So flow monitoring (Neo) and failsafes (Sav).

With PWM the flow would have to be monitored and compared to the PWM input via a lookup table, or a curve fit equation, or something like that, with a deadband for normal variation/error. It would have the usual tradeoff between sensitivity and false-alarms. I would like to do that but I do not think the Adaptronic is set up to read in an input (flow meter) and compare it to an output (PWM duty cycle), at least not to that level of sophistication. I also do not want to add another controller.

Failsafes. So from this previous thread...
https://www.miataturbo.net/forum/t38494/
- I'm already implementing #4, that is using multiple nozzles that are sharing a common plenum.
- I will probably still do #2, that is, use a switch at the outlet of the pump to monitor pump pressure and add fuel or retard timing if the WI is commanded on and the switch does not change state.

#4 protects somewhat against a clogged nozzle, but not against a dead pump, dry tank, or a catastrophic leak. #2 is the opposite. It protects against a dead pump, dry tank, or a leak, but does not protect against a clog. The two are complimentary. It is not a foolproof scheme of course, but it is relatively cheap and easy to implement.

Also, as extra insurance, I could dyno tune with the WI off, then add the WI on top of that as extra protection.

So, seriously, any EEs or Techs out there got an idea what I can use for a cheap PWM generator to bench test the HSV? I would think a waveform generator would do it as long as it can produce 12V on a 12 ohm load? I could get one from work, maybe, but do not want to take a chance on damaging something expensive if I can get something cheap on my own.

 

You can buy old function generators on ebay for like $40.

 

Can I run them at a fixed frequency with a square wave, and vary the width (time) of the pulse? Pardon the ignorance but function generators are one piece of bench top equipment I have not used before, at least not enough to remember anything about the specifics.

What about doing something really klugy, like using a waveform generator on a PC (like some freeware app) and using the headphone output to drive a power amp, and adjust amplitude (gain, volume, whatever) until I hit the right 12V-14V peak voltage? An audio amp is made for about the same resistive load, and is capable of higher peak voltages than what I need, and can provide enough power. Crazy like a fox, or just crazy? I have all the crap I need on hand to put that together.

 

Yes, a function generator is designed to do EXACTLY what you just asked. Freq, Duty, wave type, and amplitude can all be set independently. You can get an old school one with dials for cheap. Def something to have around when designing/messing with analog and digital circuits. I recommend just buying an older used one, they last forever and its nice to have one on your bench.

 

Smaller PUMPS:

$55
Chris Coffee Service - Ulka Vibratory Pumps EAX5 52 Watt

$64
120V Ulka Vibratory Pump - Espresso Machine Vibe Pump - Espresso Parts

Pump curves:
http://images.google.com/imgres?imgu...%3D42%26um%3D1

 

Neither says anything about flow rate or compatibility with methanol.

 

http://www.ulka.it/admin/moduli/m003...g_ULKA_web.pdf

Some datasheetage. Says suitable primarily for water, my guess is that it doesn't have viton or buna-n orings. Another issue is that for the pressures you want >=1Mbar-ish it maxes at like 200-250 cc/min. So for this application and power levels it might be fine. Over that you need more than 1 pump (another shortfall of the old aquamist pump). Also you have no built in method of maintaining a constant line pressure, you would need some sort of super high pressure regulator with a tank return.

 

So at 4 bars pressure the E5 will deliver 400 cc/min.
That's about 20% the fuel flow rate at 300 hp / 11:1 AFR.

What water flow rate do you need and at what pressure?

 

All mainstream WI kits operate at at least 150PSI in order to get good atomization. 4bar is like 60PSI. Subtract boost pressure from that and you have actual pressure. That assumes that you have a high speed valve. If you use a check valve then you can subract that opening pressure as well. So 4bar is suddenly not adequate. So your small pump becomes an issue for the following reasons. A single pump is likely not adequate for high HP, the flow rate at high pressure is poor, you must have a special high voltage power supply, you must devise a custom pressure regulator/fluid return, and possibly/probably incompatible with methanol.

Suddenly the aquatec/shurflo pump becomes attractive because it has all these issues solved.

 

Plus I already have one It takes up more space than I like but it is in place and operational.

More failsafe thoughts. If I am unable to set up #2 above in logic on the Adaptronic, or for those who do not have an Adaptronic or the like, there is another simpler option. Not a failsafe, but a warning light. Tap off the pump power (at the relay) and send it to a pressure switch at the pump outlet. Wire 12V to the common lug and wire the normally closed (NC) side to one terminal of a dash mounted warning light. Ground the other light terminal.

When the pump is powered on, the dash light will light up and remain lit unless the outlet pressure breaks the NC circuit. It could be kind of annoying though. It would come on for a brief instant every time the WI operates.

The same scheme could be used to trigger the alternate map input on the MS, or on the Adaptronic for that matter.

 

Pressure switch and a small accumulator.

