Porsche back in Le Mans!

[WhiteBlue]

34.4 cc/s of gasoline, a strange number indeed, relates to 1180 kW input, 34% efficiency means 400 kW or 550 Hp. Still more the the 917 ever had in 1971.

I have checked your effciency figure and it does not add up for me. In F1 we will have 35% if we use 46 kJ/g, 448 kW and 27.8 g/s. ...

34.4 cc/sec equals 25.5 g/s at 0.74 density, gives 1180 kW input with 46.4 MJ/kg, 34% of that is 402 kW or 546 Hp at 0.735.

You don't seem to understand my point. I think you are not using the right efficiency for the 2014 LMP1 engine. You use 34% indiscriminately for F1 and LMP1. When I checked F1 I found that it is probably 1% higher. That stipulates that the Porsche engine with the more liberal rules and the lower fuel flow must be even more efficient. My point is that we can expect the best petrol LMP1 engines to reach at least 38% thermal efficiency on their own before any compounding or energy recovery. That is a difference of 4% which sounds small but isn't. Variable geometries and valves and variable multi stage turbos should make a big difference. LMP1 has no injection pressure limit and no limits on ignition. They can use piezo valves or laser ignition at outrageous cost if they feel that it helps. I'm sure there will be a thunderstorm of inventions.

[xpensive]

I most obviously did, in all honesty, I chose 34% in order to hit 400 kW and 550 Hp.

I'm just a great fan of even numbers WB, mea culpa.

[WhiteBlue]

Does somebody have a good idea what kind of AFR such a sper efficient petrol turbo engine is going to have? I think we can safely assume that the LMP engines will not exceed 10.000 rpm. They will be superior in efficiency compared to F1 and F1 caps it at 10.500. We do have the power and if we make an assumption for a 2L cubic volume - as some insiders suggest will be done by Porsche - we could precisely determine what kind of intake pressure you need to achieve this.

[Blanchimont]

This graph shown on wikipedia mentions an AFR of 12,6 for maximum power and 15,4 for minimum fuel consumption.
Race engines with limited fuel consumption want to achieve both goals, power and efficiency. So maybe they are run slightly rich with an AFR of 14 to 14,5? In this region power and fuel consumption are not far away from their optimums.

[xpensive]

Does somebody have a good idea what kind of AFR such a sper efficient petrol turbo engine is going to have? I think we can safely assume that the LMP engines will not exceed 10.000 rpm. They will be superior in efficiency compared to F1 and F1 caps it at 10.500. We do have the power and if we make an assumption for a 2L cubic volume - as some insiders suggest will be done by Porsche - we could precisely determine what kind of intake pressure you need to achieve this.

I'd say about 1.6 Bar absolute for the 550 Hp, at 34% efficiency.

[WhiteBlue]

In fact I suggest we provisionally assume lambda =1 and an AFR= 14.7. At 23.2 g/s fuel it would need 341 g/s air. At 25°C the air is going to have a density of 1.184 g/L. This brings us to 288 L/s of air. At 10.000 rpm a 2L NA engine would consume 166.7 L/s. That would require just 1.7 bar intake pressure to get us the air needed for our fuel flow. It sounds awfully low to me.

Of course this figure will rise if we assume even lower rpm which would in fact be beneficial for combustion and avoiding friction losses. Lets not forget that the Audi turbo diesel is the opposition and that thing currently revs at just 5.000. If we make the assumption that they will run 2.5 bar intake pressure it will bring the revs down to 6.800 rpm. My guess is that the reality will probably be somewhere between these two values.

If we assume an efficiency of 38% a fuel flow of 23.2 g/s would deliver 406 kW or 544 bhp. That would not be a shabby power considering we also have 6 MJ electric energy for our 200s lap to burn. If we assume 70% WOT equivalent of the electric motors we would have 42.8 kW or 57.3 bhp peak power from the electric system. Over 600 bhp for an efficiency formula does not sound so bad if you have all wheel drive and high downforce aerodynamics.

The Toyota V8 engine btw is said to have 500 bhp with unlimited fuel supply probably 27% higher. A high efficiency Porsche would not look bad in comparison with a Rebellion running that engine, in fact it would run rings around such a competitor. Would it be enough to beat Audi? Difficult to say. I don't think they can do it in one year. So Audi is a relatively safe bet next year again.

