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Old 05-04-2010, 01:17 AM   #1
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Default Water Injection control scheme question

Though this is water injection related I am posting this question hare since it is specific to the Adaptronic.

I am setting up a pulse width modulation (PWM) high-speed valve (HSV) regulated port water injection system. This is the Aquamist HSV and their recommended PWM frequency is 30-80Hz, with 50 Hz preferred for fixed frequency drive. I have it connected to one of the Adaptronic high current outputs and the PWM regulation working. It is pretty slick the Adaptronic can do this, adn it was easy to set up. I used Aux Out 2 which is normally used to actuate VICS in the 99-00 cars. My VICS is gone (gutted manifold) so I am using the VICS valve signal for the HSV.

I am considering how to scale the PWM duty cycle (DC) of the HSV based on one of the many inputs available. What I would really like to do is scale it in a manner that would track the fuel injector flow rates. That way the water would match the fuel flow say at 10% volumetric. At first I thought that scaling based on injector duty cycle might work, and even mentioned this in another thread. But now I am not sure it will work. Since the PWM frequency is fixed and thus does not increase with the injector frequency (RPM based) I do not think this scheme will work. In other words, a fuel injector can stay at a fixed %DC and still create more flow by firing more often (RPM increase). So the HSV flow would stay the same even though the fuel injector flow is increasing with RPM.

The usual method of scaling with MAP could be used, but that does not ratio well with fuel flow rate either.

There are a bunch of inputs that can be selected for controlling PWM %DC. So I am looking for ideas on how to scale the water injection HSV %DC. For example, is there a way to create a function that would calculate flow based on fuel injector DC and RPM, and scale the HSV PWM accordingly?

I suppose I could drive it with the second map and treat it as a two-stage injection system. However I have plans for the second map and thus may not want to do that.

Thanks in advance. I posted this up at the Adaptronic web site as well. I asked the question there once before a few months ago and did not get any response.
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Old 05-04-2010, 09:44 AM   #2
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Well your fuel map is all open times, you can have it be a percentage of that. Which would be best because you would then have a percentage of total fuel injected which is what you want. IDC is just an arbitrary value here since you are able to control the valve directly from the ecu. IDC would only be important using a 3rd party system that is seperate from your ecu.

I don't have wari in front of me but i know you can set up fuel map 2 to be percentage based off map 1. like all cells filled in 0.10 for 10%. And have that map drive the HSV.
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Old 05-04-2010, 10:39 AM   #3
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Hey Tex,

You can also use your second ignition map for duty cycle. The conversion is funky, but I'll see what I can find out on how to get degrees to DC. Alternatively using logic functions and a standard output I think you might be able to get something accomplished.

Best,
Travis
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Old 05-04-2010, 11:08 AM   #4
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Quote:
Originally Posted by neogenesis2004 View Post
Well your fuel map is all open times, you can have it be a percentage of that. Which would be best because you would then have a percentage of total fuel injected which is what you want. IDC is just an arbitrary value here since you are able to control the valve directly from the ecu. IDC would only be important using a 3rd party system that is seperate from your ecu.
Yes I considered that. But like I said, I do not think that will work since it will not scale flow with RPM like the fuel injectors do. The PWM frequency on Aux outputs is fixed. For example look at an Adaptronic fuel map row for pulse width versus RPM (constant MAP). IIRC it is pretty flat and even drops off at higher RPM due to the reduced VE. Correct me if I am wrong here.

Quote:
I don't have wari in front of me but i know you can set up fuel map 2 to be percentage based off map 1. like all cells filled in 0.10 for 10%. And have that map drive the HSV.
Yep I could do that too. There is a post on the Adaptronic board about how it works (not in the manual). You set the output to be driven by 'PWM fuel 2' and 10 = 100% DC. But like I said I would like to keep that second map for something else. I would like to be able to eventually switch between E85 and pump gas maps with a switch. If I do not switch over often I could always load a different map but maintaining the configuration on two maps can be a PIA.

Last edited by ZX-Tex; 05-04-2010 at 11:26 AM.
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Old 05-04-2010, 11:11 AM   #5
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Quote:
Originally Posted by TravisR View Post
Alternatively using logic functions and a standard output I think you might be able to get something accomplished.
Yeah I am wondering... if you 'AND' two logical outputs, and they are outputting a %DC, does it multiply the two together, or does the 'AND' function only work for boolean variables? I suspect it is the latter but I need to RTFM on that.

Anyway, except for losing the map, I like the 'PWM fuel 2' method (using the other map) so I may have to just do that if I cannot figure out another way. I am not looking at implementing E85 right away so I can always figure out something later if I have to.

Here is that discussion from the Adaptronic forum
http://adaptronic.com.au/forum/index.php?topic=120.30
You can use the 2nd fuel map as your PWM source. In it, 10ms will correspond to a duty cycle of 100%, 1 ms to 10%, etc. Select your appropriate PWM output as a "PWM Fuel 2" and then you can map your duty cycle against load and engine speed using the 2nd fuel map.
You can also use the second ignition map instead if you like - 50 degrees = 100% duty cycle.
So if you're using a single variable (MAP or TPS) for tuning, you can have up to two independent PWM devices mapped against the same tuning variable (MAP or TPS). No, you can't choose another variable, and you can't do it if you're using MAP and TPS combination tuning.

Last edited by ZX-Tex; 05-04-2010 at 12:32 PM.
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