OverLOAD

I've seen claims of 15% hp gains, and 25% mileage gains from settings up a direct water injection system in the intake.

I'm curious if anyone else has heard of/seen this before, or has any experience with it.

There's a couple of sites that sell kits:

http://www.racetep.com/wik.html
http://www.turboice.net/

The whole premise is that the water or methanol mix will evaporate in the intake, and cool the charge, plus it will 'boil' & burn off in the combustion chamber, increasing net power..

I figure that if I really could spend just $300, and get my 'rated' hp from 238 to 274, that would be very impressive..

Any comments? I'm very interested in getting this kind of setup, and wondering if there would be long-term damage, like rusting, or seal-detioration problems..

wakeech

uh, that works for (rather poorly) designed forced induction systems, where severe thermal inefficiency is a barrier to higher hp for the hardware, but as far as all-motor tuning goes, that doesn't really do anything, as it doesn't really change the net pressure in or out of the engine at all.

Lensman

It worked well on the P47 Thunderbolt but on an RX-8: I don't think so...

syntrix

Yeah, it's a band aid.

Anyone ever pull apart a honda engine that was s/c's with WI at anywhere near 30-40k miles?

It's not a pretty sight.

Just remember that the water/meth displaces air and fuel.

turboice

I will start with the pop publication catch phrase - "band aid" - if I were to quote someone it would be someone other than Corky Bell. He is a fine tuner - but his popular writings vary significantly in the amount of research he actually performed. Unfortunately he is oft quoted by the employees of another talented tuner whose skills I do respect - but also respectfully and through research thoughtfully disagree with. Corky Bell hit so many areas dead on and then wandered into other areas with little consideration to the millions of pages of research performed by engineers that were peer reviewed prior to publication - unlike his own work which was not subjected to critical engineering review. If you want to quote someone quote Heywood, quote Taylor, quote Glassman, quote Sir Ricardo - quote people who are willing to have their work peer reviewed prior to publication in respected journals rather than by an editor who is concerned with selling a pop book. Heywood's book is a graduate text book in almost every automotive engineering course offered in the U.S.

Injected water and methanol are less than 2% to the induction charge, they cool the charge making it denser - oxygen concentration is increased not displaced. Fuel dumping to cool the cylinder is highly inefficient due to fuel's poor specific heat and actually does contribute to poorer power both by actually displacing oxygen and by the damage excess unburned hydrocarbons cause to the combustion process and entire system - even if water did nothing at all but cool at least it is already in a form that is a major byproduct of complete combustion - steam. Water injection displacing air is pure myth and I challenge anyone to find a technical paper to support the claim - they don't exist. While to the contrary support that oxygen content is increased has been found widely in many studies.

As far as pressure goes - water and methanol injection does change both max pressures and BMEP - it decreases max pressure while increasing BMEP - both desirable outcomes. See the link below for documented research of this outcome.

Dumping fuel to overly rich conditions does far more damage to an engine than water injection could ever be forced to do. Steam is a major result of hydrocarbon combustion - it already exists in heavy concentrations in the combustion chamber and exhaust. The addition of the small amounts in injection applications are not causing additional damage - it is impossible for it to result in more damage than driving only in 100% RH.

Read the paper here. This has been widely reviewed by others and heavily contributed to by them (to its vast improvement each time I am able to update it) and I always seek further supported feedback to improve its usefulness in actually providing supported conclusions rather than sound bites.

Due your own research look into studies on water injection in SAE and NACA papers there is too much for any one person to ever get through.

Oh and stop by the Aquamist booth at SEMA and see who else is there that has been working with water injection...

r0tor

iTrader: (1)

We use water injection on our big *** gas/oil turbines at our power plant. While it does give a boost in power, it also cuts the life of the turbine by a factor of 2 or 3 because of the extra wear imposed on the turbine blades from corrosion and pitting. Keep in mind this is on an engine that doesn't have the harmful effects of the water getting into its lubricating oil on top of the extra wear.

turboice

Water injected into an internal combustion engine does not get into the lubricating oil either - oil repels water - however oil does not repel gasoline - excessively rich fuel mixtures will wash the cylinder walls of their lubrication very quickly. I have seen new spec built motors gain a quart of "oil" every 3,000 miles from running overly rich fuel mixtures - now that is destructive imagine the viscosity losses when you have a quart of gas in your sump. When fuel is used for knock control rather than combustion it takes 6 times the amount of fuel to do the cooling and knock suppression done by water.

Sure liquid water sprayed in front a high velocity blade will cause wear - given time liquid water created the grand canyon. Again - we are talking about water at less than 2% of the induction charge and huge amounts of steam already exists in the exhaust whether you like it or not the little extra on the induction has a small effect on the amount created during combustion and left in the exhaust.

I must admit ignorance on the specs of the RX-8 - just how rich do these even run at full load? If they are not running richer than 12.0:1 there would be no appreciable power tuning benefit from water injection - at best it could be used to lean a bit and get better economy.

