69 camaro ls1 twin turbos

[gEtyOpAPiOn]

so i bought the turbos ...i would like to know on how do you control the boost with the waste gate ...is my first time and im not familiar on how waste gates work ...as in they sell them with different springs ....so is that mean that they are non adjustable ? how can you adjust the boost as in goin 7lbs for street and maybe 10-12 on race gas for the track ? any help would be apreciated thanks

[Y-TRY]

Okay, here's how it works:

The wastegate is made up of 3 chambers. I don't know the actual terms but just follow along... From the Bottom-to-top

1) Exhaust chamber. This is the base of the wastegate that bolts to the exhaust. It has a valve in it that rides up and down in a guide, just like in a cylinder head. When the valve is open, the exhaust gasses are diverted through this chamber and away from the turbo, letting the turbo slow down. (On Diagram, has Inlet/Outlet)

2) The Bottom Chamber. This bottom portion of the wastegate is seperate from the exhaust chamber. It's roof is a flexible diaphragm. There is a port on the side of this chamber that is referenced to a boost source (either the manifold -better- or the turbo). The valve , which passes through the exhaust chamber also passes through this bottom chamber and is attached to the diaphragm. This chamber always has the same pressure as in the manifold, or wherever it's referenced. (On diagram, has "Bottom Port")

3) Top Chamber. This chamber holds the Wastegate Spring. It's floor is the diaphragm listed above. The spring is compressed between the roof of the top chamber and the diaphragm. The spring holds the valve down proportionate to the spring rate. There is also a port on the top of this chamber, which is usually referenced to the boost controller. (On Diagram, has "Top Port")

With me so far?

How it works: As boost builds in the manifold it also builds in the bottom chamber and exerts a froce 'up' against the diaphragm, trying to lift the valve. When this pressure exceeds the 'down' pressure of the spring then the valve is lifted off its seat and the exhaust gasses are able to pass through the exhaust chamber (usually back into the exhaust system after the turbo, ie downpipe).

A common regulator type of boost controller helps bolster the spring rate. One side of the controller is also hooked to a boost source. You can control how much of this boost passes through it by a dial or screw. (Think water faucet). That pressure then passes into the Top Chamber. That boost adds to the pressure that the spring is pushing 'down'. You can only add as much pressure to the top as your boost reference is seeing.

So, you could have a 10psi spring, then add 5psi of air pressure in the Top Chamber, and the manifold/bottom chamber would need 15psi to overcome the 'down' force being exerted on the diaphragm from the top to raise the valve.

Maybe a link would help. Only really pay attention to the top of the page for this discussion.

Click and go to Page 5 (http://www.turbosmart.com.au/pdf/FG-EBOOST-40-60.pdf)

Another tip worth mentioning: The pressure inside your header or exhaust manifold is also exerting a force 'up' on the face of the valve. This will try to open the valve. You will also have to factor that pressure into your boost setting. This is why you can't just double the boost. For example- If you want to reach 20psi, it will be hard to get there with a 10psi spring and 10psi through the controller. Depending on many factors, you'd probably only see about 16-17psi. It's be better to start with a 15psi spring and add from there, just for example.

Good Luck with your project. For yours, go with a spring that max's-out at your LOWEST desired boost (6psi) and use the controller to dial in the rest of the boost, if you can.

[gEtyOpAPiOn]

oh great thanks for that very helpful information so if i get a 6 psi spring i can basicly boost it up ..hehe to like 8-10 lb

[Y-TRY]

It's also worth mentioning....

There is another type of Boost Controller. I think that TurboSmart diagram calls it a "gate valve" or you can call it a bleed valve...

On this type of controller the Top Chamber and port are ignored. Instead of adding pressure to help the spring this type of controller "tricks" the wastegate:

The gate valve bleeds away pressure ahead of the Bottom Port. If the Manifold is seeing 10psi it bleeds away an amount of that so your wastegate only senses 6, or whatever you set. So it delays the valve opening by how much boost you 'hide' from the wastegate's Bottom Chamber.

It's important that this type of valve requires that you DO NOT reference it to the manifold. Otherwise, it'll be open to the atmosphere and would cause a vac. leak in normal conditions.

My car is carb'd and I went with simple. I use a TurboXS Dual Stage controller. On this, the controller has two solenoids that are electrically switched. I run a 9.7psi spring but the controller's first setting is at 10psi and the 2nd at 18psi. I can switch between the two setting on the fly from a switch in the cabin. I also have an MSD BTM that has a dial in the console. On race gas days I can switch to the 2nd boost setting and dial-in more timing without making any other changes. Pretty sweet.

[Fuelie Fan]

How do you get a boost reading without referencing it to the manifold? Or do you mean don't go directly to the manifold without a check valve in between?

[Y-TRY]

Most diagrams will show the boost referencing from a port on the compressor housing of the turbo. The turbos actually have tapped holes for fittings there.

I guess it's easier to package that way, but I think it's more accurate to reference what is actually going on in the engine. That second type of controller has to be attached to the turbo. I plugged the holes on my turbos and referenced the manifold (I have the 1st type of controller)

[EFI69Cam]

Is is correct that factory EFI turbo engines have a computer controlled waste gate? So the computer can control boost based on knock throttle position etc

[Y-TRY]

Yes. But I have no idea how those work.

[J2speedandcustom]

Is is correct that factory EFI turbo engines have a computer controlled waste gate? So the computer can control boost based on knock throttle position etc

Most of these are a boost controller, which is hooked to the wastegate. Depending on the ECM you can regulated boost a few ways. VSS "vehicle speed sensor", load through the rpm band, etc.

[68RallySport]

I thought i saw a 69 with no hood and two turbos sticken out it at the muffler shop a couple days ago, took the TTA down to napa and i drove past and i think i saw it at the shop, unless u guys got more then one red 69 with turbo's!!!