MS2 Fuelab 41401 PWM Control

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MS2 Fuelab 41401 PWM Control

Postby Rick Finsta » Sat Aug 23, 2014 11:59 am

Firstly, great service and ultra fast shipping so thanks on all accounts there.

I am running a MS2 v3.0 on a V8 with bank-to-bank low-z injectors, Stepper IAC, and high current spark control through a dizzy (Pin 36). I'm getting set up for flex fuel control which limits some of my wiring options for this, but I want to make sure I understand what I'm doing here. I want to control the pump speed on a Fuelab 41401 pump using their grounding PWM control.

Firstly, JS11 is going to be run with a 10k resistor (connected to 5V through another 10k resistor) into SPR4 so I can use the SPR4 (Pin 6) as an input from a flex fuel sensor at some point in the future.

I have NO idea how to wire the board as I was hoping to "insert" it into the FIdle circuit so I wouldn't have to run another wire in the loom (Pin 30 already exists). I think this means removing Q4 and Q20 and using those solder pads (like when I was trying to run a PWM idle valve) but I am pretty much an electrical idiot. If you could let me know what I have to pull off the board and where to connect IN, OUT, 12V, and A_GND I'd greatly appreciate it. I was going to mount the TIP122 to the case remotely (that is, run jumper wires from the legs of the transistor mounted on the case to headers on the PWM board).
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Re: MS2 Fuelab 41401 PWM Control

Postby jbelanger » Sat Aug 23, 2014 3:27 pm

You don't need the whole FIdle circuit, i.e., Q4, Q20, R19, R39, D8. So you would connect IN to the R19 on the side connected to the MS2, connect OUT to pin 3 on Q4 or the cathode side on D8, connect 12V to S12 (not S12C) and connect A_GND to the anode side on D8 or the ground side on R39.

And running wires to a remote TIP122 is not a problem. You could also mount the PWM converter board to the case so that the TIP122 is mounted to the board and also has the tab on the case.

Jean
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Re: MS2 Fuelab 41401 PWM Control

Postby Rick Finsta » Sat Aug 23, 2014 6:07 pm

THANKS!

It looks like it is working; I haven't scoped the output yet but FIdle is showing 1228Hz on my multimeter (38.375Hz X 32 Multiplier) which is close to what it is supposed to be (1248Hz). This is only on the stim, but hopefully I can get it in the car and then test the fuel pump response.
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Re: MS2 Fuelab 41401 PWM Control

Postby Rick Finsta » Wed Aug 27, 2014 5:53 pm

Okay the pump isn't responding so I'm going to try a pullup resistor from the 12V to the control terminal as suggested by another MS user. The factory uses a 90k resistor across the 12V and control terminal to tell the pump to run full speed, and that same resistor put across the control and GND terminals puts the pump into full time low speed. Using this supplied resistor resulted in some degree of pump control but only from about 90-80% duty cycle, whereas it should be from 90-20% duty cycle (though I've heard 30% and under are finicky). So I'm thinking that the larger resistance value isn't working with the fast control signal and I need to go with something like a 1k? I was going to try it out and see if it works but wanted to run it by you to see if you had any insight, Jean. Thanks again!
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Re: MS2 Fuelab 41401 PWM Control

Postby jbelanger » Wed Aug 27, 2014 6:21 pm

If the factory uses a 90k resistor, I would not go with a 1k right away. I would try to go with slightly lower than 90k down until you have full control. So start with around 50k and then 20k, 10k...

Jean
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Re: MS2 Fuelab 41401 PWM Control

Postby Rick Finsta » Wed Aug 27, 2014 6:30 pm

Thanks!

Using the I/O test mode if I turn FIdle to ON I am only seeing .5V at the control wire - I'm also seeing the frequency (with the test signal set to 100% duty cycle) jump around a lot and I'm not sure what that means as it worked fine on the stim and gave a nice steady frequency on this same multimeter.

