Worth noting that Stefan Bellof's Porsche 956 very probably had some restrictor plates or some such reducing how much air it could breathe in (its successor, the 962, usually did in race trim) when he set the old record. The 917/30 was probably the only Porsche that ever raced without significant technical rules in place designed to slow it down.

> The 919 Evo holds the Spa Record because the F1 record was done under all sorts of homologation restrictions. A sub-5 Ring time would easily be possible with a non-homologated F1 car similar to this unrestricted 919.

It's all about how much money you are willing to spend and how far you're willing to deviate from the tested racing formula, right? The 919 Evo is very fast but there are a few really obvious ways they could spend more to make it faster. I don't think they even re-geared the transmission for this track (he was hitting the rev limiter), and while they've changed some of the aero I think the powertrain was using retuned, existing stuff. It could be a much more powerful car. I mean, the gasoline side of the powertrain is a 2-liter four cylinder...