Additional safety !!!!!

[DuMaurier 7]

Recently I ran into a problem that cost me two apex seals and some other engine parts , now I haven't gotten the DDS2 yet so I had no "low Flow" protection . What happened is this , the suction filter for my pump became clogged causing the pump to loose suction , I do have a run light and was able to pick up the problem after I saw that the pump was staying activated a long time after I stopped boosting (it only runs a few seconds at a time) , during the "run" I was thinking that I had used up my systems reserve (three accumulators) and the pump was directly supplying the water for injection.
When I stopped and popped the hood the water pressure gauge was reading only 30psi .!!!
I have since installed a little system to monitor the water pressure , yes I know that I could use a gauge but , I dont have room for another (I have 10 additional gauges in my 7) and during a high boost , high speed run , gauges are the last things I look at !!.
What I put in is a pressure switch that triggers a relay when the pressure falls to a preset low .This illuminates a warning light and simultaneously kills power to my boost controller to allow the wastegates to immediately reduce the boost to 3.5 psi .
When I get the DDS2 I will have both pressure and flow protection , hopefully saving me from another disaster . :?

[FordNut]

Recently I ran into a problem that cost me two apex seals and some other engine parts , now I haven't gotten the DDS2 yet so I had no "low Flow" protection . What happened is this , the suction filter for my pump became clogged causing the pump to loose suction , I do have a run light and was able to pick up the problem after I saw that the pump was staying activated a long time after I stopped boosting (it only runs a few seconds at a time) , during the "run" I was thinking that I had used up my systems reserve (three accumulators) and the pump was directly supplying the water for injection.
When I stopped and popped the hood the water pressure gauge was reading only 30psi .!!!
I have since installed a little system to monitor the water pressure , yes I know that I could use a gauge but , I dont have room for another (I have 10 additional gauges in my 7) and during a high boost , high speed run , gauges are the last things I look at !!.
What I put in is a pressure switch that triggers a relay when the pressure falls to a preset low .This illuminates a warning light and simultaneously kills power to my boost controller to allow the wastegates to immediately reduce the boost to 3.5 psi .
When I get the DDS2 I will have both pressure and flow protection , hopefully saving me from another disaster . :?
At what pressure is your sensor set to activate the warning indicator? Is it an adjustable sensor or fixed setting?

[DuMaurier 7]

yes its adjustable , I am using an adjustable 2-10 bar pressure switch, I have it set at 85psi , since I run about 130psi line pressure. Some may say that this addition is unnecessary , but with a 1000 hp bb turbo that gets to full boost (25+psi) by 3500 rpms , I can detonate with very little boost pressure since the air flow is quite high. I also have my ignition maps advanced a bit to help enhance the boost response and low boost performance.

[Richard L]

I think you could use another pressure switch that will detect presssure over 135 psi so block jet can be detected? I am sure the Shurflow pump will make 150psi when blocked.

[DuMaurier 7]

Good idea !!, one of you switches 2-10 bar should be able to do that withou failing . right ???.

[Forum Admin]

It will only work if your shurflo pump will increase pressure whern blocked OR slight pressure drop during injection. Since the Shurflo flows so much, it might not lower the pressure when a small protion of the water is being used by the jet?

[DuMaurier 7]

But coming to think of it , the Shurflo pump has a built in pressure switch that would not allow the pump to run over a certain preset pressure, so even if a jet is blocked the pump wouldn't do anything .
The only protection I would have for a blocked jet is the low flow disable feature offered by the DDS2 ( when I eventually get it of course).

[hotrod]

One possibility for a low tech electronic blocked jet detector would be to use a pressure drop across another orfice up stream of the jet.

[ jet]---------------[psensor 1]----------[orfice]----------[psensor2]--------[control solenoid]-------------[pump]


If you were to put a configuration like this in place. I would expect to see:

1. solenoid off, both psensor 1, and psensor 2 would have an equal low pressure approximately equal to the intake air pressure.

2. solenoid open, jet flowing normally, psensor 2 would have a pressure reading near line pressure but slightly higher than psensor 1 due to flow induced pressure drop across the orfice.

3. solenoid open, jet clogged, psensor 2 and psensor 1 would have equal pressures at line pressure.


Not sure if you could find a good balance in size for the orfice so it did not unnecessarily restrict flow but still induces enough pressure drop for a comparator to detect and light a warning light.

The bad news is you would have to calibrate it for each jet size, as changing the jet size or even the supply pressure would alter the pressure drop across the orfice.


The electrical equivalent to the hydraulic circuit would be:


[load resistor]----[ v1]------[voltage drop resistor]----[v2]-----[relay]---[battery]


You would be detecting the hydraulic equivalent to the change in voltage drop across the dropping resistor if the load resistor fails open, or very high resistance.

You might be able to subsitute a final filter for the pressure drop orfice and use its pressure drop. You would then be able to detect both blocking of the final filter, and blocking of the jet, or no pressure at the jet when the solenoid triggers indicating no water flow (reservoir dry or pump failure) when the system should be spraying.


Larry

[DuMaurier 7]

I have decided to bite the bullet and buy two DDS2 kits , one for each stage of injection. I will be utalizing the low flow "trip" thats available on each ,so that a low flow on either stage will disable my boost . One is wired to kill power to my controlers solenoid control valve and the other will trigger an electro / pneumatic valve that will be installed on the air supply to the TOP of the wastegates diaphragms . Once activated this valve will vent the air supply , thereby allowing the uninterrupted pressure on the underside of the diaphragms to cause the gates to be pushed open.
The sensing of the flows will take care of any blocked jet scenarios , once fault conditions are detected , the nevt valve will stay open and the wastegates solenoid will also go to the "failed " off position and vent any air that would have been routed to the top side of the gate.
I am also changing out my astegates springs to the lowest ones available , so my wastegate only boost pressure will move from 11.5 psi down to 3.5 psi , since 11.5 psi on a 91 lb/min turbo can still cause a lot of damage when /if things go wrong.

[SaabTuner]

An easier check system would probably be a couple temperature sensors. One just before the injector and one about a foot after. The second one should be slightly lower temp than the first.

Also, don't the turbo wankels have a knock sensor of some kind? There's a gauge for that which "knock link" sells (or something similar) ... it has a face that will change colors with varying grades of knock, and an analog needle. I know you didn't want to watch any more gauges, but I thought it would be worth noting since it will change colors if there's a problem so that you don't have to watch it like a hawk.

A PTC resistor, like used in a MAF sensor, would certainly be able to keep track of the cooling effect of the water (or normally air) across it, and it's designed to react quickly. Unfortunately, for it to be useful, you'd need two, one before and one after, to keep close enough track of the WI's effect.

Adrian~