Water injection is for knock suppression and combustion control - and to the extent that a car is normally tuned to run richer than 12:1 the knock suppression it brings permits tuning to leaner than 12:1 and all gasoline motors that I am aware of produce maximum BMEP somewhere between 12:1 and 13:1 AFR. I assume this holds true for rotary motors as well.

The power that water injection enables a tuner to achieve is directly related to how rich the motor has to run without water injection. It benefits a motor normally requiring 10:1 AFR to be knock free more than one that normally requires 11:1 AFR to be knock free which again is more than would be achieved with one that normally requires 12:1 AFR to be knock free.

It is not for all applications it is for applications where fuel is being dumped solely for knock suppression and is meant to be used in place of that otherwise excess uncombusted fuel that is firstly a poor coolant and secondly interfers with combustion and BMEP by encouraging the first step of oxidizing to CO but discouraging the second step of oxidizing to CO2 where the most power is released in cumbustion.

wakeech

hey Ed, welcome, and its great to have another member onboard from whom i can obviously learn a lot

wicked stuff Ed. thanks for all the good info.

aside from RX-8 tuning issues (as obviusly injection systems aren't really a concern for all-motor tuning) water injection has always intrigued me as an idea, but had always been marignalized by all i'd read thus far (yes, Bell's book is where i got "band aid", but was some of the only literature i could find... i'll look harder for your references).

as a sort of day dream, i'd always wondered about the thermal effects of (LARGE dose) water injection on efficiency; hydrogen combustion is only about as efficient as combusting hydro-carbons, and i was wondering what a good process fo extracting more work from the heat generated would be, short of creating a magically more effifcient engine. could water injection be effective here??

r0tor

iTrader: (1)

That is totally untrue. Water will mix with lube oil very easily at small amounts. Around .05% - 1% water the oil becomes cloudy, around 5% water the oil looks like yellow baby puke. Basically what happens is the water starts to precipitate out carbonate thats put in the oil to make it a caustic (acid promotes rust so it interacts with sulphuric and carbonic acids from combustion to keep the oil a caustic).

If gas is getting into the oil, the water will as well. The only difference is gas is soluable in oil so it will only thin the oil. Water isn't soluable but will cause a precipitate.

turboice

A lot of the information is really hard to get through as well since it is usually very technical and I do not have the background to get it all without reading it many times and asking others what it meant in English - my hope is that my paper remains technically accurate while being more readable. Bell's book is good - there are just corners of it where he didn't have a any exhibitable basis for the conclusions - and not enough people question it. If it hadn't been for my own use of water injection on and off for 20 years I probably wouldn't have thought twice about the claim.

With regards to the mechanical efficiency of the internal combustion engine I am not aware of any effectiveness other than its ability to suppress knock and its contribution to the the CO => CO2 reaction (the water method Harris refers that I included in my paper). I honestly don't know for sure if more water would cause some partial hydrogen combustion to occur - but I doubt it based on the reactions that I have seen laid out as occurring in carbon combustion, the large amount of OH radical present to capture any free hydrogen (rather than further oxidixing) and also based on how much the motor will bog if you add too much through injection even while continuing to reduce fuel. I suspect the large amount of carbon present prevents hydrogen combustion from occuring - but don't know for sure. I buy about two books a week and need to get the Ricardo book so I can better understand references to his testing with large amounts (50% water to fuel) of injected water - but on the surface it appears only effective with large available amounts of air and fuel which would further lead me to believe it is not contributing any hydrogen combustion of the sort you appear interested in. We still can't burn water .

pr0ber - Once again you reinforce why on technical matters I really should have reference first - I have no reference other than the layman's understanding that oil repels water and obviously at the threshold of contact (or a reaction to additives that are not repulsive that I was not aware of) and my understanding must not be true based on your comment.

Based on my experiences with water injection the condition and wear in the cylinder are far better than similar motor setups that used gasoline for knock suppression. Taking my previous understanding of the reaction of water to oil lubricant as erroneous there must be some other explanation as to why I have not seen evidence of water accumulation in the sump in my implementations but have seen fuel accumulation in rich fuel mixture applications. Pure speculation here (and I do try to admit when I am doing so) but perhaps then the residual barrier of end gases near the surfaces play some role in preventing the injected water from conacting the lubricant and entering the crankcase. Or perhaps the decreasing droplet size and eventual evaporation of the water as it approaches the heated surfaces dilutes the water/steam concentration to a point where its effect is diminimus. Either way - in implementations I have been involved in I have never seen unusual or excessive wear or corrosion.

You have also added something else I need to research. When I am shown to have misunderstood something - I will seek to correct it and the input is always helpful and the paper was a far cry from its current state without such input.

T-von

If some of you guys want some info on WI, do a search at the Rx7club. Zerobanger has a custom setup that runs in 2 stages. He loves it. His works so well that when I install my WI, I will try to eliminate the intercooler. His WI setup lowers intake temps so low that it makes his small intercooler useless(and thats running around 15 psi). I'm doing this because I can't stand all the heat soak.

turboice

For those interested in discussing the topic of water injection broadly and across makes - I have started a noncommercial board for water injection discussions both from a theory and application standpoint.

3 days old...

Water Injection Forum