Why do you need a fixed pressure anyway? It's got a flow curve, your nozzles have a flow curve, they meet somewhere. Apply power to pump when you need flow. Adjust flow with your HSV.

And, without a pressure regulator, if 1 of your 4 nozzles clogs, the increased pump pressure will force a bit more flow from the other 3, helping your failsafe.

 

Why do you need super atomization? Even with less atomization, the water will still absorb heat during combustion.

Aren't those Shurflo piglets are only good for 60 psi?

 

You know I thought about that, though I am not sure that is true. I think the flow rate is so low, that the shurflow pump is effectively dead-heading or running at max pressure most or all of the time anyway, so a clogged nozzle would not create that much more pressure in the system. Thus there would not be an appreciable rise in flow at the other nozzles. Right?

One way to know for sure, test it. Along those lines, I found this shareware PWM generator by the way. It is free for 30 days.
Order - PWM Generator - The PWM Generator can generate PWM signals in real time.You can save 4 memory presets and the software supports multiple sound cards.

Maybe I can hook that up to an audio amp and I'll have my function generator. I sure would be pissed though if I fried the HSV screwing around with this.

 

yeah the pressure will pulse in a predictable range unless you experience a nozzle clog. In your position to limit your water usage you should probly scale your pwn usage at the 40% + point becouse since you are IC'ed etc you would just be wasting water spraying at anything less.

 

Smaller droplets = more surface area. More surface area = better vaporization.

Pretty much all nozzles you see for sale for WI are rated at 100PSI. Apply less pressure than that and you get less flow and larger droplets. The point of the HSV is obviously to control flow. You want to maintain a constant pressure so that you have a consistent droplet size and therefore consistent vaporization of the fluid into the air. Progressive systems that do not employ a HSV control output through pump speed. They are not the best because they have inconsistent pressure (low pressure at low output). The best system would constantly have high pressure, even at low flow, and control flow with a high speed valve like the aquamist kits.

The entire point of a good system is performance and consistency. DIY is all well and good, but you still want to achieve the same results.


If you think that increased pressure isn't beneficial I will go ahead and say that you are COMPLETELY wrong. There is a reason that F1 fuel injectors operate at 4+ MPa (aka 40+ Bar). They realized long ago that super small droplets increase their detonation resistance and power substantially.

 

the sureflow pumps are stock 140 psi my snowperformance stuff was rated at 70 psi. Any way you cut it though you can just do the math to figure out your flow per any given pressure situation. just like we do with our injectors.

 

1) Why wouldn't the water give up its latent heat of vaporization eventually, whether it's before it enters the cylinders from fine atomization, or from the heat of compression if the droplets are large? Detonation typically happens due to auto-ignition of end gases; by that time even larger droplets will have vaporized, cooling the charge. Do you have any links to papers that say otherwise?

2) The big Shurflo pump will not change its outlet pressure much if 1 of 4 nozzles clog. The smaller pumps will; thus if you size the nozzles for proper flow with a smaller pump, and 1 clogs, the pressure will rise and the water delivered by the other 3 will rise.

3) How fast does the HSV pulse? How far is the HSV from your nozzles? How much compliance do the lines after the HSV have? I think your lines are somewhat flexible, between the HSV and the nozzles. Thus any rapid pulsing will be lopass filtered - i.e. the nozzles will not show pulsed flow. The nozzles will not see pulse pressure behind it. Instead, the nozzles will see some constant, reduced *pressure* when the HSV is pulsing. There goes your fine atomization. There's a reason injector pintles open right at the tip and not upstream.

How fast does your HSV pulse relative to the injector pulses and are they sync'ed? If they are sync'ed, how does the dynamic distribution work out even if the nozzle has pulsing output? The air entering the cylinders is pulsed.

I think you have the right idea having 4 nozzles, but the nozzles will all have some relatively constant flow proportional to the HSV duty cycle.

Having said that, even with effectively variable pressure driving the nozzles, I would think you'd want at least 15 psi head; if you had a max of 60 psi available, a 4:1 ratio, that only gives you 2:1 available ratio of flow.

Looks like the Shurflo pumps are regulated at 70 psi. .. ??

 

What he said.

 

they are fully adjustable from 0-140 psi with some going up to 200 psi

 

I measured mine a few months ago. It's making about 150 PSI, and has been quite happy with this for years.

Actually, yes: http://ntrs.nasa.gov/archive/nasa/ca...1993093245.pdf

Summary: this is a NACA paper which documents the anti-knock effect of atomized (but not vaporized) water in the combustion end-zone. In this particular study, they've cut right to the chase and are injecting water directly into the combustion chamber late in the compression cycle. In other words, the idea that water injection suppresses knock by evaporatively cooling the intake air during its trip through the intake tract is refuted by this study.

Obviously, good atomization is still required.




Not really regulated, per se. They have a simple on/off switch which opens the circuit when pressure rises above a certain level. The activation point is generally adjustable via a screw in the top of the pump head.