Stock pwm fuel pump controller capacity, max current throughput etc
 

Does anyone know what the limits are on the stock pwm fuel pump controller in our machines?

I'm talking maximum current throughput at 100% pwm duty cycle, or max wattage rating etc?

I'm dropping in a GM 65psi 250 lph fuel pump assembly from a Camaro Zl1 on my swap and just want to make sure the stock controller is up to the task.

I haven't tested the pump for current as my meter only goes to 10 amps and don't want to risk it but from what I'm seeing online it looks like the pump should be somewhere around 16-17 amps max at 13.5v.

I don't have your answer but I guess ask why you're bothering with the fuel pump swap. The stock fuel pump is big enough for a stock power LS engine. And there are multiple fuel pump upgrades on the market that drop into the stock basket

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The pump/hanger assembly is cheap and easily found.
And because I'm making a completely new tank from aluminium.
And because there will be zero doubts as to whether or not it will be suitable for my application.
And because I want to.
And because I'm weird and like a good challenge.
And because the stock supply/return regulator built into the stock hanger is a bottleneck for pressure/flow, as far as I know.

I have an LS3 in mine. No issues with upgraded pump, stock FP regulator

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Removing the stock regulator from the hanger assembly, showing it to suppliers, none of them are able to provide a replacement regulator in the same packaging that provides 58 psi and 250 lph flow.

The best they said they could do was 3 bar, 44 psi and 190 lph flow.

Sure, perhaps that is actually enough to still work in our application and yes, awesome that you're able to make it work in your application without issue. Not arguing with you there.

It's just my ocd that tells me no amount of oversized pump within the stock assembly could overcome the limitations of a stock regulator so instead of trying to fight it, considering I'm making a new tank anyway, and considering you can get an entirely new assembly with pump and built in regulator to suit for $250 then why not just remove all doubt and replace the whole damn thing. In the future if something of it fails, it will be easy enough to pop the tank access hole under the seat and just replace the whole unit again quite easily and cheaply.

A number of us also go to the extent of installing surge tanks with high capacity pumps that can meet the instantaneous fuel needs of the LS, and I'm confident some of that decision is likely because of the limitations of the stock regulator built into the hanger not being able to supply 4 bar at a high flow rate. I don't want to have a surge tank elsewhere in my car, so as I am fabricating a whole new tank, why not, right from the outset, gift it with a fuel pump assembly that is totally fit for purpose. If I design the baffles correctly and perhaps also load it with some foam, I should surely be making a great effort towards solving the fuel supply piece of the puzzle and be making something that performs just as well as any aftermarket surge tank stapled in to the stock tank setup can.

Anyway that's my thought process. I'm probably wrong. And probably wasting money. But that's the way I'd like to tackle it. And as I am currently working on my pwm radiator fan controller solution, I thought "hmmm I better do the fuel pump too at the same time" because hey its basically the same thing just in a different part of the car and for a slightly different use.

The LS engine or more accurately the fuel injectors, can't function properly at 44psi. But the stock fuel pressure regulator does output 60psi at any GPM/LPH. Just because aftermarket companies can't match it doesn't mean that it's not doing it. As far as a surge tank is concerned: if you're building a fuel tank, you could simply build your surge tank into it, so it's all internal. Generally surge tanks use a fuel pump to stay full, which only requires a very small fuel pump. And then a second pump to generate fuel pressure. This second pump needs to be sized for the motor. Or you could bypass the stock regulator somehow and use an external one.

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Hopefully my awesome baffles and foam setup combined with the in-basket regulator doing it's supply/return function continuously with a ZL1 pump is going to be as close to a surge style solution as I can get, whilst keeping it simple with a one pump, in-tank setup.

Anyhow I think I'm going to replace the stock pump controller anyway. I've just realised that I'll need one for my beach buggy build (I have a VW chassis and was planning to use my FA20 and as much of the Subaru setup as I could in that).

