I have a question for anyone out there with a non- sequential setup in their 3rd gen with a HKS Blow off Valve or any aftermarket or even stock blowoff valve. I just got my car back with a non- sequential setup. Still getting used to how it feels compared to the sequential setup, but I'm liking it so far. The one thing I noticed right away was when I used to have the sequential setup, when I would watch my boost gauge building pressure just under vacuum and let off on the throttle I would here the blowoff valve go off and as I would go under boost, not even full boost, just a few lbs of boost the blowoff valve would be even more noticeable when I would let off on the throttle. I was running 13 lbs of boost with the sequential setup. Now with the non sequential setup, they put a basic map in there for now that runs the turbos at 10 lbs of boost until I get it tuned. With the non sequential setup the turbos are both kicking in around 3500 rpms I would say, but I only here my HKS Blowoff Valves sound fully like around 4500 rpms. I don't hear it at all if I am under vacuum and let off on the throttle and even if I go under boost and let off on the throttle at around 5 lbs of boost, I barely hear anything. I only hear the sound of the blowoff valve when I let the boost climb to 10 lbs. Is this normal in a non sequential setup? Car is running good, I just really loved always messing around being able to hear the blowoff valve sound when ever I wanted to even under vacuum.

 

It's normal. On the stock twins they start building boost really quickly so when you let off the throttle there is already positive charge air in the pipings and your blowoff valve lets off a nice whoosh. When you go nonsequential the turbos dont build boost as quickly anymore. I'm running an Apexi blowoff valve. When I went nonsequential the same thing happened to me. The exhaust now has to power both turbines at the same time so it takes more exhaust energy to work both turbos to build boost. And full boost dont really come on till like 4500 rpms. I only really hear my blowoff valve when I really get on the throttle and let off or to change gears.

 

So I guess, pretty much, I'll have to live without the whoosh sound from the blowoff valve that I was so used to hearing. I guess once I get adjusted to having the non sequential setup, I'll forget about enjoying the whoosh sound so often. If I were to go single, I know I would still have some turbo lag compared to the stock twin sequential setup, but would the blowoff valve work more like it used to when I had the sequential setup?

 

The BOV sound isnt directly related to having twins or single, sequential or parallel configurations. It is directly related to pressure.

So to answer your question, if you switch to a big laggy single turbo, you'll notice the same trait. If you throw on a single, quick spooling turbo, it will return to similar operation as the original sequentials.

 

Ummm... You will never hear a blow off valve when under vacuum... at least... not to any real extent. (Some might argue that a bov will make some noise due to the momentum of the compressor wheel and the closing of the throttle butterflies... but I digress)

Vacuum means that the engine is pulling more air than the turbos are pushing...

So if you change the RPM at which you leave vacuum and go to boost, then you change the RPM at which you will be able to hear a BOV working.

 

I understand perfectly now, thanks for all the answers.

 

just thought i'd throw this out there. just for fun I pulled out the chrome insert that makes the chirp sound (8 allen bolts on the front). MAN does it sound better. it's a solid woosh that is semi sleeper, but sounds way better than the gay chip typical BOV sound the HKS has out of the box.

 

Personally I love the way the HKS BOV sounded right out of the box, but either way even if i were to take off that chrome insert, it wouldn't make my BOV work how it did before when it was a sequential setup.