Date: Wed, 23 Dec 1998 13:54:04 GMT
Subject: Re: More thoughts on my pinging problem

In article <>, (Firestarter) wrote: > This is a continuation from my earlier post entitlted "Turbocharged > engine pings under boost". > > I have a theory. I first thought that the O2 sensor would benefit my > turbo system, but now I am thinking it may actually be causing my fuel > enrichment problem. > > Here's the reason. > > The oxygen sensor's job is to keep the mixture within an acceptable > range (for emmision purposes). I came to the conclusion that the O2 > sensor's goal is to make up any deviation caused by wearing > components, changes in altitude, temperature, etc. > > The system has a set of known variables it goes by but relies on the > reading from the O2 sensor to keep these in range in case something > changes. > > That's the problem with carburators. You set them to run at a given > temperature, humidity and altitute but when you stray away from those > conditions, the mixture changes. > What! carburators. This may go along way to explaining your problems. Two friends of mine had MINI's fitted with the MG metro turbo engine. This is basically an A-series engine with a way to big turbo slapped on and a *special* modified SU carb. What we found is that it is basically impossible to tune/modify this engine satisfactorily. If you are using a standard carb I guarentee you it will NEVER work. You could spend for ever playing around with various jets etc. The reasons fall squarly at the carb and the ignition. We could NEVER get the cars to run right under the transient states of coming onto and off of boost. Turbo cars have to retard the ignition quickly when the boost comes on and enrich the fueling as you know. However you will also need to keep the fuel going in on overrun as a turbo running lean on over run is a very bad state of affairs. We used to some times get flame through the inlet because of pre-detination followed by stall of the inlet gases. This is very bad. My personal experience tells me that the best thing is too NEVER turbo charge an engine that wasn't specifically designed for it. Remember that a turbo engine also has different pistons-rods-crank and always a totally different cam to an atmospheric engine. As a taster to just how expensive doing it properly is look up the cost of a set of Mahle or Cosworth turbo pistons compared to standard pistons. My advice is to ditch the turbo kit right now and instead spend your money on a gas flowed head, racy cams and a fully balanced engine. Don't bother with lightening and polishing its a con to impress ill-informed customers. I am also not impressed by the "bolt on power" type turbo kits many supposed engine tuning shops sell. These are mostly complete BULLSHIT and whilst may give you more power will kill the engine. Believe me serious turbo charging costs serious money. P.S. The spider is a nice car! you can do alot with this engine without turbo's. NJH. -----------== Posted via Deja News, The Discussion Network ==---------- Search, Read, Discuss, or Start Your Own

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