So I searched a bit and did not see the answer. Pardon me in advance if I missed it.

So Devil's Own has a version of the PWM control box that will control the pump based on a voltage input of 0-5VDC. See here, bottom of the page:
Progressive Water Alcohol Controller DevilsOwn Injection

If the MS could be rigged to output a voltage that is proportional to the injector pulse width, then it could be sent to this controller. Then the controller could be used to vary the PWM signal to the pump, and viola, WI flow proportional to fuel. It seems like this would be better than flow proportional to MAP, as is their traditional setup. I know that MS can send a WI signal that is PWM that follows the injector PWM signal. Is there a cheap and easy way to change that to 0-5V?

Alternatively, did anyone ever identify an inexpensive PWM valve that could operate at low Hz?

Finally, I was wondering... What if the PWM WI signal from the MS was used with something like a solid-state relay in place of the Devil's Own controller to drive the pump via PWM? Could that work? I have a parallel install so I am not using the IAC circuit as far as I know.

 

The MS isn't outputting a voltage, as it's grounding then ungrounding the fast-activating valve at the same rate as your injectors.

MSnS-Extra Hardware Manual

 

Yeah I know. That is why I am asking if it is possible to modify it (internally or externally) to output a voltage proportional to the injector PWM, instead of just another PWM signal. This would allow it to interface with the DO controller.

 

Easy enough to find out.

Measure the PWM frequency of the devils' own controller. I'd do it, but my car is in Florida and I'm not. Probably be a month or so before I'm back home.

Compare this frequency to the range of frequencies likely to be encountered at the injector driver outputs during boosted operation.

Are the two similar?

 

Good question Joe. I was hoping someone knew the PWM output frequency to the pump for the DO controller. If you do not know, then probably no one here does

I have access to the equipment needed to make the measurement, like an o-scope, and a power supply to stimulate the controller (MAP simulation). And I'm willing to do the measurement. What I do not have is a controller as I have not bought a DO system yet. I can either buy one, and then sell it if I do not use it, or borrow one. Or, just call DO and ask them, though I am not sure they would give up that information

 

There are some specs for the controller on the page you linked to:

Controller specs:
Input voltage 10-15v
Input current
Standby 60ma
100% duty cycle 10A
Sensor input range 0-5v
PWM output 30hz
Duty Cycle 15%-100%

Is this what you are looking for?

 

Damn, I missed that. OK I am an idiot
Thanks freeberg.

Are there any EEs out there who know if a solid-state relay (or something like that, IGBT, whatever) would work for this, and how to apply one? I am not sure if it will need any support circuitry (like a filter), or if it can just be hooked up like a mechanical relay. The idea would be to use the MS output to drive a relay that would PWM the power to the pump.

I am assuming using a mechanical relay would not work as PWM would result in too many cycles and it would fail quickly.

 

I'm confused, why have MS control the DO controller?

I see two options, have MS control the fast-acting valve or Have the DOWI control the fasting-acting valve.

 

^^Well, that would be too simple, so I have to complicate it

I am investigating under the assumption that it is better to proportion WI with fuel, than with boost. Correct me if I am wrong here.

Using the MS directly to PWM the pump would be nice since it could be proportional to fuel flow rate (injector PW) and not to boost, like the DOWI system. PWM of the pump could be cheaper than buying a fast-acting valve (the usual way to proportion WI with fuel) if the drive electronics are cheap.

But if it is not possible to PWM the pump directly, then the DOWI could be used to PWM the pump based on a 0-5V signal from the MS (proportional to fuel), and perhaps still be cheaper than the valve. But, the MS would have to create the 0-5V signal.

Yeah the MS controlled fast acting valve is probably the most direct way to get WI proportioned with fuel, but from what I understand the valves are still expensive (like the Aquamist one), unless someone has found a cheaper one, which is why I asked.

I am asking several questions at once here, sorry about that. To summarize:
1. Could the MS PWM output that is proportional to injector PWM be used, with a high-speed relay, to drive a Shurflo pump?
2. If not, could it interface with the DOWI controller by producing (via a simple mod) a 0-5V signal that is proportional to injector PWM?
3. Is there a cheap, fast-acting valve out there and thus #1 and #2 are moot?
4. Should I just run WI proportional to boost and STFU?

Thanks

 

WI proportional to boost should work just fine IMO

 

Um tex being boost proportional is fuel proportional take a look at your fuel charts as you ramp boost man u will see that.

 

For one, pulsing a pump's power isn't gonna give you a proportional amount of water. For this reason alone I wouldn't waste my time building a setup to do this. But also the electronics to run it will be a pain. And also it won't spray as well at low PW's from running less pressure.

I would either get a high speed valve and do it right, or run one or two stages of WI. But you've probably already got the DO fancy kit, right? If so, just use it the way it comes. No it's not ideal, but unless you're getting very aggressive with the WI, it won't matter.

 

Leave it to the newbs to point out the information hiding in plain sight.

Did we ever find a cheap one that worked in our frequency range? It comes up from time to time, lingers for a while, and I lose interest.


No.

Say you're doing 3,500 RPM at 14PSI. Throwing some hypothetical efficiency numbers into the air, we'll say you're flowing 13 lb/min of air, and thus 1.1 lb/min of fuel. Your WI system is referenced only to MAP, so it's flowing "X" amount of water.

Now you're at 7,000 RPM at 14 PSI. The same assumptions now move 26 lb/min of air and 2.2 lb/min of fuel through the engine, however the WI system is still flowing "X" amount of water, when it should be flowing 2X.

Granted, I doubt that most of us are genuinely equipped to gauge and tune for this sort of thing. Myself, I just used the little calculator on DO's site, chose my nozzle accordingly, set my controller for 100% at ~13 PSI, and I just live with it.

Works for me.

 

What Joe said on fuel not being proportional to boost.

I do not have the DO PWM controller yet so I am considering my options before I buy anything.

Pat the DO controller uses PWM to vary the pump output and so do a couple of other systems I looked at. It works. In fact one discussion I read talked about how the PWM frequency selection is important since if one uses a frequency that is near a mechanical harmonic of the pump, then it could overstress the pump due to resonant excitation. Makes sense to me. This is a typical design consideration.

 

I know, let me clarify what I meant. A given PW% to the pump that % of the size of the Nozzle you are running. I know they do it that way cause it's better than nothing vs. 100%, but it's still not great.

 

or an easy solution:
run the DO prop controller's power through an extra output on the MS. S1et the output to trigger based on a condition such as IAT >X°. While not the exact solution you're looking for, it's quick & dirty, easy, & effective.

 

Pat OK I see what you mean and I agree. The WI flow rate will probably not scale exactly linearly with PWM duty cycle.

Ben that is an interesting idea, that is powering the DO controller based on IAT temperature. And it could be done with a standard relay.

At any rate thanks guys. I was just looking for an assessment of what the latest is on WI before I take the plunge.