Thread: 496 fouling plugs

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Originally Posted by jerry clayton

So just what is the absolute pressure at 9200 ?????????IIRC? you lose about one inch pressure per thousand feet--because of the low MAP it will be feeding lots of fuel---------------
Sable Systems

Jerry, not to argue with you, but the fuel map looks at rpm, MAP, and then assigns fuel flow which on the E Street is then going to be trimmed in a feedback loop using the wide band O2 readings. If the O2 reading is good, then you take the barometric pressure for the day, which at 9200 feet is going to be about 21.2 to 21.3, and subtract the engine vacuum at any given rpm to yield MAP. Indeed the MAP numbers are going to be significantly lower than they will be in KC or St Louis, where our barometric pressure is generally around 30 inches of mercury. You're in the ballpark on the change, it's 0.89inHG per 1000 feet of elevation change. The Fuel map takes all of this into account, but it will be operating on a reduced range of pressure until the car goes down the mountain. This is why one would NOT want to block out the portion of the curve above say 23inHG - the engine would have no map for operation if the car left home. (PS - I didn't see your Sable Systems attachment before I replied, not that it really matters.)

Bob, I'd keep the E-Street over going back to a carb, especially at your altitude.