OK - so if you plot enough cars, you should be able to generate a delta of your calculator's error against the known performance stats - this should give you a starting point of the effects of downforce
The issue I have with this approach, is that cars that actually produce positive downforce (at least where the manufacturer has published it) are so fast that road test magazines always don't measure performance at he top end. Stats up to 150mph for a car that gets there in 20 seconds but then does another 40-50mph don't really show the full picture. This is
why I want to calculate downforce - it's this final part of the story I want to know. It they published the numbers I'd need to work it out, I wouldn't need to work it out!
Personally, I think you're opening a can of worms, as some cars (Coupe included, IIRC) have negative downforce at speed
Yeah, well aware of that
but, my thinking is that once I have the downforce thing worked out, I should be able to use data for cars I have 0-top speed data for to work out how much lift they produce!
You can't change your calculator to accommodate extra (or less) weight, as this isn't how downforce works. The actual weight of the car isn't changing, its only the rolling resistance, due the downforce.
This is one of those rules that I struggle with. If a force is pushing a car down, then it must be harder to accelerate.
If I had to choose between two cars that were identical in every respect, save for downforce (i.e. drag was the same too - a more efficient system was in place), I'd have my money on the car producing less.
If the answer is that it
is faster, then where else but weight would this go in the calculator?
If you try to fudge the calc by adding weight, you're going to screw the rate of acceleration.
Similarly, if you try to adapt drag, you're going down the wrong route, because drag doesn't increase with downforce (in fact potentially, drag could decrease with downforce, as the air under the car speeds up as the ground clearance decreases)
The thing is, I've applied the rule to two cars so far. It's terrible and unrealistic I know, but I quickly chucked in a fixed rate of increase e.g. 100kgs @ 186mph = 50 @ 93mph
However for the two cars, it corrected the performance data almost perfectly, both cars by 2 seconds to the speeds below.
Giulia Quadrifoglio
20s to 150mph vs actual 19.9
190.2mph top speed rather than 190.8 (some would call me pedantic...)
Koenigess Regera
20.5s to 249mph actual 20.9s
CD won't change much really though - if the springs moved that much from 450kgs at 250mph (spread over four wheels) imagine how much it would dive with four times as much weight on the front axle under hard braking!!
I think the answer is to incorporate the ability to include rolling resistance from tyres, which will increase as the contact patch area increases due to downforce - does the calculator have the ability to use different tyre pressures, or does it always assume a constant?
It doesn't include rolling resistance. Perhaps this has been offset by the natural lift of most cars so I've gotten away it to date?
And no, it doesn't factor in tyre pressure either. There are a few variables that I chose to keep out. It's more about road cars than anything else. Having read up on why a drag car can pull of the line faster than a 4WD car, I made the decision that that part can FRO!
Apparently, it allows the wheel to essentially push
backwards against what may as well be a wall. Even my obsession doesn't go that far