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Understanding AFR

Discussion and questions related to the course Understand AFR

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I have a flex fuel set up on my WRX 2015. For ethanol use.

If I had to add a meth injection to this setup ( with the ethanol flex fuel still installed)

1. Will it be good for the car and will it work ?

2. Can I expect better performance gains ?

3. Where would the spray nozzle best be installed

4. Can I run the meth spray using my ethanol tune considering that meth requires a lot more fuel enrichment AFR than ethanol ?


Hi Ismail,

Personally I don't see much advantage to methanol or water/methanol injection on an ethanol based fuel. Particularly with ethanol contents above about 40-50% knock is generally less of a concern and the benefits of WMI are not usually seen. To answer your specific questions though:

1. Yes it will work but the gains will really be prominent only on pump gas or low ethanol concentrations.

2. As discussed above - Gains won't be much if any on higher ethanol contents.

3. Generally you're best to place the nozzle pre throttle body but after the intercooler outlet.

4. The WMI provides its own fuel (methanol). in general you'll need to trim fuel out when the WMI is spraying regardless whether you're running pump gas or an ethanol blend.