It's the evaporative properties of the spray (water/alky) during the phase change from liquid mist to vapor that provides the cooling that allows the lean air/fuel and higher boost. Correct me if I am wrong about that. How do you know that you are getting that phase change and not leaving liquid in the cylinder? My fear is cylinder wash. Without alky/H2O injection, this is what you can get with too rich of an afr. With injection, I fear that the alcky/water can also wash oil off the cylinder walls. I'm wondering if this is what's happening to guys that had good compression in all cylinders until after installing alky injection kits.


Dang it, I can't edit the title. Excuse the "your's." It's supposed to be "you're."

If you have a wide band sensor, you might have some clue of the aafr for a short term, then you must alter your alky/fuel ratio before long term damage is done - I am talk in term of days rather minutes.

I have to assume all alky injection will be reflected on the wideband, evaporated or not.

I am not sure on the speed of the phase change but I am going to assume that most of it happens inside the cylinder where it would have the greatest cooling effect. IMO you should have it tuned with the injection so you are running the proper air/fuel ratio.

Water will not show up in the reading, and that is what is most likely to stay in the cylinder since it takes IIRC 3x as much heat energy for the phase change than alcohol. If this is something you worry about, you may be better off using 100% alky instead of a water mix as the alcohol will be used in combustion. I haven't heard of anyone worrying about cylinder wash issues while using E85 and they run absolute AFRs of 7:1-8:1 while in boost.

It's the evaporative properties of the spray (water/alky) during the phase change from liquid mist to vapor that provides the cooling that allows the lean air/fuel and higher boost.

The phase change and intake air cooling is a benefit of running alc or water over petrol, and just sets up the mix for the more important stuff. With water injection, the water gets between the different fuel and air particles and cools/slows combustion. This makes it so running a leaner a/f ratio, adding timing, and boost gets the temp and speed of combustion upto where it use to be. Alc is kinda like water, but it's a fuel. Having any higher octane fuel will allow ya to run leaner a/f ratios, more timing, and higher boost(well, in general). Alc has the benefit(over higher octane petrol) of better heat absorbtion attributes, and we use more of it to get a given a/f reading which both help cool things down and allows for even more agressive tuning.

Back to the subject though. Running too much injection is relative, but there are some standards people use to determine how much they should inject. Ie-If you're injecting the same amount of liquid or less after injection as b4 injection, chances of cylinder wash will probably be the same or less. This obviously isn't true if you replace all the fuel with water, but................ What I mean to say is, if you want, you can make your injection system help your engine run healthier then b4 injection at hard throttle. That's basically what they do anyways. I mean imagine how health a wrx engine would be at 25psi on 93 octane with 23 degrees of advance without injection:).

peace

I know you don't just slap the system on and go. You tune for it. I was just wondering if the system could have possibly contributed to loss of compression on a few of the tuned injected cars that I have seen posted on these boards.

Imo if a car with an injection system encounters cylinder wash, it's not the fault of the injection system unless the system malfuntions in a certain way. I mean, if a system works like you think it should, a contributing factor of cylinder wash would be the tune more then the system. Course this might not be the case. Depending on how the flow of a system is controlled, many things can happen. This is true with the fuel system too though.......

peace

I was just wondering if the system could have possibly contributed to loss of compression on a few of the tuned injected cars that I have seen posted on these boards.

Not in the context you appear to be thinking. Cylinder wash and higher ring wear rates take a good deal of time to be an issue. In most setups your actual duration of spray is very small. An internal combustion engine can ingest a stunning amount of water without any damage. It only reduces power output. During WWII they did tests on aircraft engines where they injected so much water, that they had liquid water pouring out of the exhaust headers. It caused no damage to the engine, but did reduce the 2000 hp output of the engine to about 600 hp.

Like any performance modification, if folks do on tune properly, they can wound an engine this applies to alcohol and water injection just as any other power upgrade.

As long as you take precautions to prevent accidently running without injection when you intend to, your good to go.

Larry