[Aquamist]

Originally Posted by The Hut

I completely understand the technology and purpose behind water+meth injection, however, I've seen many times (not only on these forums, with pics included, but also in real life in a few friends garages) what methanol can do to aluminum. The wear and corosion is increased quite a bit. However, I've also seen the internals of engines, running the same exact setup for many, many miles, with no wear.

So I can't say with 100% certainty that meth is necessarily bad for aluminum block and heads. However, I'm not rich enough to pay the price for any significant engine damage, yet have just enough money to get myself in trouble...

So this leads me to a question that I can't seem to find a solid answer for: What if any are the pros and cons to running ONLY water injection and no methanol???
From what I understand, it obviously isn't going to be as effective, but does anyone have any experience running only water and what were their findings...?

I doubt the same set-up will act differently on the same engine. It is just not possible to generalise this way unless the two engines are put in a controlled environment with identical run time on a “static” engine dynometer. If this is the case, then we can start making claims of this myth.

However, you could be right under certain circumstances such as the same system is used on the same engine - but driver habit must be taken into account.

Comparing an aggressive driver to a more sedate driver will make your claim more likely even the system setting is identical. I can explain why I make this line of reasoning.

On the current market, there are basically three types of systems – Single stage (On/off), Progressive Pump Speed (PPS) and PWM Inline Valve (PWMV). The first two systems are lower in cost and tend to be more popular. Due to popularity, there are more companies fighting for a small niche market. Cost is a mainly the driving force to acquiring a larger market share, as they are basically of the same construction- a pump speed controller, a nozzle and a diaphragm pump.

One item I believe is the root cause of the corrosion problems. Instead of putting an “inline solenoid valve” to shut off and start the spray instantly, a spring-loaded checkvalve is used. So what is the difference between the two…

A motorised pump often runs up to 4000rpm will not stop and start on demand. Mechanical inertia always over-ride the control signal, however sophisticated the electronics are claimed. In other words, law of physic rules.

A 20psi Checkvalve will let fluid through when the line pressure exceed 20psi and shut when the line pressure drops below 20psi. Regardless the type of system, Single stage or PPS, the water pump will at some time ramp to the high speed to create pressure. Let say the pressure peaks to 100psi, the user suddenly snap the throttle shut, either from braking or gear changing, the pump is not going to stop instantly but continues to make pressure and deliver fluid – Checkvalve has no ability to stop the flow as long as the pressure is over 20psi. This is the moment where “unplanned” fluid is being injected and line the inlet tract with fluid. Some fluid will find its way into the manifold via the small gap of the throttle plate. If throttle is not re-applied instantly to dry the walls, the residual fluid will slowly but surely cause corrosion, especially over a long period.

Top chart: Manifold pressure and FIDC. Logged in real time road driving conditions.
Bottom chart: Blue trace = PPS system real time flow - see the "over-run" relative to the manifold pressure- especially between "3-4" and after "5"

An inline solenoid will prevent this as it will not be affected by the fluid pressure. It is governed by the internal spring (over one hundred psi) and electromagnetic circuit. Some PPS system makers only offer this as an option. As the PPS system market is driven by cost and no doubt end users will keep pressurising the makers to bring prices down. Since you will only get what you paid for, there is no uncertainty who is to blame.

Lastly, why does the aggressive driver is more likely to accumulate internal corrosion? The simple answer to this is – more opportunity for residual fluid liquid lining the engine internal due to attaining higher pump speed so the pressure decade is slower, allow more “over-run” events. Some PPS systems are now offering 250psi pumps without an inline solenoid valve. This is a typical marketing hype without responsibilities…

The PWM valve system uses an inline solenoid valve by default, so I did not need to make any reference to this regarding “deliver over-run”. This is only my view, do not treat this as gospel.

[The Hut]

Originally Posted by Aquamist

Checkvalve has no ability to stop the flow as long as the pressure is over 20psi. This is the moment where “unplanned” fluid is being injected and line the inlet tract with fluid. Some fluid will find its way into the manifold via the small gap of the throttle plate. If throttle is not re-applied instantly to dry the walls, the residual fluid will slowly but surely cause corrosion, especially over a long period.

Great post! Makes perfect sense!

Any pros and cons to water injection only, versus water and meth though?

Thanks for your input.

[Aquamist]

Originally Posted by berdugo

thanks Richard for the great info you posted.

I wanna know how does a stand alone ecu like motec can control the PWM type WI system?? is the meth pump always connected to the ground and the 12V is supplied by the motec directly or using a relay to do that, is it pulsated 12V supply? thanks in advance

I have missed this post completely, sorry.

The motec no doubt can send out PWM signal to control an inline valve or pump. Here is a general criterion that can be applied:

PWM valve (full-lift type):
- PWM Frequency between ......... 20Hz to 80Hz
- Winding current demand ..........~1A
- Valve break-through pressure ....... 200psi+

PWM pump:
-PWM frequancy between 100Hz to 30Kz
- 60W pump current demand ........... ~5A
- 100W pump current drmand ......... ~8A
- 150W pump current demand .......... ~12A

Please note that motec needs some kind of electronic current amplify to drive the pump. A relay can handle the current but too slow to response to the required control PWM frequency.

You best bet is using an inline valve (high speed) with Motec.

I forgot to say, Aquamist HFS-5 (up to 80Hz) or HFS-6 (up to 260Kz) can receive PWM signal from motec.

[mister_skinny]

great thread! Can you guys recommend brands? or at least give an example of a brand of each type? Thanks

[Aquamist]

1) On/Off system (singler stage):
Every company have this one.

2) Progressive Pump speed system (PPS):
Every company except Aquamist and FJO

3) PWM valve systems (same as fuel injection):
Aquamist and FJO only

[Aquamist]

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new technical update

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[ImranM847]

Feel like updating with the direct port info?

[Aquamist]

I will put all the bits and pieces together as soon as I can get sometime. It is a worthwhile investment. Meanwhile, there is good write up on a GTR using this configuration here:

Waterinjection :: View topic - 760whp skyline with direct port water injection (corrected)

[Aquamist]

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new technical update with video links and examples
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