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Pete Lyons' fantastic Can-Am Cars in Detail:
March/April 2013
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All news content copyright Michael J. Fuller, unless otherwise noted
2012 Audi R184.25.13

>>Of course everyone knows the current regulations  (ACO2004) limits the rear overhang dimension to 750 mm.  And Audi's R18 is designed taking into account that maximum dimension.  But with the rear wing out to 750 mm, Audi had offset the engine cover bodywork a few inches forward such that the bodywork and the rear wing weren't on the same plane at 750 mm, creating a staggered trailing edge.  And with the bodywork so follows the diffuser, per the regulations.
Audi R18 LM, Monza testing April 2013So Audi has been testing at Monza with their Le Mans bodywork.  The primary feature of note is that Audi has extended the rear bodywork out to the 750 mm maximum.  That means the engine cover is a whopping ~138 mm longer (roughly 5.4").  I suppose that makes it a “long tail.”  I guess it's all relative.
1988 WM P88 Peugeot
And with my grumpy pants firmly on, here are some REAL long tails.  I feel bad for today's generation...

WM Peugeot P88 (1988)
Porsche 956 Long Tail, Le Mans 1986Porsche 956 Long Tail (1986)
1970 Porsche 917 Long TailAnd the ultimate...

Porsche 917 Long Tail (1970)

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Audi R18, Silverstone WEC, 20134.21.13

>>A rumor began circulating at Silverstone last week that Audi was utilizing a blown diffuser aero solution.  The source of this rumor turned out to be none other than Toyota, so it came with the credence of the one outfit who's probably looked hardest at the Audi but that also had a working knowledge of what could and couldn't be done within the regulations given their own LMP1 design and build (and usually suggests they themselves are contemplating the same).  

Now, the idea to do a blown diffuser has been kicked around for some time, the problem is the regulations limit the openings into the underfloor.  Looking at that governing document, Article 3.5 states that the only openings allowed in the floor are for the air jack,  ride height sensors, a maintenance hatch, the fuel overflow pipe, as well as the normal openings for tire clearance.  So for all the potential desire to utilize the aerodynamic benefit of an activated diffuser (and of course there are some draw backs as well), right out of the gate there's that one stumbling block about how to even go about it.

The rumor was pretty specific and mentioned the possibility of blowing the exhaust into the wheel well.  That's interesting...But the first obstacle for Audi was the single exhaust layout they have for their single turbo.  And over the course of the Silverstone race weekend confirmation came (via Race Car Engineering's man on the scene Andrew Cotton) that Audi had actually split their exhaust into two...

When you're on the back end of a known change without an obvious reason, usually there's a primary driver upstream some where.  A little more prodding and an admission that Audi were doing something aerodynamic with the exhaust came spilling out and Toyota's suspicion was right after all (Audi sources wouldn't tell Cotton where they poked out of the car only to say it, “helps with the air behind the car, reducing drag.”).

But first things first, what about the effective mass-flow from the turbo diesel exhaust pipe, surely there's not enough velocity to the exhaust after its tour of the exhaust impeller to do anything worth while?  Or, at least that had been the thought for some time.  But sources told me that apparently,  “...there's enough.”  

So, with it established that there is enough mass flow energy from the diesel exhaust to use it for an aerodynamic purpose but that you can't directly plumb the diffuser, so what can you do with it?  A little more reading of the regulations took me back to the allowed openings and what Toyota was saying, wheel wells.  The thought then fixed on, “...minimum gaps necessary for wheel and suspension part movements.”  If you can't add any new holes, why couldn't you use any legal existing ones?  For instance, could the exhaust be fired out the openings in the floor for wheel clearance?  How could that work?  What about via the Coanda effect?  Was it possible to wick the exhaust stream up into the diffuser from the wheel well openings and influence the diffuser that way?  

That might be overstepping the possibilities too much and for now I don't think that's what Audi is doing.  I get the idea that they're doing something more pedestrian such as using the exhaust to fill in behind the rear wheel wake.  This is mainly based on what sources told Cotton.  I have confirmed that the exhaust is in close proximity to the rear tire and the comment was made that for now the exhaust heat isn't having any effect on the tires.  But this only confirms the general area where the exhaust is going, not what's being done with it.

