Richard L

iTrader: (5)

It is my attempt of explaining how different type of systems work and its advantage and dis-advantage, based on current systems offered. It is a my view and findings, please do chime in and discuss.

1) Single-stage
2) Two-stage
3) Progressive Pump Speed system (PPS)
4) PWM Valve controlled system
5) System that will integrate well with third party controllers.
6) Direct port



The single stage WAI (water alcohol injection), as the heading implies, is not as basic as most people expects. It some cases, it will out perform a two-dimension progressive system. Please do not underestimate it. I will try to explain briefly why after the next few paragraphs.

Having a single trigger point and a fixed flow rate, one will get to know its effect on your engine very quickly. Due to its consistent repeatability, it is very easy to tune. This type of system is normally set to start spray in the peak torque region, where the engine is most likely to knock.

As the RPM climbs, the ratio of water to mass air tends to decrease. This may not be a bad thing because the tendency to knock is also lessen as the wastegate starts to open and prevent the boost pressure from increasing further. The volumetric efficiency of the engine also decreases as RPM climbs, breathing in less air. This also has the effect of reducing the engine's tendency to knock, demand of WAI flow is less. Unfortunately some engines do require continuous WAI flow at higher RPM due to heat build up through friction and turbo efficiency.

A 2-D pump speed system based on manifold pressure is a little bit tricky to tune compared to the single stage system. The user has to set the start and finish pressure points, those points are sometimes set at a considerable distance apart. Matching those operation points in a 3-D environment such as RPM/Boost ramp (nonlinear) is quite difficult. We will be discussing it in more details later.

FOR:
1) Low cost, simple and dependable.
2) Easy to tune
3) Very effective on a stock factory set up with a few pounds of boost extra.

AGAINST:
1) Dynamic operating range is narrow, may not be as effective on a high RPM knock suppression.
2) For high power/ high % alcohol applications, considerable fuel has to be taken out (boost clamp) to make the afr tolerable. Some sort of failsafe mechanism is necessary to prevent engine destruction when the WAI fails to delivery the correct flow.


At present, adding a second manifold pressure switch to active an additional solenoid valve at a higher manifold pressure is the definition of a 2-stage system.
This arrangement gives the system greater flexibility as well as extending the flow range. It addresses the problem associated with the single stage system, too much flow at the start and not enough when RPM climbs beyond the wastegate setting.

As the system is based on boost trigger, it still won?t address the RPM related flow. For a turbo charge engine, the most significant active regions are the boost ramping stage and engine?s maximum torque range. A two-stage system fits these two regions nicely, allowing the some form of cooling demand during the ramp-up stage. The second stage provides the in-cylinder cooling and knock suppression as the engine is under the most stress or highest BMEP (Brake Mean Effective Pressure).

FOR:
1) Relatively low cost to give mark improvement to the single-stage system.
2) Provides well defined triggering points during the boost cycle.
3) Minimising the under/over flow problem.

AGAINST:
1) Trigger points requires some time to set up.
2) Triggering points may differ on each gear if you have a fast spool up turbo
3) Require a bit more care during tuning

END
----------------------------------------------------------------------------------------------------------------------------------------------------------------

Does the pump speed controller perform better than a two-stage system, you are about to find out.

Changing pump speed merely put more pressure behind a nozzle, hence more flow. This type of system is commonly known as a progressive system (pump-speed).

Let us examine how much a M5 nozzle will flow between 40psi to 160psi. According the chart below (Published by Hago, a well know US oil heater nozzle manufacturer), the flow starts from 200cc/min and ends at 400cc/min., when pressure is increased from 40psi to 160 psi.



Almost all PWM pump controller on the market uses Shurflo pump, designed to operate between 0-150psi. The heart of the system is an electronic motor speed controller, vary the speed according to a sensor. It could be a MAP sensor, a MAF or any sensors that read engine load. It is normally a 2-dimensional system. A manifold-pressure type system does not take into account of any RPM change.

A swirling type atomising nozzle requires a head pressure of at least 30psi to produce a decent mist. Droplet size is very important to the inlet cooling ability and even cylinder distribution. Let say the system pressure starts at 40psi (as shown on the chart) and ends at 160psi. One can assume you will get a 4x flow range? In practice, not so, according to the chart, you will only get a flow change from 200cc/min to 400cc.min (see M5) instead of 200cc/min to 800cc/min. Flow/pressure obeys the square-root law.


Being "progressive" implies a reasonable dynamic range between start and finish. How progressive? Almost no one ever questions this. Most people just assumes it covers all the flow requirement between 10psi to 20 psi of boost once the range-dials are set on their pump speed controller. In practice, you cannot expect the same M5 nozzle will serve a wider operating range between 5-25psi by merely changing the dial, the range is governed by the law of physics and not a technically advanced motor speed controller.

