Question for you turbo...

[Brett Dikeman]

At 4:40 PM -0700 8/24/00, james accordino wrote:

>Certainly no turbo expert, but I thought that you are
>describing  a pop-off or blow-off valve.  High boost
>pressure opens it, pressure escapes and equalizes, and
>the spring slams it shut.

>I thought a bypass valve was controlled.
>The valve passes some air back farther in the pipeline
>to keep airflow up and turbo spinning.  Yes, NO,
>partial credit?

partial credit :-) They both have the same goal; keep the turbo 
spinning and keep things from blowing up from the pressure surge. 
The blowoff valve is -never- meant as a form of boost regulation.

Blowoff valves are incredibly poor choice for almost everyone, 
certainly a poor choice for a vehicle even closely resembling a daily 
driver.  They offer high volume, but they release metered air, and 
cause the mixture to suddenly, violently, become -VERY- rich.

I'll wager some of these guys with 1.8t's running around with huge 
blowoff valves, impressed with the "Poosh!" noise, are going to be 
very sorry when their catalytic converters are molten globs from all 
rich running and raw fuel.

Brett
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Brett Dikeman				Systems Engineer
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