TOMEI POWERED Dissects the FA20 | Flat Four

• CAMSHAFT & VALVE SPRINGS

The FA20 allows for large changes in cam timing via Variable Valve Timing (VVT) adjustments. Unlike many other VVT cam gears that lock at the max- retard position, the FA20 locks closer to a middle position (30 degrees retard and 40 degrees advance from the crank angle) when the engine is turned off. Obviously, this large overlap is not for high-rpm output at idle. Instead, it induces exhaust gas recirculation when necessary to reduce emissions.

The cam profile has an aggressive convex design due to the use of the roller rockers. Valve stem diameter and face diameter are the same as the 4B11 with the same bore diameter.

Camshafts and Valves for the FA20 engineThe FA20’s cam timing, duration and lift is quite aggressive for a factory engine. Fortunately, computer controlled VVT allows it to idle and pass emissions.

The stock valve springs have sufficient clearance before bind at peak lift, so there is room to increase the cam lift over the factory cams by 1.0 mm. TOMEI POWERED believes that manufacturing a performance camshaft with a higher lift and similar centerlines to the stock cams will be difficult. Increases to cam timing would be minimal with these parameters.

Lightweight materials are not used, unlike other modern engines. Valve spring rates are set high to suit the high-lift cam profiles.

Valve springs inside the FA20 engineRoller rockers, high-rate valve springs and high-strength steel retainers keep the valvetrain in order.

Valve

Stem Dia. Face Dia. Weight
IN 5.5 35.0 45.5
EX 5.5 29.0 37.0

Valve Spring

Free Length Set Length Set Load Lift Height Lift Load Compressed Height Retainer Weight
GRB 44.6 36.0 23.0 26.6 53.9 23.0 11.8
GDB 36.2 18.7 26.6 51.0 24.7 13.8
FA20 40.7 32.1 22.1 21.37 60.8 19.2 11.38

Valve Spring Load

mm 21.0 20.5 20.0 19.5 19.4 19.3 19.2
kg 62.4 65.0 66.4 69.9 72.4 78.5 101.1

Camshaft

Duration Max Valve Lift Max Cam Lift Cold Valve Cam Clearance Center Line VTC Degree OF Change Weight
GRB IN 244 9.2 9.4 0.2 132 45 1250
EX 256 10.2 10.5 0.4 132 40 1200
FA20 IN 255 (252)* 10.75 6.87 0.10~0.16 68
EX 255 (252)* 10.47 6.77 0.21~0.27 54
*Measured Value, Rocker Ratio: 1.5866, Base Circle 34φ

Piston to Valve Clearance (Contact Point) INTAKE Max Advance Timing

Crank Angle -10.0 244 -5.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0
Valve Lift CNT. PT. 6.73 256 6.17 6.02 6.24 7.00 8.06 9.54 11.28 13.60
Valve Lift 3.41 255 (252)* 4.23 4.77 5.57 6.08 6.82 7.28 7.94 8.35
P/V 3.22 255 (252)* 1.84 1.15 0.57 0.82 1.14 2.16 3.24 5.15

Piston to Valve Clearance (Contact Point) EXHAUST Max Advance Timing

Valve Life CNT. PT. 11.24 9.55 8.11 7.15 6.55 6.39 6.59 7.31 7.31 8.36
Valve Lift 7.53 7.08 6.39 5.91 5.18 4.68 3.93 3.45 3.45 2.75
P/V 3.50 2.26 1.51 1.03 1.16 1.50 2.45 2.45 3.65 5.40

138-014-TECH-FA20-TDC