I'd still like to know what the stock controller can handle though, if anyone has an idea. Of course I could take it out and keep loading it up until it fails and work it out myself, but why destroy it with testing if someone else already knows?

Thanks for your input on pump ideas.

If you're running a return system you'll need to bypass the stock fuel pump controller

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Stock fuel pump controller will run a hellcat pump. I think I am around 65 psi fuel pressure.

Stock pwm fuel pump controller capacity, max current throughput etc
 

Stock fuel pump controllers are cheap used on ebay. There is no rating of any kind anywhere I can see on any of the components. It has a huge heat sink on the back. Just send it.

https://uploads.tapatalk-cdn.com/202...4cfb558b41.jpg

Brilliant! Thank you.

Might get one and load it up with a good 20 amp load for a few hours and see if it survives.

That would be alot of wideopen, 24h lemans?

Hehe yeah I guess!

My thinking is that if my pump is going to use circa 16-17 Amps at full speed and I add an extra 20% (thus my 20 amp idea) and the controller can survive this for say two hours straight then surely in real world use it will survive.

And if it doesn't survive, I'd rather know this and solve it now. I'm already on the path to pwm control of my rad fans, so a little extra work on this part is not a whole lot of additional work.

I think a jeep and a chysler mini van has a heavy duty pwm fan controller, replacements are on ebay with the connector.

Great! Thanks for the tip!

Why not just install a fuel pump relay and not have to worry about it?

Good point!

But, if I have the ability to drive it dynamically and not always slam it at full speed for its entire life, why not give that a go?

You ever wonder why every OEM manufacturer uses pwm control plus the majority of standalones?

I'm gonna assume OEMs do it to simplify plumbing, reduce noise, possibly safety, computerized feedback for check engine lights, and surviving repeated exposures to being 99% empty. I'm sure there are some other reasons. But the point is, aftermarket/race applications don't have the same concerns as OEM. Standalones probably do it so they can mesh with OE systems

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Pwm is better in every way.
Two 285 Walbros push 4.5 gallons a minute hooked to a relay, why would you want that at idle? They also would use 35amps at 40psi base pressure at idle together.

Well I had some fun today doing fuel pump controller tests.

Disclaimer: I'm using the canbus translator from AGT engineering. I'm not sure of what effect this translator has on the waveform that drives the fuel control module outside of what a stock Subaru ecu would do, however I would like to assume that they've done their best at replicating stock Subaru behaviour.

So first, I scoped the output of the e38 x1 pin 50 "Fuel Pump Relay Control Primary". Just as per the work I've been doing on solving my radiator fans, the output is a nice 10 volts usually high, pulls to low style pwm square wave running at 128hz. Various fuel pump percentage settings, all the way from 1% to 100% produce the 128hz waveform with lowest duty cycle (1%) spending most amount of its time high at 10 volts and the least amount of its time at 0v. Enter 73% and 73% of the time the waveform is 0v and 27% of the waveform is 10v. All as expected.

But then scope the input to the fuel pump controller and things change. The biggest difference is that the controller is basically being driven with pulse frequency modulation at various frequencies to represent the percentage of fuel pump as controlled by the e38 (not by a varying duty cycle 128hz pwm as what's coming out of the e38). So for example the e38 punches out 128hz and 46% duty cycle, well the fuel pump controller, from the canbus translator, is now receiving a sync pulse at 48hz. Dial the e38 up to 85% and now the fuel pump controller is receiving a sync pulse of 85hz.

Another interesting find is that anywhere from 1% to 35% duty cycle as pumped out of the e38 does not produce any sync pulse from the canbus translator to the fuel pump controller. The e38 is happily pumping out its 128hz waveform at various duty cycles between 1 and 35% but lo and behold any of these numbers don't produce a result at the fuel pump controller input. It is only when you pump in 36% does the translator suddenly kick into life and what do you know, it's a 36hz pulse.

