BlaCkPlaGUE

I was thinking the other day about BOV's and such when I came across a little idea. Say your maximum PSI you ever want to achieve in your car (before you think your going to detonate) when you drive is 15. Now the wastegate controlls this obviously and if your intake exceeds your set psi, the wastegate starts to open.

What if your wastegate siezed up, or the vac hose burned off, or who the hell knows, but your wastegate doesnt work?
As a failsafe, what if you rigged up a sort of blow off valve type device that worked the same way a wastegate did, except instead of cracking open at a set PSI, it would just pop open and not shut until you reset it again? That way all your boosted air will go out this hole until you reset it, and if it ever did pop, your PSI would never exceed what you set it to. You could hook up a seperate air filter on it or whatever so that when it does pop and your idleing, it does not take in unfiltered air.

Would this be a dumb idea? explain?

Im still learning, be easy ok?

DCrosby

That would be a pop off valve, and Blitz or Greddy makes a bov, which has two hoses one for pop off, and one for blow off.

Then There's a Greddy Pop Off Valve, that opens @ preset PSI, and closes once, you get off the trottle... so no filter needed.... This will bring out the trolls from under their rocks spewing all kinds of hate about compressor surge... as the compressor is spinning freely now, and that will wear out your bearings if not kept under controll or you figure out why you're exceeding the pressure you set....

Be Safe !

-DC

BlaCkPlaGUE

ha!

had no idea it was something you could buy! cool, thank you.

BLUE TII

iTrader: (9)

Yes, I had the occasions(s) to test my Greddy "pop off valve" as I had boost creep problems.

Works well to limit boost, though it IS hard of the turbos in the same way an intercooler hose popping off mid boost is. I doubt a turbo would live too long using this as a boost control, but works well as failsafe.

A couple tips I learned from using it.

Setting the opening pressure level. I have seen many people ask how to do this online since the instructions are in Japanese. There is a chart in the instructions that basically says "number of turns" on one side and "opening pressure" on the other.

So a "turn" is one full rotation of the allen head stud ONCE YOU FEEL IT CONTACT THE VALVE and the resistance to turning goes up.

Convert the Japanese pressure measurement to one you are comfortable with and choose an opening pressure that is a bit above your max desired boost and below the limit you can safely tune your fuel system to (yes, you should always have SOME buffer). Remember, boost controllers often spike boost above the set pressure just before the wastegate opens, so you probably need at least 5psi above desired boost level at least.

This will get you pretty close to the right opening pressure. Now you can stick a little grease (or I preffer Hylomar as it doesn't thin w/ heat) on the on the piston valve that is exposed through the pop off valves exhaust port.

Go for a drive w/ everything working as it should to achieve your desired boost. Check the goo on the piston to see if it has been pushed off the piston as the pop off valve opened.

If it has moved, tighten the valve a BIT and try again.

If it has NOT moved loosen the valve and try again. Then go to the above step once it does open.

That will get you just about the right opening pressure for the pop off valve. You may find you can hear it when the pop off valve opens as it is a PHWWW rasberry sound as it cycles and if is stick way open you should feel the compressor surge if you are familiar w/ turbos and the datalogs will show the Intake Air Temp spike rapidly.

Remember to always tune WAY rich over your desired boost level, this will usually help keep boost creep down or safer- the only way it won't is if for some reason you also have excessive ignition timing retard turning your turbo into a jet engine.

Falcoms

What I was just thinking about (even though I have never owned a turbo 7) for a falesafe device would be running a BOV and use that as your variable, but set the wastegate to whatever your maximum PSI you would ever want to hit is. In doing this, you have a failsafe backup so that if your BOV somehow sticks shut, your handie dandie little backup just lets out the exhaust gas pressure, and in doing so, releaving the manifold pressure. Just a thought. I honestly have no friggin clue about turbo systems, I'm just trying to get an idea I've had out in the open and see what everyone says.

surfpac

You can get one of those pressure relief valves from McMaster.com for less than $50. Ain't pretty but serves the pupose as those name brand ones.

Zero R

iTrader: (1)

You can run no wastegate and just a popoff valve and blowoff valve despite what a lot have said it can be and is done. I wouldn't recommend it on smaller turbine housings though.

Falcoms

What would be the smallest turbo that you'd run no wastegate on (GT series)?

AntiVenom7

well not to be dumb, because i know i am. but why would it be hard on your turbo if say. your normal pressure is 15 and the wastegate/boost controller keeps it there and you set the pop off valve to 17psi. in that case the pop off valve should never open and therefore not harm the turbos.

am i thinking about this the wrong way?

Zero R

iTrader: (1)

Once I get some time I would like to see just how small would work well. It is labor intensive to keep pulling off and putting on turbine housings and run the car again. The concern with the smaller housing is back pressure getting too high and causing detonation from dilution due to reverse flow.

Falcoms

I know what you mean based on all the threads about people trying to figure out how to pull the turbo to port the wastegate (and they're just stock turbos, not the big honkin things you play with). How about this question, though: Why do you say that you would not reccomend running just a BOV with a wastegate backup on a smaller compressor housing? Is it because the turbo could overrev and explode into millions of little pieces or what?

I am sorry if I'm asking "basic" questions, but I am rather new to this whole concept (I know how the turbo works, thats a start, right?) and am trying to get a firmer understanding of the setups available.

Zero R

iTrader: (1)

I'm not saying running just wastegate and BOV would be bad at all. I was just making a point that you could run no wastegate at all. On a smaller housing you will need to for the reason I stated above.