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Water Methanol Injection Strategy

Webinar Questions

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Hi Andre, In the webinar your approach to w/m tuning was to add timing and boost. Did you experiment with a reduction in fuel relative to the w/m injection. A number of manufacturers mention a setup procedure of adding the w/m injection gain until the AFR drops 1 full point and then scaling back your primary fuel until the original AFR target is achieved. Also some claim you can go so far as to tune a combined fueling target as much as 1 full point leaner, say a boosted car from 11 to 12. I realize that each car/application is different. I guess what I'm really curious about is whether the best approach is to focus on the fueling side or whether attacking the timing and boost in a w/m setup is a better approach?

Yes, it is possible to lean out the air fuel ratio when running water or water/methanol injection, however I'd suggest this will be dependent on the actual application and how much fuel you were relying on pre WMI to prevent detonation. Remember that one of the reasons we are using a rich mixture under full load is to control combustion temperature. Since WMI also achieves the aim of cooling the combustion temperature, we can potentially lean out the air fuel ratio when running WMI.

Typically you won't see a significant difference in power based on AFR unless you're running very rich, so I wouldn't necessarily expect to see a power gain as we lean the AFR out while running WMI - Of course the dyno is the best place to test and confirm the results for your specific application though. If you aren't seeing a power difference, I always tend to aim for a safe and conservatively rich AFR.

Also it's worth mentioning that the change in AFR will depend on what you're injecting. For example 100% water will have no affect on the air fuel ratio since it's not combustible. A 50:50 mix of water and methanol will result in a richer mixture if you aren't accounting for it with the ECU - For example on our 86 the closed loop control was pulling out an additional 10-15% fuel when the WMI was active.