So does anyone know if A: the stock Subaru ecu also drives the fuel pump controller via a variable frequency sync pulse? And B: does the stock ecu have this "only starts driving the fuel pump" at 36hz or more issue?

Then I moved on to the output of the fuel pump controller. Basically all that is happening is that the controller is dumping out a DC level. At the lowest working frequency of input of 36% the voltage output was something like 8 volts. Push the controller to 100% and it is dumping out a good 12 volts. No matter where I set my scope for time scale, I cannot see any pulse width. It is honestly just pure DC driving the pump at a varying voltage.

So again, some of these behaviours may be from the canbus translator, however they could well be in line with the standard Subaru behaviour.

Does anyone else have the same experience as this?

For me, I want to drive my camaro pump with true pwm, something like 20khz. Also I want to be able to have the range from 1% to 100% as needed. Why? Because I want to. Maybe it's pointless or overkill but having this level of control will make me think I've done it "properly". So I am going to splice into the output of the e38 pin 50 directly and have that running the fuel pump controller instead of passing through the canbus translator. I will also find a controller that can take a 128hz in, variable duty cycle pwm and then dump out a 19/20khz pwm to the pump.

Much of the work I'm doing on solving the pwm radiator fans will end up applying here, I'm sure.

Most bigger aftermarket pumps use or highly recommend a relay, or use a hob switch triggered at set vacuum or boost to trigger higher volt/output or if a dual pump setup a hob switch to activate the second pump.

Most quality aftermarket pumps have no issues running at 100% all the time. They are designed to.

The reason oem use controller is probably for numerous reasons, heat being one,

in-tank pressure regulators probably can’t regulate enough when pump is at 100% and fuel consumption is low IE at idle is another.

Cost and simplicity is another, and probably trying to use and design something that can run for 200k miles with no issues in an oem setup.

You can also get aftermarket controllers wired into the relay if you really wanted.

I think you want that for more instantaneous and stable fuel pressures when you're using giant injectors. You don't need the computer to see dropping fuel pressure, then tell the pump to go faster, then get your pressure back. It's just always there. It surely can't be better in every way or people wouldn't switch away from it

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The ecu activates the injectors in milliseconds, i think it could up the fuel pump controller output before low fuel pressure.

I had another play with the fuel pump PWM output of the e38 today.

As it was putting out 128hz and my fans were also set at 128Hz I gave it a long shot that perhaps changing the fan frequency may also change the fuel pump frequency.

There was no change though. No frequency I entered into the fan pwm frequency had an affect on the fuel pump pwm frequency. So it looks like the fuel pump pwm runs at a fixed 128 Hz.

I wonder if HPTuners has any ability to add a function to change the fuel pump pwm frequency? Fan frequency is available, so what would be so impossible to expect that fuel frequency could also be adjustable hiding somewhere in the e38?

On another note in my playing with the fan frequency I again tried my large frequencies and still hit a 9.33Khz ceiling. Interesting was the fact that at this frequency I noticed the square wave didn't seem to look as clean as the square wave coming out at 128 Hz. I didn't try a bunch of different frequencies to test my theory though.

If I end up using a fan controller that passes through the input frequency to the fans, well then I guess I'll have more work to do on that part because ultimately I would rather be running both the fans and the pump at high frequencies, less audible, hopefully more efficient etc etc...

At this stage I am expecting the Crown Vic clone fan controller I am going to try will not pass the frequency through and simply dump a DC level to the output. As for the fuel pump controller, I bought a Dorman 902-310 to have a play with that and see what I could do. I believe that will pass the pwm frequency through, but won't know for sure until I get my hands on it. If I can't get that to a useable solution then I think I will try a Cytron MD25HV as it uses a fixed 16Khz output and accepts a wide range of pwm input frequencies.

Just read an article from onallcylinders. Stated more consistent pressure at the rail due to proximity of the regulator, and more consistent fuel temp as advantages.

https://www.onallcylinders.com/2017/...m-right-video/

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