2stroke1971

I’m working on my sons 89 crx, b16. Trying to button up a few things with th basic turbo kit we are putting in. It’s the first turbo I’ve dealt with although I’ve been working on cars a long time and I’m an industrial mechanic/machinist by trade.
This will be a basic setup, minimal boost, 8 pounds or so, no intercooler just dipping out toes in th the water.
As for the waste gate , there’s a barb on top and a threaded hole for a fitting in the base. From what I’ve read it needs to be hooked to the turbo housing to reference boost pressure. First off, I Don’t see any ports in the housing for a fitting. Nowhere in the intake piping to grab it either.
My son says we can use engine vacuum since a vacuum port will be pressurized in a boost condition..:so something in the throttl body?? Doesn’t seem to make sense to me.
Also despite all I’ve read about solenoids, controllers, and multiple hoses, he tells me we need only the one line to the wastegate (at a bare minimum) to make it work.

Then theres th blowoff valve which , if we install it, requires a vacuum reference...which in my mind a tap into the throttle body would be the ticket ..but following my sons logic, that would be under pressure under boost, right?

So all engine vacuum sources become pressurized? Certainly not pressurizing th brake booster?!?!

In short—wastegate needs boost pressure reference, bov needs vacuum reference: my son seems to think boost/vacuum are one and the same as far as referencing the two devices and so could both read from the same area..like two ports in the manifold.

And what IS the simplest bare bones method of controlling a wastegate? Personally I don’t know why it would need any plumbing or references... the purpose is to limit boost pressure no? So a spring loaded poppet valve would simply yield and open at some pressure according to the spring ... or is it just a diaphragm that operates it? Seems needlessly complicated if so.

come to think of it a bov and waste gate both limit boost pressure, bov by blowing off excess boost, waste gate by slowing the impeller. Both could just b at the minimum, spring loaded valves with a mechanical adjustment.

thanks in advance for any input!!!

Txdragon

In short, your son is right. Also, get an intercooler. Even a small, 300hp rated will suffice. Pipes may be harder to source for the rex, but, best to keep it safe.

Txdragon

BOV isn't controlling boost in any way other than venting a pressurized system (pipes and intercooler) when a valve (throttle body plate) closes.. The only way that a BOV will dictate how much boost you're getting is if it's jacked up and leaking.. also, the wastegate needs to remain closed in order for the turbo to even begin building pressure or you may never even hit your intended boost level to begin with, so a mechanically adjusted frankenpiece would be out of the question.

Don't try to reinvent the wheel. If you're looking to go cheap, there are inexpensive options available.

DaX

iTrader: (1)

Even if the turbo's compressor cover had a port, best practice is to run the wastegate boost/vac reference to the intake manifold. And yes, you can get away with just one vac/boost source plumbed to the BOTTOM of the wastegate - that is the most simple setup. The wastegate is not simply a poppet valve - it is a spring loaded diaphragm. The top port with the barb fitting allows boost/vac to be applied to the top of the diaphragm, and the bottom port with no barb on it allows you to plumb boost/vac to the bottom of the diaphragm. Access to both sides is beneficial when running a boost controller - this will allow you to change the pressure at which the wastegate opens, and with a computer controlled solenoid, you can vary the wastegate opening based on all kinds of inputs, like what gear the car is in - this is essential for traction control on higher HP setups. Do some more reading on how a wastegate works (also look for how a 3-port and 4-port boost controller works) - there's tons of info out there.

BOV will require a boost/vac reference, just like the wastegate. Connect it to the intake manifold as well. Under boost, the pressure on top of the BOV diaphragm helps hold it closed. Under vacuum, the vacuum helps open the valve, releasing the pressure on the charge pipe and reducing the chances of compressor surge. Your brake booster line should have a 1-way check valve in it to prevent it from seeing any boost - only vacuum.

2stroke1971

Awesome, thanks!
we do have a boost controller.. just a little flow control it looks like.... I suppose that serves to counter the pressure coming in from the top side port to tune when it releases.

Abd the bov lets out boost that’s in the pipe when the throttle closes. Got it!

Neat. So the BOV comes into play with the throttle closed and low pressure/ vacuum in the intake. Blows off whatever’s in the pipe regardless of how much pressure is in there.

Bov does not as I thought control boost....but....Just another thought experiment...You could have a boost limiting valve in the intake pipe...a precisely adjustable mechanical relief valve.... hits 10 pounds, opens up. Etc. I’m sure there’s an advantage to slowing the turbo by bleeding off exhaust instead, just sayin

DaX

iTrader: (1)

I realized I had a typo - if you're not running a boost controller, run the boost/vac reference to the BOTTOM port on the wastegate. I fixed it in my previous post.

The spring (pushing down from the top) holds the WG closed. When the bottom of the diaphragm sees boost, it counteracts the spring pressure until it overcomes it, opening the WG.

Txdragon

This is exactly what a wastegate does and why it needs a boost reference. It needs to "see" how much boost is is getting. The pre-determined boost spring; i.e. 8lb, 10lb, 500lb, etc. helps keep it closed until that pressure is achieved, then the valve opens, allowing exhaust gas escape before reaching the turbine. It doesn't matter if you have a 2lb spring, if you dont have a boost reference hooked up, you'll over spool that thing into oblivion. lol