Boost Control Valve

[GrndNatnl]

If I insert a fine-tune air valve (or fishtank valve) within the wastegate lines, which line or where to I splice it into? The lines are from the turbo outlet to a Y-connector. Then from the Y, one goes to the WG, and the other goes to the solenoid on top of the valve cover, with the ECM connector plugged into it.

Any advice on tuning this? How do I determine how much boost it's pushing without overboosting and blowing a head gasket? I guess run it inside the car, close it somewhat, then WOT adjust it? Or no? I'm new at this trick, so please fill me in. I'd rather just have it under the hood to avoid running hoses everywhere. So how do I adjust it carefully when I cant reach it while driving?

 

[MSDGN]

With a valve like that to control boost you basically take the wastegate solenoid out of the picture...remove the hose from the solenoid and attach the valve to the hose...as for setting boost
close the valve all the way and set a baseline boost with the wastegate rod only...then open the valve slowly and go for a blast...the valves aren't linear so each will be different and one turn or half-turn...etc will not correspond to a set amount of boost...just have to experiment and get familiar withe valve and settings...IMO I wouldn't put the valve in the car...it's handy that way but several that I've seen do that had strange boost problems...also I'd highly recommend an aftermarket boost gauge before playing with a valve....

 

[GrndNatnl]

I have an aftermarket boost gauge already. Believe me, I'm not that crazy to go fooling with boost without one.

So you're saying remove the hose from the solenoid and put the valve on the end, with the other end open? What happens to the solenoid? Should it be disconnected? Or is it ok to leave it w/o the hose connected? Thats another thing I'm not sure about causing a problem.

I would almost think that I would want the valve between the turbo outlet and the WG. Meaning, with the valve fully open, it would be normal WG operation. Thus far, closing it a little would restrict the amount of pressure to the WG diaphragm, delaying its opening process. Sort of sounds dangerous that way. I'm confused as to how the wg-solenoid works.

Thanks for the reply, too.

 

[MSDGN]

Yes attach the valve to the end of the hose...you can take off that little plastic elbow and short piece of hose if you want...I have mine mounted right next to the solenoid...just leave the port on the solenoid open or put a rubber cap on it...you have to leave the electrical connector on otherwise it will code...as for how the solenoid works it just meters the amount of air to bleed off dependent on the setting in the chip to attain a specified boost level...valve works the same way...the more air bled off the higher the boost and vice-versa...

 

[GrndNatnl]

Ok, I get it. But the only thing that still doesnt make sense is: How is the boost level higher when it's bleeding off? Wouldnt that reduce pressure? Can ya explain?

Sorry to keep buggin ya, but you're smart on this topic. I appriciate it much. Trying to get tweaks set up for Buick Race Day in a week and a half.

 

[scottyb]

The solenoid bleeds off pressure. This pressure is needed to push open the wastegate. If you took the line from the turbo and connected it directly to the wastegate actuator, the actuator would open at ~10 lbs. The solenoid vents some of the pressure out so that the lines "see" 10 lbs, while your boost is actually 15 lbs. The solenoid simply pulses a small valve to do this. A performance chip (like my RA93) pulses it longer so more air vents and I see 17 lbs.
BTW, I tried a needle valve in place of the solenoid like you plan to. I routed the line inside the car. I was getting a boost spike with this setup. It would boost to about 20lbs then settle back to 17. I assume this is because of the length of the line, and increased area to "pressurize" before the actuator saw the 10 lbs. The adjustment, however, worked very well and required almost a full turn for each addition pound of boost. A local TR guy gave me a valve that is used for hydraulics and he says it eliminated the spike with the same setup. I will try this soon.

Scott

 

[GrndNatnl]

Now it all makes sense. Thanks, both of you, for the replies and tech info. I'll be sure to look for a good quality, fine tune valve. Nothing to cheap thats either open or closed. Thanks again. Now I'm learning more and more each day.

 

[GrndNatnl]

Ok, one more thing:

I just picked up a couple nice valves today. One of them at Home Depot thats pretty fine tune, and has an in and out side. The other from the local aquarium store thats a brass valve, with 3 ports. A straight line across, and off the side is the vlave-controlled port with a swing valve on it. (Meaning straight its open, flip it sideways its closed) but still is stiff and fine-tunable. It's smaller and seems a little more restrictive then the bigger brass one, but no more restrictive then say the nylon tubing to a boost gauge, or the little vacuum connectors between the boost lines anyway.

My question is, if I use the one with the 3rd bleeder port, could I make it so that its still connected to the solenoid, then if I open the bleeder, it brings up the boost? Or is that bad? Should the ECM just be completely brought out of the picture? I figure if its possible, it would be easier to set it back to normal boost levels. Open it the right amount at the track, then when finished, close it and go home. Any feedback?

 

[nastysix]

Yes you can hook it up in line and still use the solenoid. I suggest you do, for the very reason you mentioned. I've been running mine that way since 1987. I don't even have an adjustable rod on my wastegate.
Larry

 

[scottyb]

I say give it a shot. Just don't play with the boost without a good boost gauge and scantool.