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Discussion and questions related to the course Understanding AFR
Hi there, was enough to lower the EGT from 1001 centigrades to 950? Is there a fixed value? What should I expect to see in a turbocharged v8 running around 30 psi? For example only
Also Andrew said that a turbo engine runs good at W.O.T with a 0,80 lambda value... But does that depend on turbo psi? Or tuners tunning high psi engines does this with knock signal tool because these engines are knock limited for choosing A.F.R and MBT.
Can you guys share me some experiences with high horsepower engines please? I would appreciate that.
Hello Luis! There is no "correct AFR", there are no magic numbers. It depends not only on the temperature of the exhaust gases, but also on the fuel you are using, if it is aspirated or supercharged and many other strategies that you can use. All this ultimately follows from the design of the engine and its development. This is one of the 200 questions you have to ask yourself when you start tuning.
As Rodrigo said, "it depends" - some of the other factors to consider regarding the EGTs being the ignition timing - very important(!), the material used for the exhaust manifold, the material of the exhaust valves, the material used for the turbo-charger turbine - there is at least a 150 degree range in manufacturers' temperature limits because of this, the oil-flow through the bearings that cool the bearing and/or whether the housing is water-cooled.
With the AFT, or more correctly, the lambda, different engines will respond differently to the specific lambda values - some may respond best to 0.80, others may be best around 0.90. It's going to depend" on many different factors. the primary thing there is to get clean combustion, by that I mean avoiding any detonation and/or pre-ignition and, preferably, bore wash and plug foulling from excessively rich mixtures.
Hi Rodrigo and Gord thank u all for the answer