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Water Meth Jet and IAT Sensor Placement

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Water Meth Jet and IAT Sensor Placement.

Good Afternoon,

I am working on setting up a water meth kit in an 04 Subaru STI, tuning with Cobb's Speed Density AccessTuner system. I have read some conflicting reports on the placement of the Water-Meth Jets, and I would like to hear any suggestions you would have.

Some Manufacturers suggest mounting the jets as close to the inter-cooler outlet as possible to allow additional time for the water droplets to evaporate to create greater charge temp temp cooling. However Some tuners on various outside forums, have posted that the mounting location by distance is not as critical because the point is for the water to enter the combustion chamber for cooling. Furthermore, they suggest that the water cannot evaporate within the time/distance traveled in the charge pipe, even if it is a few more feet. Given that the air charge is travelling at great speed with typical charge temps under 150 F, I'm inclined to believe that mounting the water-meth jets as far as possible would not yield any significant advantage. Additionally, if the water-meth mist is going through additional bends in the charge pipe it may become less atomized. What are your thoughts?

When it comes to IAT sensors, some outside forum posts suggest that if the water-meth jet is placed before the IAT sensor in the intake pipe, that water-meth droplets can hit the IAT sensor and create inaccurate air charge temp readings. Is this an issue I should be concerned with and should I mount the IAT sensor before the water-meth jet?

Any suggestions are appreciated. Thanks.

Test both and find out who's right.

I've always subscribed to just post intercooler for highest delta (though to be completely honest with most modern intercooler design choices the distance between outlet and throttle elbow is measured in inches as compared to feet when giant oversized FMIC's were all the rage, so i doubt it matters). Also I don't subscribe to the whole 'water droplets hitting the IAT causing inaccurate reading' hype to hold water. This applies to using K type thermocouples, GM/Delphi open tipped IAT sensors, and Autronic's proprietary (not certain of its manufacture of origin) sensors.

I will say, however, that most installs in my opinion follow some pretty poor design/implementation rules of thumb by mounting the nozzle perpendicular to the charge path. If at all possible angle the nozzle or install the nozzle in the outside radius of a bend.

Thanks for the replies.

I could experiment with having multiple bungs in the charge pipe and play with different locations for the sensors and see what happens.

I never considered mounting the water-meth jet on the outside radius of a bend, pretty interesting. Now that you mention it, it would seem that the outside radius mounting would be beneficial because a lot of air charge is hitting that outside radius of the intake tubing. I wonder how well it work to mount the jet on the outside radius of the last bend before the throttle body; maybe in a way so that the spray pattern is facing the throttle body as much as possible.

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