One of the most important, yet Often overlooked variable for making efficient and reliable horsepower is quality fuel.
Not only is the quality of the fuel important, the quantity available may be drastically limiting a modified parts combination horsepower potential.
As pictured, a Mazdaspeed utilizing a turbo upgrade along with an e85 mix is leaving a lot of reliable horsepower on the table (see area of yellow triangle).
At lower rpm, the stock fuel system and turbo are working together with enough headroom to create 350-375 wtq, which is a commonly accepted torque limit on stock connecting rods, but as the turbo starts to shine, and the tq could be carried out at the 375 ft lb level until redline, the stock fueling system can not pump enough fuel to create a safe air fuel ratio.
In short, if you are going to utilize an upgraded turbo on a Mazdaspeed, you will be limited (see necessary boost / airflow taper and previously referred to area under the curve sacrificed) by the stock fueling system if you do not add methanol injection or a 6th port fueling kit.
ARea Under the CUrve lost is a person modifying for horsepower's biggest disappointment.
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