hey guys just wondering the difference as far as air fuel mixtures between the small turbo compared to a bigger turbo. will the bigger turbo(t4) require a richer air fuel mixture compared to say the greddy turbo? just curious

 

The air fuel mixture isn't really dependent upon a particular turbo. A bigger turbo will flow more lbs/min of air, and will require more fuel, but the ratio stays the same.

 

The big difference between small and big is the matching it has with the engine. Compressor pressure ratio and flow is a function of speed, which comes from the turbine. A small turbine will spool up faster, build pressure ratio faster and match to the middle rpm of the engine.

However, to keep pressure ratio under control, you need a wastegate.

The larger compressor will match only at the high end because there won't be enough exhaust gas to power it until you get the rpms up.

Order "Fundamentals of TurboCharging" from ConceptsNREC. They also have a 4day course on it. It assumes you have an ME degree with a good understanding of turbomachinery.

If you can get the compressor maps that will really tell the difference.

Mike