At Sebring this year it was observed throughout the weekend that the two Audis had distinctly different exhaust notes.  When I asked, in retrospect, if the new exhaust layout had been on the car as far back as Sebring I did receive confirmation that yes it was; the way the exhausts are plumbed and where they exit the car imparts a much more aggressive engine note.  So Audi had previously race tested the new layout well prior to Silverstone.  

On a related note, it was pointed out that Audi's fuel consumption strategy was drastically different at Silverstone this year as compared to last year.  Compared to last year, Audi's consumption increased a substantial percentage, 15%+.  And with the rumors circulating about an exhaust activated diffuser, and with the knowledge of how their use in F1 led to higher fuel consumption (and the FIA banning those systems on those grounds), it was assumed that this was another indicator of what Audi was up to.  Remember, F1 teams ran special fuel maps that would dump fuel into the exhaust in off throttle moments in order to keep exhaust flow velocities up given the aerodynamic benefits.  But I've inquired along those lines and have been told that you can't simply burn additional diesel fuel in the exhaust system to keep off-throttle mass flow up as it has a ruinous effect on the exhaust impeller, not to mention the difficulty of igniting diesel fuel.  So let's stress this:  signs of increased fuel consumption by the R18 relative to last year is NOT indirect evidence of a blown diffuser.  The indirect evidence of aero manipulation utilizing the R18's exhaust is what's been shown above, the increased fuel consumption another matter entirely.

This further leads me to think that Audi aren't directly activating (via something fancy like Coanda, if it's even possible) the diffuser given that limitation and are instead concentrating on less sensitive areas.  

So, now you know what to look for, or at very least where to poke your head, pictures please!

Dome S102.5 wind tunnel model March 20134.9.13

>>Dome's been quiet as of late but a few images have landed on a Japanese language blog.  These appear to show the existing S102.5 wind tunnel model with developments intended for the S103.  Back in February Dome indicated that they would be in the wind tunnel with a 2014-compliant model by mid-March and be in a position to reveal images by (perhaps) May some time.  The shot here (substantially enlarged) shows nothing particularly new but for a new long endplate (arrow) that doesn't connect to the rear fender (per S102.5)...
Lotus T128 LMP2 Paul Ricard Test March 2013>>Antonio Pannullo has some really nice posters available.

Lotus T128 LMP2 Paul Ricard Test March 20133.29.13

>>Responding to the pressure to produce something of the new Lotus T128, here are a few quick images with some yellow stickies on them...

(1) Rear brake ducts (which we've just been able to make out in that image Lotus released in August last year of their wind tunnel model).

(2) More than likely a cooling duct for the LED headlights.

Of note will be the 2014 monocoque (slightly larger due to required vision templates) and subsequently altered cockpit position.

Lotus has opted to go with the open/slotted front splitter.  

While this has elements of a 2014 car in place (tub), I can't be certain it meets all the 2014 criteria given the 2013 regulations.  For instance, I can't be sure if we're looking at a 1900 mm wide car.  I'd have some doubts Lotus would run a 2000 mm wide (2013 legal) car and then chuck or modify those items (suspension, bodywork) less than a year later to run to the (between) 1900 and 1800 mm new maximum width. But the car above does appear to be running to 2013 rear wing width regulations (1600 mm wide) as the  2014 difference between the width of the wing and overall car width would be no more than 50 mm each side (1800 mm wide rear wing, 1900 mm wide car if drawn to max dimension).  The difference above looks a lot larger than that and closer to 2013 offsets (around 200 mm each side, without wing extensions of course).  So based on that I'd have to say that indeed the car is running to 2013 rear wing width rules at very least (1600 mm), and perhaps 2014 bodywork rules, thus ~1900 mm width, as it just doesn't make sense to run bodywork, etc. eligible for only one year and then have to figure a way to make 2" (50 mm) each side disappear.
Lotus T128 LMP2 Paul Ricard Test March 2013Noticed this gap on the engine cover's trailing edge, at first I wasn't sure what to make of it.  My gut reaction is that it's simply a stick on/bolt on camber change bit for the trailing edge, not too dissimilar to this item on the HPD ARX-01e LMP.  Here's another shot showing that the opening is slotted, but for now I don't think it's that significant (I don't think it's an air passage of any kind.  For now.).


