Good that some motorbike numbers already got mentioned, because that also gives a good indication of what's possible even with normal aspirated (non turbo) engines.
With productionbikes you see 4 cylinder litre powers hitting 180 bhp nowadays, and 4 cylinder in line 1000cc's revving upto 12.000 rpm. (that's pretty high..:schwitz
Although a roadcar's engine is made to last higher mileage and longer service intervals compared to most bike-engines, say 100K kilometers/60K miles is still possible with such a bike-engine before revision is needed in most cases, when treated well.
Another reason car-engine bhp's are usually much lower is because that gives the engine more and a more pleasant torque-curve for a car..
With turbo's you can double, perhaps tripple horsepowers, also on bikes, for example there seem to be a lot of turbo'ed Hayabusa's (gsxr1300's, perhaps some bored to 1500 or even bigger) around, with horsepowers going upto 500 bhp or over. Those probably won't last very long..but for racing that's not always a requirement either.
So the bhp's the LFS cars put out is just too low.
I believe there's a Hayabusa powered Caterham, the LX6 is probably based on that. (It's rev's, power, six speed gearbox and "feel" certainly seem to match to me.)
Also this is my first post on the LFS forum, hi all.
Hope it works.
(Found out about LFS about a month ago, licenced a week ago. Love it
, used to be addicted to GPL.)