August 24, 2024

Fuel Injection High Speed Bypass for NA Engines

The high speed bypass is often used in a fuel injection setup.

NORMALLY ASPIRATED ENGINES
The high speed leans out the engine as the RPM go up and the volumetric efficiency goes down. The VE is often near 100% at the torque peak. The air flow per revolution is max. A typical norm asp engine cammed up for racing may see a torque peak around 5,000 RPM. Tuning should be with the main bypass for max power up to the torque peak or just beyond. We often recommend an AFR of 4.8 to 1 for methanol fuel for the torque peak. (read more...)

April 2, 2024

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April 1, 2024

Engine Tuning Using the Main Bypass

When you’re thrashing in the pits getting ready for the next run, a quick way to update your jetting is to adjust the main bypass while leaving the rest of the jets alone.  If you have a really well dialed-in jetting combination with good fuel system pressure, this form of tuning simply controls how much fuel is going to the engine and how much is being diverted back to the fuel tank.

Tuning Steps

The larger the main bypass jet, the more fuel is diverted away from the engine.  This can sometimes feel counterintuitive.