2008 ZX10R Twin Injectors

  • Secondary 10 hole injectors spray into top of velocity stacks
  • come on at 7k & up
  • allow main injectors to be balanced for up to 7k 

The secondary fuel injectors allowed engineers to fine-tune the continuously operating main injectors for an idealized performance at smaller throttle openings of low to mid speed. Then once the throttle hits a certain point, the secondary injectors are set to kick in with additional fuel spray into the mixture for an improved top-end power output. Located higher up in the throttle throat, this extra burst of cooling fuel from the secondary injectors accelerates the flow into the cylinder for a bigger bang, and it ensures a more evenly spread of atomized fuel for a more accurate fuel/air mixing and efficient burn. This equates to cleaner emissions and therefore less restrictive catalyzers required and ultimately more power.

Supplementing these new secondary injectors are oval cross-sectioned throttle bodies in place of the earlier round units. The new shape helps increase the air velocity, improves the throttle response and permits the four intakes to fit easily in the narrow frame. Of course, the new velocity stacks are also oval shaped to match the throttle bodies and deliver improved flow efficiency.

Inside the cylinder head, the intake ports and the cam profiles were reshaped to meet the goal of more top-end performance and a quicker response from the engine.

The cams are forged chrome-moly billet and about a half-pound lighter than before and have a higher lift profile with longer duration for that high-rpm delivery goal. And they are designed for easy race tuning.

To give this fire breather a more manageable power delivery, the exhaust valves were reduced in diameter from 25.5 to 24.5mm. Making the exhaust ports narrower at the midpoint and larger at the opening improved the flow efficiency. And the combustion chambers were reshaped accordingly to finish out the top-end power improvements of the new engine.