Pressure relief valve.

[Swamp Donkey]

Just a random thought I had. Instead of a wastegated turbo, why not have a pressure relief valve somewhere that would vent at a pre-determined level.



Open at 35psi... ... to vent excess boost

Closed at anything below 35psi.



Adjustable???????



Time for me to do some research on what the main function of the wastegate is... .....



Non-wastegated turbo's are cheaper and may give you the controll element needed.

 

[eGarwood]

I think....

I believe that's what a WASTEGATE is... essentially a relief valve... and they are adjustable. NON-WASTEGATED TD's have no relief valve, so they just keep building pressure, which in turn begins to work AGAINST the engine, robbing power when the amount of air available to the engine exceeds the CFM capacity of the engine. That's why unless you can flow MASSIVE CFM's thru the engine, a wastegated type TD is better. I am NOT an authority on this though. . it's just my understanding of the the wastegates function... . Someone else wanna jump in here and help us out????

Ed3

 

[illflem]

A wastegate is more what is called pressure limiting valve. Rather than vent excess boost to the atmosphere exhaust gases are diverted around the turbo preventing the excess boost from being produced, saving horsepower. A very efficient system.

 

[HoleshotHolset]

You could install what is called a pop-off valve on your charged air side of the turbo, pre-intake... . it will vent excess boost to atmosphere (or wherever you route it to). Turbo gassers use them, usually as a pre-caution... just in case the wastegate fails. The turbo Indy-type cars use 'em... it's a big valve right on the intake manifold... . sticks out like a sore thumb. Roots blowers have 'em too... . usually on the front or back of the housing.....



Blow off valves do something similar, except they usually do it every time you let off the throttle (with a vacuum 'signal')... . this helps with compressor surge which is known to eat turbos quickly, and keeps the turbo spinning freely which helps with spooling it after shifts... .



To deal with boost right at the source we use wastegates. Some are internal or external. External wastegates are easier to tune and are capable of flowing a lot more than any internal could ever dream of. ifflem, explained it well..... all we are trying to do is make some of the exhaust gasses/heat bypass the turbine housing and go into the downpipe or vent to atmosphere... . by cutting back on the amount of flow to the turbine we get less boost.



You can use an external even if your turbo has an integral wastegate... just weld it shut. For applications where the peak boost is a very important parameter to be able to limit, having better control via an external wastegate is the way to go.



Matt