Should I dig back into the case and make sure something isn't wrong there? I thought I'd get 5V on that line but I'm honestly not sure how the test signal page works.
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Re: MS2 Fuelab 41401 PWM Control

Postby jbelanger » Wed Aug 27, 2014 7:42 pm

I'm not sure what you're measuring and where and how it is now connected and how it was connected on the stim. If you used a LED on the stim, that's what provides the voltage. If you don't have something connected that provides a voltage when you measure on the car then you can't measure it with a multimeter because it is switching between ground and no voltage (floating).

Jean
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Re: MS2 Fuelab 41401 PWM Control

Postby Rick Finsta » Wed Aug 27, 2014 8:39 pm

Sorry I'm electronically illiterate! I keep forgetting the whole grounding signal thing - It looks like if I put the output in test mode with a 10K resistor from 12V to FIdle, testing from FIdle to ground I get 7V and the proper frequency on the output. I can try to scope it and see if I'm getting the right duty cycle as well. I tried with a 1K resistor and I was back down to the 0.5-0.6V reading (from FIdle to ground) which I'm assuming is just the differential through the circuit. I have no understanding of how the pullup resistor thing works so I'm not sure why too low of a value might give that result.

Thanks again for the board and great customer support.
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Re: MS2 Fuelab 41401 PWM Control

Postby Rick Finsta » Wed Aug 27, 2014 9:11 pm

Okay Fuelab makes regulators now and looking at the literature for them that helped me out - it is supposed to be a 0-5V control signal even though the literature shows 12V. GAH! Not helping when they do stuff like that.

How do I add a 5V pullup internally to the FIdle output? If I use a 1K resistor from 12V to FIdle and a 19.5Hz x 64 multiplier signal I get great control over the range they specify in their literature. I am thinking that if I run from the 5V on the proto board to the cathode side of D8?
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Re: MS2 Fuelab 41401 PWM Control

Postby jbelanger » Wed Aug 27, 2014 9:20 pm

Yes, a 1k resistor from 5V to the cathode side of D8 will give you a 5V signal. However, that will give you an inverted signal so you will likely need to use the inverted setting.

Jean
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Re: MS2 Fuelab 41401 PWM Control

Postby Rick Finsta » Wed Aug 27, 2014 9:40 pm

Okay I was going to just invert the numbers like Guillermo mentions here and here.

ETA: Also I noticed that if I turn the input to "off" in test mode the light goes on and the voltage goes to 5V so I'm guessing swapping it to inverted is actually the better control scheme as that way "off" will be "0V" and no light and that will correspond with 0% duty cycle? I'm a little confused on how the pullup works and don't know if that is a short to ground that can cause problems...?
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Re: MS2 Fuelab 41401 PWM Control

Postby jbelanger » Wed Aug 27, 2014 10:05 pm

What you're seeing is normal and what happens when you have an open collector output. That output switches the ground side so when you use a pull up, you invert the input signal and when the input is off, the output is on and vice-versa. So using the inverted setting is the best way to go.

Jean
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Re: MS2 Fuelab 41401 PWM Control

Postby Rick Finsta » Wed Aug 27, 2014 10:12 pm

Okay - in the test mode the voltage readings from FIdle to ground don't seem to invert relative to duty cycle when I run in inverted mode - I'm not sure what that means or if it matters at all relative to what I'm trying to accomplish.

For instance, 5% is 4.6V and 75% is 1.6V, which correspond to "full power" (over 4.5V) and "lowest speed" (between 1.5-2.0V), respectively. Duty cycles in between those change at roughly 0.2V per 5%.

I think I get that the whole PWM thing means my multimeter isn't seeing what is actually going on but it seems the pump input responds to the voltage, so it is "seeing" the voltage change exactly as my multimeter does. Perhaps when I get back out to the garage this weekend the inversion will be apparent in the actual pump speed.

