[WEC] Porsche Prototype Discussion

[cokata]

Do you know what is lift and coast? Also i am very much aware that the hybrid system is part of the car. The point that i was trying to get across is that everyone is free to choose where they use their boost, and Porsche choose to use a huge chunk of it in S2, while audi spread it more evenly, and that meant that despite the fact that they are 4MJ down in total, in S1 they are boosting about as much as Porsche. That is the reason that they had a much better S1 time.

Remember that time in the beginning of the race when Lotterer just left the Porsches for dead on the start/finish straight. There it is just a straight ICE vs ICE battle and despite the fact that Audi had a bit more DF they were much quicker.

http://cdn.makeagif.com/media/7-02-2015/MMYsGA.gif
http://cdn.makeagif.com/media/7-02-2015/-iG6Yo.gif
http://cdn.makeagif.com/media/7-02-2015/l43SAY.gif

And here notice how the speeds develop along the straight with the audi matching and surpassing the Porsche by the time when they reach the middle of the straight
http://cdn.makeagif.com/media/7-02-2015/Vq1mZ-.gif

[Spyderman]

Originally Posted by cokata

Do you know what is lift and coast?

No, I'm an idiot. I don't understand why you even bother explaining yourself to an imbecile.

Originally Posted by cokata

Also i am very much aware that the hybrid system is part of the car. The point that i was trying to get across is that everyone is free to choose where they use their boost, and Porsche choose to use a huge chunk of it in S2, while audi spread it more evenly, and that meant that despite the fact that they are 4MJ down in total, in S1 they are boosting about as much as Porsche. That is the reason that they had a much better S1 time.

You may be aware of the fact the the hybrid system is part of the car, but your original argument then makes even less sense. How can you argue in good faith, that one car would be quicker than the other if one car has a major part missing?
Your explanation above only serves to support my argument: The Porsche accelerates quicker on the main straight and therefore easily reaches its top speed (or close to it) on almost every "normal"racing lap.

Originally Posted by cokata

Remember that time in the beginning of the race when Lotterer just left the Porsches for dead on the start/finish straight. There it is just a straight ICE vs ICE battle and despite the fact that Audi had a bit more DF they were much quicker.

You cant take one isolated incident and draw all your conclusions. You don't know what was going on in the Porsche.
Also - I never made the claim that Porsche's ICE alone is competitive, what I claimed was that with the acceleration advantage the current ICE it has is sufficient.
Are you seriously suggesting that I would argue that a tiny 2L 4 cylinder turbo gasoline would be competitive against a great big (in proportion) turbo diesel on its own? I'm not 4 years old. Try and understand that the Porsche is a entire "concept". Porsche wanted (from the start) to be in the maximum MJ class. They knew that in order to do that they needed to go with a small, light, and frugal ICE. Thus the current ICE. If you change the ICE, then you have to change the concept. I don't see them doing that unless regulations force them in that direction.
Audi had a chance to take on Porsche over one lap in qualifying. They refused to do it. You can read what you choose to read into that. I know what my conclusions are.

http://cdn.makeagif.com/media/7-02-2015/MMYsGA.gif
http://cdn.makeagif.com/media/7-02-2015/-iG6Yo.gif
http://cdn.makeagif.com/media/7-02-2015/l43SAY.gif

Originally Posted by cokata

And here notice how the speeds develop along the straight with the Audi matching and surpassing the Porsche by the time when they reach the middle of the straight
http://cdn.makeagif.com/media/7-02-2015/Vq1mZ-.gif

Proof that there is no earlier lift and coast by Audi. Also proof that Porsche accelerates faster.
Go back and read my original post (that you are taking exception to).

[Spyderman]

Also - Have you seen the data I posted on sector times? The overall average difference between #7 and #19 was less that one tenth of a second. That's how tight it was.

[Spyderman]

Explanation of ICE choice:
"Our choice of combustion engine was born out of an efficiency-optimised approach: a highly compact, turbocharged four-cylinder 2-litre engine with direct fuel injection. The combustion engine is supported by two energy recuperation systems". - Porsche

[GasperG]

I think it should be obvious that regulation alone dictate ICE power in different MJ class, on paper Audi is running with ~5% more power from the engine, IF (big IF) diesel engine efficiency is only 7.7% better than petrol.

