Date: Thu, 21 Oct 2004 07:25:09 +0800
From: "Justin" <>
Subject: Re: 9-5 2.3lpt PCV/breather hose burst

"Richard Sutherland-Smith" <> wrote in message > In message <> > Dave Hinz <> wrote: > >> On Thu, 14 Oct 2004 08:53:21 +1300, Richard Sutherland-Smith >> <> wrote: >> > In message <> >> > Dave Hinz <> wrote: >> > >> >> You're confusing timing with mixture. The engine management still >> >> needs to >> >> know the mass of the air in the chemical reaction so it can put the >> >> right >> >> amount of fuel into the chambers; the sensing plugs are for >> >> determining >> >> when to fire the spark. >> >> > No they are not, AFAIU they are to check the result of combustion. >> >> Nope. That's what the O2 sensor is for. Here's an article (in English >> even) that goes into way more detail than you asked for, but, er, you >> asked for it... >> >> >> >> It also has some good stuff on how water injection works in this >> context. >> >> Dave Hinz > > Yes, I have read that before, but that only SEEMS to deal with the > timing aspect of the plugs as sensors. Please don't tell me off again, > I am very sensitive. I quote from The Saab publication (270603) 1997 > Form and Function about Trionic. > "By applying a relatively weak voltage (approx. 80V) to the spark plugs, > we can measure the density of ions in each cylinder and thus determine > whether combustion was complete or if a setting needs to be changed. > can adjust the quantity of fuel being injected during the brief > moment the inlet valves are open...... which rations each and every drop > of fuel and minimises exhaust emissions." > Hilsen > -- > > Richard Sutherland-Smith > 19 Webb Road, Wanganui 5001, > New Zealand I'm not going to tell you off but I am going to tell you that you are wrong. The D.I unit or the sparkplugs can not detect combustion mixtures. The system of applying a weak voltage to the sparkplugs is to detect which cylinder is on compression stroke. It does this by measuring the voltage at the plugs that is not enough to jump the gap, but as the compression goes up the voltage will go up as the amount of air in between the gap will increase. There are also sensors in the D.I unit to detect knocking. The mixture is determined in a Trionic 7 system by the air mass meter and the two map sensors, and then is fine tune by the readings of the o2 sensor (which there is two in later models).

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