Double Diffuser on Superkart - Opinions

[Alan Dove]

Jade debuted their new diffuser at Silverstone. I thought it worthy of a new thread for analysis given I don't think I've seen anything like it before, and some might not venture into the Superkart season thread and see it. Just for those who don't know there's no homologations for chassis or bodywork, so it's pretty much open season on the development side.

So here's what they debuted







Jade run a different set up than everyone else. Most of the Div 1 grid are running inline twins, whereas jade run two separate IAME Screamer KZ 125s.

I have a rough idea how this new design works. I think the washers and fitments could be improved as the floor and diffuser itself is lovely, but there's a lot there to interrupt airflow.

They were pretty mcuh 2nd fastest behind Morley and his Anderson/VM. That set up is pretty standard but optimised a lot. There's a lot in chassis/engine as well.

[spamesjam]

It looks like a neat idea but definitely implemented in quite a brute force manner - is it manufactured as a single diffuser surface with a hole cut into the top to make the second element? Do you know if it was validated at all with flow-vis? Also I had a quick look at the regulations and as far as I can tell the relevant rule for a diffuser is this one?

“17.24.1 - From 230mm ahead of the rear shaft, the floor tray may have an angle orienting it upwards. If the latter has one or two side fins, they must not protrude beyond the plane formed by the flat part of the floor tray”

To me it sounds like you want maximum expansion from that 230mm line (I’m thinking old concave f1 diffuser style) to power up the flat section of the floor as much as possible, and then it becomes a game of moving mechanical gubbins as high as possible to get additional expansion from there. The sky is the limit with this stuff, there’s some pictures of the 2010 Renault F1 car with the double diffuser and it’s frankly ridiculous how massive the tunnels got - there’s almost always more performance in a bigger diffuser exit so to me in an open reg set with no maximum height, that’s the big aero opportunity.

I’m also wondering if it’s possible to do a blown diffuser given the position of the exhaust? In the videos I’ve seen of these karts they look very unstable on throttle so I imagine getting some extra on-throttle rear downforce could be a game changer, especially in the low speed corners. Sounds a bit expensive to develop though.

I guess one last thing that seems sensible for these things is some sort of aero-elasticity on the rear-wing? Backing it off with speed through some sort of spring or torsion bar mechanism could allow the highest top speed while adding a bit of rear grip on entry to slower speed corners. These karts look absolutely rapid in high speed, but definitely pretty lazy in long braking zones (want to increase drag under braking?) and slow speed corners so to me, I guess thats where the opportunities lie.

However I’ll caveat this by saying I know almost nothing about karts and only spent about half an hour looking at the regulations, so this is from a very idealised, purely aero perspective of a severely underqualified person. It seems to be working for Jade regardless of what I say!

[hollus]

Without the rules controling diffuser limits, it is hard to judge!

[Alan Dove]

I guess one last thing that seems sensible for these things is some sort of aero-elasticity on the rear-wing? Backing it off with speed through some sort of spring or torsion bar mechanism could allow the highest top speed while adding a bit of rear grip on entry to slower speed corners.

I had come up with a spring actuated rear wing, and then I found out someone had tried it. There a few F1 brains that turn their eyes towards superkarts every now and again. Postlethwaite did work and mopre recently I know of other interventions.

Also I actually figured out it would technically be legal to have a GPS controlled movable aero, though I think that loophole has been closed.

Regarding the floor. The rules regulate the floortray regarding when you can start it, but you can get around that if your diffuser is part of your rear wing and not floor. however things like the axle and cross members on the chassis limit that.

Exhaust blown diffusers are possible, but I've not look at implementation in detail.

It looks like a neat idea but definitely implemented in quite a brute force manner - is it manufactured as a single diffuser surface with a hole cut into the top to make the second element? Do you know if it was validated at all with flow-vis? Also I had a quick look at the regulations and as far as I can tell the relevant rule for a diffuser is this one?

It's one whole piece. No flow-vis. This was the first they tried it. I saw the CFD work, and it wasn't the cheap stuff. I think it needs a bit more refinement in terms of implementation.

Superkarts live in this strange place where it's proper mad high-end stuff, but also fellas just running out the back of vans.

I think more people should get involved.

[SiLo]

Looks like that are trying to create a larger diffuser than the regulations technically allow? This way the effective height is higher.

[Alan Dove]

Looks like that are trying to create a larger diffuser than the regulations technically allow? This way the effective height is higher.

regarding diffuser the only thing in the regulations state is the floor's 'extractor' can only begin at certain point in front of the axle. You can technically get around that if the diffuser isn't part of the floor, but it wouldn't really change that much. The hole does raise questions, but no one protested it.

In terms of angle and size, there's nothing really stopping you there. You're just regulated in terms of when you can begin the diffuser (if the diffuser is part of floor tray)

[SiLo]

Interesting, surprised with rules that are very open to interpretation, there isn't more experimentation!

[Alan Dove]

Interesting, surprised with rules that are very open to interpretation, there isn't more experimentation!

There is experimentation, but also you have to be a top-class driver to get near the limit. If the kart isn't quite right you can lose seconds. So if you have a very good chassis, a good aero platform and good engine the need to experiment to win isn't that high. A lot of the clever stuff you can't really see.

That being said, there is huge scope for doing stuff if anyone really fancied it. I often am surprised by the level of intelligence on places like this. A lot of unused potential.