2003-2005 Courage C65

Images copyright and courtesy Bob Chapman @ Autosport Image and Michael J. Fuller
Text copyright Michael J. Fuller

B-K Motorsports Courage-Mazda C65, Road Atlanta 2005The Mazda R20B 3-rotor installation in the Courage C65 chassis.  The R20B is longer than the Judd and AER engines and requires a slightly different mating unit for the bellhousing.
B-K Motorsports Courage-Mazda C65, Road Atlanta 2005The beer keg is back!  The peripheral-port induction R20B isn't much bigger than a beer keg and almost seems hidden in the engine bay.

Much has been made about this power plant but upon further investigation it is little different from the Mazda 3-rotor of years past.  The R20B is Cosmo-based and while it may be accurate to say it is of the Renisis family, it is more of a reverse relationship with the Cosmo engine begetting the current Renisis and not the other way around.  Though John Doonan does indicate that this R20B benefits from the Renisis in the area of the rotor design at very least, thus making the R20B Cosmo-based and Renisis influenced.

No matter, it is clear that the ACO mandated 49.1 mm restrictor is a burden and the 3-rotor is not developing much beyond 400 horsepower.  Due to the nature of aspiration in a rotary engine, inlet restrictors have a larger impact on rotaries than on comparable (power out put and engine capacity) piston engines.  It is our opinion that the Mazda needs to be allowed to run unrestricted.  ACO, do you hear us?

7.30.05
Apparently they did...well, hear someone.  Of course that someone was Dennis Spencer as his group took over engine development duties starting post Sears Point.  Subsequently the ACO and IMSA came to a new agreement with Mazda about engine inlet restrictor diameters and allowed them to bump the size up to 53.5 mm.

In September a new engine was introduced, the Renesis-20B 3-rotor.
B-K Motorsports Courage-Mazda C65, Road Atlanta 2005B-K Motorsports' C65 appears similar to other C65s in the series with the exception of the modifications necessary to fit the Mazda engine.  Like most contemporary prototypes, the Courage C65's radiators receive cooling air from intakes in the sidepods as well as exhaust airflow from the front nose diffuser.  Cooling is always an issue with rotary engines because the oil is used to cool the engine to a much higher percentage than in comparable piston engines.
Real world trials have shown cooling to be an issue.  One solution has been to install louvers into the rear engine deck in order to draw the heat out of the engine compartment.
B-K Motorsports Courage-Mazda C65, Road Atlanta 2005With the 3-rotor's induction being on the right-hand side of the engine (and hence the chassis), the engine intake was designed into the driver's primary roll over structure in order to avoid an overly complicated induction system fed via the passenger's secondary roll over structure.
B-K Motorsports Courage-Mazda C65, Road America 2005Developments at Road America saw the introduction of a revised engine intake.  The roll over structure mounted engine intake was blanked off and an intake periscope mounted. 
B-K Motorsports Courage-Mazda C65, Road America 2005The engine exhaust exit has moved to the side of the car.  Previously it was routed straight out the back.
B-K Motorsports Courage-Mazda C65, Road America 2005The bracket performs a rules compliance function:

3.4.5 - Air intakes :

c/ They must not protrude more than 150 mm (200 mm for
the engine air intakes) over the surface of the bodywork

11.17.05
Well that's what we thought before, but a little bit of investigation and it turns out the bracket isn't needed for rule compliance (as the intake isn't anywhere near 200 mm above the surface ofthe bodywork).  Instead it is performing a funtional aspect by keeping the leading edge of the intake level, helping to prop it up.

B-K Motorsports Courage-Mazda C65, Road America 2005This became more important when the inlet height went up exponentially (but still not above 200 mm) at the 2005 Petit Le Mans:
B-K Motorsports Courage-Mazda C65, Road America 2005The periscope engine inlet allows for straight intake runners to the airbox as opposed to bent to near vertical with the intake installation above the driver's head.

ęCopyright 2005, Michael J. Fuller