If one would want to delve deeper into the subject, as the title demands. So the subject will continue?

Just to recap, good dynamic range (pressure/flow span) is the main factor one should expect from a "progressive" WIA system. Let see what a 150psi system can really offer. We shall take into account of the effect of manifold pressure, inline checkvalve as well as minimum pressure for a good atomised spray.

For example:
1) Manifold pressure start: 10psi
2) Manifold pressure ends: 20psi
3) Inline checkvalve crack pressure: 30psi
4) Minimum pressure of the atomising nozzle: 30psi.

When the system starts: it will instantly see an initial back-pressure of 60psi and a final back-pressure of 70psi (extra manifold pressure). The actual dynamic pressure range is now from 60psi to 110psi. The system can now only manage a 35% change in flow, far from one would imagine a 150psi pump system should perform.



There are other factors that could also affect the performance of the 2-D progressive pump system. It may be a subject for a later discussion, depending on the interest of the readers. Chart below is a predicted performance of a progressive system compared to a single and two-stage system. I hope there will be people chiming in to add to this. At first glance, it doesn't appear there is a distinct advantage for adding a progressive controller. Adding a bigger nozzle doesn't alter the dynamic range, it just shifts the whole curve higher.



FOR:
1) Easy to set the start and end point.
2) Some correlation between manifold pressure and flow
3) Cost effective.

AGAINST:
1) Limited dynamic range, system becomes less effective after wastegate pressure. (see addendum)
2) Extra cost can easily be spent on a higher performance two-stage system with greater dynamic range .
3) If the 2-D system is used to replace high % fuel with alcohol, re-mapping the 3-D fuel map will be very difficult due to the wide dynamic flow range demanded by the engine.
4) Pulsing due to demand switch ~20psi ripple. (some system by-pass this switch, but risking system pressure beyond design limits). May require further explaination
5) Response time due to inertia of a rotating - laggy (start) and over-run (stop). May require further explaination

END
-----------------------------------------------------------------------------------------------------------------------------------------------------------

These systems require a stable system pressure, normally held between 100-125psi. An inline solenoid valve and a PWM controller that modulates the opening and shutting time to meter flow. Before getting too deeply into the subject, note that there are two types of inline solenoid valves on offer.



This type of system resembles the modern automotive fuel injection system. The system can also be controlled by a third party EMS with a spare PWM channel. Delivery rate can either be mapped or mirroring the fuel injector duty cycle. The latter makes tuning very simple.

The valve behaves similar to an on/off gated button on a garden hose. The longer the gate is opened, the more the flow (duration). Alternative, rapid opening/shutting the gate per second (frequency) also control the flow. The common EMS uses duration for load change and frequency for RPM change. The dynamic flow range is extremely wide, 100:1 is normal.

A WAI valve should closely match the closing and shutting characteristic of a fuel injector. This is important for fuel flow mirroring algorithm since the modern EMS has a correction stage to compensate the opening delay and shutting delay.

This type of valve resembles the action of a rotary water tap. As more current is applied to the valve coil, the valve opens more. It is a very nice way to control flow.
There are a few minor problems associated with this type of valve: Atomisation at low flow and lift variations (hystersis of the magnetic circuit), approximate +/- 10-15% flow deviations.

All in all, it will deliver liquid well compared to the PPS system. There are some similarities between the two. The nozzle tip pressure is directly proportional to the flow. This is because the proportional valve acts like a variable restrictor upstream of the nozzle tip. Resulting in: restricted flow = low pressure. Low pressure = low atomisation.

NOTE: This type of valve has a typical open time of 4ms and closing time of 4ms at its designed voltage. It is too slow to be used as a true PWM valve. Open/close speed can be increased by over-voltage pulses. The design of spider valve is also vastly different from the PWM valve.


Summary:
It is important to know some basic facts between the Proportional valve and PWM valve systems before choosing this type of system.

Here is an illustration of the difference in construction of the two valves, made by Clippard. Notice the proportional lift has a stiffer spring rate than the PWM valve, enabling the PWM valve to perofrm full on//full off a great deal easier.


Because the way the PWM system meters its flow based on a simple pulse width, it is very accurate. Further precision can be increased by introduce a suitable RRFPR to maintain Manifold pressure against water pressure. It is also possible to factor in a small duty cycle increase to the valve relative to boost increase.

Final consideration: If you are planning in future to create your own MAP via a third part system - only the "PWM-valve" can be driven directly by the ECU, matching the principle of a modern "fuel injection system" in every respect. Warning, before rushing off making your own system, Clippard valve is only rated up to 100psi, even with the smallest orifice version. The larger orifice type can only sustain 25psi. Multivalve is needed for flows over 500cc/min.

