[CROCIE JR]

Hes got some small vac. lines running to the side of the computer tower right now. Might be cooling lines of some sort. There is a diaphram, and I see some Dorman brass. I will call him tonite to check on him. He has been barking a lot, and mumbling. But mostly barking. Its hard to hear over the Beethoven.

[Joe37]

Hi guys, work is progressing on the T/A, the brakes are being finalized so the car can be moved around to get the engine out. Our next step is going to be partial engine tear down for inspection then on to the test stand for a break-in run.

I have a question about waste gates and blow off valves. Being as turbo stupid as I am, can you explain what the each do and why you need them? I only work on diesels and we never have any turbo problems other then the Ford 6.0L, and those were just bad from the get go.

We would like to limit the boost on the T/A to about 6 or 7 till it gets some miles on it and we feel comfortable with how its running since the car hasn't been road worthy since the early '90s. We are sticking with the original Turboforce parts for now as this is what the budget allows. This is also a four speed car, with a 3.42 rear axle, and with that combination, there won't be much room for error between shifts.

Joe

[Craig Hendrickson]

H-O used both a wastegate and a blow-off valve on the TurboForce, but not at the same time and not always.

A wastegate is on the inlet side (between exhaust manifolds and turbo exhaust scroll). It bleeds off exhaust flow and pressure to control the boost indirectly. A wastegate lives in a hot environment being attached to an exhaust pipe somewhere. We usually ran them without an outlet pipe and muffler; you can definitely hear the "whoosh" when it opens up.

A blow-off valve is on the outlet side (between turbo outlet scroll and the pressure hat). It opens when the boost pressure exceeds its setting so it controls the boost directly. A blow-off valve lives in a more benign environment than a wastegate and is more effective on controlling the boost into the carburetor when you go from WOT to throttles closed quickly. However, a blow-off valve potentially lets the turbo overspeed and therefore operate further away from the sweet spot island on the turbo map.

Even though the wastegate is a little more expensive, that's what I would recommend. As a matter of fact, the earlier versions of the TurboForce pressure hat had a pad cast in the side which could be machined for mounting a blow-off valve. The final and best version of the pressure hat had eliminated that pad.

Craig

[Tom Vaught]

Originally Posted by Craig Hendrickson

Even though the wastegate is a little more expensive, that's what I would recommend. As a matter of fact, the earlier versions of the TurboForce pressure hat had a pad cast in the side which could be machined for mounting a blow-off valve. The final and best version of the pressure hat had eliminated that pad.

Craig

I remember that Pad.

Tom Vaught

[Craig Hendrickson]

Originally Posted by Tom Vaught

I remember that Pad.

Here ya go, Tom:



On my 1978 Turbo Macho T/A with 1972 455 engine (not the W72 engine), I had both a wastegate and a blow-off valve. I had the last generation pressure hat specially modified by Kern in order to fit the blow-off valve. It was on the other side of the hat than shown in the above picture. It was a belt & suspenders kind of solution to boost control.

[Joe37]

What this car has must be the waste gate, its mounted down under the engine on the exhaust system. I only looked at for a minute or two. It has a small hose running to it, right dead center of the top. I assume the boost pressure opens this at a set point. Is it adjustable? The whole top seemed to rotate but it could just be loose or defective.

So if I understand this right, the waste gate controls the exhaust going to the turbo. As boost comes up the waste gate opens at a pre set pressure thus dumping excess exhaust away from the turbo. This seems like a good choice as the turbo would not need to work any harder then needed.

A blow off valve is on the clean side of the turbo and acts like a pre set pop off valve. Once it opens, the turbo can still wind up due to the excess exhaust build up in the system thus over speeding the turbo shaft. Does the turbo know the blow off is open? or does it continue building boost only to have the blow off dumping the excess away? I can see how it would limit the amount to the engine, but it seems a funny way of doing it.

Thanks for the lessons,

Joe

[twov8sandat4]

Originally Posted by Joe37

What this car has must be the waste gate, its mounted down under the engine on the exhaust system. I only looked at for a minute or two. It has a small hose running to it, right dead center of the top. I assume the boost pressure opens this at a set point. Is it adjustable? The whole top seemed to rotate but it could just be loose or defective.

So if I understand this right, the waste gate controls the exhaust going to the turbo. As boost comes up the waste gate opens at a pre set pressure thus dumping excess exhaust away from the turbo. This seems like a good choice as the turbo would not need to work any harder then needed.

A blow off valve is on the clean side of the turbo and acts like a pre set pop off valve. Once it opens, the turbo can still wind up due to the excess exhaust build up in the system thus over speeding the turbo shaft. Does the turbo know the blow off is open? or does it continue building boost only to have the blow off dumping the excess away? I can see how it would limit the amount to the engine, but it seems a funny way of doing it.

Thanks for the lessons,

Joe

From Tial's website:

Plumbing wastegates with manual boost controller to set boost:
http://www.tialmedia.com/documents/w..._wginstall.pdf

Plumbing Blowoff valves:
http://www.tialmedia.com/documents/w...bovinstall.pdf

Should give you some more ideas.

This is how my AWD Talon is setup, except I run a pair of wastegates instead of one.