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Old 04-02-2010, 01:55 AM   #21 (permalink)
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no nickname , it's just a car - '04 volkswagen golf tdi
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speed density system

..."

This did bring to mind a question -- This car has no MAF sensor, so it does not sense air flow directly. How does the ECU interpret a restricted air intake? For instance, if (heaven forbid) I mash the pedal to the floor, the throttle position sensor goes wide open, but the intake tube, being slightly smaller than the TB opening, is not allowing quite as much flow as would normally occur under stock conditions.
Does the ECU take into account engine vacuum
and other factors to compensate for the reduced air flow? This will never come into play in normal driving on this car, but I was curious about it.
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Does the ECU take into account engine vacuum
yes
it uses a MAP sensor as the primary load sensor
MAP = Manifold absolute pressure
MAP = ambient barometric pressure - intake manifold vacuum

the system is in fuel control so a slightly restricted air intake
has about zero affect on anything
except at WOT

as per EPA and iatn

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Old 04-02-2010, 02:58 AM   #22 (permalink)
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Quote:
Originally Posted by Chris D. View Post
hmmmm lets see the melted piping... bad motor mount?
Mounts are fine
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Old 04-02-2010, 03:09 AM   #23 (permalink)
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Quote:
Originally Posted by mwebb View Post

the system is in fuel control so a slightly restricted air intake
has about zero affect on anything
except at WOT

as per EPA and iatn

Thanks. That's what I was hoping.
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Old 04-07-2012, 10:16 PM   #24 (permalink)
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Quote:
Originally Posted by JoJotheTireMan View Post
That is exactly how mine is setup, hooked to manifold vacuum. Low vacuum equals CAI and high vacuum equals WAI/HAI. A3 (1993-1999) VW 2.0L air box has dual inlets and a vacuum controlled flapper to switch back and forth.
My 91 Jetta had one of those, but the cold air intake was only 1 inch diameter. I tore that whole thing out and made it a 4 inch diameter feed directly behind the headlight and I actually gained 2 mpg. But it didn't run so well in the winter; stumbled routinely...like I had water in the gas.
[edit] maybe I should have made the flapper bigger instead...

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