LMP2 Manufacturers and Engine Suppliers

[blankfile]

They won't get passed on the straights, the lmp1's just have that much acceleration

[chernaudi]

Not when Audi and Porsche last year were barely getting above 200mph. No amount of insane acceleration can make up for a near 20mph deficit in top speed.

Another reason the sonic air restrictors should come back in LMP1.

[canaglia]

Originally Posted by chernaudi

Not when Audi and Porsche last year were barely getting above 200mph. No amount of insane acceleration can make up for a near 20mph deficit in top speed.

Another reason the sonic air restrictors should come back in LMP1.

air restrictors could fit well for lmp1-l engines, but fuel-flow based engines are pretty good for work lmp1-h. At the end, surely will be gibson lmp2 engine to be detuned

[TF110]

Originally Posted by chernaudi

Not when Audi and Porsche last year were barely getting above 200mph. No amount of insane acceleration can make up for a near 20mph deficit in top speed.

Another reason the sonic air restrictors should come back in LMP1.

Nissan was doing 345kmh but they weren't passing lmp2 cars who were quicker over the lap. The p1's will be gone by the time the p2's can get their top speeds reached anyway. Their hitting 300kmh in about 6 seconds.

[canaglia]

agree, gibson engine revs over 9000rpm, high-end power.
lmp2 will get max speed when lmp1 achieved their eons before...

[chernaudi]

The Gibson V8 is supposed to make over 600bhp, as per the ACO's request for the revised LMP2 regs. The LMP1 fuel flow limiters force lift and coast, which means that at the end of the straights, the LMP1s will be coasting either off or part throttle while the LMP2s can go full pelt until the braking zone.

At LM in 2009, the diesel acceleration didn't help Audi, who could out accelerate about anything, but were getting run down by the Aston Martin Lolas that had less drag and more top end power by the end of the straights. Even Peugeot had trouble out-dragging the Aston Lolas on top end.

This might not be a huge problem at LM for one reason or another, but I can see LMP1s and LMP2s crashing into each other because of the LMP2s having more power at the end of the straights, especially in the sprint races, and especially with the pro-am drivers in the LMP2s.

But believe me, if we see enough LMP1/LMP2 accidents before or during LM, the Gibson V8s might very well get pegged back to preserve the LMP1's ability to pass them down the straights.

[Akrapovic]

The claim that a P2 will never pass a P1 due to the P1s acceleration giving it a headstart makes the assumption that they both start at the same point on the straight and the P1 accelerates off into the distance. If a P2 is on the straight first and a P1 passes it under acceleration a significant distance into the straight then there's no reason to assume the P1 will always pull enough of a gap to make the situation impossible.

tl:dr - even basic physics is more complex than scenario presented here.

[chernaudi]

And that's the problem. You're not always gonna encounter LMP1s and LMP2s crossing paths at the same time at the beginning of a straightaway. And even then, if it's a short straight, def. advantage to the LMP1. Medium length straight, probably still advantage to the LMP1 if it got to the LMP2 early enough. Long straight? If we look at Le Mans, if the LMP2 can catch up to the LMP1 once the hybrid system peters out and they're stuck coasting at 200mph and the LMP2 gains a 15-20mph advantage, we'd better hope that the LMP1 has an insanely big lead by then.

Let alone overtaking part way down a straightaway or near the end of it. That's where, be it Le Mans or any other track, especially the start/stop populated Tilkedromes, I think we're gonna have problems with LMP1s and LMP2s colliding because of lift and coast for the LMP1s vs the sonic air restrictor allowing a constant 600 or so bhp out of the LMP2's Gibson V8s.

We'll probably have to wait for the WEC Prologue at Monza to get insight to see if this will be a potential problem or not, but I can see potential for it to be a significant issue.

[TF110]

The lmp1-h's have more than enough acceleration and downforce to pull a gap to lmp2's that by the time they reach their top speed the p1's should be done with the straight. There is no reduction in fuel flow this year, so you also have to take into account the gains the p1's will make in engine efficiency.

