Audi is running a blown-diffuser on its 2013 R18 LMP1 contender, the German manufacturer has admitted.
Audi Sport head of LMP Christopher Reinke explained that the exhausts from the R18 e-tron quattro's V6 turbodiesel engine now exited under the car for aerodynamic gain.
Asked if this was akin to the blown diffusers used in Formula 1 before they were outlawed for 2012, Reinke said: "That is probably a good way of putting it. It is not exactly the same philosophy [as F1], but we have made developments in that area to use the exhaust gases for aerodynamic purposes.
"It is obviously efficient for our car, otherwise we wouldn't be using it."
Audi's blown diffuser is understood to be quite different from an F1 system, partly because the exhaust energy from a low-revving turbo engine is significantly less than from a normally-aspirated powerplant.
One theory is that Audi uses the exhaust gasses to create what one rival engineer described as "virtual skirts" to help direct airflow under the car and through the diffuser.
Toyota has revealed that it experimented with a blown diffuser on its TS030 HYBRID over the winter but decided against running the system.
Toyota Motorsport GmbH technical director Pascal Vasselon said: "We have been testing this system a lot since last season, but apparently we have come to different conclusions."
He explained that there were various reasons for Toyota's decision not to run a blown diffuser, one of which was the effect of hot exhaust gases on the tyre wear.
I don't think that anyone outside Audi knows for certain what they are using the exhaust for.