IMO, Porsche has a job to on the aero efficiency for next year if they do it properly they will stay dominant, with a margin.

[Spyderman]

Originally Posted by GasperG

I think it should be obvious that regulation alone dictate ICE power in different MJ class, on paper Audi is running with ~5% more power from the engine, IF (big IF) diesel engine efficiency is only 7.7% better than petrol.

IMO, Porsche has a job to on the aero efficiency for next year if they do it properly they will stay dominant, with a margin.

Agreed, but they are still looking for a Senior Aero Performance Engineer
There are other areas that need improvement too.

[cokata]

Originally Posted by Spyderman

Just some data analysis to illustrate the advantage of Porsche's acceleration:

Audi # 7 did 35 laps equal or above 330Km/h
Audi # 8 did 62 laps equal or above 330Km/h
Audi # 9 did 53 laps equal or above 330Km/h
Porsche #17 did 219 laps equal or above 330Km/h
Porsche #18 did 199 laps equal or above 330Km/h
Porsche #19 did 256 laps equal or above 330Km/h

You were trying to point out that Porsche has a better acceleration, but the speed trap is at the end of the straight and the audi was going quicker there barring lift and coast.

Originally Posted by Spyderman

This has nothing to do with lift and coast. Audi often braked later than the Porsche's. It has to do with acceleration. Porsche are able to quickly hit their top speed (or close to it) on almost every lap, even if they were hindered by traffic.

I asked you if you knew what lift and coast not because i think you are an imbecile, but because you were trying to make a connection between the amount of lift and coast and the length of the braking distance (pressing on the brake pedal)


In a quick recap (i'm not trying to change your opinion or something like that, i'm just giving out mine just like you did) on the exit of a corner the Porsche has a massive advantage due to it's amazing hybrid system, by the midpoint of the straight though the Audi (now both cars are using just the ICE to accelerate) is matching and even exceeding the speed of the Porsche due to it's superior engine power. And by the end of the straight with already a 5+ kph advantage on the Porsche the Audi has to lift of the thottle sooner resulting in often poorer speed trap result because it is at the very end of the straight.

Peace.

[Spyderman]

Originally Posted by cokata

You were trying to point out that Porsche has a better acceleration, but the speed trap is at the end of the straight the audi was going quicker.

Audi hit the highest top speed. How would they be able to do that if they were lifting and coasting before the speed trap?

Looking at laps equal to and under 3:25.0 ("normal" racing laps) one finds the following:

Audi # 7 top speed ranges from 292.4 Km/h all the way to 341.3 km/h
Porsche # 19 top speed ranges from 304.7 km/h to 340.2 km/h.

As you can see the range is quite similar. What really changes is when you look at the amount of laps that they do equal or below 315 km/h (25 km/h below their maximum speed):

Audi # 7 did 49 laps between 292.4 Km/h and 315 km/h
Porsche #19 did 4 laps between 304.7 and 315 km/h.

If we look at the laps with speeds between 316 and their respective top speeds , this is what we find:

Audi# 7 did 219 laps
Porsche #19 did 262 laps.

Given the data, what we can conclude is that neither Audi or Porsche had difficulties hitting close to their top speeds. What we see is that Audi was far more likely (12 times) to do laps that were off their top speed range.

Now do you understand what I was getting at?

[brownninja97]

Originally Posted by Dario911

That's the car will bring the 17th overall victory in Porsche hands. Looks great, and it runs great too: it's a Porsche LMP1, it cannot be differently.

can you do more predictions please.

[hcl123]

Originally Posted by Spyderman

Your explanation above only serves to support my argument: The Porsche accelerates quicker on the main straight and therefore easily reaches its top speed (or close to it) on almost every "normal"racing lap.

You are arguing ICE... but that exceedingly fast acceleration is due the front electric motor -> not all motors are the same, and then the diffs in MJ classes is only a question of time... no.

Of course the higher the initial momentum (power density) the shorter the time to get to the top speed achievable. In short Porsche could have the same top speed with only the ICE, only it would take much more time, meaning the straight would have to be longer... and since those straights don't change distance, the effect could very well be the top speed at the end would be lower with only the ICE.

