open-loop pwm fuel pump control for a1000

matthunter1448 · Post by **matthunter1448** » Fri Feb 27, 2015 6:21 pm

I've did some searching and am wanting the megasquirt to be my fuel pump controller for my aeromotive a1000 and can't seem to figure out how to wire it for pwm and what all is needed for it. It's not in the manuals i looked, my setup is going to be stock pump feeding a surge tank to a1000 to fuel rail to fuel pressure regulator and return from the regulator. I'm wanting to use the open-loop pwm fuel control. The a1000 from what i've found online doesn't draw anymore than 20 amps.

matt

nathaninwa · Post by **nathaninwa** » Sat Feb 28, 2015 1:05 am

Do a search for solid state relays or ssr. Ms will control the relay via pwm and run the pump the way you have the table setup

matthunter1448 · Post by **matthunter1448** » Sat Feb 28, 2015 11:14 am

so i'm just connecting to a ssr and thats it ?
somenthing like this http://www.hella.com/microsite-electron ... eLocale=en or this http://www.jaycar.com.au/productView.as ... ATID=979#1

nathaninwa · Post by **nathaninwa** » Sat Feb 28, 2015 12:36 pm

The second link is what your looking for. I use them for a cooling fan and an exhaust cut out

matthunter1448 · Post by **matthunter1448** » Sat Feb 28, 2015 12:37 pm

Will it work fast enough and not burn up for the fuel pump

Speedy_G · Post by **Speedy_G** » Sat Feb 28, 2015 2:12 pm

Inductive loads must be diode suppressed

matthunter1448 · Post by **matthunter1448** » Sat Feb 28, 2015 2:14 pm

Speedy_G wrote:Inductive loads must be diode suppressed

Idk what that means

CSXRT4 · Post by **CSXRT4** » Sat Feb 28, 2015 2:15 pm

I would try to find an oem fuel pump control unit to use. I know the 02-05 Subaru wrx has one that is pwm controlled.

I think the biggest issue is flyback voltage which is what I think speedy meant by needing it to be "diode suppressed". Oem fuel pump controllers generally have this built in.

jb007 · Post by **jb007** » Sat Feb 28, 2015 8:32 pm

I'm building a controller based upon this circuit http://www.msextra.com/forums/viewtopic ... er#p423662. I have the parts arriving next week from the USA. I will post my results when I have it built and hopefully working. You might want to look at my thread here http://www.msextra.com/forums/viewtopic ... 04&t=57366which has some comments about using SSR's as controllers... bottom line is that the majority of the cheap ones have very slow turn on and off times which limit the frequency that they can be switched. Also as others have suggested, you will need to add a diode across the motor outputs to stop inductive spikes burning out the SSR.

Jim

matthunter1448 · Post by **matthunter1448** » Sat Feb 28, 2015 8:43 pm

How many amps will that circuit support that would be easy to build

jb007 · Post by **jb007** » Sat Feb 28, 2015 9:21 pm

matthunter1448 wrote:How many amps will that circuit support that would be easy to build

It would should easily handle 60A continuous if using the BUK953R5-60 part. I will be mounting them in a diecast aluminium box, that in turn is mounted on the body near the fuel tank (my pump is in the tank). My pump (a Walbro 5CA401) would be hard pushed to use more than 10A. Maybe others with more of an engineering background could comment on the current, but my figuring is that at 60A Source/Drain current and a 0.003 ohm RDS, the power dissipation would be (60 * 60) * 0.003 = 10.8 Watts.

In your case at 20A, it would be around 1.2W, clearly you could see that having a very low RDS (low Resistance, Source to Drain) device means very low power dissipation as well as voltage drop to the motor.

Jim

matthunter1448 · Post by **matthunter1448** » Sat Feb 28, 2015 9:50 pm

just to be clear were talking about this correct

and i'll look into how much all the parts are and might test it out

jb007 · Post by **jb007** » Sat Feb 28, 2015 9:55 pm

Matt, yes that's what I'm on about. I'll be making mine next week when my parts arrive. I'll be posting results on my blog http://www.jamesobartlett.com.

Jim

matthunter1448 · Post by **matthunter1448** » Sat Feb 28, 2015 10:00 pm

please i would really like to know how it goes. is all thats in the diagram all that's needed seems a whole lot cheaper than having to buy the aeromotive fuel controller also side not how you like the 14point7 wideband?

jb007 · Post by **jb007** » Sat Feb 28, 2015 10:18 pm

matthunter1448 wrote:please i would really like to know how it goes. is all thats in the diagram all that's needed seems a whole lot cheaper than having to buy the aeromotive fuel controller also side not how you like the 14point7 wideband?

No problems Matt, I'll have to look at the circuit more closely, but all I think it might need is either a pull-up or pull-down resistor on the PWM input IC and also maybe in addition to the 0.1uF bypass capacitor a 10uF capacitor for low frequency ripple.

I'll be making a very simple PCB board to accommodate the circuit in the box I've chosen. I'll publish these on my blog. If you've looked at my blog, I've mentioned that I will be making two of these controllers, as I'll use the second one to control my thermo radiator fan.

I love the 14point7 wideband. My experience is that its more accurate and quicker than the TechEdge I replaced it with, as well as a lot smaller!

JIm

matthunter1448 · Post by **matthunter1448** » Sat Feb 28, 2015 10:20 pm

i did look at your blog love the mini (always wanted one of those)
but ya if you could please let me know your findings anything is helpful

jb007 · Post by **jb007** » Sat Feb 28, 2015 10:31 pm

matthunter1448 wrote:i did look at your blog love the mini (always wanted one of those)
but ya if you could please let me know your findings anything is helpful

Thanks, I love the Mini also.

Please feel free to leave comments on my blog, for some reason unknown to me I have had a reasonable number of visitors, but no comments. Maybe it's too boring?

I'll update this thread when I've done more on the controller.

Jim

matthunter1448 · Post by **matthunter1448** » Sat Feb 28, 2015 10:32 pm

will do when i get a chance thanks for the help

dontz125 · Post by **dontz125** » Sat Feb 28, 2015 11:00 pm

jb007 wrote:I'll have to look at the circuit more closely, but all I think it might need is either a pull-up or pull-down resistor on the PWM input IC and also maybe in addition to the 0.1uF bypass capacitor a 10uF capacitor for low frequency ripple.

It shouldn't need a pull-down resistor. If you need a pull-up resistor (open-collector PWM signal) then you'll need to invert your PWM duty -or- add a PNP / P-channel inverting transistor.

Would you be willing to test the circuit with / without the 10uF cap?

jb007 · Post by **jb007** » Sat Feb 28, 2015 11:16 pm

dontz125 wrote:
jb007 wrote:I'll have to look at the circuit more closely, but all I think it might need is either a pull-up or pull-down resistor on the PWM input IC and also maybe in addition to the 0.1uF bypass capacitor a 10uF capacitor for low frequency ripple.
It shouldn't need a pull-down resistor. If you need a pull-up resistor (open-collector PWM signal) then you'll need to invert your PWM duty -or- add a PNP / P-channel inverting transistor.

Would you be willing to test the circuit with / without the 10uF cap?

Ok, I could test both with and without... I'll press my DSO into operation to look at the noise etc if you want.

Jim.

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open-loop pwm fuel pump control for a1000

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