I think to the bonnet above the carb, but I just wanted to check and be sure.

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"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
JSP Motorsports
ICON Motorsports

 

usually you want it closest to the throttle body or carb you can get it.

yes they are vacuum reverenced

 

MANIFOLD VACUUM ONLY! If you hook it up before the throttle blades, the BOV will NEVER open.

 

I really hate to reply like this when I was the one asking for help...but come on people.


Dude I know they're vacuum referenced. I didn't ask if they connected to vacuum..I asked where. I also didn't ask how close to the carb it should be...I asked if they go above the throttle or below.


I realize I asked, but upon firther consideration thats impossible. It's the other way around...the BOV has to go before the throttle. it's the wastegates I'm still not sure about.

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"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
JSP Motorsports
ICON Motorsports

 

The BOV is connected to the manifold vacuum (i.e. between the heads and throttlebody). When the BOV gets a vacuum, it opens, letting the turbos keep spinning. When the manifold is pressurized (boost) the BOV is forced closed by the pressure, in addition to the spring. If it connected to the intake pipes before the TB, then it will never see a vacuum, and will not open. A BOV is not a pressure relief valve per se.

Wastegates can be controlled two different ways. Either by vacuum, where an electronic controller sends a vacuum signal opening it, or by pressure, where the wastegate is forced open at a certain intake pressure. I have mine plumbed to the intake tube before the intercooler for faster wastegate response, but it will have a slightly lower boost than using a signal after the throttlebody.

Both are basically air operated valves. There is a diaphragm, a spring, and a plunger. If the pressure is above the diaphragm, it pushes it down, moving the plunger. Vacuum sucks the diaphragm in the direction the vacuum is from. Clear as mud?

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Andris Skulte
Skulte Performance Designs
Z28tt-89 IROC T56 DFI Twin Turbo
http://www.skulte.com



[This message has been edited by askulte (edited May 03, 2001).]

 

Hey Jester,

The BOV physically mounts BEFORE the TB, but the signal must come from a full manifold vacuum source. Maybe I read your question wrong.

I forgot all about the wastegate question. There are three places to hook the wastegate signal line to.

1- Turbo outlet. Most Garrett turbos have a spot right on the compressor housing to hook up a wastegate actuator signal line to. Problem is that if you hook it up there, it will cause the wastegate to crack open earlier and possibly cause a slower boost rise than if you hook it up to...
2- Right before the TB. Thats a good spot too. The wastegate will still crack open at the same pressure, but a little later. May help with boost rise time too (NOT LAG!). But the best all around and the most commonly used spot is...
3- The manifold. Excellent boost rise. More accurate signal to the wastegate actuator. Its the spot that the OEM's and all of the people I know of use.

Now, after you decide which spot to use, dont forget your electronic boost controller. Less chance of boost creep. More accurate boost control. Also, some units "learn" the boost curve of the vehicle at the minimum boost level. They hold the wastegate closed longer to build boost faster. And when you turn up the boost, they control the boost spikes a lot better than the old "boost ****".

And before you ask... If you have say a 9psi spring in your wastegate actuator, it will actually start to open (or crack) at a lower psi than what the spring is actually rated at. So your 9psi actuator may actually start to crack open and bleed exhaust past the turbine wheel at 5-7psi. Just wanted to make sure you understood what I meant.

Hope this helped.

 

ok guys thanks, that all makes sense. I had my thinking backwards with the BOV..thinking it opened under excess pressure not vacuum. I guess I'll use manifold vacuum for both.


I'll be usign a manual boost conttroller for now..I can always upgrade later if I need to.

------------------
"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
JSP Motorsports
ICON Motorsports

 

OK. I was just making a suggestion. Good luck and make sure you let us know the results.