BOV in a Volvo V70 - LPT(!)

A Blow-Off Valve or Dump Valve in a Low-Pressure-Turbo (LPT)

I like the noise those BOVs make. It is better than anything else. I'm sure that most will disagree but hey, wouldn't it be boring if everyone has a the same taste!? Different strokes for different folks.

Note: have you seen my "Free Dodge Viper" Page?

After I heard a Lancia passing by and making that noise I knew I have to have such a thing. Back then I didn't even know how to create this type of sound. Here in Europe I've seen VERY few cars with a BOV. Now that I know what it is I listen better than before and detect one or the other. But there are still only very few BOV'd cars around. Most people here in Europe call it a Dump-Valve or even Pop-Off. Pop-Off is in my opinion wrong as it does not open because of boost and is no high-boost protection. The BOV opens because of a high-vacuum situation and not because of boost. So we stick with the term BOV here.
The idea of a BOV is that they will increase the performance (by increasing throttle response) and lifetime of your turbo. They relieve the compressed air that is forced back into your turbo when you close the throttle body under load, which causes a surge or backspin. The turbo will keep spinning. Repetitive occurrence of turbo surge can damage the turbo and cause it to fail. In some of the old rally movies you can hear how such a turbo surge/backspin sounds like. I personally think it sound sort of "flappy" and "unhealthy", a little like a tortured bird
Don't be afraid now if you don't have a BOV. Your car will have some sort of valve or mechanism to prevent this with one or the other way.

I drive an automatic so the "performance" thing is more or less not existent. But I was just looking for that sound it makes - I know I broke tuner rule #1 with this: if it doesn't make you faster, don't do it. The concerns I had were that I have a LPT (Low Pressure Turbo) with about 6 PSI maximum and I was not sure if this will be enough to that sound at all. And what happens when I went the air to the atmosphere instead keeping it in the closed system or route routing it back to the air box? Will it throw a check-engine-light (CEL)? Will it harm my catalytic converters? So I just had to install it to find it out.

After some research I decided to buy a HKS SSQV instead of e.g. Blitz Super Sound or Tial BOV. For me it seems to be the probably best blow off valve on the market.

This is what HKS says about this valve - HKS SSQV

The Super Sequential BOV is a pull type relief valve, unlike other BOV's which are push spring type " are prone to leaking. The SSBOV is actuated by pressure alterations only, ensuring quick valve response " complete closure during idle. Standard BOV's must utilize large valves in order to accommodate high boost/power application. However, these large valves react slowly " require high activation pressure to open. Smaller, fast reacting valves, do not permit the air flow required for high horsepower. The SSBOV incorporates both for maximum performance. It is engineered utilizing a small primary valve for ultra quick activation along with a secondary valve for additional relief capacity. The SSBOV is made of billet aluminum " emits a unique, aggressive sound.

Bottom line is it makes a really cool sound and looks great.

I bought mine on eBay and I can highly recommend the seller, Japandy, I dealt with. If you are looking for a new one I suggest to have a look at www.blowoffvalves.com. Make sure you get a HKS SSQV :-)
I've got the S15 SR20DET Kit (Part# 1421-SN023) and with some minor adjustments (made the hose shorter) I was able to fit it.

Installation, done in October 2002

This is what it looked like before I started. On this picture the cover for the throttle cable is removed to have a better view at the parts.

Then I've cut the hose/pipe between intercooler and throttle body and I inserted a T-Piece (self-made) where I can connect the hose that goes to the BOV.

This is how it looks when it is finished. The vacuum (control) line is going to the vacuum tree right after the throttle body. The next step will be to replace the cut plastic pipe with a custom made metal pipe. To start with it did not block the built-in CBV. I've done this at a later stage. Read below.

I do have a boost gauge and the interesting thing is, that I can hear it "releasing" air even when I'm still in the 'vacuum' and not yet 'boost' area. The turbo is already spinning but not making boost yet when I let the throttle go. I can hear it when I'm under little load/throttle. You can also hear the two stages (small and large valve).

Is it loud? I think I can be happy considered the amount of boost I run (.. what means loud :-)). After I blocked he stock CBV (compressor bypass valve) - see below - it was a bit louder.

How do I adjust my HKS SSQV? There is a VERY interesting article on how to adjust a HKS SSQV on 935Motorsports.

Experience so far

After driving around for about a year I blocked the stock CBV (compressor bybass valve). It is a little louder now (about 30%) and it makes the noise for a longer period of time. No problems so far. I did NOT plate the original CBV as I was too lazy to crawl into the engine bay and try to open the turbo to add a plate where the CBV is, I just installed a one-way valve inline with the hose that drives the stock CBV. You can't just block the flow to the CBV, as it would open around 6-10 PSI of pressure and you wouldn't be able to hold more boost than this. With the one-way valve you let the boost go to the stock CBV to keep it closed but you don't allow vaccum to open it.

You always hear that the BOV will make you run rich when it vents to the atmosphere as it releases (MAF) "measured" air. The ECU will throw in fuel for air that never reaches the cylinder. Hmmm, this could be different with a MAP but I don't know. Well I did not notice any 'smoke'. But I can't guarantee that it does not happen or even harm your cats. On the other hand the ECU stop should sending fuel when you let off the gas. I have it now for about five years and no problems at all. After using it for over a year I had to smog-check it and passed with no problems at all. I'll post it as soon I would detect a problem with my setup. If you are looking for more information I recommend to go to a forum of your choice. Please use the "search" functionality there because I'm pretty sure it has already been discussed over and over again. If you have a Volvo I can recommend the forum on Volvospeed.

As soon as I get the new video cam I'll post a video of the BOV

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