Anyone with electronics background!

[blueta]

I was talking to someone on another board and they had this idea. I was wondering if anyone had any direction to start something like this or if someone already did it and there are schematics around somewhere? This is for a GTP. Well here's what he wrote:
I want some way to add timing when the [alcohol] pump is going. My first plan was to spray onto an IAT sensor, and the use the air temp spark table to add timing that way taking advantage of the instantaneous temp drop. Problem here was the response time of the sensor isn't fast enough. So, my new idea is to somehow create a circuit with variable resistance based on the pump voltage. The circuit will connect to the IAT sensor (in the spirit of a happy knob), and through the air temp spark tables I could add say 2* at the resistance corresponding to 5 volts to the pump, 4* at the resistance corresponding to 12 volts to the pump, etc...

Any direction would be appreciated.

 

[NJVetteGuy]

It's quite simple, just use a relay with 2 sets of poles. In a normal state with no alky system operation, wire the IAT return to the PCM through the normally closed contacts. Wire the relay to activate with the alky pump. When the relay activates, have the 5V ref from the PCM looped back through a 4.7k ohm resistor(PCM will see 52 degrees and put it at the most aggressive point in the timing map) to the PCM IAT input. PM me if you need clarification.

 

[blueta]

Thanks!

 

[Razor]

On a simple hobbs switch I can see it. Problem is if the pump is driven by PWM we have our issue. The issue being how the drive affects a relay. Let alone becuase signal is present doesnt mean you have alky. The delayed response of the temp drop may not be a bad thing. At least its a sure thing guarantee'ing alky is in the motor before timing is increased.

If your pump doesnt pump.. you will now have increased timing.. possibly creating a mess.

 

[blueta]

Well thanks for the help so far. I sent this guy the link so maybe he could come over and chime in more about what he's looking for and the problems he encountered so far.

 

[gibby]

Well, it was my idea. The PWM of the controller would probably confuse a standard relay, I hadn't considered that.

A little while ago, I wanted to activate a solenoid. I built the recommended MOSFET circuit, but could not for the life of me get it to work . The same type of circuit would work here I guess..........

I need to do more specific testing with the temperature sensor (i.e. actually spraying onto it and measuring response time) but I think it could be slow enough to not even register until it is too late, especially in driveability situations like a quick downshift.

As I am typing this, another idea comes to mind. I have some room to work with in my throttlebody since I removed the stock MAF sensor and went with an 85mm outboard. But, there are commercially available "leak detectors", the parents have one beneath the ice machine because that house has wood floors.

So, depending on the size/shape of the sensor used to detect liquid, I could possibly hang its sensor right behind the nozzle........... and thats all there would be. Have it flip a relay instead of a really loud, annoying siren. If the siren goes weeee wooo weee wooo, then I am back to the PWM problem I guess...... It is something I will look into.

One last concern, I had a 94 Jeep Grand Cherokee a few years ago. 5.2 v8, full time 4wd, I/E/Mopar ECU, electric fan conversion, and some other small stuff. I used an IAT knob with it, that had a toggle switch on it. It would throw a code if you toggled while the vehicle was running. I don't think that the GTP will have a problem with it, but I haven't actually tried it out yet. Oh well, if it does throw a code, then I will just disable said code

Edit: NJVetteGuy, I actually have the tuning ability to change nearly everything in my PCM. The basic layout you described is what I have planned, except have maybe 3 or 4 settings that correspond to the lowest temperature cells in the PCM (-40*C). The idea is to avoid accidentally adding timing when the IAT sensor is in normal operation, but be able to reference specific cells with a large, otherwise unsafe timing addition when I would like. So, for example program +6, +4, +2 degrees referenced at -40*C, -30*C, -20*C. Flip the knob to read -30, when it is toggled I get an additional 4 degrees of timing.

Another related note, I am not sure where the IAT sensor is on the turbo buicks, but for my car, it is before the compressor. The act of slapping on a smaller pulley, spinning the SC faster, and increasing outlet temperatures beyond what is expected (as stock) severly limits the usefulness of IAT data. I generally do not like to lie to the PCM by spoofing signals, but that is my rationalization.

 

[blueta]

I can't remember for the life of me where a stock IAT goes in a buick, but I can tell you that it was before the turbo on my 84 (kinda hard to put it anywhere else on those ), and I had a hole drilled in my K&N for it on my 87. I could just go look at my neighbors (he has 2 stock 87's), but I would imagine they are still before the turbo.

 

[gibby]

Well, I am still an idiot. I will just set up a 1/8" NPT "T" fitting before my check valve, get like a 50 psi hobbs switch and a relay and do it that way. Everything else was just too complicated

 

[NJVetteGuy]

If you wanted to stay electronic, there's some nice ICs out there with programmable digital inputs, that could easily be configured to do what you need. You could use an SSR to operate a standard relay coil, or do everything in the chip. There's not exactly a lot of current for the IAT circuit, so there wouldn't be much worry of burning anything up. Maybe if I have some spare time I'll fire up my development board and burn a chip for you.

 

[PhilM]

Yea, I think even a PIC could do this in about 100 total lines of code (C)?

 

[rocket468]

blueta You will also need to re-flash your computer to add timing over the iat, The stock timing over the iat is pointless to mess with. I have mine reflashed to add or pull up to 10deg of timing. I would just get a happy knob or an iccu if you can find one. Iccu can add or pulling timing over the nitrous trigger built into it. You might try contacting tech edge directly if you want to buy it. I talked to zoomer and he dropped that line along with the afc line. So its only the tech edge i believe. Best bet may be to get one used they may have completly scraped them because they are so expensive to build.

I am not sure what alkycontrols pmw specs are. There is more to it than the simple pulsing of the current. I am sure he knows enough about what he is doing that it will work fine. I believe he is an elec engineer so he probley knows far more than I do about circuit design. This is a realy basic circuit design. I know ours will not affect a relay and solenoid I made sure it woudn't . That’s why we have a separate unit for alky and nitrous / propane.

 

[gibby]

Well, the more I think about it the more I like the pressure switch idea. Razor brought up a good point that voltage to the pump does not necessarily mean its spraying, that coupled with the PWM problem is turning me away from the electronics side.


With a 50-100 psi Hobbs switch, I can ensure that I only bump the timing once the flow is going, and that is what I am looking for. Now, to track down this Hobbs switch........

 

[Razor]

Well, the more I think about it the more I like the pressure switch idea. Razor brought up a good point that voltage to the pump does not necessarily mean its spraying, that coupled with the PWM problem is turning me away from the electronics side.


With a 50-100 psi Hobbs switch, I can ensure that I only bump the timing once the flow is going, and that is what I am looking for. Now, to track down this Hobbs switch........

You may have one already available to you. I cannot on this thread get into it. Drop me a call during the week.. i'll explain.

Cheers

:wink:

 

[Roger]

The Spark Translator Mike Licht sells has an input which changes timing when it sees 12v.

 

[gibby]

You may have one already available to you. I cannot on this thread get into it. Drop me a call during the week.. i'll explain.

Cheers

:wink:

Wink wink huh ? Well, unfortunately it is now the weekend, so I don't want to call and bother you. Would you feel comfortable PM'ing me the info? If not let me know a good time to call. Thanks

Edit: Beep beep: What is: the bypass switch on the pump? Doesn't it still pulse though? I guess I still need more explanation :frown: