Water injection has been kicked around for a couple of years now. I’m interested in those that have it on turbo rotaries and what their experiences have been both positive and negative. I have only had mine for a few weeks in the winter so I can’t post much. I’ll know more in the summer. I do know that it does reduce air intake temps. My only test showed about 15F cooler air intake temps at high boost and rpm. Not a good test as the outside temps were 22F and the IC pretty much cooled it way down.

Ken, 58 years young
'94 white, pep, red leather,
mods: Hayes/KDR street port & polished,
3mm Hurley racing seals,
upgraded coolant seals,
Power FC ecu, Commander, Datalogit,
XS T04e single turbo kit,
GReddy SMIC (400+cu.in.),
Aquamist 2s water injection kit,
Pettit ss resonated MP,
Pettit ss cat-back,
RP Racing fuel pump,
1600cc injectors,
Profec B(15&22psi),
3-Bar Map Sensor,
Centerforce clutch,
Racelogic Traction Control,
Under pulley kit (no air pump),
Pettit short shifter kit,
LaBreck's bushings,
Evans Coolant
http://nopistons.com/luv94rx7.html
http://flathat.woodstream.net/LUV94RX7/

 

For the benifit of others.

I have been running WI for 5 years now, first time I mentioned it on here I got laughed at a few years ago "newby syndrome"

I have positive and negative experiences running it over that period. To clear things up i will start with the negatives and explain the reasons behind it and what the solutions are (in my case)

Negative 1
Not knowing what ratio of water to fuel to run
*fault, excessive power loss.
*fault, engine misfire or choking feeling.
*fault, excessive water consumption.

Negative 2
Poorly designed system
*fault, non atomized injected water can be ineffective & in worst case cause impellor damage if injected before turbo in this state.
*fault, can cause engine failure if you have a cheap system that has poor design and if it fails and you have no safe guard then expect engine failure.

Negative 3
For high HP applications you need CDI ignition
*fault, with stock ignition at a rate of 15% water injection rate you will loose power on stock ignition when running straight water.

POSITIVE 1
Ability to run much higher boost pressure on pump fuel

POSITIVE 2
Internal cooling of the engine, not achievable with any other way legally on the street or on a race track when running petrol.

POSITIVE 3
Keeps engine internally clean, not carbon build up & hence no associated power losses

POSITIVE 4
It is FREE ! NO hassle, NO special fuel, NO bullshit ! Just fill the tank when you fill the fuel or check the engine before you run it, can be set up with level warning if you are scared you may forget to fill it.

POSITIVE 5
Reduces peak pressure in the engine, but increases BMEP, therefore providing you with more power, this is the greatest benifit by far and has been well documented by engineers across the world since 1930. A water injected engine has less peak pressure stress and much substaintially lower peak temperatures but maintains a higher average BMEP hence giving higher power. HIGHER POWER WITH LOWER PEAK STRESSES BOTH MECHANICAL & THERMAL

So there it is from my accounts, I still run it on my daily 560bhp (street trim, air filter,muffler, pump gas) 13BT 1st gen, I know without it I most probably would not still be using the same engine block for the past 5 years (only 1 rebuild "seals no major engine parts").

 

Do the lower combustion temps reduce exhaust velocity and affect turbo spool?
Aquamist has a chart that shows intake temps can be below ambient, but still recommends a IC. Why?
Is there a worthwhile benefit if you run boost at or below 15 psi?

 

It will not affect spool noticably unless you are out by allot on the amount you are injecting in relation to the fuel requirement of the engine.

The amount of water you need to inject into the engine at an airflow rate to support 500+bhp or even lower amounts of engine power on a forced induction engine is very large upwards of 30 to 40% fuel flow this WILL reduce engine power compared to a system that runs a charge cooler, it will also excessivley cool the inside of the engine droping the thermal efficiency. the best rates for maximum gains tend to be in the 10% to 20% water/fuel rate wich means you realy need to run a charge cooler of some type while using petrol.