I feel air restrictors are not the way to go for equality in lmp1. That leaves too many variables. Giving everyone the same amount of fuel is a set formula. That leaves it up to the teams to gain power through the engine and ers efficiency. With air restrictors, a team gets pegged back or forward and there's the possibility of sandbagging to fool the rule makers into giving you a break.

[Akrapovic]

Originally Posted by TF110

The lmp1-h's have more than enough acceleration and downforce to pull a gap to lmp2's that by the time they reach their top speed the p1's should be done with the straight. There is no reduction in fuel flow this year, so you also have to take into account the gains the p1's will make in engine efficiency.

If they both start at the same point, then yes. But racing doesn't work like that - they don't all line up at the start of Mulsanne and let the P1s accelerate off. A P2 could be on the straight for quite a while before the P1, and whilst the immense acceleration of the P1 will allow it to catch and pass it, there will be a point where the speeds of the classes flip round - a tipping point. If the P1 catches the P2 late on a straight then when they hit the flipping point, the P2 will be closer.

[chernaudi]

Also, the factory LMP1s are supposed to be taking a pretty big aero hit this year with the reduced rear diffuser exit height and increased height on the front diffuser lip. Granted, Toyota and Porsche are claiming that they're back to 2016 levels of downforce and aero balance, but the LMP2 new gen cars are built to the old LMP1 aero regs and are 100mm/4 inches longer on overall length.

[TF110]

Originally Posted by Akrapovic

If they both start at the same point, then yes. But racing doesn't work like that - they don't all line up at the start of Mulsanne and let the P1s accelerate off. A P2 could be on the straight for quite a while before the P1, and whilst the immense acceleration of the P1 will allow it to catch and pass it, there will be a point where the speeds of the classes flip round - a tipping point. If the P1 catches the P2 late on a straight then when they hit the flipping point, the P2 will be closer.

That's not a negative imo. There's only a couple straights long enough on the calendar that the high top speed will be a headache for lmp1's to pass lapped lmp2's. And every race has traffic, just because lower class cars have more power now doesn't mean it's a problem. But say it is, I think the ACO will step in if there are issues and then maybe they'll stop cutting p1's so drastically.

[chernaudi]

Or peg back the LMP2s? I don't think that 600+bhp is necessary for a pro-am prototype class. The GTE cars barely make 500bhp as it is. So taking away about 50 or so bhp from the Gibson V8s probably won't hurt too much.

[TF110]

I think they're going to be fine. They should leave the lmp1's alone and let them make their gains as is in terms of the fuel flow. The lmp2's won't make the downforce of the p1's even with this year's cut. I think by the time the new rules come around, the hybrid cars will be near the 3:17's like a couple seasons ago.

[carbsmith]

Air restrictors are completely obsolete in modern prototype racing and have been for a while. They were brought in during the 90s so that teams could use off the shelf Group C engines, stock blocks, etc. with radically different configurations on some degree of even ground instead of having to build new engines to save money. Aside from the Aston V12, basically no one has done that since the early 2000s. For the last few years of them every engine in the class was a purpose built engine right on the displacement limit, so the air restrictor did literally nothing but make the engines really inefficient with abnormal performance characteristics.

The only really bad thing about a fuel formula is that with modern technology it makes normally aspirated engines unappealing, but a normally aspirated engine last won Le Mans in 1999 anyways.


What makes lapped traffic difficult is when the cars have really different corner speeds but accelerate similarly for most or all of the straights, the LMP1s are still going to blitz an LMP2 on acceleration everywhere but the end of 1.5km+ straights and they should corner very similarly.

[Richard C]

Originally Posted by carbsmith

Air restrictors are completely obsolete in modern prototype racing and have been for a while. They were brought in during the 90s so that teams could use off the shelf Group C engines, stock blocks, etc. with radically different configurations on some degree of even ground instead of having to build new engines to save money. Aside from the Aston V12, basically no one has done that since the early 2000s. For the last few years of them every engine in the class was a purpose built engine right on the displacement limit, so the air restrictor did literally nothing but make the engines really inefficient with abnormal performance characteristics.