Ultimate CC

iTrader: (122)

Very nice write-up...love the detail...

Richard L

iTrader: (5)

Almost all progressive systems use a checkvalve between the pump output and nozzle for the reasons listed below:

Positive effects (well documented):
1. Retain some pressure in the line to compensate the next injection event. A 20psi loaded checkvalve will keep 20 psi of pressure in the line after injection.
2. Stop water being siphoned into the engine if the water jet is installed in the vacuum side of the manifold.
3. Prevent emptying the entire tank into the inlet tract if the tank location is higher than the jet (gravity fed) or the car is parked on an incline.
4. Stop some dribble after an injection event. Even when the power of the pump is switch off, the inertia of the rotating mass keeps the pump running for a second or so.

Negative effects (less well documented):
5. The presence of a checkvalve has a very significant impact of the dynamic range of a 150psi progressive pump speed system. A 20 psi checkvalve inline will instantly drop the 150 PPS system down to a 130psi span.

6. A normal nozzle requires ~30psi for produce a decent atomised spray. An inline 20psi checkvalve means the pump has to produce 50psi to produce a decent spray.

7. Let say the PPS system’s starting point is at 12psi boost, the system will now require 62psi to produce a decent spray. Some vendor will tell you a check valve will not impede flow once it is opened, true. But it will tax the pressure heavily where the PPS system relies heavily upon.

8. When the PPS system arrives at 24psi boost (end point) manifold pressure, the dynamic pressure is now further taxed. Before not too long later the dynamic range of a PPS system is now from 62psi to 126psi – translate it to flow: 176cc/min to 326cc/min, a mere 84% percent increase.

9. I have taken some data from a reputable PPS system manufacturer, a 150-psi 60W Shurflo flow pump has the follow characteristics:

M2 nozzle with 1/8 ID hose 180psi
M3 nozzle with 1/8 ID hose 160psi
M5 nozzle with 1/8 ID hose 135psi
M14 nozzle with 1/8 ID hose 105psi

From the figures above, the pump is only capable of sustaining 135psi system pressure on a M5 nozzle. Despite claiming the pump is capable of flowing one 3-4 litre per minute, conveniently missing the pressure parameter. The above PPS system maker is the only one that published these figures in public – thumbs up for them.

Summary:
Some PPS system makers are now offering an inline solenoid upgrade so that the dynamic range is improved by a good margin. Not sure why they didn’t include it in the kit at the beginning. Many PPS systems run their pumps up to 200-300psi - something I have questioned Shurflo, they said NO, NO and NO - no "ifs" or "buts". They are looking into a higher pressure pump but not yet done and will not be released until they are comfortable with it. I have a meeting with the Shurflo's director of engineering at our works two months ago during his UK visit - he confirmed the imaginary 200psi+ pump (8000 series).



It appeared Shurflo is the main supplier of the majority of water/alcohol injection systems makers. So it is more appropriate to take a good look into them first. You will be amazed to know how many pump variations Shurflo offers over the standard "off the shelve" configuration. I was told it has over 300+ "custom" configuration is still active.

Pump motor:
Currently, there are three frame sizes: short, medium and long stack, covering three power rating of 60W. 100W and 150W.



Pump cam angle:
Cam angle dictates and governs the final specifications of pump's flow rate, pressure. Shurflo offers: 2, 2.5, 3.0, 3.5 or possibly more profiles. Depending on the application, WAI makers can select the most suitable cam for their system.

At first glance, using the highest lift cam will produce the most flow and pressure. But if this cam is matched with a small motor, it will cause undue stress on the motor winding. This is very similar to going up a steep incline on high gear where the car's engine and gearbox is being stressed.

On the other hand, a low cam angle will produce less pressure and flow. Some PPS manufacturers prefers using the low angle cam because of the following:
1. Less stress to the diaphragm - long term mechanical reliability
2. Less stress to the motor - lower running temperature.
3. With in flow range up to a 600-800cc/min or so, there is ample pressure generated to hold the system at 150psi.
4. A much smoother control range from a PPS controller. High cam lobe tends to ramp up too much pressure with the same duty cycle applied.
5. The pressure spike is also much smaller, this allows the peak pressure closer to the "150psi demand switch". Overshooting will cause the infamous "pulsing" often associated with a PPS system.
note: a system advertised as 150psi@3 litre/min will NOT out-perform a 150psi@1 litre/min system. Often, the latter is a much better system. As far as the raw material cost difference is concerned, there is NONE. In these days, hypes rules the market.

By-Pass pump (no demand switch):
Shurflo Offers a huge range of internal by-pass valve to overcome the necessity of using a "demand switch" . Excess pressure is being "by-passed" internally by a set of spring load poppet valves (x3).

