legacycentral bbs

ok i ordered a front mount the other day and have a few questions so im ready with the right parts befor i jump into the instal next week.

1. will rubber conectors form the home depot work or will they melt under temps?

2 what is the turbos outlet diamater and same on the tb?

3 where can i find a flange to conect the stock bov to the piping?

and finaly a little ot tho

how do you take the fron bmper cover off

Turbo outlet is 1 7/8", or pretty damn close. TB outlet is 2.75".

Don't use home-depot connectors, go to a speed shop and get Samco style silicone hoses.

Weld a bung to one of the pipes for the BOV. Don't use the stock BOV though, you will overpower it almost immediately. Get a good aftermarket peice and recirc it or run it atmospheric.

what do you mean over power it. i remember some who were running a stock bov and doing just fine with higher boost level.

I have a stock BOV running 20psi on my TD05 its fine......

I am also using the stock bov. no problems.

Hmm, I was having problems with mine at 15psi

Mine must have been bad.

I thought the turbo compressor outlet was closer to 45mm, or 1 3/4".

I don't believe the common wisdom about blowoff valves "leaking under heavy boost."

I think it's got a kernel of truth, but that it's ultimately misguided. Here's what I can figure, from examining our stock valve, the stock valve from a new age WRX, the stock valve from a 1st-generation 626/MX-6/Probe, and the stock valve from a 1st-generation DSM.

The stock blowoff valve's position is controlled by the pressure differential between its inlet and its vacuum port. The inlet is normally connected to the compressor outlet, and the vacuum port is normally connected to the intake manifold.

The valve is sensitive to the difference between compressor outlet pressure and manifold pressure. When this difference exceeds a certain threshold, the valve opens to relieve pressure.

Ordinarily, the only time compressor outlet pressure vastly exceeds manifold pressure is when the throttle is shut during a shift, or when the engine is idling or nearly idling.

Buuuut.... What happens when you add in an intercooler? Pressure drop! The intercooler represents a flow restriction, so intercooler inlet pressure is higher than intercooler outlet pressure.

Well, intercooler inlet pressure is the same as compressor outlet pressure. So, once you install your intercooler, compressor outlet pressure is suddenly automatically less than manifold pressure.

At fairly low boost, that's not a big deal.

But, when you start turning the boost up, the pressure drop across the intercooler also goes up. That 15 psi at the manifold, Phil, was probably like 20ish psi at the compressor outlet. At full boost, your blowoff valve was seeing a pressure differential of 5 psi! Under normal circumstances, a 5 psi drop between the compressor outlet and manifold means that the throttle plate is closing, which means the valve should open.

There are two ways I can see to solve the problem. One is to improve the flow of your intercooling setup. The other is to move the blowoff valve to be between the intercooler and throttle body instead of between the compressor and the intercooler. That's what they did on the new age WRX; the blowoff valve is on the intercooler's outlet end tank. That means that the intercooler's pressure drop shouldn't matter. In fact, from what I can tell, a stock WRX blowoff valve configured like stock will never "leak boost" until you reach a pressure high enough to actually destroy its diaphragm. I would imagine most front-mount intercooler setups also put the valve on the intercooler outlet side, with the same benefit.

Cliff's Notes: If your blowoff valve is leaking at high boost, it's really because your intercooler setup is restrictive. Either make it flow better, or move the valve to the other side of the intercooler.

ummmmm...... I beleive we are talking about fmic's right now, its common sense to put the bov close as possible to the throttle body so that the air continues to flow in one direction, also so that it plumbs back into your turbo intercooled air.

what you say is true to tmic's but for a fmic the bov location is better being as close to the throttle body as possible.

We're agreeing, rsstiboy. I'm saying to put the valve close to the throttle body too.

but the question is where do i find a flange to conect the stock bov to the pipeing

make one up, i had to...

Or get a valve that's already mounted in some pipe. I could sell you the valve from a stock 1st-generation MX-6 that's like that... I can get you a picture if you like.