• 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.
The 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.
Roller 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 |