Originally Posted by Spyderman

Also - I never made the claim that Porsche's ICE alone is competitive, what I claimed was that with the acceleration advantage the current ICE it has is sufficient.
Are you seriously suggesting that I would argue that a tiny 2L 4 cylinder turbo gasoline would be competitive against a great big (in proportion) turbo diesel on its own? I'm not 4 years old. Try and understand that the Porsche is a entire "concept". Porsche wanted (from the start) to be in the maximum MJ class. They knew that in order to do that they needed to go with a small, light, and frugal ICE. Thus the current ICE. If you change the ICE, then you have to change the concept. I don't see them doing that unless regulations force them in that direction.

There is nothing frugal about Porsche ICE, its compact yes, but in F1 they extracted more than 1000hp from 1.5L of displacement. Of course fuel flows were immensely higher... and so also the RPM.

Its all about power density and fuel flows

Porsche 9000 rpm x 2L = 18K x 3BAR(turbo) = 54K litres of air per minute (at 14.7:1 air:fuel)
Audi 4500rpm x 4L = 18K x 3BAR(turbo) = 54K litres of air per minute(at 22:1 air:fuel)
Toyota 8500 x 3.7L = 31.45K litres of air per minute (14.7:1 air:fuel)

(values are not linear, extrapolated top boost pressure takes time to get to the max, and admission temperature is also a big factor)

So Porsche burns more fuel per minute and runs with more fuel MJ per lap than Audi... they have the same air breathing potential, but diesel needs ~49% more air for the same amount of fuel... so for Porsche small marvel, the efficiency of transfer of 'burning' energy to mechanical energy is quite lower than in a diesel( don't blame diesel).

Size is relative don't let it foul you... and also displacement... if they wanted to be 'frugal' on the fuel for the tech, the approach is kind of a success, but to be competitive that "tiny" engine runs most of the time(if not all the time) with considerably more RPM than Toyota as example (the theoretical 'air aspiration' potential of Toyota is not realized in practice, air density is lower(hotter) inside admission manifold than out, it needs an intercooler, but none thought of it for a NA yet))... so Porsche most likely can burn more fuel than even the bigger V8 of Toyota.

The problem with small displacement engines is the 'torque,' specially at lower RPM (to a point)... handicap that even Tubocharging can't hide ( improves torque a lot though)... Porsche all power train is marvellously well balance with the proper gear ratios for the hybrid power, but if all of a sudden we were to withdraw the hybrid parts, the one which would suffer considerably more would be Porsche... the same if we consider others matching exactly Porsche hybrid power ( the other side of the equation).

yet there is nothing 'frugal' about that engine( perhaps a V6 on the 'torquy inclination' could be much better... like Nissan.. ).

[hcl123]

Originally Posted by cokata

You were trying to point out that Porsche has a better acceleration, but the speed trap is at the end of the straight and the audi was going quicker there barring lift and coast.

There is some but not much. I think Audi drivers are of used to it, but when they need to make a dash for a corner for a pass they do it. It has to do with a strategy to save fuel, but where they save the most fuel is in 6th and 7th gears, specially the 7th, where the engine barely passes the 4000 rpm (yet enough to top speeds above 340kmh).

If fuel energy were the same, 4500 rpm or more in 7th gear would be possible... and top speed your guess lol

[Spyderman]

Originally Posted by hcl123

You are arguing ICE... but that exceedingly fast acceleration is due the front electric motor -> not all motors are the same, and then the diffs in MJ classes is only a question of time... no.

Of course the higher the initial momentum (power density) the shorter the time to get to the top speed achievable. In short Porsche could have the same top speed with only the ICE, only it would take much more time, meaning the straight would have to be longer... and since those straights don't change distance, the effect could very well be the top speed at the end would be lower with only the ICE.



There is nothing frugal about Porsche ICE, its compact yes, but in F1 they extracted more than 1000hp from 1.5L of displacement. Of course fuel flows were immensely higher... and so also the RPM.

