Cylinder Port Timing
From Wikispreedia
Contents |
Port Timing Table
Variator Equipped Transmission
1987 SE 50 | 83-84 Aero 50 | 85-87 Aero 50 | 88-93 Elite SA50 | 94/2001 Elite SA50 | Urban Express NU50 | 1982 Express Sr NX50 | ||
BBDC | Exhaust Open | 78 | 71 | 76 | 80 | 79 | 67.5 | 67 |
ABDC | Exhaust Close | 78 | 71 | 76 | 80 | 79 | 67.5 | 67 |
BBDC | Scavenge Open | 57 | 52 | 57 | 56 | 56 | 47.5 | 47 |
ABDC | Scavenge Close | 57 | 52 | 57 | 56 | 56 | 47.5 | 47 |
Fixed Ratio Transmission
Spree 84/85 | Spree 86/87 | Iowa Spree 84/85 | Iowa Spree 86/87 | Elite SB50 | Elite SB50P | 1977-81 Express NC50 | ||
BBDC | Exhaust Open | 71 | 73 | 70 | 71 | 77 | 74 | 65 |
ABDC | Exhaust Close | 71 | 73 | 70 | 71 | 77 | 74 | 65 |
BBDC | Scavenge Open | 52 | 54 | 50 | 52 | 60 | 57 | 47 |
ABDC | Scavenge Close | 52 | 54 | 50 | 52 | 60 | 57 | 47 |
Port map measurements
A degree wheel may be utilized to generate data similar to above using reference points of TDC or BDC. Another method to mapping port timing is to take measurements of the ports. A piece of paper may be cut, and installed with it's edge at a reference point, such as the cylinder top.
- Each port is rubbed to emboss the port shape
- The paper is removed and rubbed with a pencil, charcoal etc to reveal the embossed edges
- Measurements can then be taken
- The rubbings are of immediate value in comparing or duplicating a given design.
- If desired, knowing stroke and rod length (check the web for calculators) this info can be converted back to degrees
Member donaudi provided port info for Mallosi MHR and Polini Corsa cylinders shown below:
Polini Corsa port map
Malossi MHR port map
Author: mousewheels
Measurements: Donaudi
Fabrizi portmap
Member DirtyE mapped a Fabrizi 50mm bore as captured below:
Author: mousewheels
Measurements: DirtyE