Driving Aquamist 2c high speed valve with stand alone EMS

[b_boy]

Please excuse my utter ignorance of most things engine tuning.

I'm going with the the ECU that Ed mentioned, the Element-Hydra, with maps from Phil Grabow--former TurboXS employee. I just bought a Aquamist 2d from Ed. I have the USDM WRX STi 2.5L EJ257, and I too would like to use the ECU to drive the water injection system.

The Element has fuel injection controls as well as a few "extra" controllers for things like water injection.

I'd like to set up a 3D map for water injection but I am at a loss as to what parameters will be best for the ECU to track and alter water injection to suit the engines needs. RPM and boost are givens for water injection, but I'd like to add in something like EGT temp or air temp at the throttle body, scaling water injection when temps rise.

Let's say we use: Load x Boost x RPM x Temp at Throttle Body (TTB).

The water injection map will mirror (scaled down) the fuel injection duty precisely according to the tune without WI plus additional water as boost increase. So load and boost go up so too will the percentage of water (I think). Let's say at a load value of 2, boost value of 3 psi we will inject 5% water (as a percentage of fuel) across the RPM range (that is the 5% value holds, but more water is injected as the RPM increases with the fuel injector duty). At full boost, say 17 psi, and a load value of 5, we will inject 15% water (the load and boost have consorted to raise the percentage from 5% to 15%). Now I'd like to scale water injection such that an addition 1.5% of water is injected for each 10 degrees C above 40 C TTB. So, if the outside air is 40 C (100 F) instead of our usual 20 C (here in Seattle), the controller would be injecting an additional 3% water changing the injection range from 5-15%, to 8-18% of total fuel.

I have three basic questions:
1) Am I crazy, does it matter to scale with outside air temp, boost, and load?
2) Where do even begin with the 3D map values (I can't find any 3D water maps)? How does one develop such a map?
3) Let's say I manage to get a 3D map from someone (maybe from Richard L) do I need to worry that this 3D map is good enough for my engine, with my mods, etc?

I basically think that the "customization" to my mods will come from paralleling the fuel map (and anti paralleling the fuel dumping). So I think question 3 is answered to some degree.

EGT seems to be a means of developing a water injection map, but the number of test points to create such a map is just mind boggling. I can't imagine injecting water at each load, boost, RPM value to the point where EGT is lowered, and then backing off on fuel to reach stoichiometric, then adding water back to lower detonation if needed.

From what I have read a fine tuned map like I describe using EGT is not necessary; there is a fairly wide range of water percentage for each point that will "work". None the less I think a finely tuned map would not be unwelcome to the community. (Cylinder pressure based map has been discussed, but it's a pipe dream right now).

The first two questions are totally up for grabs. I'd be interested what percentages of water injection the TEC3 users are using and why/how they decided to go with those values.

[Charged Performance]

The closest public one I am aware of right now is the system 2s document from ERL/Aquamist. They have an example of how a potential 3d water map would look graphically with explanations of the increases and decreases along the axis.

Using that as an example of the shape a tuner would start with the set up non-WI tune and add water in on the points most stressed and requiring the richest fuel and least ignition advance. The water added should ease those requirements permitting fueling to be reduced and requiring ignition to be advanced. It becomes an iterative process at this point until the tuner is satisfied that the tune is achieving the sought after objectives.

In this case with Phil I would expect it to be some significant power improvement with good realiability and stability - not the ragged edge. But I am pretty sure that is what you are looking for.

[Richard L]

A simple map created by the MF2 based system (system2s) fro general use on a turboed engine.





Here is a MAP created by our discontinued, 12-year-old flash-based, 16-bit mirco-controller WI system for the turbo Bently, it has 128 rpm locations, 64 load location and 256 level of water injection %. Flash memory was the "State of the Art" technology at the time - we were one of the first company that employed it commercially.

The system was completely self-learning due to the huge memory loactions: 128 x 64 x 8-bit word, it was naturally impossible to map manually (8192 cells). The follwing map was created in just 15 minutes of driving on a test track when boost was increased from 6 psi to 15 psi. The only input was a dedicated knock signal line provided by the factory ECU.

If anyone want us to re-manufacture this system, let me know. Please don't ask the price.

[Charged Performance]

Another starting point would also be the fuel maps being employed.

Using the IDC of the injectors vs RPM & MAP for the initial duty cycle of the high speed valve with jets sized to a % of the injectors' potential would start you at approximately the same point as the 2d. From here the WI map could be modified based on torque and knock feed back as fuel and timing are adjusted to the targets. Of course from this standard starting point fuel and timing need to be adjusted to make use of the starting injection map.

If the fuel and timing in an area of the map are at desired levels but torque has fallen off from prior results, reduce the water injection rate at that point assuming knock isn't being encountered, which it shouldn't be.

If knock is being encountered prior to the fuel and timing desired for an area of the map, increase the water injection rate further at that point to permit tuning to the desired lambda and timing advance.

[b_boy]

Thanks for the replies guys.

Well I can see why you went to a more simplfied map with MF2, that matrix is dizzying.

I have studied the graph in the MF2 manual many times. It's easier to read in color ;-) Thank's Richard. Here is what I don't understand: the "injection rate %" description of the Z axis.

A: Is that the percentage of water injected compared to fuel?

B: Or is it the percentage of time that the water injection valve is open, thus the "rate" would depend on the jet size/flow and pressure?

Based on what I have read, 65% of fuel (the peak at 1 Bar boost) as the amount of water injected is very high, and I would have to assume no intercooler in the works. Option B seems the more likely interpretation, but I really don't know.

