Does anyone know for sure that the Fb25 (as found in the 2011+ forester, and soon to be 2013+ outback/legacy), the FB20 (2012+ impreza) and FA20 (BRZ/FR-S) have an open deck? Or a Semi-closed? I have looked for this info on and off for a few months, using google but there is no one who can say for sure it is open or semi-closed. The general consensus is that it is Semi-closed, but no one has actually seen it, or talked to anyone who has seen it, etc. So if anyone has taken them apart or has access to that info that would be greatly appreciated!
there are so many misconceptions and misnomers with open, semi, and closed deck anyway its a moot point... you can build any of the blocks to whatever potential you want really, it just costs to play the game.
Yes, with enough money you could do anything. The reason I am asking is because the EJ series engines (all the n/a ones for the last decade, and a few years beyond that in the US) are open deck, and you can add small turbochargers to them, running roughly 6-7 PSI of boost without damage. Extremely impractical and expensive, and you can't mod from there very much because to get any more power means a lot more money, and in the end it is just cheaper to swap in a factory turbo engine. If the new N/A engines (both FB and FA) come semi-closed, that they could take more boost, and if the Forester XT (Outback XT is already a gonner, same with the Legacy GT) ever go away, it would still be possible to build a pretty nice turbocharged sleeper without a motor swap/sleeving the engine and so on. It is just a completely idle question, just for information, as so far, the answer is absolutely no where on the internet.
Eh, that's really true, but its not worth arguing since you're obviously set in what you'd want to do.
Is that supposed to read "that's not really true"? Anyways, no, please explain any misconceptions I may have. I can take being wrong. They way I currently understand it, is that because of the greater amount of reinforcement around the cylinder, that allows more boost to be held, because it's 1) reinforced and 2) the head gaskets seal better and a few other factors. Open and Semi's can have reinforcement added, but done improperly (or with a different alloy) can cause heating up differences, and problems arise. Turbochargers that I have seen being run on previously N/A subaru's seem to run in the area of 200 to 230 HP at the wheels, which is quite respectable, but a Semi-closed will go even further without having to pull the engine and reinforce it? I don't actually plan on doing this ever, but the question seems to pop up on Subaruforester.org, and no one is able to give a for-sure answer as to the new FB/FA engines.
yeah, not true. the semi closed blocks typically have two extra supports on each cylinder from what I've seen, and those supports still only go less than 3" down the bore, thus can still shift, expand, crack, ect... the stock wrx blocks (2.0) have no issues running higher power than stock and they're open decks. beyond that, even with the STOCK fa20 you get the added benefit of direct injection, which will help with timing and detonation issues dramatically. theoretically, you could run decent power on the new block completely stock and not have the det issues due to the direct injection. the whole "open, semi, and closed" argument seems to be overblown, IMHO, seeing as all forms of the block have been proven over a number of years and you'll likely break a rod or factory piston before anything else. if we're talking in general, sure, inline engines where the stress is higher and more specific around the cylinders (like a nissan, honda, vw, ect...), where as the subarus only have 2 (or 3) cylinders stressing eachother at a time, and even the "open" blocks will have two points of contact at a minimum per cylinder. ultimately, I doubt you'd run into issues until you really start to push the block, and even at that point you'll have more issues with the pistons, rods, and other misc parts most likely. atleast this is what I've seen and noticed over the years edit: moral of the story is a lot of whats talked about is myth or assumption, and with the added perks created by the DI, I doubt you'd run into issues unless you're going real big, real fast, and even then you'd likely see the failures elsewhere in the system
Agreed, semi-closed is overrated. Most factory turbo 2.0s are open deck, and the cylinder walls are not the weak link. They spin rod bearings far more often than cylinder wall failures. That does change as the cylinder bore increases though. The 2.5s have much thinner cylinder walls than the 2.0s, and the 2.5s have cutouts to allow access to the bolts that hold the block halves together, which mean even thinner spots. The limitation to the n/a blocks are the heads/cams, compression, and management. An EJ22e block with EJ205 heads, a Bosch high pressure fuel pump, VF39 and standalone management would be an awesome platform, and open deck. The point is, there are a lot of other factors that will determine the "boostability" of the F series engines.
Ask AWDImprezaL about his 2.2L open deck factory N/A motor that is boosted and has been running for like 200k miles.
if there's anything that's going to slow your plans to boost, it's the 12:1 compression ration that comes stock in the BRZ