This type of configuration is more suited for PWM valve system rather the PPS system. The pump is switched on prior just before injection on and attains a "steady" line pressure continuously through out the entire delivery cycle.

Only a very small numbers of PWM valve WAI manufacturer uses this set up.


Regulating pump pressure steady (with on-demand switch):
Other than employing the bypass valves, the water pressure can be limited by using an "on-demand" switch. This method is simple, every time the pump hits the "set pressure" of the on-demand switch, the 12V feed to the pump is interrupted. Shurflo recommends this method should only be applied to application where the usage is intermittent and not cyclic use.

Against the recommendation, there are WAI systems on the market employ this technique to control water pressure. Most PPS systems only hit this pressure at peak injection pressure intermittently so long term damage to the pump is not severe. Pressure spikes of 20psi+ exists.

If this method is being used to regulate water pressure on a PWN valve system, it is a completely different story. The "intermiittent" use now becomes " cyclic" usage. This will create long term problem on the switch as well as the pumping mechanism. Water pressure will also suffer from pressure spikes, sometimes as much as 20+psi spike. Using a low hysteresis switch may reduce the ripple but the other half of the problem still remains.


to be continued...

dubbleugly01

iTrader: (24)

this is excellent Richard, thanks a ton.

........ patiently waits for the PWM valve controlled system write-up.........

SlowCar

iTrader: (4)

I've seen 3 wai companies pushing injection pumps outside the safe operating limits of 150psig/35psig

2 shurflos: one to 250psig and another to 220psig

1 flojet: from 35psig to ~100psig (and they blame failure of pump because customer use a "wrong" kind of VP methanol)
http://www.flojet.com/files/rlf_series_f100-196.pdf

This is just wrong!

cpoevo

iTrader: (1)

Are the shurflo pump a positive displacement pump? I have never had one apart to look at it and I dont work with diaphragm pumps.

JPSR20DET

Excelent thanks for the info.

Richard L

iTrader: (5)

Not quite, but close.

If the diaphragm is made of metal instead of rubber on cam, it will be a positive displacement pump.

Whoosh

iTrader: (19)

I have to question your logic on item No. 6. A spring loaded in-line check valve containing a 20# spring will require 20# to open. In this point we agree, but once opened the downstream line pressure will see the same pressure as the upstream side of the check valve. This of course does not take into account the pressure drop across the valve (Cv), pressure losses due to frictional losses of the pipe (f) or pressure drop across the spray nozzle itself (Cd). There are other factors to be sure (bends, fittings, etc.), but you do not add the spring pressure and the desired nozzle pressure to determine your required pump pressure.

cpoevo

iTrader: (1)

that is correct. A 20psi check valve will not adversely effect your pressure.

dubbleugly01

iTrader: (24)

I'm on the same page as Richard. As long as there is fluid flowing, the check valve will cause a 20# drop.

Whoosh

iTrader: (19)

What do you base your opinion on? My information is based on 37 years in the engineering business. I size piping systems, valves and pumps on a regular basis. I would refer you to Crane Flow of Fluids Through Valves, Fittings and Pipe manual so that you may see the error of your decision. As I stated earlier, there will be a pressure drop, but depending on the orifice size of the valve it can be less than 1# and as high as 3-4#.
I find most all of what Richard has written to be very informative and accurate, but on this one case, he is quite wrong.

Richard L

iTrader: (5)

Thanks for chiming in, I share your input. It is a difficult one to explain.

The easiest way to determine if there is pressure drop or after the checkvalve is setting up a test rig - a video to record the test and post it here.

I have all the equipment at our works and If enough people want this done, I am more than happy to set it up.

Before we go further, do you think the the following set up is acceptable?

I can only do this with air as I can generate accurate and stable air pressure much easier than water.

Pressure source => gauge => checkvalve=> gauge => variable restrictor (jet replacement)

Back to your theory, if the pressure is the same between the two chambers (before CV and after CV) the CV should close?

dcorn

iTrader: (1)

The way you describe the progressive controller for the turbo is interesting. A turbo spools up and reaches a set psi, then the rpms keep rising as the boost stays the same. Technically the injection system sprays the same amount of water/meth/whatever after that set boost level and at any RPM. Correct?

What about a centrifugal supercharger? I am about to put on a progressive kit like this, but my blower starts building boost at about 3500-4000rpm and reaches 10-11psi by redline. There is no boost plateau so the injection should keep increasing up until I shift. Should I set the controller to peak the injection pressure at a lower rpm than redline or should I set it at my maximum boost so that the power keeps building throughout the rpm range?

Lots of stuff to think about, definitely subscribing to this thread.

cpoevo

iTrader: (1)

^You will see a pressure drop across the valve. You will not see a 20psi drop across the valve, there will be a pressure drop across the valve just a very small amount. You also have to consider flow through the valve not just the pressure.