Date: Mon, 28 Jul 2003 15:26:07 +0100
From: "Andy Hookins" <>
Subject: Re: Gas economy

"'nuther Bob" <> wrote in message news:9a7aivs9j3ndjv97gl90k0gn59qusjmj6inopsamcom... > On Mon, 28 Jul 2003 09:13:05 +0100, "Andy Hookins" > <> wrote: > > >"Chris O'Malley" <> wrote in message > >news:VPHUa.53995$ > >> Why is there a difference between summer and winter? > >> > > > >I don't know exactly, but I can see it very clearly as i plot > >MPG through the year. > > I think it's almost entirely the warm up time. I see mileage as > low as 14mpg when the temps get down there. It comes back up > once warm. I think the difference is all that gobbling of gas > while the engine is cold. That's only part of it, warm up only accounts for a few minutes of my 45-60 minute commute. There's got to be more to it. BTW the owner manual has a nice graph depicting relative engine efficiancy against engine deperature. > If you have a turbo, the compensation is the added boost you > get from a nice cool winter charge. Oh yeah :-) the Trionic-5 system works to a fixed boost pressure - although intake temperature is measured it is only used for fuel metering purposes. Cooler - denser air at the same pressure > greater air mass > more fuel to get the right mixture > more power :-) Later T-7, I suppose T-8 on the 9-3 sport sedan too, aim to deliver a fixed engine torque, so boost pressure is slightly lower in cold weather :-(. I don't know if the 'hot-wire' AMM used in the APC system behaves like the older T-5 or the newer T-7/8. AndyH '94 9000 CDE > Bob

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