turbo charger design
 

Hi

I have just taken a gale banks water cooled hot side housing of a rayjay, and noticed they have a hole cut as a by pass round the tubo blade.

I thought about welding it closed and installing a spring loaded cold side blow off type valve instead (cheaper than a waiste gate+ easier to install). So I have maximum power when getting onto the plane.

Also will this hole stop over revving of the turbo, and do turbos suffer from over revving

Holes are about 10mill wide.

There is no waist gate or blow off valve installed on this twin turbo gale banks kit, and this is obviously the crude metering system.

What I would like to know is the perameters of such a design. Why was it built like this. The hole looks part of the casting, buy why did Gale banks design it without a waist gate?

My only thought was this reduces high load on the drive while getting onto the plane.

Maybe I just object to loosing power this way, and therefore should leave it alone. As this is what I will do if I dont find out why it was so designed

The hole was Gale banks way of bypassing exhaust & limiting total boost. In a 454 stage III setup a 1/2 hole would produce a max of 10 lbs of boost. 3/8" hole about 15 lbs boost. I taped the hole & screw a pipe plug in hole to plug it. I then used die grinder & smoothed out the plug. PFM made a turbo kit that restricted the turbo output to limit boost. The problem with doing that is that the turbo is producing max boost, max heat, & max exhaust restriction. The way to do it is to install wastegates. I am assuming the reason that they did not install wastegates was first the cost, having to deal with the heat, & having to deal with the plumbing. If you go with the waste gate you will get max boost at low rpm's & then when the wastegate gets to it's pop off pressure it will start bypassing some of the exhaust, thus limiting boost the motor sees. If you want to install wastegates expect to pay about $800.00 for the wastegates. The other advantage of wastgates is you can plumb it so you have a dial on the dash & you can just dial in the max. boost you want.

Did you fit wastgates, and what sort of kit is the one pfm makes. I dont know who they are.

I wondered if it was possible to run some kind of ball and spring pressure valve, that I would be able to plumb into a small 1/2 inch pipe that by passes the turbo. As thee is no real place to mount a waistgate with ease, all the exhaust manifold pipes are water jacketed, so getting into them is difficult. I know I can find spots where I can fit the half inch pipe without cutting through the water jacket.

Do you know of any such valve that would fit in the exhaust apart from a wastgate. Cost is the main preventative.

I had M&W twin turbo setup. I had a pop off valve that you talked about. It worked ok, I could limit my boost to 5-6 lbs with no trouble. I too believe a wast gate is the way to go though. Your turbo won't be working so hard at higher rpms. When it works hard it heats up the intake air a lot more than it need so. Cooler air means more power and less chance of detonation.

You could close it off, make a pop off valve, then install and intercooler. But that will cost you another $800-1000. And raise the height of your setup.

Where is that hole bleeding exhaust to? Into the engine compartment?

CM- Hole bleeds exhaust past the turbine. Instead of the exhaust having to go thru the turbine it bypasses to the back side of turbine. Thus the turbine gets less pressure.

PFM is no longer making these parts that I know of.

The pop off valve will not work with a gale banks setup since it is a suck thru system (carb ahead of turbo so all pressurized air has fuel in it.

You cannot eliminate a waste gate and install just a blow off valve. A blow off valve is to prevent a surge when the throttle is closed to protect the turbo and should be used in combination with a wastegate which actually meters your boost at WOT conditions.If boost goes above your set point the wastegate bypasses exhaust and slowly lowers boost to keep it constant. A blow off valve cannot due this. When pressure builds too high without a wastegate The valve opens and dramatically lowers boost pressure. A blow off valve should never open under throttle.
Martin.

exactly, can you say boom? not the kind of boost your looking for,

Kit comes with salt water intercooler. Ther only way a pop off would work is if the air goes into a fuel/air seperator if they exist then back to the flame arrestor.

I have messured the hole and its 1/2 inch. I am concidering plugging it to the 3/8 you mensioned.

how would you go about ensuring fuel does not venture down the pressure line that actuates the waist gate.

Am I right in saying it could ignite?