Thread: BOV orientation
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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,274
Someone posted those anti-lag links farther back in the timing thread.

It mentioned retarding the timing around 40deg after TDC during gear shifts so the mixture is still burning when the exhaust valve opens.
Venting metered air to atmosphere would increase the afterburner effect and secondary combustion in the exhaust headers.
It also said they had 1.2bar at idle in the Subaru rally car from all the combustion going on in the headers.
Sounds crazy for anything other than racing and trying to be competitive within the rules.

The intense heat kill turbos and exhaust headers in a short time, and if it wasn't a factory engineered system in a water cooled engine with thick wall exhaust headers it would probably be an endless source of very expensive repetitive problems.

In my opinion setting up the 930 emissions air injection diverter valves to inject more air during deceleration is another bad idea. Especially from a turbo making around 14.5psi into an exhaust manifold that would have 25psi or more from all the combustion going on to spin up a turbo while the engine decelerates.

I don't think the small volume of air you can get through the factory spider and air injector nozzles would help anything and if you've ever removed those steel air injectors on a few 930 engines you'll see that the tips of them are often melted or burned away.
Add more air through them and they'll get even hotter, so where do the melted burnt pieces of steel air injector go.. just where you don't want them - right into the spinning turbine wheel.
Old 12-08-2009, 04:13 PM
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