There seems to be a lot of misinformation/hearsay in this thread. I hope the following helps the OP make an informed decision.
1. Blow off valves (BOV's) and dump valves are the same thing. They're just the different names different countries give them.
2. The R26 will come with a re-circulating BOV as standard, as will all turbo cars.
3. The BOV's sole job is to divert any unused, compressed charge, from the turbo, that's in the intake track when the throttle plate(s) are closed. The idea behind this is to stop the turbo from stalling, theoretically extending it's life. And, in doing so, reducing the time it takes to spool up the turbo again, reducing 'lag'.
Obviously, a re-circulating BOV will do just that, re-circulate the un-used charge, back into the intake system, normally into the air box so that it can expand again.
A vent to atmosphere (VTA) BOV will again, do just that. Vent the unused charge into the air, making the whoosh or whatever sound.
If you don't use a BOV, you wll stall the turbo between gear changes. Although with modern turbo's, it's very unlikely to reduce their life by any large margin, it will increase the turbo lag. This will of course make the cars acceleration worse. It will also cause what's known as compressor surge. This is the tssh tssh tssh sound you may hear on some turbo cars. This is not wastegate chatter as, there is no such thing. If you have an adjustable BOV, you can purposely make this noise, if it floats your boat.
The Prodrive P2 also makes this noise but, because of the intake system and turbo it uses, it sounds more high pitched.
If the R26 uses a MAF or AFM to measure intake air capacity, you might have problems fitting a VTA BOV as, the engine will actually see less air than the MAF is telling it so, more fuel will be dumped in and, the car might stall etc...
This isn't always the case though. I use a VTA BOV on my Pulsar and that uses a MAF. It never stalls but, I'd suspect it does run quite rich on high load gear changes.
If the car uses a MAP sensor to instruct the ecu as to how much air it's ingested, you'll be totally fine.
If you are keeping the car running stock boost levels, the stock BOV will be fine. If you're going to up the boost or, just like the noise, I'd personally recommend a 'pull' type BOV, that uses a piston and not a diaphragm. These work differently to most BOV's as, they pull the piston to vent and not push it. This gives them very good leakage resistance and they'll stay closed at idle. Practically eliminating idle stalling. Something like the HKS SSQV would be ideal although, don't buy a authentic one as, they're very overpriced. Hunt around on eBay for a replica. They're exactly (yes, exactly. I've seen them in pieces) the same thing at around 1/4 the price.
I hope that's answered your question ?!
As you can see, there's no good or bad about them really, it's just what you want out of it, at the end of the day.
Paul