Its all about power density and fuel flows

Porsche 9000 rpm x 2L = 18K x 3BAR(turbo) = 54K litres of air per minute (at 14.7:1 air:fuel)
Audi 4500rpm x 4L = 18K x 3BAR(turbo) = 54K litres of air per minute(at 22:1 air:fuel)
Toyota 8500 x 3.7L = 31.45K litres of air per minute (14.7:1 air:fuel)

(values are not linear, extrapolated top boost pressure takes time to get to the max, and admission temperature is also a big factor)

So Porsche burns more fuel per minute and runs with more fuel MJ per lap than Audi... they have the same air breathing potential, but diesel needs ~49% more air for the same amount of fuel... so for Porsche small marvel, the efficiency of transfer of 'burning' energy to mechanical energy is quite lower than in a diesel( don't blame diesel).

Size is relative don't let it foul you... and also displacement... if they wanted to be 'frugal' on the fuel for the tech, the approach is kind of a success, but to be competitive that "tiny" engine runs most of the time(if not all the time) with considerably more RPM than Toyota as example (the theoretical 'air aspiration' potential of Toyota is not realized in practice, air density is lower(hotter) inside admission manifold than out, it needs an intercooler, but none thought of it for a NA yet))... so Porsche most likely can burn more fuel than even the bigger V8 of Toyota.

The problem with small displacement engines is the 'torque,' specially at lower RPM (to a point)... handicap that even Tubocharging can't hide ( improves torque a lot though)... Porsche all power train is marvellously well balance with the proper gear ratios for the hybrid power, but if all of a sudden we were to withdraw the hybrid parts, the one which would suffer considerably more would be Porsche... the same if we consider others matching exactly Porsche hybrid power ( the other side of the equation).

yet there is nothing 'frugal' about that engine( perhaps a V6 on the 'torquy inclination' could be much better... like Nissan.. ).

N.B. DIESELS ARE NOT AN OPTION FOR PORSCHE.
No one is saying the the small Porsche engine is more frugal than the diesels. What is being claimed is that the current engine is frugal for a petrol turbo engine.

The V4 was chosen due to stiffness, size and efficiency. I doubt that they will move away from this overall concept unless forced to by rules and /or the competition. If however they are forced to change their ICE , then expect to see a change in the overall concept of the car (and in the end this is what is important).

[Richard C]

Thanks for editing out the large GIFs. This page was blow up my older iPad!

Richard

[hcl123]

Originally Posted by Spyderman

N.B. DIESELS ARE NOT AN OPTION FOR PORSCHE.
No one is saying the the small Porsche engine is more frugal than the diesels. What is being claimed is that the current engine is frugal for a petrol turbo engine.

The V4 was chosen due to stiffness, size and efficiency. I doubt that they will move away from this overall concept unless forced to by rules and /or the competition. If however they are forced to change their ICE , then expect to see a change in the overall concept of the car (and in the end this is what is important).

I'm saying the same thing... a possible (eventual) change of engine by Porsche depends on what the competition can do (namely Toyota.. Nissan i think they have to re-engineer a lot to be competitive). While they maintain their huge advantage on electric motors i believe they will not change(its more than just the 8 MJ).

The lack of 'torque' of the engine(not potential 'hp' which is a question of more rpm) is more than well compensated by the torque of the electric motor.

And then there is the position of the VAG... i think they maintain Porsche and Audi essentially because one is developing diesel tech and the other petrol tech... so called fast diesels, and small compact powerful 'downsized' turbo petrol engines, all goes hand in hand with the current road car trends... so there is a 'market trend' also in Porsche choice.

What begs the question since its all the same group, is if they will allow Audi to use the electric tech of Porsche ( with 6 MJ last year Porsche already had this great acceleration potential, and most likely Audi will jump to 6 MJ next year...).

[brownninja97]

Originally Posted by hcl123

[B

What begs the question since its all the same group, is if they will allow Audi to use the electric tech of Porsche ( with 6 MJ last year Porsche already had this great acceleration potential, and most likely Audi will jump to 6 MJ next year...).

I think it surprisingly might be possible, well even if they dont get permission then some specs might get copied. My thoughts is that there are some sneaky employees swapping information which because pretty obvious after the fancy endplates which will likely get banned at some point.

[bobec]

I wonder why Porsche don't use a boxer engine. A flat-4 maybe (or even a flat-6 if they need more power). It's what Porsche is know for, and the sound is nice and distinct.

