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Date: 6 Jan 2003 16:35:49 GMT
From: davehinznopsamcop.net
Subject: Re: SAAB 2-strokes: how polluting are they?


Someone who looks an awful lot like John Davies <johndaviesNOSPAMnopsam.net> wrote: > 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. Well... from 1963 until the last 2-stroker in 1967/8, oil injected engines were available. Until about 1966 it was the high-output engines (the red painted ones), after that I believe it is all of them. > 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. Start with a oil injected engine, go with a synthetic 2-stroke oil like a yamalube - it's a good start. Lots cleaner burning than the original oils were 30 years ago. > 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. Well, it's pretty precise for mixture, but it's tricky to not get the unburned fuel out the exhaust ports. > 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? The resonating chamber ("front muffler") is critical in dimensions, so I would think that they've given quite a bit of thought to that. > 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. For production cars, yeah, so it seems. Pity too, because the things that made it smart then, are still valid reasons. > 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, have you driven one of these? How dirty do you think they are? Not to be unnecessarily nasty here, but it seems that you're not all that familiar with them, yet you seem to be knowing just how bad they are. What is your direct experience with them, please? Dave Hinz ('60 93f, '63 GT-850, '65 96-Special, '71 97, '72 96, '99 9-5se)

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