I'll be trying out a similar setup to yours in the coming weeks and would like to incorporate two pressure sensors as well.

Would anyone care to discuss the effectiveness of a pressure based failsafe vs a flow based(both with upper and lower limits)? I'm sure there's a reason why most of the failsafes on the market use a flow sensor rather than a pressure sensor to determine a failure in the alky injection system. Is there a scenario for a failure that the pressure based system would be incapable of detecting?

 

I am kind of lost what your getting @ because the flow detector, uses the fluid pressure to determine if alky is low, too high, or none flowing @ all. Just explain a little more I can be slow @ times


LMK

 

Not necessarily. Most flow sensors have a paddle wheel inside that spins by fluid flow and signal is regulated by spin speed.

 

An example would be the flow sensor included in the Aquamist DDS3 failsafe package. This sensor uses a magnetized turbine wheel in conjunction with a hall-effect sensor to determine fluid flow. You set the upper and lower flow limits and if fluid flow in your injection system slips out of this flow window, the failsafe is activated.

Thats what I'm referring to in my post above. I'm asking for reasons why a flow based failsafe may be better than a pressure based.

 

OOOH yeah your right, see told ya I was slow @ times

the one I have senses it by pressure, it works the same way as the pressure sensors use to arm w/i found in most kits but it uses fluid pressure rather than boost pressure.

 

It seems like you answer you own question, because the pressure sensor can only monitor one thing @ a time to switch to a safe boost. Its either monitor low fluid or monitor higher fluid, no middle ground.

 

That's why I was talking about using two pressure sensors. One to watch for low pressure and the other to watch for high. An example would be if your operating pressure is somewhere around 90-100psi, you could set one sensor to detect pressure drop(line leak/pump failure) below say 80psi and the other to look for pressure above 110psi(clogged nozzle).

That's just a rough example but I'm wanting to compare a pressure based failsafe system like that to a flow based like the aquamist dds3. Both utilize an upper and lower limit.

Basically I'd like to know if and why a flow based system would work better than a pressure based? Anyone can chime in on this also.

 

I know what your saying brotha

we have the low pressure side squarded away (drawn up), let me think on how to wiring up the high pressure side so they all work together. I should have something drawn up by tonight, work is not a good place for thinking.

again great idea

 

Sounds good. I've got a schematic drawn up with fancy pictures and colors I may post up later. It's done for the most part although the difference with mine is that I'm running an ebc. I'm having the failsafe kill the ground to the ebc which will drop boost down to wastegate pressure. I also threw in a couple LED's to show a fault(yellow) and when the system is at operating pressure(green).

 

DUDE I GOT IT, I guess I lied about thinking @ work. The **** just hit (well all my ideas work like that LOL). I will drawn it up in about an hr, just got off work. Its on a notebook paper right now LOL

 

Ok from the list of parts in the first post you will have to buy a second flow sensor monitor. We have come to the conclusion that the pressure sensor cant monitor both high and low fluid level at the same time. As you can see in the diagram below there is a second flow sensor monitor. This one will only monitor high fluid pressure aka nozzle clogging and the other will still monitor low level. First you have set the HFS (High Flow Sensor) to reasonable high level (120ish maybe higher you will have to play around to get a good adjustment). Then set LFS (Low Flow Sensor) to a nice 60-90 psi. Now to the breakdown, once there is a clogged nozzle the pressure real reach to the set pressure (remember dont go to high we want to catch this). Then it will tripper the ground to the inroute fuse and pop it (most alky kits are wired that way using the relay). Now you dont have any power to the pump, which will equal to no power to the boost solenoid, then equals to wga pressure. The LFS will still work the same way. I hope this makes sense.

So inconclusion we can waste $3.50 for a pack of fuses, rather they pay a couple thousand for a new motor.

 

bump for some feed back

 

You may want to start a thread in the other water/alcohol inj forum. Might get some more attention in there.

As for your last schematic, I'm not sure I really like the idea of blowing fuses when there is a failure. Especially the idea of killing power to the pump. If you've got a partial clog but are still flowing alcohol, I'd think the best action would be just having boost drop to wastegate pressure only. That way you still have some alcohol being injected.

I'm not totally sure how other failsafes do it but I'd doubt they kill power to the alky system when theres a flow failure.

I have a schematic I'd like feedback on also but I may post it up in the general water/alcohol inj forum. And I don't want to sound like I'm completely bashing your idea. I just don't quite agree with killing power to the pump during a failure.

 

You could also pick up a circuit breaker for pretty cheap. Just an alternative to replacing fuses. Have it kill power to the solenoid only and leave the pump out of it.

 

Come on man read read read when you kill the power to the pump, it will go to wga pressure since the power wire to the boost solenoid is tied in to the power wire to the pump. If the pump doesnt get power then the solenoid doesnt, no power to the solenoid=wga pressure. this is the same concept as having low fluid. No ground=no power to the solenoid=wga pressure. since the pressure doesnt carry enough volume to complete the ground in the flow sensor.

you really think I am that crazy to kill the pump in high boost when my car is meth dependent not to mention I am running some high timing tables LOL

so now you kind of can have an idea, when your car goes into fail safe. I know your not bashing bro, and thats why I wanted feedback. Sometimes I can explain things a little off or my idea is plain out crazy