astracrazy wrote:where the exhaust has to be is further forward than you'd expect. I'd say its right from what you see
The tail light must be placed at least 595mm behind the rear wheel centre line, so you're talking about the exhaust being 5mm behind the tail light, and hence behind almost all of the rear wing structure (likely only end plates behind there) The exhaust being in front of the monkey seat is deffinately not allowed.
Also, the box for the monkey seat begins at 500mm behind the rear wheel centre line – so we're deffinately talking about 10cm behind the monkey seat here.
From what I understand from article 5.8.4d, the exhaust must "Be positioned in order that the entire circumference of the exit of the tailpipe lies between two vertical planes normal to the car centre line and which lie between 170mm and 185mm rearward of the rear wheel centre line", so the exhaust exit is at least 410mm ahead of the taillight (595mm - 185mm).
That said, why is the position of the taillight a determining factor here, when we're talking about bodywork?
Article 3.10.4 allows bodywork more than 500mm behind the rear wheel centre line but within 75mm of the car's centre line to be between 200 and 400mm above the reference plane, and nothing in article 14.5 (about the tail light) says that bodywork can not lie behind the point at which it is mounted, as long as it is "clearly visible from the rear." Since the tail light is centred at 300mm (+/- 5mm) above the reference plane, it need not have a significant bearing on the monkey seat.
It is absolutely possible to have a monkey seat directly behind the lower 50mm of the exhaust exit, as long as it is far enough rearward. The effectiveness of it from an exhaust-blowing perspective obviously diminishes the further away from the exit it is, which is the idea behind the bodywork exclusion zone in 5.8.5 (a right circular cylinder, 30mm greater diameter than the exhaust exit, on-axis with the last 150mm of the exhaust pipe, extending as far rearward as 600mm behind the rear wheel centre line). Note, as a couple of others have posted above, that the exclusion zone's end-point in terms of length is not changed by the exhaust exit position - it "...extends rearwards as far as a point 600mm behind the rear wheel centre line...", so you could have bodywork as close as 415mm behind the exhaust exit, both above and below the tail light, between 200 and 400mm above the reference plane.
Also, according to 3.10.5, "No part of the car less than 75mm from the car centre line and more than 350mm behind the rear wheel centre line may be more than 400mm above the reference plane." So, from 350mm behind the rear wheel centre line forward to the rear wheel centre line, there is even more freedom with regards to bodywork in the centre area less than 150mm wide. Outside of the cylindrical exclusion zone specified in 5.8.5, you can have bodywork up to 400mm above the reference plane right from or even before the exhaust exit, so you could actually start an open-topped channel of sorts around that exclusion cylinder to funnel exhaust gases and other air onto the monkey seat from much further forward.
I would also think, for the purposes of blowing on the monkey seat, it would be better to have the exhaust exit horizontally, so you could use less angle of attack on the winglet for the same effect, thereby reducing drag from other, non-exhaust airflow.