French Grimes Race Systems

Fuel Injection Development Program
Offers Injection Customization to enhance performance

We have adapted different injection systems for performance in specialized areas.
Shown above is a Motec, multi-piece cross-flow injection for small block Chevys.

The maximum power that any engine can produce depends on the quantity of air that moves through it. Anything that increases the amount of air moving through an engine at a given speed always offers the possibility of additional horsepower at that speed. All engine induction systems are sensitive to intake tuning.

Fuel injected engines with individual intake runners are particularly sensitive to ram tuning effects. Relatively long runners have lower resonant frequencies than shorter runners, just like organ pipes, and they produce the greatest ram effect at lower engine speeds. That equates to increased low end torque. Short intake runners enhance an engine's high speed performance.

The cross sectional area of the intake runners is also important. For a given amount of airflow, meaning a given engine displacement and speed, the velocity of the airflow in the intake runners will proportional to their cross-sectional areas.

The larger the runner area, the lower the airflow velocity will be. Lower airflow velocities experience less flow resistance, or drag, within the manifold and thus moves air into the cylinders for a given vacuum signal. On the other hand, lower velocity airflows do not produce as great a ram tuning effect as faster airflows, nor do they carry fuel droplets along as well as faster airflows.

The cross ram is an example of a long runner IR (individual runner) system. It allows longer runners, while maintaining a lower profile. Long runner manifolds increase engine torque, usually between 3500 to 5000 RPM, and may maintain torque increases up to 6000 RPM. Upper RPM output usually suffers when using a longer tuned length IR. Using traditional vertical injection runners we have documented stack length changes from 1" to 26". Extreme changes in runner length helps demonstrate wave reflection effects. Shorter IR runners increase top end power at the expense of low end torque.

Plenum style manifolds generally provide a broader upper the RPM power band. Impressive top end power is a hallmark of common plenum manifolds. In the early 1990's Brodix built a plenum injector called the 'Armadillo'. We were involved in the nozzle design and location. That injector failed to capture the sprint car market. It was, however, well ahead of its time. The lessons learned from the Armadillo are still very relevant today. We can help you choose the correct system.

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