temperature & fuel mileage

[jdbubb at verizon.net (Dan Bubb)]

Engines need a lot of enrichment when they're cold. It can easily be as much as 50% additional fuel on a 30? F start that will taper down until the engine is around 160? F. Plus engines need an after start enrichment for 30-60 seconds even on a hot start. If you normally drive short distances those enrichments alone can make a big difference in your mileage. Less % difference for longer commutes.
As far as the hiss on pressing the brake pedal, that is normal. The vacuum in the booster is released somewhat when you press the pedal (there is actually a foam sleeve around the brake pushrod that is a filter for the air entering the booster) and the hiss is air entering the booster from the passenger compartment side.
Pumping the pedal repeatedly can introduce a fair amount of air into the engine and make it rev up some.
Dan 

From: "Foxx (in a box)" <foxxinabox@xxxxxxxxxxxxxxxx>
To: "scirocco list" <scirocco-l@xxxxxxxxxxxx>
Sent: Wednesday, May 02, 2007 10:17 PM
Subject: temperature & fuel mileage


>   i've been griping about the MPG in my '85 and can't seem to find the 
> problem. with the cold weather i was usually lucky to get 24 MPG. i 
> think there is a vacuum leak from the brake booster (hear a hiss when i 
> press the pedal) and tried pumping it vigorously (the pedal). i was in 
> for a pleasant surprise tonight when i filled up and got 29.4 MPG. does 
> the warm weather really help the running of the car that much or has the 
> rubber simply expanded somewhere and stopped a leak? just seeing if 
> anyone has past experience. thanx.
> 
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