Originally Posted by LeeH (Post 8117321)

Audi's just lucky that their cars were still under warranty.

Originally Posted by RedBaron (Post 8117126)

I still do not understand why they put a V4 engine in a race car. Was it to save space for all of the electrical junk?

Originally Posted by Noah930 (Post 8117136)

Not exactly sure. In the February Christophorus (Porsche) magazine, the head of the 919 program cited reasons of using the motor as a stressed member and certain "thermodynamic benefits." The exhaust flow powers not only a turbocharger, but also some sort of a "dynamo" for energy recovery (Christophorus is more marketing than technical). Perhaps location of those ancillary components is benefitted from the engine's V-configuration.

The rules don't specify cylinder count, displacement, or fuel type. But depending on the power of the hybrid system, there are varying amounts of fuel the car can consume per lap. More available hybrid power, less fuel allotment.

Originally Posted by Flieger (Post 8117467)

90 degree V configurations are almost universal in the world of stressed engine cars (where the engine block is part of the chassis, bolted to the driver holder and with the suspension mounting to the gearbox) because it is stiff in basically every plane. A flat engine is floppy in vertical bending, an inline is bendy in lateral bending. The V configuration also allows better diffusers than a flat engine as well as a lower crank centerline, so it can actually have a lower cg.

4 cylinders because there is an optimal displacement for an individual cylinder with a given fuel. This has to do with the combustion efficiency (one reason why you need twin plugs with large bores). The bore/stroke ratio also gets dictated by thermodynamic efficiency.

When you have an optimized single cylinder engine running on the dyno you can then decide how much total displacement you want and therefore how many cylinders. No matter the displacement you make the same power essentially. But gasoline engines can't run super super lean like a diesel when you have a safety car or something, so there is an advantage to having a small gasoline engine and having to wait for the power to come in at the top end vs. the low down grunt of the diesel. Of course you have the hybrid system to fill the low down torque need.

The fact that Porsche are running batteries also certainly pushed them towards a small engine so that they could still meet the minimum weight. A short engine like a flat 4 is also going to be more rigid than a longer one.

I am surprised that Toyota stuck with the big 4.0 liter V8 naturally aspirated.



It's better that the LMP cars are super fast on the straight so that they can zip by on a relatively easy part of the track, vs. having to dive-bomb corners like we saw with McNish a few years ago.

Originally Posted by Lapkritis (Post 8117557)

On top of what Fliegler says I would add fewer points of failure on 4cyl than say 6cyl or 8cyl. Fewer pistons, fewer valves, fewer injectors (saw a few failures of these), etc... the replacement for displacement is forced induction.

The lean burn diesel is tough to mimic with gasoline... this technology has been proven reliable outside automotive applications in remote power generation. They run cleaner and more reliably when tuned properly in this condition.

Originally Posted by Deschodt (Post 8117538)

That's funny... because it's oh-so-true of their street cars ;-) ($6000 of warranty repair on mine already)

Hey, Porsche led before the car broke. For a return that's pretty good. It's not like they won straight away with the 908s/917s either...