HomemadeTurbo - DIY Turbo Forum - what in your opinion is the best BOV?

Honestly for you guys running a VTA/speed density system, it's really not going to matter a whole lot if there is a very slight leak. Either way what you see at the manifold is what your basing your fuel/timing off of, so it's not like you have to deal with leaner values on maf systems. I've used alot of different bov's, so here's my take on the ones I've used.

1. 1st gen DSM - great piece for the money, cheap and does the job. Def. not fancy and unless you do the mod don't expect it to hold over 18psi without leaking (not that too many on this site will hit that number).

2. Evo 9 MR metal diverter valve - just like it's older DSM counterpart, but with larger inlet/outlet ports and no need for adapter plates. Higher spring pressure and can easily hold 25+ psi, downside is smaller boost pressure setups will get some surge from it.

3. Apexi twin chamber - Definitely a baller piece, but does exactly what it has to do and can do it past 30psi. Adjustable spring tension for lower boosted applications, and is a piston style so you don't have to worry about seals and diaphragms tearing. Very pricey though.

4. HKS SSQV (real one) - Also another good one, but a bit on the pricey side. High spring pressure can cause some surging along with having to pull the piston against boost pressure. The real one I had never leaked.

5. SSQV knock-off - Lower spring pressure so it didn't surge as bad as the real piece. Lower price too, but it did leak a bit and the vacuum port like to fall out so I had to jb-weld it back in. You get what you pay for I guess. :P

6. Greddy Type-RS - Another real deal one, high spring pressure again, but you can at least take it apart and remove one of the two springs inside to lower pressure. Mine didn't leak for 4 months, then the seal started to dry out. Leaked pretty bad after that. Also the replacement diaphragms are really expensive.

7. Type-S knock-off - Worked ok but leaked like a sieve. Anything over 12psi on mine liked to push the valve open. Made a god awful squeaking noise too. Junked it after that.

8. Turbo XS RFL/Type-H34 - Good valves, but have a tendency to stick if they get dirty. The knock-off ones tend to have alot of issues with them, so I wouldn't even bother if you really want an RFL. Just put a light coating of lithium grease on there and they're fine. Piston style that doesn't leak at the seal, but will leak out vacuum at the piston. Usually it works to your advantage to let it slowly leak, especially on maf equipped cars like my Evo, because I can tailor the maf scaling to reduce stumbling issues normally associated with those setups. Only real thing I hate about this valve is how you adjust spring pressure...you have to take it apart and add shims inside the piston. Too many shims and you surge, too few shims and you pop open too early. For you guys running below 20psi I don't think you'll have any issues with that though. I sit at 23psi right now, so it's a pita to set the pressure just right. Uber ------' loud too if you're into that.