If it's option 'B', then the amount of water injection is not readily determined from the graphs. Is the water injection rate the maximum 150 ml/min from the standard 0.5 mm jet at 4 bar pressure? Thus we are looking a percentages of this rate?


So Ed, I would like to do just as you say "with jets sized to a % of the injectors' potential".

In either case I don't know what the "% of the injectors" number is-- 15%, 25%, 50%.

If the max water rate is 25% of the max fuel injection rate, and Richard's graph is showing 65% of 25%, that's a 16.5% water to ratio to the fuel. That seems about right.

Let me know the many ways I am confused.

[Charged Performance]

I believe that is B. or the water injection duty cycle you see there. Again just gives you an idea of the shape not the exact flow rate.

% of potential is based on your fuel injector's flow rating at the pump pressure being regulated.

For your goals depending on the load point you would find that from 12% to 20% water to fuel will likely be the result.

If for instance you have 400cc injectors your potential on the fuel injectors is 1,600cc. To make sure you can reach 20% if you needed to you would select a jet combination that have a potential of 320cc or 20% of the fuel potential.

This can be achieved with an Aquamist pump using a 100cc accumulator (even more easily using the STi water tank pump as a primer) and a 1.0mm jet. You could bench test the system to play with the water pressure switch to get that flow by engaging the hsv fully for one minute with the jet in a measuring container.

Now if a particular point is at 70% IDC for the fuel injectors and you put the water injection cycle at 70% also you will be at 20% water to fuel. 52.5% water injection cycle will put you around 15% water to fuel and 35% WIC would be at around 10% water to fuel. The exact percentage on a point by point basis is going to be trial and error. This is because there are very few identical setups to copy across several of the same car and almost none at this point for the STi as to my knowledge in the US none are on stand alone yet.

Starting from the optimal nonWI tune I would advise Phil to use water injection rates at 50% of the initial fuel injection cycle map - this would give around 10% water to fuel across the water injection map. Without fuel and timing adjustments the car will have lost torque at this point. Reduce fuel and increase timing to the new knock threshhold and see where that ends up. As fuel is being reduced the water to fuel ratio will be increasing as well since they are still at 50% of the initial fuel values.

In either case try not to get below 25% water injection cycles - if any points need this low an amount you probably need to use a smaller jet instead and increase the cycles.

Phil has the experience to feel out where adjustments are needed between the three variables from this initial point.

Treat it kind of like race fuel except that you can actually adjust the octane of the fuel itself - the water injection rate.

Invite him over to read this thread as well.

[b_boy]

Thanks Ed,
That makes more sense that the graph is reading % duty of the HSV. I understand it's an iterative process, I just want a base to start from and I seem to have it now.

Using the 3D graph from Richard if I set his maximum water injection rate of 65% duty at somewhere around 20-25% water:fuel and scale the rest of the map I'll come out fairly close. So at very low boost and medium load you are injecting (~5% duty on graph) or 1.5-2% water:fuel.

Why do you encourage water duty >25%? If you drop below that duty are you getting pulses of water such that each cylinder is not seeing a homogeneous mix of water:fuel. I'm cool with doing it, just wondering want the reasoning is.

[Charged Performance]

There is another post around regarding this. But when the duty cycle is low the high speed valve is not open long enough to fill the hose before jet and give good pressure during the cycle. If you have a need to use a duty cycle less than 25% you probably should go to a smaller jet or lower pressure and raise the whole map.

[BMWTurbo]

Hi Guys,

I'm sorry to mine an old thread, but it makes more sense then starting a new onw for a similar question.

I have been using a home brew W/I system for a little while now and think I'm approaching it the wrong way.

I have the nozzle fitted cirectly into the throttlebody of my 2jzgte engine and I'm injecting through a '400cc/min' nozzle via a solenoid valve that is either On or Off. I don't have any fancy control over this only an On/Off switch.

The engine makes somewhere over 400rwhp and I'm at around 70% injector duty on 650cc/min injectors (6-off).

My trigger point is 3800RPM where the second turbo comes on and both turbo's run at about 23/24psi boost.

Working through the above I'm starting to think that I'm injecting way too much at this point (prompted by the fact I changed the plugs last night to NGK BKR7E's gapped to 0.7mm and I'm having the engine miss from the opening of the W/I valve until about 5500RPM where is cleans up).

The 10%-20% stated is a percentage of actual fuel injected and cannot be derived back from injector duty and injector size due to the fact the injector duration isn't enough to use this as a percentage.

IE I can't say 70% duty of 650cc/min injectors = 455cc/min roughly x 6 = 2730cc/min

So 10% of 2730cc/min = 273cc/min.

However that 273cc/min would be if the injector duration was the whole revolution but this changes with RPM.

With a single trigger system, is the calculation different then the usual percentage I see generally referred to?

I don't really want to gap down the plugs if I don't have to the engine feel much nicer at light loads with 0.7mm gap then it did with the old plugs gapped to 0.6mm.

I have what I beleive are decent coils and I'm also running a HKS Dli.

One calculation we have used for single stage systems is this: You want to start injecting before the torque peak. So on the dyno plot, find the RPM where the TQ is climbing to peak, and look at the HP at that point. Multiply the HP number by 1.5 to get CC/min of an injection amount.

We usually use crank hp numbers for the calculation.

Now, if the car were at 250hp during the ramp, then the jet would be a 375cc as a starting point. Not far from where you are. You can run your numbers to see what it actually is.

One more item to consider, injecting at the TB puts a lot of large droplets in the chamber which can blow out the spark. One thing I would try is moving the jet further away from the manifold, as close to the exit of the IC as possible.