Thank you. There has been a constant drum beat in this forum for a return to sonic air restrictors in prototype racing. I think they are viewed through rose colored glasses with respect to their effectiveness and in which situations they can be made to obtain the desired results. IMHO, they can be engineered around if enough money is applied and probably only work in spec (no development allowed) or BoP (restrictors part of a larger effort to adjust performance) scenarios.

Richard

[chernaudi]

Well, consider this, the air restrictor is a $5-10 dollar piece of aluminum. The fuel flow meters cost about $2200 per unit if I remember correctly. Not to mention all the other widgets that make them work right. Not to mention that they can be "engineered around" too because they're not 100% accurate.

[Richard C]

Originally Posted by chernaudi

Well, consider this, the air restrictor is a $5-10 dollar piece of aluminum. The fuel flow meters cost about $2200 per unit if I remember correctly. Not to mention all the other widgets that make them work right. Not to mention that they can be "engineered around" too because they're not 100% accurate.

I know this is an LMP2 thread so it is slightly off topic, but here it goes!

That is fair comment on cost of the meters and the unsaid cost on ancillary items as well. However nothing is 100% accurate, nor expected to be. I would hazard a guess that the fuel flow system is "significantly" more accurate than a sonic restrictor especially when applied in various scenarios (i.e. engine configurations). Sonic restrictors are simple passive devices in which I am pretty sure the performance (i.e. accuracy) can only be expected to perform under a specific set of conditions. While the fuel flow system has fewer variables over a wide performance range. So, as best as I can tell, outside of the initial introduction in F1 (and drama with Red Bull pushing the envelope with respect to flow rates to make up for an underperforming Renault engine), and a single supplier (I think more than one exist now), talk about inaccuracy seems to have died away.

I suspect ultimately that the LMP1 manufacturers prefer the fuel flow over some type of air restriction because they know it's harder to game. Meaning it's not an area they have to try to spend in to find a way to cheat (or bend the rules if you like) and they know the other guy is in the same situation. While the FIA is involved in both F1 and LMP1 from a regulatory perspective, it's also interesting that both series use the same basic solution. It has to be more than just the ability to define single specs (and sensor homologations) for both series.

I always like to use the example of the Porsche flow rig that somehow was able to flow better than it should have. Fuel rigs used a simple spec physical flow restrictor. Similar concept to a sonic restrictor for air in that it can be engineered around (which Porsche did for the fuel rig).

IMHO... In a non-BoP prototype series with deep pocketed sponsors, those $5-10 restrictors would turn into large amount of dollars spent to get around them. It works in BoP series, because if you cheat around it, they just reduce the size of the restrictor in "your" car, or air flow is just one of many factors to dial back the speed. If it worked that well, it would be the only knob to turn up/down and they wouldn't have to be changing it so often in BoP series (such as GT racing). It can work in lower end series in which the players don't have the budgets to spend to engineer around it.

Richard

[Akrapovic]

There;s nothing but anecdotal evidence on the fuel flow meters, but IIRC they were massively out - far more than the air restrictors, or what was expected. There were stories of the factory teams buying batches of 20 of the flow meters and using the best set, which were giving a significant performance increase.

I'm not arguing air restrictors would be better, just mentioning that there were some shocking stories about how poor the accuracy was with the fuel flow meters, and the cost associated with that.

A good example of the limitations of air restrictors was in IMSA, where Audi handed a set to IMSA and pointed out they were legal, but gave massive performance boosts. IMSA asked Audi not to bring it, and they didn't, but to Audis surprise somehow Lambo got it and turned up with it.

[Richard C]

Originally Posted by Akrapovic

There;s nothing but anecdotal evidence on the fuel flow meters, but IIRC they were massively out - far more than the air restrictors, or what was expected. There were stories of the factory teams buying batches of 20 of the flow meters and using the best set, which were giving a significant performance increase.

