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Re: Too Rich?
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Posted by Dean (more from Dean) on Wed, 5 Jun 2002 09:20:11 Share Post by Email
In Reply to: Too Rich?, soon2be, Tue, 4 Jun 2002 22:06:43
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All turbo charged engines run rich when on boost. The rich mixture is the only thing that stops detonation that would occur at such high pressures with a non enriched mixture. So when on boost, there is soot. Some of this gets on the cat and spark plugs, but that burns off when not on boost.

Many non turbo engines will also show soot on the tail pipe. For higher compression engines, the mixture is also enriched. Some vehicle will not show soot if the driver is very easy with the throttle.

When either engine type is running enriched, there O2 sensor is overwhelmed and not of any use for closed loop AF mixture control. So the engines run 'open loop' at full throttle. So at full throttle the engines are producing lots of CO and particulates and unburnt hydrocarbons. The testing standards for pollution ignore full throttle conditions. As engines are at full throttle for such a small amount of time, this is not a major issue.

If you go in for n emissions test and have been on boost alot recently without extended highway cruising to burn off carbon deposits from being on boost, I would be concerned that during the testing, carbon in the cat could be burning off which would create elevated CO during the emissions testing.

After a while, check your plugs. If you are on boost and doing lots of city driving, your plugs might be getting deposits on them. If so, and your engine has '7' heat range plugs, then switching to '6' heat range might provide for much cleaner running plugs.

Clean your injectors with Techron Concentrate every 8K miles or 3X per year. A sure sign of fouled injectors is hard starting in the fall with cooler weather while summer grade fuel is still in distribution. The RFG-II fuels with there lower volitility, especially in summer grades, seems to create more deposits. A poor spray pattern can also direct fuel onto the cylinder walls which can create severe wear problems. So the problem can be much more severe than the anoyance of reluctant starting.

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