2013 Audi R18 E-tron Quattro3.16.13

>>The mystery surrounding Audi's new hybrid engine system gets a bit has been verified that my speculation was correct inasmuch as yes, the now-you-see-it-now-you-don't bulge (1) in the engine cover is related to a new hybrid engine system that Audi has been running in testing.  It was the source of that odd engine note everyone heard out of the Audi in testing at Abu Dhabi.  

As I mentioned back on March 9 (see below), the FIA has weighed in and as a result the system has actually been effectively banned.  And it sound as though it won' t necessarily be eligible next year.  While I would suspect at this point Audi and the FIA would be attempting to work this out, I'm being told as I write this that this is it and the system will not be raced at all.  Though it's hard to imagine Audi would walk away that easily from what I'm told has been 15 months of R&D.  Watch this space?

So, what is (was) the new mystery hybrid system?  I hear through the grape vine that it is an "Air Hybrid" system and understand that it works like this:  a compressed air reservoir is charged by the engine cylinders during braking/coasting and then released on acceleration, eliminating turbo lag.  The beauty is that it augments the engine without the need for heavy, environmentally unfriendly, batteries.  Peugeot-Citreon is currently developing a similar system for their road cars with the intention to introduce it in the near future.  So there is immediate relevance (there's that word) to mass-produced road cars, quite unlike Audi's flywheel system currently being used to recharge the R18's batteries, or any hybrid system being raced on any race car in LMP or F1 for that matter.  That's where that "relevance" term sticks in my craw: show me relevance to mass-produced cars and I'll be happy.

It's my understanding the contention with the FIA regards when the compressed air system opens and adds air to the reservoir as apparently it allows boost reduction once the restrictor flow limit is reached.  Of course this isn't an issue under 2014 rules as inlet restrictors are eliminated next year in lieu of fuel flow restrictors, so perhaps there's more to the story.

2013 Audi R18 E-tron Quattro3.9.13

>>Audi's PR machine has started to warm up with Sebring only a few days away.  The take away are computer renders of the 2013 Audi R18. Those are interesting as they show Audi's execution of the not-so-clever rear (why "not-so-clever" you ask?  See my August 25 entry) wing extensions (1).  Last year Audi insiders intimated that they too had wind tunnel tested a similar solution as early as late 2011.  They were described as "draggy" then (considering Toyota were using them and it was agreed they probably were giving up horsepower, it didn't necessarily make sense...but if they had less drag to begin with...this is just a side point), but with all of last season and an off season to develop, can we assume their (small I'm sure) drag penalty has been eliminated now that they are on the 2013 Audi?   Let's hope so as Audi is now only claiming 490 hp (*wink wink*) for the 2013 R18...

The other thing I noticed was that the bulge seen in the engine cover (2) back in January is gone.  Significant?  Initially I was told that it was there because the exhaust was re-routed at the rear of the car, so it's elimination was potentially noteworthy (you just don't change something like that then change it back).  Yes, I did considered a reworking of the engine cover surfaces as a likely answer.  But then there was a report at Sport Audi that caught my eye because it mentioned a "system" that Audi was intending to use this season had been "banned" by the FIA.  There was no mention at all anywhere as to what this system was and inquiries along those lines generated silence.  But now I'm understanding that there is a connection to the eliminated engine cover bulge and the "banned" system.  A little more digging and it turns out the system, whatever it is, wasn't banned; the FIA simply tweaked the parameters along which its performance was calculated and thus it became nonviable.  Our guess is that it was an exhaust gas energy recovery system...

Oh, it would also appear that Audi will be running a 2012 spec car alongside a 2013 car at Sebring based on the renderings they've released of the 2013 Sebring liveries (the #1 car is in 2012 spec, the #2 car in 2013 specification).

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>>These have sat around for far too long without any analysis.  At this point I can't be bothered to compare this latest update (the latest that are in my posession) to the previous update of the ACO2014 rules (10.15.12 entry), so here they are.  And the 2013 rules have been on the ACO's site for some time, I'm posting them here for the first time.

2014 LMP1 V05 regulations
2013 LMP 1 & LMP2 regulations


ęCopyright 2013, Michael J. Fuller