My opinion is that nearly 100% of what information that floats around on this topic is anecdotal. Especially as most is negative opinions by those with an axe to grind. I have actually looked and had a hard time finding real quantifiable evidence around the "actual" accuracy of the sensors published by someone who didn't have a specific agenda (such as Red Bull Racing in F1).

If you look at the specs for the sensors the measurement accuracy is specified to be roughly +/- 0.25% to .5% (depending upon which part of the spec you look at). To me that is pretty darn good. You can find some scientific and product specific articles online that talk about similar accuracy in industrial settings for physical flow restrictors, but for static flow only. So I think sonic restrictors can be pretty accurate in a steady flow, but less so in dynamic flow conditions (which would be race conditions).

Now is a good time to point out that the two systems do two different things. One measures actual flow under "all" conditions, while the other limits maximum flow. And that if you are looking to do more than just limit maximum flow, you can't do that with the sonic restrictor. What happens below maximum flow is unknown and also likely not reliable in dynamic conditions. But if you are looking at just full throttle power only, they can be effective at times (ignoring for the moment attempts to defeat them).

Back to the flow sensors... There was one initial supplier (Gill) in which there were complaints. My best guess is that they were not initially working to the defined spec (probably too much variance from unit to unit). A second supplier (Sentronics) has since been added. I suspect that with the added competition the bar has been raised and overall quality, accuracy (and calibration) is better than at launch a few years ago. I have no idea if teams today prefer one supplier over the other.

There were discussions on this forum in which numbers as high as 3% error were reported, but I take those with a grain of salt. For example you had teams such as Red Bull who were modifying the sensors post calibration (and later claiming they didn't know they couldn't) and that may have been a contributing factor in initial accuracy. Red Bull was also using this information to justify them breaking the rules by not using sensor data to measure flow rate and rather decided to use a mathematical model based upon predicted injector flow rates, number of injector pulses, etc. Which IMHO is another can of worms with respect to accuracy.

Richard

[chernaudi]

Of course, how this talk on air restrictors vs fuel flow meters began was the LMP2 cars don't have to "lift and coast" like the LMP1s do at the end of the straights. This is in concert with the 150bhp power increase that LMP2s are getting this year.

I hope that it won't be a "problem", but it could be given the different ways that the 600 or so BHP is achieved in both LMP1 engines vs LMP2 engines.

[TF110]

So what lap times are we expecting at Le Mans? If they're close to 3:25, my hope is they speed lmp1 up instead of slow lmp2 down.

[chernaudi]

How fast were Rebellion in LMP1L last year? Probably looking at similar times or a couple of seconds slower.

[Mike E]

"The new regulations for LMP2 this year, coupled with developments with the tyres, have resulted in some impressive times set by the prototype runners earlier this week.

Back in 2016, the best lap time set by an LMP1 L class car was a 1:21.6, with the quickest LMP2 time being a 1:25.4. This year, the LMP2 runners have not only destroyed the best time set by their predecessors, but come to within a second of the fastest lap by LMP1 L.

The time set this year was a 1:22.4, with the majority of its gains coming in Sector 3 which features the long back straight. In that part of the track, the car in question gained over eight tenths on the 2016 LMP2."

http://www.dailysportscar.com/2017/0...-notebook.html

[silente]

I wrote an article some time ago, about some simulations i did with an 2017 LMP2 vehicle model.

You can find the results in this post in my Blog:

https://drracing.wordpress.com/2016/...ats-the-story/

You can also find a couple of videos here:

https://www.youtube.com/channel/UCm_...VlEe-N4cuPgv7g


The lap times i mentioned in my Blog are a bit outdated. My simulations show the following results as of today:

Silverstone: 1.45.8 (1.45.5 possible)
Monza: 1.36.45
Spa: 2.03.6

I have no data about a possible Le Mans configuration, but also with these "sprint" setup, the model shows top speed between 315 and 320 km/h at Paul Ricard on the mistral straight (308 in Monza).