Alfa 2.0lt of Giulia/Stelvio
Alfa Romeo 2.0 multiair ( Giulia / Stelvio ) -> Custom camshaft stage1 profile
As we had promised , we couldn’t leave this fabulous engine without taking care .
Custom profile stage1 is ready and officially released .
Designing an upgrading profile for the latest generation of multiair , is a challenging process for several reasons.
First of all roller cams demand very careful ramp designing in order to stick within manufacturer’s strategy for low stress and fatigue . Also , deviations from the designed pattern are not allowed at all , as rocker ratio will multiply them and actual profile applied on valve will be significant different from the initial design.
Furthermore the intake profile makes use of this weird extended opening ramp ( exactly the same we met on the 2.4 Dodge multiair ) .
This weird ramp lifts the valve about 1mm for 100 degrees before the main opening ramp. What is the purpose of this design ;
-At idle and low rpm the ramp is not used at all in order to maintain the appropriate cylinder compression.
-At low med rpms , ramp is used in order to achieve an over-scavenging of the cylinder and spool up the turbine faster.
-At med rpms the extra ramp is used in order to achieve maximum torque by pumping the maximum amount of a/f mixture inside the cylinders via the maximum overlap.
-At high rpms a part of the ramp is used in order to create the appropriate overlap which will help the filling of cylinder, but at the same time will prevent the exhaust gas reversing which will cause power loss. That way it achieves the maximum power. Furthermore, at high rpms intake mixture has enough kinetic energy to overcome the inertia of decreasing space created by upcoming piston and thus we are able to push more mass of mixture inside chamber. If the whole duration of the ramp was used at high rpm , a part of incoming mixture would escape at the exhaust creating power loss again.
We have measured and calculated the specs of stock lobes by using rocker ratio 1.6
Intake: 5.2mm / 8.3 mm peak lift
429 deg. duration @ 0.1 mm
Exhaust: 5.3 mm / 8.5 mm peak lift
251 deg. duration @ 0.1 mm
Stage1 camshaft for 2.0 multiair:
We have managed to reprofile stock lobes within manufacturer’s heat treatment , maintaining original values of surface hardness as always.
We have increased total area by increasing the lift at certain range without affecting the overlap strategy we have designed and without affecting at all the multiair system function and reliability.
* +15hp/20nm at completely stock engine
* +23whp at hybris setup with identical map settings ( boost , timing , afr )
* Up to +40/60nm with remap at a given setup
* -200rpm faster turbo spool up
* +300rpm before peak flow/power point occur
* +300rpm revving ability