Symptoms of too much Water Injection

[JohnA]

Originally Posted by Slump

This is a dyno of my car.

The blue line is "too much water", and the red line is a more correct amount of water.

The only difference between the two dyno runs is the adjustment of the quantity of water injected using the Aquamist MF2 controller (part of the System 2S).

Interestingly, the blue 'drowning' run also appears to be much richer in fuel.
Did the extra water fool the oxygen sensor, or did you also change the fuelling as well?

[Richard L]

Originally Posted by Slump

This is a dyno of my car.

The blue line is "too much water", and the red line is a more correct amount of water.

The only difference between the two dyno runs is the adjustment of the quantity of water injected using the Aquamist MF2 controller (part of the System 2S).

What jet size were you using for this chart?

[Richard L]

Originally Posted by JohnA

Interestingly, the blue 'drowning' run also appears to be much richer in fuel.
Did the extra water fool the oxygen sensor, or did you also change the fuelling as well?

I am also interested...

[Gelf]

Yes, we need info on the effects of WI on the oxygen sensor :!:

[DuMaurier 7]

You can feel the effects of over injection and if you have an exhaust tem. gauge you'll see it there too . I've meen over injecting for a little while , my exhaust temps moved from 1400 deg. F to 1000 deg.F , there was also a slight reduction in the "harsheness " of the car 's power.
My a/f ratios were also fairly rich 10-10.5 : 1 without any ignition breakup or bogging ! , Thats because I have an MSD 6 A on each of my leading plugs. :!:

[hamton]

I want to start WI for my car, but I noticed in the dyno below, a user that used WI, he lost power from 3500RPM and higher. Under 3500 RPM there is a huge gain. Is this the result of too much water or the ECU being too sensitive? Now he has other mods along with a custom tune.

http://forums.swedespeed.com/zerothread?id=42148

Info about the car at the time.
2005 Volvo S40 T5 with custom catback exhaust. At stock, the car produces 218HP / 236 ft-lbs torque. The 2.5liter inline 5 engine uses a small low pressure turbo that produces a max of 10psi.

In the forum he specifies he was using an aquamist is 1S system. triggered 0.5 bar. 0.6mm injector.

I have basicly the same car with a few other mods: BSR Stage 1, K&N, EuroSport catback. The BSR raises the psi to 15 and I'm guessing more fuel delivery. I was planning on using Aquamist 1s with .5mm injector and 100% distilled water but after seeing this, I'm a little discouraged. BSR does not do custom programming. I'm just curious if the same power loss will happen to me.

[hotrod]

The Buick GN folks frequently would tune by "feel" and discribe the effect of too much water injection as the car begins to "feel soggy". The throttle response gets softer, and it just feels a bit sluggish.

In that dyno plot I suspect what you are seeing is the result of improved air density at lower rpms. The cooling effect due to evaporation would likely increase your VE significantly especially in the lower rpm ranges where the mixture spends enough time in the manifold for some evaporation to take place. WI tends to slow down the burn speed slightly so it in effect would retard the ignition timing slightly. At low rpm that is not too big a deal but the combination of excess cooling lowering cylinder pressures at high rpm and not enough ignition timing would effect top end more I suspect.

If he could lean out his fuel mixture at high rpm he would probably get his power back for two reasons. Combustion temperatures would increase due to the leaner mixtures and he would get a slightly faster burn.

What the Buick GN guys would do is keep increasing injection rate until they felt that soggy feeling in the engine response, then they would lean it out, add boost or increase timing advance until they started to see signs of detonation or the car slowed down. Then repeat the cycle until the car no longer gets quicker.

Each car is unique in its needs so you can only extend someone elses dyno experience in a general way. Just give the car what it wants. If you make small incremental changes and monitor how the car responds it will tell you what it likes.

Larry