So which is it? Well, maybe it isn't either as AutoExpress reported that the R8 would ditch the V8 for a twin turbo V6 engine. Does anyone know what the hell they are actually talking about? Probably not.
What we do know is the R8 will be replaced in the next couple years with a car based on the new Lamborghini Huracan platform. The Huracan has a naturally aspirated 5.2 liter V10 featuring both port and direct injection. It is essentially an updated version of the V10 the R8 has now so we can probably pencil that motor in for the new R8.
The wildcard is the motor slotted below it. If the R8 gets the 4.0 TFSI V8 there is no reason to get the V10. The V8 is cheaper, offers more torque, and is easily upgraded. Automobile reports 460 horsepower and 369 lb-ft of torque for the twin turbo V8 R8 which seem to be numbers they just pulled out of thin air. We all know RS6/RS7 put out 100 more horsepower than this from the motor and gain a ton of power with an ECU tune so the V8 twin turbo would basically trounce the V10 for less money.
The truth is that at this point only Audi knows what will happen with the new car. One of the three reports discussed above will be correct. Whomever it is will likely claim 'they got it right' and if they do not they will just ignore their previous report. That is how it works now.