We adjusted the new model slightly. The new diffuser design produces massive values in the CFD calculations. With a design that is based on a stock car we have a considerably better downforce/drag-ratio than the group C Le-mans prototypes before the rule changes. The Nissan P35 at best achieved a downforce/drag-ratio of 5.36. Our most recent value is 5.69.
As for how realistic our CFD values are, we won't really know until we are able to take the car to the track.
We had a great idea and completely redid the diffuser. The new diffuser produced a much larger low-pressure area than before and thus produced much more downforce than any of the previous versions. We can likely further improve the model with a few small changes so we will continue the development.
We tried an even more extreme-sized diffuser, which again increased the downforce, but only by a very small amount.
There is something strange going on in the model. We will have to analyze the flow field and model carefully. The opening angle and the area ratios of the diffuser seem to be much larger than should be possible based on public knowledge. The flow "should" separate from the surface of the diffuser at much smaller values so it's a bit unclear how good our aero kit actually is. We are especially going to investigate the mesh and turbulence parameters.
Our new CFD hardware has enabled us to use a much more accurate mesh, this change resulted in a 5% performance increase of our GT aero kit. The mesh could clearly be refined further since the result did vary. The variations were not that big though, so we can safely assume that the main flow pattern is correctly resolved.
We'll continue developing the GT's body kit quite reassured that the results give a reasonably accurate indication of whether we're going in the right direction or not.
After some small shape optimization and a extra wing profile at the rear end our latest CFD results are now 3994N downforce for 1025N drag at 144km/h.
Our effective pressure point is slightly off from our target, though. We need more downforce at the front. Working on the front end was our next attention point anyway, so hopefully we'll arrive at optimum downforce at just the right pressure point so that as little compromise as possible is needed to get the correct aero-balance.