Honda waves the wand over the 2007 CBR600RR

In the four years since its introduction, the CBR600RR’s high-powered 600cc inline-4 engine has proven itself to be a force to be reckoned with both on the street and on the circuit. Delivering a broadly responsive range of power and acceleration, its compact configuration also helps realise optimal mass centralisation for a significant contribution to the RR’s quick handling.

However, for the CBR600RR’s next generation, even greater efforts to reduce size and weight were needed to achieve its new development goals of even sharper and more responsive handling, as well as significant increases in its power-to-weight ratio. So, an entirely new engine was designed and developed, incorporating much of Honda’s most advanced race-bred high-performance engine technology to create a more efficient and powerful mill featuring the smallest size and lightest weight in its class.

The Smallest and Lightest Engine in the 600cc Class

Achieving the new RR’s stated goals of sharper and faster performance necessitated not merely a reworking or redesign of an established engine configuration, but an entirely new rethink from first drawings to final assembly. The end result is, in a word, remarkable. Not only are the new engine’s front-to-rear and top-to-bottom dimensions by far the smallest in its own 600cc class, its front-to-rear length is also smaller and more compact than any inline-4 engine in the 250cc class as well.

This new engine’s smaller dimensions were achieved through a total rethinking and, among other changes, repositioning of the engine’s main shafts within the crankcase in a tight triangulated configuration that narrows the crankshaft-to-countershaft distance by over 30mm. Combined with detailed changes elsewhere in its design, these closer dimensions make possible a drastic reduction in crankcase size and, by extension, weight. The crankcase castings alone weigh over 900g less than its predecessor, representing the largest part of the engine’s exceptional 2kg reduction in weight compared to the current model.

Other modifications to reduce engine weight include a new magnesium head cover (330g lighter), new nutless connecting rods, new single exhaust valve springs matched to smaller and lighter lifters, a smaller new neodium ACG magnet and many more detailed changes that all add up to the realisation of the new engine’s astoundingly smaller configuration and lighter weight.

Stronger Performance

Of course, for an engine designed to be competitive on the race circuit as well as on the street, the other primary goal in the development of the CBR600RR’s new engine was gaining a stronger, more widely useable range of power and performance. Many of the new technologies and improvements made were developed and tested on the CBR1000RR Fireblade and adapted to the new engine, including modified intake and exhaust ports and changes to the intakes velocity stack lengths and taper, and to the ECU programming governing the control of its two-stage PGM-DSFI fuel injection system. The CBR’s lighter weight new stainless steel exhaust system also features new in-line exhaust valve to control exhaust pressure for maximised performance.

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