VTEC Racer - the most common failure types on FI engines are detonation induced. Usually you'll end up hurting a bearing in the bottom end or breaking a piston ring land (or ring itself). The former will create a knocking noise under light engine revving, the latter can be hard to diagnose except with a leakdown or compression test.

On a normally aspirated motor, the most common failures are valve related and rod related. Either you'll float a valve and make contact with the piston (in the case of big cams and high revs) or you'll actually break a valve, but the latter is rare. Rod related failures usually means breaking a rod bolt or the rod itself at high rpms. This means big trouble. The higher the rpm, the more of a potential problem you'll have.

s2kpdx01 - Open deck blocks actually aren't quite the liability that they're made out to be. Yes, closed deck blocks are much better for big hp numbers, but I've dyno'd and tuned several 400+ whp 2.0 liter Civic turbos recently. In all cases, they were using race gas and right around 1 bar of boost to produce those hp levels. That's really not a lot of boost, and therefore stresses on the sleeves aren't that bad (all the engines were sleeved with aftermarket pieces btw). I don't see any reason why an S2000 at 15 psi couldn't make even more hp since it has more rev capacity and a better flowing head. I think 450 whp at 1-1.2 bar would not be problematic, but it would have to be on race gas. I think that on pump gas you won't see turbo S2K's pulling more than about 375-400 whp. Its just too dangerous.

In order to close a deck, you can usually insert a block guard, or you can have the block pinned with reinforcements. Either one works well to improve strength (and you need to for some of the 700-800 hp turbo Honda motors in the top drag racing ranks), but there are cooling issues inherent to these mods, especially the block guards. For a drag motor this isn't an issue, but for street driven engines it is.

The most common failure on high hp turbo hondas appears to be early wear of the bottom end. Even with proper tuning, no detonation, etc., the bearings just aren't designed to take 450-500 crank hp. In fact, they were designed for less than 200 hp with maybe 50% over capacity (100% maybe, but I doubt that, more in a second on why). While you are trying to make sure that peak cylinder pressure occurs well past TDC, you're still building tremendous pressure before your optimal peak pressure point, and that strains the bearings on the rods and crank. There's not much you can do here, because Honda went with relatively small bearings to reduce parasitic drag and help make high rpm power naturally aspirated. For a drag motor that gets torn down regularly, this isn't an issue, but again, for a street car it is.

Personally, if I was building an FI car, I'd shoot for about 340-350 whp on pump gas with a nice fat torque curve. On race gas for the strip, 400whp would put you deep into the 11's if you could put it to the ground. I'm sure the F20C bottom end is tougher than the B'series stuff, but I don't know how much tougher, so only time will tell if it will hold up better to boost.

UL