2 June 2018

Had the week off so between honey-dos and being on-call, the diffuser was built. As background, the vertical strakes were going to be aluminum, but later, because there’s a fair likelihood that at some point they’ll drag on the street, I switched to HDPE (high-density polyethylene) because I had it, and because it seemed like it would wear more gracefully, unlike aluminum that would bend and stay bent.

Having made the decision to go with “wearable” plastic, the vanes and end plates were initially going to extend lower, such that there’d be only 2.5″ of ground clearance. The idea was that they’d “self adjust”, but after thinking it over, that seemed like a recipe for disaster. Images of having the leading edge(s) catch on something and having the entire assembly pulled off the car didn’t seem impossible. For that reason they were trimmed back so they’re even with the bottom of the car. Anyway, on with the pictures.

There was an aspect of HPDE that I casually considered, that it’s rather heat sensitive. Since there’s a lot of air flowing past the exhaust where it exits into the left-most tunnel, how hot could the air really be? The answer is illustrated in the last picture – “hot enough” (and this was a casual drive, I imagine on-track I’d be dripping melted blobs… sigh – they’ll be replaced with aluminum.

I’m sure you’re wondering whether the diffuser works – good question. My imagination thinks so*, and I can offer that leaves fly up behind the car. But, sometimes leaves flew up behind the car before. My thinking is that it can only improve airflow and at track speeds, will very likely be doing its thing. Oh, and the rear wing will be placed above the trailing edge, which enhances diffuser flow even further. There’s simply no easy or safe way to test it out on the street.

* Of course, after I change the oil on a car, I swear it runs smoother, so there’s that…