Request engine modification
#32421 from Jonothan Benefield · Not recommended · Minutes (2022-04 Fastrack)
Thank you for your letter. The Club Racing Board does not recommend these changes. Nothing in the P1 rules prohibits the use
of individual throttle bodies (ITBs) on a Honda FD2 engine. Honda FD2 owners have two options: they can use OEM parts with
the 64mm single throttle body and no SIR at 1,400 lbs. minimum under Line G, or they can add higher performance pistons,
rods, and cams and use ITBs with a 30mm SIR at the same weight under Line H. In addition, nothing in the rules prohibits
enlarging a Honda FD2 to 2.3L and using higher performance parts and ITBs with a 30mm SIR at 1,445 lbs. minimum under Line I.
A CN Honda FD2 engine is permitted to run without an SIR under Line G because the OEM parts (including the 64mm single
throttle body) limit the power such that an SIR is not necessary. Competitors who wish to modify a Honda FD2 in the same way
that competitors modify the Mazda MZR are free to do so under a spec line appropriate for the displacement. What the rules do
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not allow is adding ITBs and/or higher performance pistons, rods, and cams to a Honda FD2 without using an SIR. This would be
unfair to other competitors whose modified engines are required to use an SIR.
Data obtained at the 2019 Runoffs from a Norma M20FC using the stock Honda FD2 under the CN spec line showed that the
car’s acceleration rate was fully in line with and at no disadvantage to the Elan DP02-Mazda 2.5L cars from which data was also
obtained. Please see the response to letter #27639 in the December 2019 Fastrack.
P1 is the most technologically advanced and open class in SCCA's Road Racing program. Competitors may choose the chassis,
engine, and tires they wish to race, and the rules allow for improvement of aerodynamics, suspension, brakes, and other
systems to make a platform more competitive, so it should not be assumed that manufactured cars like CN cars will be able to
run at the front without modification. This additional development results in increased performance in cornering, braking, and
top speed, which are not subject to the BoP process and are factors entirely within a competitor's control.