Boost and Air-fuel mixture

[Marc Swanson]

> 1- To much boost  I am running the stock WG spring and I am getting 12-15
> LBS of boost? I thought the stock was 6 lbs?

yes, thereabouts.

> I checked the WG diaphragm and
> didn't see any holes (I know that doesn't necessarily mean much).  Any ideas
> why I am getting this much boost.  Oh - stock ECU also

if you have the stock ECU your fuel pump should be kicking out at around
10 psi for overboost cutout.

The other thing I would look at closely would be your lower wastegate
hose.  If a hole develops in that hose, your WG will never open
(depending on the size of the leak).

> 2- Air - Fuel mixture.  I just installed a JC Whitney air-fuel mixture
> gauge.  At idle or when I lift off the gas I get slightly rich reading.
> Under boost I get a lean reading. Is this correct?

no, you should be a touch lean at idle and rich or stoich on boost.
What is your static mixture set at? I think you should be reading ~50%
duty cycle with the engine warm at idle IIRC.

>  I thought I wanted a
> rich reading under boost but then I am don't completely understanding all of
> what happens on the CIS system.

the desired AF ratio for street cars is the same be it EFI or CIS.  you
want a lean burn when the engine isn't working hard to save fuel and a
slightly rich mixture on boost/WOT.


Later

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Marc Swanson, Software Engineer
Sonitrol Communications Corp.
Hartford, CT

Email: mswanson at sonitrol.net
Phone: (860) 616-7036
Pager: (860) 948-6713
 Cell: (603) 512-1267
  Fax: (860) 616-7589
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