Advantages: If you are NOT pushing past the exhaust backpressure limits, then you have no wastegate to bleed off exhaust and you won't loose boost.

Disadvanages: If you ARE pushing past the exhaust backpressure limits, then you risk damage to your turbo.

A wastegate is designed as a "safety" release. Smaller turbine housings need a wastegate to bleed off excess exhaust pressures to keep from creating too much of an imbalance with the compressor side. For example, if you disable the wastegate on the stock turbo, and routinely push it well beyond 25 lbs of boost, you will most likely kill the turbo in a very short amount of time.

 

oh ok I have been running about 31 lbs of boost with my stock turbo

 

Ouch, I guess that explains the problems you are having now. /ubbthreads/images/graemlins/crazy.gif

BTW, I still like your post about the race against the Dodge. /ubbthreads/images/graemlins/biggrin.gif

 

if I wam running 31 with a stocker what do you think I will get with a upgraded one?

 

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if I wam running 31 with a stocker what do you think I will get with a upgraded one?

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You can actually lose boost with a larger turbine housing. However the drive pressures will be dropped a bit. Also an upgraded turbo can flow more air, so even though the gauge might not read as high, it doesn't mean you will lose power.

FWIW, my BB turbo made 31 lbs peak boost. The stock turbo made 30 lbs peak boost with the exact same mods. So you don't always lose boost with a larger turbine housing, it just likely that you might.

 

Usually a non-wastegated turbo is efficient enough to produce moderate boost while keeping drivepressure down. I have a 1.15 A/R turbine housing, and i have not tested it, but i have seen on record that this combination will keep drivepressure:boost at a nice 1:1 ratio up to 39psi of boost. They are so efficient they do not need a wastegate.

 

I don't know this, but.....I have often wondered if Ford designed the waste-gate so that it would open when it did not need as much boost as the turbo was trying to make (i.e. if the turbo was trying to produce 10 lbs of boost, but the engine only needed 5 lbs to mix with fuel). An open waste gate would relieve back-pressure and increase mileage. AGAIN....I DON'T KNOW THIS...JUST THOUGHT IT COULD BE.

 

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An open waste gate would relieve back-pressure and increase mileage

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Yes an open wastegate relieves backpressure, but it also acts as an exhaust leak. So in effect you lose mileage if your wastegate is opening prematurely. It's simply designed to protect the turbo from going kaboom.