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Regarding the Audi R10 TDI exhaust shape, why are the end of the exhaust pipes ovals instead of a standard circle? Most of the other LMP cars have circle exhaust even the peugot 908 (diesel) has cicrcular exhaust. So why does Audi use ovular shaped exhaust ends?

Thank you!

does onyone remember the Galmer Indycar ?Alan Mertens went to extremes with blowing the top of the diffuser ,his design had the exhaust tip flattened and spanning almost the complete width of the diffuser roof.This gave positive interaction with the diffuser as the high speed exhaust gas effectively elongated the diffuser.Maybe Audi chose to do something similar but not as obvious.
Or do they just spread the fumes a bit out so we can´t see the smoke?

they may want to have a flatter exhaust and need the cross section. TDI with catalytic soot filters don't produce smoke and don't stink. Diesels are really clean nowadays.

I think it's just for a different look or exhaust note. Not going to be much of a perfomance issue unless it is quite a different shape like the flat one noted above. Do you have any pics of the Audi & others?

The gap between the top bodywork adn the diffuser is small so an oval shaped exhaust makes sense.

I think Zac must be correct.

here are some pictures of the R10 TDI and the 908 HDI

The aerodynamicists have a fixed height diffuser and want a low and clean deck above it, then the engine guys want big exhausts. The compromise is the oval tail pipes, low enough to fit and wide enough to have the right flow characteristics.

Scarbs

Scarbs, how restrictive are the particulate filters (FAP on the Pug) on those two engines? Would that also explain why the cars are so quiet?

Look at the size of the filters (in the pic above) then look at the horsepower and torque figures . They don't clean them for the duration of the 24hr race, either.

The volume of the car is a bit to do with the revs too, only upto around ~5/6000rpm iirc.

Diesel particulate filters are not serviceable. Diesel soot gets trapped in a special mesh, the soot gradually builds up increasing resistance to flow. The increased resistance raises the DPF's internal temperature high enough to orderlessly and without particulate emissions burn off the excess soot. Temperature and back pressure are paramount and are usually closely monitored. It's common for diesel engines to enter a regenerative mode and fuel is injected in the exhaust stroke to rapidly increase the exhaust gas temperature and clean out the DPF. This is especially common on large displacement trucks, and in an race car application I would assume there would be sufficient amount of heat to operate the DPF without any extra help. Keep in mind the last 24 hour race was run on biodiesel witch significantly reduces particulate emissions.

The particle filters are positioned as close as possible to the turbos (in the case of the radical diesel) as they work most efficiently at high temperatures as stated by schoner. Ill see what other information I can get as currently doing work experience on the radical sr10

I don't think this was planned since the begining, so I just throw it as food for thought, but the lastest development that occured on the R10 saw the addition of a midwing under the rear wing, and a significant amount of the body work over the exhausts has been cut away

Pic from Mulsanne's corner:


Although this update has been analysed to be purely aerodynamical, it is difficult to think exposing the bottom exhaust like that has no effect on their temperature, and on the pressure building behind them. It is pure speculation, but I would suggest that the ovoïd shape ensures a larger contact area with the descending airflow, thus providing better cooling of the exhaust tip than it would have been with a round one. (obviously that observation is only relevant in this very case where the above bodywork has been cut away tho)



Also, I have noticed the new Maserati Gran Turismo "S" has oval exhaust tips too. In this case it has probably all to do with style rather than efficiency, but for sure those tips must be of the same size than the doubled rounded ones of the original version, so this is an interesting geometry choice nontheless. Note that it seems there is a sort of splitter in the Maserati's exhaust.(or are my eyes deceived?) Any idea of what it might be?