a big incentive to be conventional. For Ferrari and Mac, they are the most powerful (or so it looks) so the disincentive is strongest. Ford have just learned about V10s and look to be knocking on the door, so they would be unlikely to change. Honda have a lot of knowledge from Mugen, and it makes sense to build on this rather than go out on a limb. However, Honda have frequently gone where no man dares to tread before, so we can hope. I still think that V12s are much less likely than V10s.

[Christiaan]

In as far as I can see, if Nuno's simulation is true, then factors like weight and fuel consumption will be overshadowed by the gain in Hp.

Condider my reasoning. Say for the WORST case scenario a V12 engine weighs 20% more and carrys 20% more fuel, this by mere V10:V12 proportion. For a 100kg engine with a 60kg fuel tank that is an overall wieght gain of at 32kgs which represents about 5% of the total DRY mass of the whole car and even less of the fueled car.

Now a V12 seems to produce slightly more than 10% more power for AT THE VERY WORST CASE a 5% weight penalty. Using simple Newtonian mechanics,

Power = Force x Velocity

The drag force on the car will not change (V12 or V12) thus if the power increases so will the top speed. So a V12 will have a higher top end speed, which is independant of the mass gains.

If I modify the above equation to consider the acceleration of the car I come up with an expression that accounts for power dissipated ito overcoming the drag force and power dissipated into overcoming the cars own inertia(Newtons 2nd law). I simplifies to

Power = (F + ma) * v
where F = aero-drag
m = mass
a = acceleration
v = velocity

It is clear from that equAtion that the power is to overcome inertia is directly proportional to the mass. Based on that, given that two otherwise identical cars had a V10 and a V12, they would both experience the same drag. The V12 car would be 5% heavier but have 10% more power. It would therefore accelarate much better.

This is analysis is only true of course if the V12 torque and power curve is simply a 110% scale of that of the V10.

[PDA]

Christiaan - in reality, it would be even more beneficial. Most cars (except Benneton) run with varying amounts of ballast weights, so the increased weight might mean that less or no ballast would be used. the weight would not be so low or placed to such advantage, so handling would be marginally worse, but this may be overturned by the increased acceleration. O would love to see (or rather, hear) V12s, but I don't think we will, at least next year.

[Christiaan]

As I said PDA, this was only a worst case scenario, so I expect a V12 to be even better.