what is better? i currently have an hks blow off valve on my 996tt. would a diverter valve be better for performance and better for my engine?

 

same thing .... , in order to run your DV's vented to atmosphere you will need to be running a blow through system.

you are only running one hks blow valve on your car ? vented to atmosphere?

 

yeah, i only have on blow off valve which is vented to atmosphere. should i have two and where would the other one go?

 

check you f hose each end of the f goes to a dv , you should have two, if the they are stock get rid of them they are plastic and will start honking as you lose boost...will send pic if you like

 

to the other... valve? lol.

i know of kits that they sell so they don't re-circulate into the system. AP has one i believe.

 

ok here ya go they hard to see. the 2nd one livesjust behind the 1st you can see the evo logo on the 1st dv

 

i know they do ,but im afirm beleiver that if that car does not have a blow through system, they should not be vented to atmosphere.

the way they do it is i belive only half dumps to atmposohere , so the car doesnt throw codes.

 

this can't be anything like the cow fart tax can it??

 

One isn't better than the other - they both relieve pressure when the throttle closes so the compressor wheels don't get hammered. The difference is one vents to atmosphere, the other vents back into the intake of the turbos post MAF. The MAF is important here - it measures the air intake into the engine and supplies a signal to the computer so it can then meter fuel. If you vent to atmosphere you dump air that has been metered and the car can run rich since the engine never sees that air - this only occurs when it dumps but it can sometimes stall then engine and the ECU will likely throw a code. If you've got the stock intake setup with a draw through MAF it's probably better to recirculate the air rather than dump it - the dump will be quieter however. If you've got a blow-through MAF (NOT stock at all so you'd know) then dumping to atmosphere or recirculating is fine.

One valve or two? Honestly if the valve is a decent size for the airflow it's fine to just run one but stock our cars run two small(ish) ones that are prone to failure. the whole point here is to relieve the pressure in the turbo plumbing when the throttle closes, how you do this be it one valve, two valves, or three valves or more doesn't matter so long as you do it quickly and can seal back up for more boost when the throttle opens again

 

Hey thanks for the info! Ya it's a pretty good size blow off valve so I'm assuming it's sufficient.

 

In actual fact they are 2 names for the same thing. Most efficiently they are vented to the intake of the car to help with reducing spooling slowdown when the throttle body is closed.

Blow Off comes from the Rice rocket brigade that like to hear their cars "Blow Off". A complete waste of valuable air pressure in IMHO simply to hear a sexy (debatable) noise.

More importantly they protect the Turbo secondary impeller from shocks resulting in back-pressure from a throttle close.

SWR

 

lol...

 

How's this a waste exactly? Blowing to atmosphere vs blowing to the intake - the pressure is relieved either way. The attraction of the noise is a matter of taste <shrug>

 

When it is exhausted to atmosphere it just dissappears, when it is exhausted into the air intakes the resulting pressure help to keep the turbos spooled and reduces lag. remember all this is happening very quickly between gear changes. The more faster you can keep the turbines spooled the better. Based on the "Every Little Bit Helps" principle.

If one are in a Subaru WRX I suppose the sound may help one feel they have a race car. IMHO The Porsche does not need it. Anyhow, I could not hear the resulting Whoosh! anyway with my Gen II.

SWR

 

Sorry, I don't buy it. Unless that air is directed right into the turbine inlet - which I think some rally cars may have done - the air isn't going to show any measurable benefit IMO. Someone's going to have to find a citation showing some measured difference before I'll be convinced. The volume of air moving in an intake tract to the turbo is enough that I don't see this helping - especially since one end is essentially open to atmosphere anyway out the air cleaner! If you put a gauge on that intake tract at the turbo I predict you'd see no pressure rise when the DVs pop and no measurable difference in spool vs blowing to atmo. Pressure on a good shift returns so fast it's amazing.

FWIW I'm very aware as to how fast this all occurs. My Supra blew to atmosphere and I did more datalogging on that car car than anyone I know short of a pro tuner - hundreds of hours at least under all sorts of conditions. You'd be surprised at how fast the turbo is back up to speed when you crack the throttle back open and the BOV closes. I logged turbo response specifically when folks tried to tell me I had used "too big" an intercooler on my car for the stock turbos and would see "lag". Yes, I logged it with a few other single turbos too As is often the case this turned out to be "common sense" not being true. When you consider the volume of air it takes to pressurize a running engine it's pretty amazing to watch how fast boost recovers on a shift - big IC or not. Even if the BOV returned the piping completely to ambient pressure (I'll bet it doesn't) the turbo moves some serious air and re-pressurizes in the blink of an eye.

BTW if you've ever wondered what it's like to not run a BOV or DV at all listen to a stock or lightly modded Buick GN. When you get off the gas in one of those you get to hear all sorts of noises as the turbo chokes on the bounced airstream. THAT most certainly has to have an effect!

P.S. FWIW I'm not a big fan of whistles, chirps, and other crap done on these things - some Japanese BOV literally had whistles in them! While maybe fun for a couple of shifts it quickly becomes VERY annoying - yes I tuned a car with one of these for over a week. That said blowing to atmo reduces plumbing clutter a GREAT deal. No goofy F-hoses or badly crimped intake tracts and the valve can be placed darn near anywhere without regard to having to get the air to the backside of the MAF through some tortured path. Going blow-thru to get this simplicity is pretty tempting since I happen to be chasing a boost loss issue right now with the DV circuit being a prime suspect!