There are failsafe, failsafe and failsafes...

[turbojack]

Is your car tuned for the W/A being used? If so you ideally want to have a failsafe interfaced so as to help prevent damage to the engine if theres a instance of W/A supply of system failure.

Direct detection:

1. Fluid tank level sensor :
Advance warning but only good for early warning but little use for system power failure or blocked nozzle.

2. Loss of system power:
If power is interrupted to the WIA system, it will de-energize a relay and performs "Plan B", will not detect blocked jet or cut pipe or no fluid flow.

3. Inline pressure gauge:
This is very cost effective but require user paying attention.

4. Inline single pressure switch:
If the system looses fluid pressure during activation, an inline preset pressure switch can action a boost drop etc.

5. Two inline pressure switches:
Detects blocked nozzle (over pressure) and "lost of fluid pressure" (under pressure). This method is quite cost effective and within DIY capability.

6. Flow switch:
In inline flow switch, comprised of spring-load magnetic plunger inside a tube where the water flows through. The rate of spring determines the proximity of a reed switch again the magnetic plunger deflection. Output: on/off. - cost: low

7. Turbine flow sensor:
Good for progressive system but requires complex electronics circuitry to report a difference between the "actual" and "planned" flow in real time.

More..?

In-direct detection:

1. Knock detection:
This a by far the simplest, comes free with your car. It will only work up to certain power upgrade. Beyond a few PSI from stock, the ECU's ability to wind back ignition would be heavily taxed and may not dial in enough retard to cope with heavy knock. Don't forget, retarding ignition will also drastically increase your combustion temperature - not good.

2. AFR tracking:
If your ECU is capable of regulating the afr at WOT, it will be very effective. Unfortunately factory lambda is not of the "wide band" type so without equipping yourself with a wide-band lambda probe system, it will not work very well. The reliability on this method may lie on the accuracy of you wide-band interfacing mechanism. Method is effective but no good for mix other than high concentration of alcohol.

3. EGT tracking:
This method is rarely considered. Reading EGT has many benefits, it can indirectly estimate your afr, you ignition timing and more importantly, when is your pistons are about to melt. It is a pity that not many EGY gauge gives you an analogue output so that you can use it for "Plan B" if the EGT exceeds certain preset value. I believe the SPA digital gauges has a "hi/lo" detection circuit inbuilt and an output capable of switching a relay. Need some research.

3. PWM vs pump cycle-rate tracking:
This method can only be incorporated by the manufacturer of the water/alcohol injection systems. It looks at the duty cycle of the WI system (PWM type only) against the predicted flow relative to the pump speed. If it is out of the predicted envelope, it outputs a "fault signal" to switch a relay. Difficult to incorporate into a rotary pump due to the lag time caused by the rotating mass of the motor.

3. PWM vs flow sensor tracking:
Self-contain system that reads the actual flow against the WIA valve's PWN or a fixed flow system. Very reliable but require some electronic processing.

4. Inlet temperature tracking:
If two temperature probes are placed "before" and "after" the water jet, any temperature differential will indicate the presence of "latent heat" at work.

I leave it as it is until the this topic attracts more interest. It is important to know what how "safe" is a "failsafe" . If anyone and suggest more method, please post here and I will update this database of this failsafes.

A rotary sensor:


A piston flow switch:


I have put the failsafe details on each of the WI kit manufacturers, re: "whose, who, what...." thread.

This thread deal mainly with different kinds of failsafes. Some failsafe is more safer than others. If you can think of any other safe way to detect WI failure, please contribute - I will put them in on the first post.

I am trying to urge people to consider the importance and effectiveness of a failsafe system before tuning your engine too aggressively.

As WIA become more and more popular, there will be occasions where tuning boundary is pushed beyond SOA "Safe Operation Area". The functions of the "failsafe " mechanism becomes paramount.

[Darkhunter]

im looking to get my kit soon what would you personally recommend for safety, i was thinking flow sensor with low fluid warning.

Im not going to depend my whole tune with meth if the meth fails im going to tune it so i only have like 7 degrees knock.

thanks

[turbojack]

I'm going to make another thread that goes into details of the system I prefer. In the who what where thread theres links to the web sites of the various kit makers and I think you could look at them to get idea of whats offered.

If I go into detail on my preference here, then the thread will turn into a poop fest in marketing and not education.

Given above, you ideally want to seriously look and think about failsafe for when your tune is dependent on the injectant. If your tune is not dependent on the injectant then you can be more basic in your approach.

IMO if you run an A/F less then 12.0 without W/A you should be Ok without serious monitoring and falisafe functionality. Once you go leaner and then you should have a very good monitoring and failsafe setup. So for example, say you have a flash tune for pump gas with W/A injection thats semi aggressive but not on the ragged edge. If you did have an issue with fluid supply or component failure you could be OK from a perspective of instantly doing engine damage ..............obviously knock counts and such would go up and you would really not want to keep your foot into it. Now if you have 2 maps and the second MAP is heavily dependent on the injectant you need to have a system that instantaneously employs a built in failsafe functionality in order to protect the motor.

Also, want to note that on an SRT-4 and many other factory cars the weak link with regards to knock is the factory pistons ring lands. With regards to running a little leaner for power via tuning, its a higher danger when stock. Built motors use pistons with thicker ring lands that can better withstand performance tuning and higher boost. Built motors can sometimes run with a leaner tune due to the build up.........12.5 is a number typically thrown around all over the net, however 12.5 IMO is not a good idea on stock setup.