Yes it will be a benifit @ 15psi, it will give you the cooling in the engine + you can run the engine not as rich which means extra efficiency + reduced wear or you can use it as a saftey system to account for hot days and variable fuel quality with the confidence of knowing that the WI gives you an extra saftey blanket, for track days (circuit racing or extended high speed running) it is exceptional, when others are struggling you will have extra cooling capacity and resistance to heat stress encountered in this type of activity (this is the main reason I started using it) ESPECIALLY IN THE EXHAUST TURBINE & In the seals in the engine, NO SIZE RADIATOR OR OIL COOLER WILL COOL THIS totally, the only way to have this under control is via fuel dumping at WOT full power conditions i.e. very rich 10.0:1 or 11.0:1, back when I was only at 320bhp level.

 

What are the effects of running WI along with Nitrous. MY car will be a well rounded vehicle, and i already have the NX kit. But for longevity of the engine and some insurance, i'm am considering WI. I don't see why you couldn't run both. Since the N2O is somewhat like adding more boost, in the sense that you are introducing more O2.

 

fastrotaries, I am not sure on the exact answer as I do not run nitrous.

I have herd that when you run this sruff you need higher octane fuel and a retarded spark (presume for the higher combustion pressures and temperatures)? So it should help out as WI reduces these peak stresses as mentioned before.

 

In WWII the fighters used both succesfully, but i don't know if you can only get away with this, with high octane gas. I guess i can start low and work my way up.

 

Here is another good technical description from an engineering type person on the benifits of WI




by Greg Hermann

If you can get water into the intake air stream--well atomized, but not vaporized until
after the intake valve closes, there are some significant gains to be had
on a turbo motor by means of water injection.

Evaporating the water during the compression stroke makes the compression
stroke into something that more nearly resembles isothermal compression
rather than the more usual approximation of adiabatic compression. This greatly
reduces the temp at the time the spark goes off, but also greatly reduces
the amount of negative work required during the compression stroke to push
the piston up.

Yes, because the peak combustion temp is lowerer, there is also less power
available on the power stroke, but the net difference between the gain and
the loss here is about 1.5% to the good side.

BUT--because the temperatures through the latter part of the compression
stroke and power and exhaust strokes are lowered by about 650 or 700
degrees F, the total energy lost to the cooling system is SIGNIFICANTLY
reduced, as well. This reduction in loss gives another significant gain in
net power.

There are other gains that can be had as a by-product, as well. Because of
the lower temps, the engine will be more durable. Because of the lower
temps, you can get away with higher compression, more boost, or cheaper
fuel, or some combo of these three before you get limited by detonation.
Because of the lower temps, you can also set the piston to bore clearance
considerably tighter, and thus gain better ring sealing, lower leakdown
rates, and thus a bit more power. Because water is a highly polar
molecule,
the mere presence of H2O in the mixture of combustion gasses is a _VERY_
powerful detonation deterrent--and thus you are able to get away with yet
another increment in boost/compression/fuel price IN ADDITION to the one
gained for the other reason described above.

Only when you inject enough water so that there is not enough heat/work
available (note that both uses of the word "available" in this note have
been according to the rigorous thermodynamic definition of the word)
through the course of the compression stroke to evaporate ALL of the water
by the time the spark goes off do you start to lose power. I have been
through some pretty detailed thermodynamic calcs on what goes on here, and
it all of what I have stated above is born out by the numbers. It is also
supported by what Riccardo published about his research on H2O injection.

It is interesting to not that an engine that burns straight methanol sees
many of the same effects. But, a stoich mixture of straight methanol has
so much cooling effect that only about 1/2 of the methanol is evaporated by
the time of the spark! Thus, the first portion of the combustion heat goes
to evaporate the rest of the fuel, and NOT into power! While methanol has
more heat of combustion per pound of air breathed through the engine than
gasoline at a stoich mixture, this combustion cooling effect is why a
methanol fueled engine has relatively poor thermal efficiency.


T he still soggy mixture at TDC and the spark is why a methanol engine
that is not fully warmed up has such a strong tendency to foul its plugs.

 

Rice-Great stuff

 

Yeah Rice, thanks a lot for your posts here. I have wondered about WI ever since reading of how the old fighter planes used it in combat to save their engines during large boosts of power. The P-51 Mustang engine was supercharged for altitude use, and using the supercharger at lower altitude for takeoff or combat could have been possible with water injection for the detonation-deterring reasons stated above.

When (if) I put a supercharger on my NA FC it will have a water injection setup so I don't pop that 9.7:1 compression ratio engine.