*scratching head*

EDIT: NEvermind when I use inverted and actually "run" the ECU on the stim the values in the table are changing voltage in line with 20% = off and 95% = full speed.

THANK YOU!
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Re: MS2 Fuelab 41401 PWM Control

Postby jbelanger » Wed Aug 27, 2014 10:23 pm

Rick Finsta wrote:For instance, 5% is 4.6V and 75% is 1.6V

That is an inverted duty cycle. A normal duty cycle is 0% = 0V and 100% = 5V.

Use whatever makes you feel more comfortable. So if what you have now makes more sense to you then leave it like that. As long as you know what is needed to get what you want and that you have the full range, it's not an issue. So don't over think this.

Jean
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Re: MS2 Fuelab 41401 PWM Control

Postby Rick Finsta » Wed Aug 27, 2014 11:16 pm

jbelanger wrote:So don't over think this.


Have you been speaking with my wife? :ugeek:
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Re: MS2 Fuelab 41401 PWM Control

Postby Rick Finsta » Sat Aug 30, 2014 4:34 pm

Got it back in the car and working. About 14% Duty Cycle is full speed, and then it drops a bit until I get to 43% duty cycle, at which point it starts to stumble a little bit. It is giving me a nice range to tune with and also sounds a lot healthier than it did with just their pullup (well, pull-down) jumper installed to keep it in low speed all the time.
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Re: MS2 Fuelab 41401 PWM Control

Postby jbelanger » Sat Aug 30, 2014 4:41 pm

So how did you wire it in the end?

And if you want to have an increase in duty cycle mean an increase in fuel pressure, you can simply use the inverted mode (unless that's what you're using now). I know I would personally prefer to see this but that's just a question of perception and it won't change the operation. Of course, you'd have to adjust the values you use accordingly (100% minus your current value).

But if that seems more confusing, just ignore it and continue with what you have.

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Re: MS2 Fuelab 41401 PWM Control

Postby Rick Finsta » Wed Sep 03, 2014 2:14 pm

Jean, I wired it as you suggested above by removing the FIdle components and splicing this in. I mounted the TIP122 w/ insulator on the case end next to the DB37 so it will still clear a MS3X board later on if I upgrade (likely will go MS3-Pro if I upgrade at this point, though) and used one of the spacers and the Q16 poly screw as a standoff mount, with the other side of the board resting on a small transistor (Q10 or Q14 don't remember). I have brought the 5V pullup in through a 1K resistor to the cathode side of D8 and then I ran the FIdle wire to the middle terminal of the pump (the control signal terminal).

Everything is working GREAT in test mode but the pump is not wanting to stay on during cranking - I am trying to figure out if I have something in my tune that disables the FIdle during that time, or if the lower battery voltage during cranking is affecting the control signal somehow. If it catches right away she'll fire up but if I crank for more than a second it won't fire as the fuel pump is pulsing too much on and off.

I attached the .msq if you want to take a gander, and I will try to get a picture of the mounting solution later this afternoon when I'm home.
Attachments
Cutlass_MS2_Sep_14.msq
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Re: MS2 Fuelab 41401 PWM Control

Postby Rick Finsta » Thu Sep 04, 2014 9:04 am

Okay so for the record this is actually a 41402 pump - just the 41401's bigger brother but I wanted to mention it as I noticed the discrepancy looking through my notes last night.

That said I was using inverted mode, and when I switched back to standard last night, my control issues during cranking went away, but the duty cycle table did NOT invert (so 16% is full on and about 37-38% is as slow as it goes before starting to stumble). I'm guessing there is something we don't know about how this is controlled internally to the pump. I'm going to call the head engineer over at Fuelab today and see what's what. The other gentleman on the MSExtra board that got this working had issues over time and I'm wondering if the control signal can screw up the controller if the polarity is incorrect over time.

But,t he good news is for now it works and this was (hopefully) the last thing I needed to fix before firing it up!
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