[chernaudi]

The diffuser types used at the rear of modern LMP1s could be a consideration--Porsche 956s and 962s didn't have the best of diffuser tunnel designs due to the boxer engine.

Rear diffuser tunnels on modern LMP1s might not be as aggressive, but I'd bet that the cylinder heads on a boxer engine would still get in the way.

That, and as early as 1998 (if not earlier) Porsche decided that the stock-block based boxer engine was starting to get past it's best by date. Hence the V10 from the never raced LMP900 car and the V8 from the RS Spyder.

[Starfish Primer]

There was also a late effort to use a 928 based V8 twin turbo in the 962. I think it was Kremer but I´m not fully sure.

[Pole2Win]

Originally Posted by chernaudi

The diffuser types used at the rear of modern LMP1s could be a consideration--Porsche 956s and 962s didn't have the best of diffuser tunnel designs due to the boxer engine.

Rear diffuser tunnels on modern LMP1s might not be as aggressive, but I'd bet that the cylinder heads on a boxer engine would still get in the way.

That, and as early as 1998 (if not earlier) Porsche decided that the stock-block based boxer engine was starting to get past it's best by date. Hence the V10 from the never raced LMP900 car and the V8 from the RS Spyder.

From what I remember, in 1998 Porsche won but the Mercedes were the fastest cars...

[Richard C]

Given the use of tunnels and diffusers, flat engines are a non optimal choice. Nobody would willingly use one given the current regulations. A winning car is going to use a bespoke design that leaves no performance on the table unused. V engines are compact and structurally stiff. That is why they are used.

Richard

(I think this is my 1000th post. Thanks Ten Tenths for being a great place to visit! )

[hcl123]

Not only that... engines have become much more complex in the intake and exhaust designs, with backpressure prevention features, intercoolers, wastegates, ERS-Hs etc , they need room... just to see the size of those F1 exhaust manifolds is mind boggling... a boxer i suspect would be just too close to the flat bottom to allow that creativity.

[Pandamasque]

Originally Posted by bobec

...and the sound is nice and distinct.

Flat-4 will sound more or less exactly like a V4 (or even i4) provided the exhaust system is traditional. I'm not an engineer, but I have a good ear for engine sounds. So I was first surprised to hear that Subaru lost its trademark flat-4 sound with newer cars (even BRZ and STi models), and then I was surprised to learn that it really had nothing to do with the engine being a boxer.
https://youtu.be/PGykinGlPno?t=1m9s

[Spyderman]

Flat 4 is not likely to happen. The current V4 is a very wide V4 ( it is thought to be almost 180 degrees). Porsche looked at all possibilities when first developing this engine. They choose what they consider to be the most appropriate for this concept.
Porsche are looking at downsizing most of their road going engines, so it would be a little incongruous for them to move in the opposite direction with their motorsport program (given the ties that they like to make between their motorsport program and their road going technologies).

It is important to remember that the Board approval of the LMP1 project was in part based on the concept of a small turbo engine with a powerful EGU.

I simply don't see them straying too far from this unless they absolutely have to.

[hcl123]

If i'm not mistaken the V4 of Porsche is 90º (not primarily balanced 720/4 =180->boxer) and normal config with exhaust outside of V.(needs proper counterbalance weights in the crankshaft)

Who is the widest is Audi with a 120º V and exhaust top inside of V.(primarily balanced 720/6=120)

[Richard C]

I can't find anything online that confirms the V angle. Porsche's own illustrations show what looks to be a 90 deg engine. However, Porsche has shown some level of misdirection in these illustrations such as the suspension design. So they could be doing the same with the engine, but I actually don't think they are.

The engine illustrations show exhaust ports on the outside of the V and the associated exhaust routing up and over the heads to the turbo. Photos of the real engine show enough detail to show the illustrations are correct regarding turbo and associated exhaust locations.

Typically wide V engines are designed to lower center of gravity, but likely at the expense of compactness and rigidity. As mentioned flat or 180 V engines also result in exhaust issues. You have to raise the crank height (not good) to be able to route exhaust. Overall, I would be shocked if it wasn't a 90 deg V and really shocked if it was anything close to a 120 V, but never say never.

Richard