I think it’s fair to say I’ve been down the road of aero on our platform. My first full setup was a 67” APR wing paired in the front with a generic front lip to fill the space between the bumper and an APR composite (the cheaper stuff, not the expensive honeycomb) splitter. Racewerkz Engineering designed the shape of the splitter for APR and installed it. That setup also had AJ Hartmann canards and hood vents and top-of-the-wheelwell vents. That setup worked well. The car was fast. But you could not easily tune the splitter. And it was not chassis mounted. And it was always in quite a bit of danger of being ripped off during an off-track excursion (gasp! Do those happen?) But still fast!
Over the course of many years, the APR splitter got sort of saggy a bit. It had seen a lot of action. It was rubbing the ground and grinding away into oblivion. I don’t blame it. It’s a thin composite sheet. I definitely got good value out of it. If you’re on a tighter budget, I think it’s a very viable way to go.
But then Zebulon hit the scene on our platform thanks to the efforts of Ryan@Zebulon and Chris Mayfield (fsmtnbiker). The Zebulon splitter is simply in a whole other category—chassis mounted, easily tunable angle of attack, hidden gas shock front support rods that give the splitter the ability move upwards if it slaps the ground, super stiff carbon fiber—you can LITERALLY stand on it when it’s on the car, and every one is custom built so you can choose exactly how far out it sticks from the front bumper, if you have a class restriction. But it’s more expensive than the APR. And it’s more work to deal with building an air dam to fill the gap between the bumper and splitter.
Ryan from Zebulon told me awhile back that pretty much any splitter in the front will help quite a bit with guiding air over the car versus allowing the air under it, and that it’s diminishing returns by switching to another splitter in terms of just sheer downforce. So he warned me that when switching from the APR to Zebulon, it would not necessarily be night and day difference, but, yes, it would be more downforce and I would have far more tuning options to create the aero balance I wanted.
Now, as far as canards——they are NOT creating any big downforce. I still have them and it takes very little downward pressure to make them flex. The point of the canard is to SHAPE the airflow over the front wheels. After my VIR crash, I had to replace the bumper and start over. Amazingly, the splitter was able to be repaired after going straight into a tire wall. And Ryan from Zebulon helped me relocate the AJ Hartmann canards to a spot on the bumper where they could more effectively guide the air OVER the front wheel well arch. I originally had them lower, and he recommended putting the upper ones as high as possible given the M3 bumper. So, if you look at old bumper vs new bumper pix of my car, you can see the top set of canards are quite a bit higher up than they were on the old setup. Basically, the front wheel well is a turbulent mess. Without any mods on a street car, air gets in there and the wheel is spinning and the air gets trapped and it becomes a high pressure area which is the last thing you want. So, vents allow pressure to escape, and the canards flow air away from the wheelwells in the first place.
Hood vents are also for pressure release to prevent air pressure from building up underneath the hood, and for air flow. Some car magazine actually put an M3 in a wind tunnel and calculated that a stock M3 at 120mph generated 20lbs of uplift just from air pressure under the hood. The hood vents also encourage airflow through the engine bay that may make it more efficient for air go through the radiators, which helps with cooling.
Canards, wheelwell vents, hood vents——none of these things have a large effect on the car by themselves, BUT there is no doubt that together, as a system along with the splitter, that they give the car incredible amounts of front grip when setup properly.
Below, you can see the new canard setup versus the old setup. The canards were so flexy, that I connected them with a metal strap just to try to give them the chance of flexing less. You can see the strap in the bottom photo connecting them.
New:
Old:
