MSD Digital-7 W/Boost Retard Curve
With the support of an MSD Digital-7 ignition control box, we were able to include a special boost timing retard curve that allowed our engine to run the maximum amount of timing from idle to peak rpm. The Digital-7 with boost retard control uses a MAP (manifold absolute pressure) sensor to detect boost in the engine and then references a user-built timing retard program that will decrease the engine's total timing by as much as 1 degree for every 11/44 pound of detected boost.
Fuel, Timing, And Air Temperature
The three key ingredients to making power from any engine are fuel, timing, and inlet air temperature. The least fuel matched with the most timing and the coolest air charge will always net the most power.
Cold, dry air is packed with the most oxygen possible, and oxygen makes combustion. And the fewer fuel molecules present the more room there is for oxygen. Therefore, a powerful engine will compress as many oxygen molecules into a cylinder as possible while mixing with the minimum amount of fuel necessary. When this mix happens, a perfectly timed spark is required to light the compressing mixture as soon as the piston reaches top dead center (TDC). If the spark occurs too late, then maximum compressible power will be lost, and if it occurs too early, the piston will have to fight its way to TDC, placing the engine's internal rotating assembly under extreme stress, also known as detonation.
Detonation will occur if any (or all three) of these key variables is mismatched, and it is the number-one leading cause of death amongst power-adder engines. Supercharged, turbocharged, or nitrous-fed, they will all give up the ghost if the engine's tune-up isn't spot on.
Spark timing is essential to making big power from any engine. We used a Digital-7 boost programmable ignition box with matching MAP sensor to pull out 2 degrees of timing for every 1,000 rpm to achieve a 6,000-rpm total timing curve of 29 degrees. | 
Our non-intercooled engine ran its dyno pulls for approximately 3 seconds across the water brake, making peak carburetor-hat inlet air temperatures of 187 degrees at 6,000 rpm. While an intercooler will rob some boost, it will also lower air temperature significantly during real-world operation, all of which we will be showcasing in an upcoming issue. | |