Date: Mon, 06 Jan 2003 15:55:09 GMT From: John Davies <johndaviesNOSPAMnopsam.net> Subject: Re: SAAB 2-strokes: how polluting are they?
On Sun, 05 Jan 2003 23:11:52 GMT, "Scott" <mtnbikernopsamete-nospam_triad.rr.com> wrote: >I'm curious as to whether anyone has hooked their stroker SAAB up to an >exhaust emission analyzer to see exactly what sort of CO, hydrocarbon >levels, etc. it produces with the original equipment. Two-strokes have a >reputation for being 'dirty' - I'm just trying to quantify this. I know >some great advances are being made in 2-stroke technology for off-road >bikes, snowmobiles, and the like - has anyone made any successful >modifications to a vintage 2-stroke to reduce emissions (new carburetors, >catalytic converters, etc.)? > >I'm starting the search that might lead me to buying a 93 or 96 but what I >can find in regards to 2 stroke motors concerns me. My current weekend car >isn't 'green' by any stretch of the imagination but what I've read leads me >to believe that a 2 stroke might be exponentially worse. > I don't see any practical way to clean up a dirty vintage two-stroke, except by engineering some sort of oil injection system. I believe the Saabs required a fixed pre-mix, like your chain saw. Most two stroke street motorcycles used a variable ratio oil injection pump connected to the throttle cable - it backed off on the ratio at idle and low power settings. They were still very messy at full throttle. How you would actually fit such a device to a Saab engine is beyond me.... If the rig failed, you would seize the engine in no time. Two strokes are inherently dirty because of the basic design - fixed timing ports in the cylinder wall don't allow precise control of the fuel mixture. High output engines actually rely on the exhaust wave reflecting back into the cylinder to cram the wasted fuel air mix back into the cylinder for combustion (the so called "tuned pipe" or expansion chamber). I have never heard of a two stroke car that had such a sophisticated exhaust - maybe someone could correct me here...Did the rally Saabs use a tuned pipe? In case you were not aware, most manufacturers of off-road equipment are drifting to four stroke engines. Honda and others are producing four stroke outboard motors. It is only a matter of time before the two stroke is dead. My advice: Buy the old Saab oil burner, but plan on not putting a lot of miles on in it, for the sake of those around you. John Davies Monroe WA USA 2001 Saab 9-5 Aero Wagon 2000 Audi A4 quattro 1.8T 1991 Jeep Cherokee Laredo 4x4
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