Aim of W/M (water methanol) injection:
1. Induction cooling: a large amount of heat is absorbed during evaporation.
2. Octane boosting and knock suppression: Methanol - suppresses knock by octane supplement. Water suppresses by slowing down flame speed.
3. In-cylinder coolng: reducing peak combustion temperature during evaporation.
4. EGT reduction: reduces temperature stress to exhaust valves and turbo turbine blades.
W/M System basics:
5. Delivery: Pressurized W/M pushing through an atomizing nozzle
6. When to spray: W/M System is normally triggered by engine load sensor
WM system options:
7. Single stage system (SS-S): full spray after triggering
8. Double stage system (DS-S): A second nozzle is activated at a higher engine load
9. Progressive pump speed system (PPS-S): A motor speed controller progressively increasing pump speed to attain high line pressure to increase flow.
10. PWM valve system (PWM-V): Same principle as a standard fuel injection system, flow is controller by an inline valve.
WM system availability from WM manufacturers:
11. Single stage: All manufactures make them
12. Two stage system: Often needs a second pressure switch added to the single stage system
13. Progressive Pumps Speed system: all manufacturers except FJO and Aquamist
14. PWM valve system: FJO (cell by cell) and Aquamist (IDC tracking) only.
Not all the progressive systems are the same (PPS vs PWM-V):
15. A PPS system normally costs about 30% less than the PWM valve system.
16. A PPS (progressive pump speed) system cannot be compared to a PWM valve (similar to an OE fuel injection system) system. At best the dynamic flow range of a PPS system is x2. This calculation is based on a pressure change of 60psi to 240psi. For a "pressure change" of x4, you will only get x2 flow change.
17. For "PPS" system to work as well as a "PWM valve" system (at worse x10 dynamic flow range), the PPS system needs to have a pressure change of 60 psi to 600psi!!!
18. The other important factor most people missed is the response time to a load transient. A rotation mass as in a PPS cannot suddenly speed up and slow down. This leads to a delay in a "ramp up" and a delay in "ramp down". A PWM valve system response to load change in a "thousandth of" a seconds compare to "tenth-of" seconds. This leads to inconsistent AFR during load or gear change.
For more in depth details study of the systems go to the link below:
Indepth study of WAI injection systems
Quick run down of "water injection" and "systems"
Linear Mode