I am hopefully going to start engineering school at Oregon State U and later on, I should do my thesis on water injection.

 

I find it interesting that many people have bad things to say about water injection. That it's voodoo, that it merely covers up for a poor turbo selection or poor tuning or poor fuel.

I find it interesting because people used to say similar stuff about intercooling.

Today, I can only think of ONE production car that does not use intercooling - the Lotus Esprit V8 - and that is because the turbos are only there to tweak the torque curve, provide noise reduction, and as a rules tweak for certain racing classes. Intercooling is acceped as normal and almost mandatory today.

I firmly believe that the same will be true for water injection. If GM had stuck with turbochargng in the 60's (which they would never have done for many reasons) then everybody would probably percieve water injection as entirely normal and almost mandatory. The Olds turbocharged 215 V8 in '62-63 had factory water injection and a control system that prevented boost if the system was low on water aka "Rocket Fluid".

 

Rice, why not cool and add power at the same time by using straight methanol?

 

The main benifits of water is to prevent detonation. I have not heard of anyone that used water properly that has detonated his motor. To me injecting straight methanol will not reduce your intake air temps or combustion chamber temps or clean you motor or reduce your EGT as much as straight water.

Ken

 

I'm not at all sure about the methanol keeping the motor cleaned out but I've always been told that the methanol will drastically decrease intake/combution temps.

 

I agree, but not anywhere as good as water.

Ken

 

Last time I checked methanol costs a lot more than water and is dangerous to your health.

Ken

 

Methanol can also contribute to detonation since it is a fuel! Water is not a fuel, it is for our intents and purposes inert, which is why it helps prevent detonation.

Methanol added to water does prevent the water from freezing, for those people who drive their cars where it's cold. Windshield washer fluid is water, methanol to prevent freezing and aid evaporation, and dye to help prevent people from drinking it, but I really wouldn't want to find out the longterm effects the dye might have in an engine. It sure as hell gets pretty crusty after the washer fluid evaporates!

 

I've been playing a bit with my Aquamist system and I believe that I am convinced that an upgrade to a variable rate system is a must have.

Rigged up a switch to engage the WI so I can monitor air temps ... while at partial throttle & 5 psi in 4th gear spraying for a few seconds the result is a 4-5 degC intake air temp reduction(using a 0.9 Aquamist injector). However, a full 4th gear pull while spraying will usually net a 1-3 degC increase. This tells me that I may not be spraying enough under the air flow conditions of full throttle/boost & high rpm. My system is the basic fixed rate using a single injector activated by boost only.

Anyone care to comment on how I may improve upon the entry level Aquamist system?

 

Forgot to mention where I inject. I have an FD with a large stock mount IC, the injector is mounted in the outlet tank of the IC, across from and firing into the outlet pipe. After a few runs the entire pipe from the IC to the Greddy elbow is noticeable cooler than without WI.

Originally had it in the Greddy elbow but occasional water leaks spraying onto the ignition were causing issues.

 

I was under the impression that most of the benefit from WI occured during/after combustion where the water absorbs heat rather than a reduction in charge temp. Perhaps an EGT measurement would be a better ruler here?

 

I had the 1s kit and upgraded to the 2s kit for a few $100s. It's a complex setup, I'd download the .pdf from the Aquamist site before you upgrade and look into it first. Richard Lamb from Aquamist will be very helpful if you need help. He wants to see more people in the USA go with water. Being in the UK they do very well in Europe with their product. It's taking time to catch on in the USA. Maybe because of Corky Bell's book that I think was published back in "62 and is somewhat outdated. WI has come a long ways since "62.

http://www.aquamist.co.uk/

Yes, after heavy duty runs with WI the intake after the IC is very cool to the touch.

Ken

 

I thought meth was good because it burns slow. I dont think it would help anyless than straight water but for convience Id rather run straight water. If I still lived in WA Id mix to prevent freezing. I kinda like this idea of water inj and im happy to see people are running it. Hopefully when I start to need it I can goto some of you guys for advise.

 

How is the aquamist system 2c? I have an E11, this is my first experience with ems, so Im still learning the ropes.. I could run the mist effeciently with one of my PWM outputs? Im not sure if I can make a dedicated map for controling the watervalve. Any help would be great.
sky