Back in the day we made a simple water injection system and showed decent gains. I'm thinking of making one for my Fit and was wonder if anyone wants to collaborate on it?

The system I made before does not use a water pump and just use manifold vacuum to atomize water and pull in the vapor. The flow demand is based 100% on a flow valve and manifold vac. So it's good for cruising but NFG under heavy load.

I think a 5 to 10% gain is possible with no side effects other than refilling the water when needed.

Back in the day the best part of this was the timing could be advanced as it reduced the tendency to detonate (pre ignition). That is not an issue wit the Fit but wanted to mention that for the kids.... The Fit actively changes the advance based on load and signs of knock like just about every car made these days. On the Scan Gauge you can see this clearly.

 

Definitely worth trying, but I don't know if the Fit has the compression or cylinder temps to take advantage of water injection. I'd definitely go water/methanol if I was going to do it, but just not sure if there will be any gains.

The best gains I got with my specV was by removing the grounding the knock sensor so it never retarded the timing. The knock sensors in those cars are way over active. Low compression plus premium fuel should mean no retarding ever.

 

I also had a SpecV before the Fit

 

I too wonder if this would work. It goes against the popular opinion as to what you should do with the inlet air on modern EFI cars for fuel efficiency. Everybody seems to think that the warmer you get the air the less fuel the car would use, which would seem logical to a point. There are plenty stories all over the forums of "warm air mods" that increased fuel efficiency.

The logic works out. If you warm the air in the inlet track you will use less fuel than a cooler inlet track (less dense air, thus less fuel needed to reach stoich). But the logic also tends to fall apart on today's modern EFI engines that use a Inlet Air Temperature (IAT) sensor. The warmer the air, as read at the IAT sensor, the more timing the ECU pulls from the engine, thus reducing power and increasing fuel consumption. It seems like a Catch 22 to me. I've been monitoring IAT on my Fit and consistently see between 8 and 10 degrees warmer than ambient on the gauge while moving.

So, to me the water injection thing is intriguing. On one hand I could see it lowering inlet air temps, thus requiring more fuel to burn the denser air charge. On the other hand I again see it lowering IAT sensor readings thus allowing the ECU to add more timing and increasing fuel economy. Will the lower IAT correlate into enough of a timing change to make any kind of real difference in economy? I don't know. From what I've been monitoring on the ignition timing through the ScanGauge there is already a lot of timing put in at the low load and throttle positions I use during acceleration and cruising, somewhere around 30 degrees during acceleration and 40 at cruise. I don't know of many engines that do much better on a difference of timing on going from 40 to 50 degrees. In addition, there has to be a point where the ECU won't give any more. There has to be a point where a traditional ICE won't run on a given ignition lead, but then again, these engines are getting to be pretty advanced for ICEs. So, my suggestion: try it and let us know!

 

The injected water VAPOR would be pulled in by manifold vac after the Throttle Body. That's a great deal different than your thinking on how to.

I know how I'm going to connect it, just need to find the bottle and a good spot under the hood for it. I will T into the 11/32 vac hose that feeds the Power brake booster. I'll be using a small gauge hose with a check valve into the top of a bottle to created vac. A 2nd small hose with a fish aquarium bubble stone will be at the bottom in the water and feed air from the top outside the sealed lid. That end will go to a small valve outside the bottle and I'll use to regulate the incoming air and bubbles made. The vac line in the top will suck atomized wet air into the eng via manifold.

Not sure the corrosion potential from the intake port and inside the intake. I know most of it is aluminum, but will have to look close at that. Corrosion is a real possibility based on past experience.

 

So, with the water vapor being injested after the throttle body the IAT sensor wouldn't even see the temperature drop. I guess ultimately the O2 sensor would read the difference from what the ECU calculated originally and just alter the fuel supplied based on the long-term fuel trim. Like I said, I'm anxious to see how it affects the fuel economy. Keep us posted.