Contour Enthusiasts Group Archives Forums Modifications Forced Induction Discussion on BOV's

Now most know I am building a larger intercooler but to upgrade boost levels one must change all things to compensate for higher volume of air. I have the original XS type S BOV which is only good up to 15psi on small displacement motors. So therefore it might be good up to 500cfm.

Now I am shopping for new ones am more I read more I get confused on which one works best for my application.

Now the differences I noticed is that some come with larger diameter pistons to relieve high volume of air quickly reducing compressor shutter.

Next difference is some are adjuustable with bolt and nut to adjust the stiffness of the spring others use washers like mine and other use a boost controller to control.

There are different flange styles which basically make certain ones harder to fabricate than others.

Then they have one who have horn to magnify the sound levels and other which have ports manchined in them.

Now I looked on EBAY since prices are cheaper there too. The greddy type r are running ballpark of 200.00 and the HKS a little cheaper which is a weird design too. I noticed that there are some Tial 50mm ones which are for high power motors which are about 200.00 too but you have no adjustment besides spring changes.

I noticed there are knock-offs of each brand so are these from anyone knowledge as good as the real one. If so they are about 100.00 cheaper too.

SO basically I don't know what I should stay away from or what may be too small to use. I will flow the maxinum air from my T3/T4 so I want to make sure I am making the right choice.

I am trying to make the setup less expensive but effective in the best way if that sounds valid. I like to find one that has aluminum flange that can fit on a 3" base circular one too if not I can make a two bolt flange work too.

Any suggestion guys would help me decide on the purchase. Thanks

Never ever ever buy a knockoff. That is real bad idea, because they tend to leak.

HKS and the Greddy are very similar. From my understanding they will hold up to 25 psi easily. Pretty reliable if installed correctly.

For the money Tial seems to be a good choice. The fact a lot of high powered cars use them is a good sign. Anyone I know who has had a Tial BOV has never said anything negative about it.

For the record I have a Forge Motorsports BOV which is boost rated through springs like the Tial. Haven't had any issues at 20 psi.

Tial is one of the few afermarket BOV's designed properly. Go with it and never look back.

I have a TIAL going on my current project. I takes a larger flange, but if you can make it work, go for it.

hey Chris do you have measurments on the flange so I can determine if I can weld it on my intercooler.

Forge is very good.

One of the biggest things in deciding what is good and what is bad is first of all the design of the BOV. This has been discussed before but a lot of the cheap BOV's have the same surface area of the valve face and the surface area that the manifold pressure is pressing on the back side. What happens when you have this situation? A lot of leaky BOV's.

A properly designed BOV will hold an insane amount of pressure because it is designed to always have the manifold pressure holding the BOV closed pressing on a much larger surface area than the face of the valve itself (which is of course also subject to manifold pressure). This creates a huge difference in pressure on the back side of the valve which means it will hold until the cows come home.

Most of the ones that people complain about having to dink around with washers and springs all the time are the first type. The latter type often have adjustments as well but it's really not to help hold it closed, it's to set at what vacuum the BOV will open at.

OK.. that's my BOV ramble for now...

And just to throw it in there.. if you have a drawthrough MAF use a BPV.

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