2017 LMP1 front fenders

[dujedcv]

Can someone please explain the exact reason and the purpose of the enlarged frontal area of the front fenders on the 2017 Porsche 919 and the Audi R18?

As seen on the newly-surfaced photo of the stillborn 2017 Audi R18:
https://pbs.twimg.com/media/DBQdp3YXYAAkk6o.jpg

And the 2017 Porsche 919:
https://storage.googleapis.com/gtspirit ... brid-6.jpg

And for comparison, the 2016 919:
http://www.car-revs-daily.com/wp-conten ... rid-31.jpg

A comparison between the 2017 Porsche 919 and Toyota TS050:
https://pbs.twimg.com/media/C8MPuBIUAAAeePE.jpg:large

[godlameroso]

If the regulations don't mandate it, then I suppose bigger fenders means less space for the front wing, but also gives you more air flow control over the unsprung part of the car.

[wesley123]

I saw this post on Reddit, I'll drop my comments here;

A more efficient trailing edge is my best guess. With a wider front it can start the outward shape sooner, leaving more unobstructed space for the diffuser. This would be useful this year because the legality panels aren't mandatory anymore, which were an obstruction previously

Pre-2017 rules required bodywork in this area so manufacturers put panels in this area. These pose an obstruction for the exit flow. 2017 rules dont have this requirement anymore, thus airflow out of the diffuser is unobstructed.

So I think it is so they can bring the trailing edge of the fender further forward, maximizing exit area for the diffuser. This seems to be the goal on the 919 as they also have brought the sidepods as far back as possible

[roon]

The starting point of the trailing edge taper is still dictated by the width of the tire + the internal fender gap needed to accomodate steering angle. I think these pontoon fenders may have more to do with either yaw stability or lift reduction.

[rjsa]

I have been trying this on my MVRC challenge car and to be honest didn't see much difference. Now that's just trying to reduce bonnet/fender lift, and it did alleviate the low pressure hotspot downstream, but nothing really worth writing home about on the numbers.

I don't know what else it messes with downstream on the Porsche. And without the whole setup is really hard to say exactly where it matters.

[roon]

It seems like it would divert relatively more air around than the sides, and less over the top i.e. less potential for a low pressure over the top of the fender. The roundedness may help keep flow attached around the sides of the fenders through a variety of yaw angles and thus provide more consistent flow over the top of the front wing/diffuser and around the sides of the car.

[Sevach]

The low downforce Toyota is a bit more Porsche like.


Compared to



If you look at what Porsche was doing last year.

High downforce


Low Downforce


It seems like those boxy fenders reduce drag somehow.

[outsid3r]

It seems like those boxy fenders reduce drag somehow.

I think the reason behind it is simple(-ish) really... Boxy fenders separate most of the airflow horizontally (as if you have a vertical fin) while a ramp-like fenders separate airflow both horizontally and even more so vertically, creating more downforce (and more drag)

Edit: Please note that I don't even consider myself at a novice level when it comes to aerodynamics, so bear with me if my reasoning doesn't make sense at all

[rjsa]

The low downforce Toyota is a bit more Porsche like.
https://cdn-5.motorsport.com/images/mgl ... in-yuj.jpg

Compared to
https://cdn-5.motorsport.com/images/mgl ... ui-kob.jpg


If you look at what Porsche was doing last year.

High downforce
http://www.car-revs-daily.com/wp-conten ... rid-31.jpg

Low Downforce
http://www.infomotor.com.br/site/wp-con ... 80x800.jpg

It seems like those boxy fenders reduce drag somehow.

What I see on both size is a 50~100mm difference on the bonnets trailing edge, what means that's how deeper the front diffusers are.

Now if you look at the 2017 & 2016 Porsche:



You'll see they got rid of the very pronounced venturi formed between the nose and fenders.

[Sevach]

It seems like those boxy fenders reduce drag somehow.

I think the reason behind it is simple(-ish) really... Boxy fenders separate most of the airflow horizontally (as if you have a vertical fin) while a ramp-like fenders separate airflow both horizontally and even more so vertically, creating more downforce (and more drag)

Edit: Please note that I don't even consider myself at a novice level when it comes to aerodynamics, so bear with me if my reasoning doesn't make sense at all

I agree, the low downforce versions seem to direct air towards the flank of the car while the high downforce seems more minimalistic with air going inside and over it.

[Sevach]

The low downforce Toyota is a bit more Porsche like.
https://cdn-5.motorsport.com/images/mgl ... in-yuj.jpg

Compared to
https://cdn-5.motorsport.com/images/mgl ... ui-kob.jpg


If you look at what Porsche was doing last year.

High downforce
http://www.car-revs-daily.com/wp-conten ... rid-31.jpg

Low Downforce
http://www.infomotor.com.br/site/wp-con ... 80x800.jpg

It seems like those boxy fenders reduce drag somehow.

What I see on both size is a 50~100mm difference on the bonnets trailing edge, what means that's how deeper the front diffusers are.

Now if you look at the 2017 & 2016 Porsche:
https://storage.googleapis.com/gtspirit ... brid-6.jpg
http://www.car-revs-daily.com/wp-conten ... rid-31.jpg

You'll see they got rid of the very pronounced venturi formed between the nose and fenders.

So improved front diffuser efficiency while also reducing drag? That's what i'm getting.

[Sevach]

Porsche fenders got a lot smaller, and rounder, after Le Mans.

[Cold Fussion]

That's a pretty radical change.

[johnny comelately]

Great to find this subject as when the Porsche 919 first came out (2014/15) it looked like blunt force trauma to the victim air and after reading the posts i'm still not sure, could the lighting apparatus needs be some of the answer?

[sandrosm]

Great to find this subject as when the Porsche 919 first came out (2014/15) it looked like blunt force trauma to the victim air and after reading the posts i'm still not sure, could the lighting apparatus needs be some of the answer?
https://upload.wikimedia.org/wikipedia/ ... rid_20.jpg

The upright fenders have the main function of diverging the air to side instead of going over the top of the mandated big extracting holes over the wheels creating more downforce although with a poor lift to drag ratio. It's generally a less draggy solution and it actually makes sense. To understand what I'm saying, here is a photo of an early 2014 Dome S103 windtunnel prototype model that took this concept to the extreme.


In the final version it was not as pronounced, though:



(It was not very successful but it looked amazing )