View Single Post
mark houghton mark houghton is offline
mark houghton's Avatar
Join Date: Jul 2008
Location: Central Washington State
Posts: 3,893
Originally Posted by lucittm View Post
See Mark's post #9 above. When the fuel pumps shut down you don't get a sudden lean condition, you get a sudden shut down condition.

When my switch opened under hard acceleration both of my hands came off the steering wheel, that's how hard the engine kill is.

This experience has been appropriately coined as the "face in dash syndrome". Lucky if you don't break some teeth when it happens. Violent, to say the least, usually resulting in choice expletives...WTF!?!?!...until you realize it was just the overboost sensor protecting your investment.

Yes, logic does suggest that with no fuel, you get a lean condition. But we're splitting hairs here...that condition lasts for a micro-second, during which time the engine shuts down and no air is being drawn in. Although the ignition is still firing the plugs (the OB sensor only shuts off the fuel in a CIS 930), there is no heat of combustion going on - thus no risk of damage.

Good discussion! I still say that Porsche put that protection there for a purpose, and with our aging cars (and aging WG's) I vote for keeping that protection active.
Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 08-23-2010, 12:21 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #15 (permalink)