SC - broken bypass valve

[SliderNH]

Just put on a boost gauge last night and I was getting Wonky readings. -22 at idle, -26 at full vac, and reading a high of -1 at WOT (usually about -4 at WOT). First thought was a faulty vac connection. NOPE. I poked around the engine and online and found out my bypass valve is broken. I noticed it was staying closed 100% of the time. Thought that was weird till I noticed the vacuum nipple on the bypass valve is completely broken off. Then I learned the vacuum line that comes off the back of the SC is supposed to be connected to the bypass valve. Before all this, I thought it was just for measuring boost output. I bought the SC used, and this is how I got it, PO never told me about the broken nipple, and I've never been around a fully functioning SC'd 4runner so I had no reason to assume something was wrong. Now I know, And now I feel like a complete dumbass. I ordered a new bypass valve, hope it will be here by the end of the week.

Whats my risk of running the SC in its current state? That is: bypass valve always closed, bypass valve-to-boost port nipple broken off (not connected to boost port), and the boost port is connected to the URD controller, boost gauge, and Fuel Pressure Regulator (Free FMU Mod).

After I get the new bypass valve installed, What should I expect to see for boost/vac numbers? What should I expect to feel? increase torque? What should I expect to hear? The bypass valve whistle as it opens and closes?

 

[4-Ripcord]

So the SC is not connected to the bypass valve via the vacuum line in the above image? That port it is supposed to be plugged into is just open to the atmospheric pressure? That is causing you to lose a lot of your boost. Its fine to drive, but im sure you have noticed that lack of power.

Once you get the new valve in properly. You shouldn't hear anything except the SC whine, and the rattle at idle. IDK about vacuum numbers, but boost should be around 7 I think with that 2.2 pulley.

Hope that gives you a bit of info.

 

[SliderNH]

Yes, the Port on the bypass valve is open to atmospheric pressure. Unless its blocked internally by crud or something. If my gauge is correct, I am not running any boost at all. Which is weird considering it does have a significant amount of power over stock. Keep in mind I have no idea how much power. I have not ridden in any other SC'd vehicle, not to mention another SC'd 4runner, so I have nothing to compare mine to.

If I have a vacuum leak why is the vac -22 to -26? Wouldn't it be more like 0 or -5?

 

[SliderNH]

AGH! I'm all jacked up

I had things all wrong. I am a complete noob. Problem One: I thought the vacuum line coming off the back of the SC was the boost port. Problem Two/Three/Four: I connected the Fuel Pressure regulator, the URD calibrator, and boost gauge to that same vacuum line. Problem Five: I don't have the vacuum line going from the bypass valve to the back of the SC. Sheeeesh.

 

[4-Ripcord]

Yeah that'll do it, lol.

The boost port in the diagram should be routed to the FPR behind the supercharger. The URD computer's boost input, boost gauges, etc should be T'd off that line.

The vacuum line is just for that bypass valve, nothing else.

 

[BigFishAllDay]

Good posting, Ripcord! :thumb3:

 

[SliderNH]

Yeah that'll do it, lol.

The boost port in the diagram should be routed to the FPR behind the supercharger. The URD computer's boost input, boost gauges, etc should be T'd off that line.

The vacuum line is just for that bypass valve, nothing else.

Yep, cool. Thanks for posting that picture, too. I saw that last night but I guess I needed to see it again. God:ybrick:

Hopefully home depot will have the correct size brass fitting for the boost port.

So since I've been running the URD, boost gauge, and Free FMU off the vacuum and not the boost, I'm curious what that has done to the system. Poor URD controller is going to be confused when it sees boost instead of vacuum. Dang. I wonder if I broke anything...Thanks for getting me straight!:hatsoff: