355gta

I am still new to the turbo ting and i have been doing alot of research but can't seem to answer these two or three little questions. On my 50mm external wastegate and my blow off valve i have two vacuum lines that go to them. I know one is for boost reference for controlling them but the other i do not know. Also, the top of my wastegate has a threaded hole where the adjustment screw should go, but it is missing. I took the wastegate apart and i do not see how this screw could possibly adjust anything. There is nothing for the screw to press against to stiffen the spring. I figured there would be a small flat round piece which could increase spring tension and raise the could level but nothing. I have pics with arrows pointing toward the vacuum lines and the screw assembly. If anyone can help it would be great. Thanks

junkcltr

iTrader: (1)

Quite a few people get confused with the threaded holes. Both holes are there to install a fitting for vacuum/boost. That wastegate is not adjustable with a rod. It is designed to be adjusted with a boost controller (electronic air valve, mechanical check ball w/ spring, etc).

The two holes are so that you can install a boost controller. One hole allows boost to pressure one side of the rubber diaphram and the other is to counter-act that pressure using a boost controller.

Without a boost controller, one hole gets manifold boost pressure and the other hole is open to free air. You apply the boost line to one hole (the center hole from memory). The other hole gets a fittling to free air. You should test that you have boost applied to the correct hole before running the engine. Use an air compressor with a regulator and slowly turn up the pressure and watch for the exh. valve to open as you increase the pressure (max. of 15 PSI or so). Or you can take it apart and see which hole feeds air to the opposite side of the wastegate spring...that is where the boost pressure should go.

EDIT: Looking at the pic, the top hole is for the boost inlet and the bottom hole is for the free air fitting. Do not plug the free air hole. If plug it the wastegate will not open. It will air bind it. Make sure to test with an air compressor before running the engine.

355gta

thanks for the help. does this apply to the bov in the same concept, but instead of controlling boost it releases it.

junkcltr

iTrader: (1)

They kind of work the same way:

A wastegate has a valve that the exhaust is trying to push open. A spring tries to keep it closed. As intake boost gets higher it helps the exhaust by pushing on the spring and allows it to compress and open the valve. When chosing a wastegate spring one needs to consider the valve size in terms of how much intake boost it will take to open the valve.

A blow-off valve has a valve that the intake is trying to push open. A spring tries to keep it closed. Only when intake pressure is high enough, the valve will open and vent off pressure. It is the same way the wastegate works, BUT without the pressure port help on the spring.

You can't interchange a WG and BOV. You always need a WG, but don't always need a BOV.

Six_Shooter

iTrader: (2)

On the wastegate the boost refernce, or the line that has boost pressure, usually attached to the intake plenum, or the outlet of the compressor, goes to the bottom fitting to lift the plunger off the seat of the wastegate. If the boost presure line is applied to the top hole, or opposite end of the wastegate of the exhaust inlet, the wastegate will never open.

junkcltr, the BOV will actually lift off the seat easier with boost pressure applied to the port at the bottom of the BOV, much like the wastegate and with some BOVs is actually needed to open the BOV.
What you will usually find is that the bottom chamber of the diaphram takes pressure from the intake tube, sometimes there is a drilled port through the base of the BOV that samples the intake tube pressure, this will help lift the plunger off the seat , when boost pressure is removed from above the diphram where that line is attached to the intake plenum, so that when the positive pressure is present in the intake plenum, there is also positive on the top of the diaphram to keep the BOV closed. This effectively equalizes the pressure above and below the diaphram that means that it is only spring pressure keeping it closed.

junkcltr

iTrader: (1)

That makes sense. I never looked at one close enough to see the port hole.

355gta

Thanks for the help. I guess it sounded like I did not know what they were for or how they worked. I definitely understand all of that or i would not be taking on such a big project. I just was not sure why my wastegate had three open ports. i thought the one on top in the center was for adjustment, but it sounds like it has to be left open to the atmosphere. The bottom line, which is under the diaphram needs to have positive boost pressure to help lift the valve from its seat. The top line, which is next the the one in te center that needs to be left open to the atmosphere, I am still lost on. As for the BOV, the bottom line should go to the intake to reference boost and the top should go past the throttle blades so that when they close, the psitive pressure from the intake tube and the negative pressure from inside the intake(because the closed throttle blades)will work together to discahrge the boost as the throttle is released. Right. All i need to know now is the top line on the wastegate and to make sure i understood correctly that the center one in the top needs to stay open. Thanks

junkcltr

iTrader: (1)

I have a similiar or the same WG as you sitting in a box. I took it apart when I got it months ago to see which port was which and to make sure there was no internal deffectsf. I will take a look at it again tomorrow (maybe tonight) and let you know how the ports connect to it.

junkcltr

iTrader: (1)

Yup, I have the same wastegate. Six_Shooter is correct on the lines.

Connect the bottom hole (single one all by itself) to compressor outlet or the intake manifold.

Leave the top center hole alone.

Put a fitting to free air in the top hole on the edge of the WG.....or connect it to the boost controller if you are using one.

Six_Shooter

iTrader: (2)

No, the TOP port goes to the intake, and the bottom port would either stay open or better yet, attach to the intake tube, for better plunger lift off.

355gta

thanks, that clears it up. six-shooter, you are right, i got mixed up in typing. I am not sure how the top hole on the edge will connect to the boost controller. that should be the hole on bottom to limit the ammount of boost it sees to lift the valve, right. Because all a boost controller does to the waste gate is "fool" the spring to believing you are only making 10 psi(if that is the spring rate) even if you are running twenty. It basically controls the "vaccum" going to it.
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Also, what do you mean by free air. I am using an electronic boost controller so it does not matter but I am wondering what you mean by that. If the top center hole is open, with nothing screwed into it, then why would the one next to it need a fitting then nothing, just to draw air. I think I am not understanding th free air term completely. I really do appreciate all this help as well. I almost have the rest of the cage done, then it is on to plumbing all this. Still have a lot more to do after that though.

junkcltr

iTrader: (1)

I think Six_Shooter and I are saying the same thing.

Another way to say it:

Connect the side port to the intake manifold or compressor (it is below the diaphram).

Leave the port at the edge of the "hat" open (free air), or connect to the low side of your boost controller, or connect to the compressor inlet (air filter).

Plug the port at the center of the "hat"

EDIT: read this: http://www.theturboforums.com/smf/in...?topic=79997.0
It will also give you the correct thread size.

355gta

Thanks for all the help. I appreciate it. I am currently fabbing alot of stuff. I am going to try to get some pics on my website soon.