[xpensive]

...
That would require just 1.7 bar intake pressure to get us the air needed for our fuel flow. It sounds awfully low to me.
...

Not at all, it's about there or thereabouts.

[WhiteBlue]

That would require just 1.7 bar intake pressure to get us the air needed for our fuel flow. It sounds awfully low to me....

Not at all, it's about there or thereabouts.

Yep, that is clear when you run the base case calculation with 10.000 rpm. But will they actually rev that high? As I said I have my doubts. Porsche will have Audi as their benchmark.

Their friend Baretzky is already working on another evolution of the turbo diesel engine which will not be initially handicapped by BOP measures. Audi will have just the same amount of energy per second which will be a lot more than they had this year. They had the air restricted and could not fully exploit their power potential do to excessive fuel tank limitation. Next year they are likely to bring an even more efficient engine and they will probably run without BoP handicap if they are clever. All they have to do is sandbag it until Le Mans is upon us.

[lpatterson]

Has anybody else here on the forum heard, that Martini & Rossi are supposedly going too come on board as the team sponsor.

[WhiteBlue]

http://www.pitpass.com/50638/Webber-mak ... LMP1-debut

The WEC regulations stipulate that manufacturers run hybrid vehicles in the top class for Le Mans Prototypes (LMP1). In developing the all-new LMP1 race car featuring a very efficient, high-performance hybrid drive, Porsche engineers face major challenges that can only be solved using innovative solutions. Therefore, the race car features a hybrid system that consists of a four-cylinder petrol engine with direct injection and two energy recuperation systems. The recovered energy is stored in a battery until retrieved by the driver. A powerful electric motor then provides additional drive to the front axle. However, the WEC rules limit the amount of fuel as well as the electrical energy, or so-called boost, available to the driver per lap. The development of such a highly-efficient drive will have positive influences on the development of production sports cars at Porsche.

So it is a four cylinder engine as I have always suspected.

[Holm86]

http://www.pitpass.com/50638/Webber-mak ... LMP1-debut

The WEC regulations stipulate that manufacturers run hybrid vehicles in the top class for Le Mans Prototypes (LMP1). In developing the all-new LMP1 race car featuring a very efficient, high-performance hybrid drive, Porsche engineers face major challenges that can only be solved using innovative solutions. Therefore, the race car features a hybrid system that consists of a four-cylinder petrol engine with direct injection and two energy recuperation systems. The recovered energy is stored in a battery until retrieved by the driver. A powerful electric motor then provides additional drive to the front axle. However, the WEC rules limit the amount of fuel as well as the electrical energy, or so-called boost, available to the driver per lap. The development of such a highly-efficient drive will have positive influences on the development of production sports cars at Porsche.

So it is a four cylinder engine as I have always suspected.

Good to see you back And yes you got that one right.

[marcush.]

It´s a V4 as I suggested looong ago

[marcush.]

so after my initial suggestion of a flat 4 I started to think of v8 cut in half -the other way round...Porsche have a tradition of taking things already available off the shelf and creating something new out of the same...(flat 12 from flat 6s ,v12 from v6 ,etc etc..)

and an inline 4 doesn`t ...not much speakin in favour of a 4 cylinder package ...apart from being able to cut your existing v8 longitutinally ... but you could as well chop of 2 cylinders each side and make it a v4 ...right? that would open a lot of package space ....

th.

[Holm86]

Are you sure its a V4??? Looks more like an inline or only the one half of a boxer engine in this video :

[youtube]http://www.youtube.com/watch?v=l73GShcEFa0[/youtube]

Looks a bit to short to be the head of a in-line 4. But I cant see the other bank is its a V engine.?

Edit: sorry its the one cylinder configuration he was talking about at the start. It only has one exhaust outlet.

[langwadt]

...
That would require just 1.7 bar intake pressure to get us the air needed for our fuel flow. It sounds awfully low to me.
...

Not at all, it's about there or thereabouts.

the ambient temperature is might be 25'C, the charge temperature will be higher