Fuel Lab Pumps take PWM directly...

[Rick Finsta]

I was just researching some fuel system options, as I decided the Walbro 255lph just isn't going to cut it except for tooling around on the street (BTW do we have a "for sale" forum here?), and saw that Fuel Lab's pumps take a PWM grounding signal directly. Sounds like a great way for us street/track guys to regulate fuel flow when we don't need 100% output, seeing as there are generic PWMs on the MS3. I think I'm going to pick one up and use the PWM input for a High/Low speed switch (it's designed for that) so I can basically be running a 500hp and 1000hp capable pump at the same time with just a dash switch to select them, all in one pump body. Neat!

[gurov]

I was just researching some fuel system options, as I decided the Walbro 255lph just isn't going to cut it except for tooling around on the street (BTW do we have a "for sale" forum here?), and saw that Fuel Lab's pumps take a PWM grounding signal directly. Sounds like a great way for us street/track guys to regulate fuel flow when we don't need 100% output, seeing as there are generic PWMs on the MS3. I think I'm going to pick one up and use the PWM input for a High/Low speed switch (it's designed for that) so I can basically be running a 500hp and 1000hp capable pump at the same time with just a dash switch to select them, all in one pump body. Neat!

you wouldn't really need to switch anything on the dash, generic PWM can base output on RPM vs MAP, so you could have it increase flow as pressure rises, but i think this could make for some tricky tuning, as the injectors normally have a different response time to pressure. and your VE map will now be dependant on the fuel pump's PWM map.

worth a try, i guess... ve live should be able to take care of the various transient points.

[Rick Finsta]

The switch is for high/low operation independent of PWM; I guess I wasn't really clear on my intent (I don't have MS3+3X yet but will be upgrading, so I'm planning for the upgrades now). Since the pressure regulator will still be taking care of the pressure at the rails, this would only control volumetric flow (which of course changes based on what the engine is eating and what's being returned). I just ordered one up and I'll let everyone know how it works when I get to that point! I was thinking of just using duty cycle as a function of engine load. It goes from (<20% PW = pump off) to (20-90% PW = varying speed), and then (>90% = pump max flow).

[racingmini_mtl]

Is the PWM just a control signal or does it actually drive the pump and take the full current? If it is the latter, you'll need to use an external circuit since the MS3x PWM circuit will definitely not be able to handle the load.

Jean

[jsmcortina]

If it is a logic signal (hope so) then it could be possible to add a feature for PWM fuel pump control using the standard output. As Jean says though, you need to confirm the current demands on that input.

James

[gurov]

If it is a logic signal (hope so) then it could be possible to add a feature for PWM fuel pump control using the standard output. As Jean says though, you need to confirm the current demands on that input.

James

looks like external speed control http://fuelab.com/images/fbfiles/files/ ... ctions.pdf in addition to the positive and negative supply to the pump.

When duty cycle is between 0-20%, the fuel pump is turned off. A duty cycle between 20%-90% will be
variable speed between minimum and maximum speeds, while duty cycles between 90% and 100% are maximum Speed.

Square Wave Signal, at
Recommended frequency: 500-
1500Hz, (shown at 50% duty cycle)

[Rick Finsta]

Yup what he said. I figured you might need a converter/multiplier circuit to get the PWM signal (it's a grounding control signal, as far as I can tell) up to the range required, but I'm not familiar enough with this stuff yet to say for sure.

[gurov]

Yup what he said. I figured you might need a converter/multiplier circuit to get the PWM signal (it's a grounding control signal, as far as I can tell) up to the range required, but I'm not familiar enough with this stuff yet to say for sure.

well, idle control has a 1.5khz option, so it's possible somehow, perhaps generic pwm could be expanded to have the same frequency range.

[VolvoGuy50]

Yup what he said. I figured you might need a converter/multiplier circuit to get the PWM signal (it's a grounding control signal, as far as I can tell) up to the range required, but I'm not familiar enough with this stuff yet to say for sure.

well, idle control has a 1.5khz option, so it's possible somehow, perhaps generic pwm could be expanded to have the same frequency range.

Yeah, that's a but dumb that the Generic PWM can't do high-frequency mode.

I've been working on a way to drive my supercharger's speed controller (other thread, long story), and there are driver modulus which can adapt incoming PWM to the correct PWM for the device being driven. In my case, a PWM-Chop DC motor controller.

[wes kiser]

If you read the fuel lab documentation, you will also find it is very easy (without PWM) to toggle the pump between "high" and "low" operation by simply grounding the third terminal with some voltage resistors as voltage dividers.

On "low" those pumps still flow a huge amount of fuel. With the pump curves, I would be inclined to just run it in "full low" most of the time, and toggle to high above some speed and load threshold. They also overheat and fail pretty quickly in full high.

[gui67]

We already spoke about Fuellab pumps and pwm control in this topic:
http://www.msextra.com/forums/viewtopic ... 25&t=33070

For the moment I can stay at low speed without any control, but hope the pwm outputs will be unlocked to higher frequencies in the future (for these that are able to go higher)
the other solution seems to be the pwm multiplier board from jbperf:
http://jbperf.com/pwm_converter/index.html

[jsmcortina]

It isn't a case of "unlocking them" it is a case of writing new code to use hardware PWM on the outputs that support it. Presently they use software PWM.

James

[Rick Finsta]

The 41402 pump should be just a little bit more than I need on an engine or chassis dyno the low setting, but will be more than enough on the street, and probably not quite enough for the drag strip, so the high setting at least for the track will be necessary for me I think. Heck, I was using a 140gph pump for my carb setup (inertia on the track, and all that). I think I'll be firing up the MS for the first time using a GLS392 and then swapping this beast in before I start road testing, and hopefully after upgrading to MS3+3X. James, I'd love to see a direct logic level grounding control at 500-1500Hz for this, but seeing as there are easy workarounds (like the freq multiplier boards or repurposing another output) I would think it's low priority.

[Coutsi]

Any plans on updating "Fuel Pump and Pressure Control" to allow higher Output frequencies?

Of course I could use frequency multiplier, but adding more circuitry around ECU makes things more prone to fail.

[jsmcortina]

Any plans on updating "Fuel Pump and Pressure Control" to allow higher Output frequencies?

Not at this time no.

James

[Rick Finsta]

James, as I've been redoing my v3.0 board wiring as part of my upgrade to MS3+3X and migration to a turbo setup, I also was hoping to see higher than 250Hz frequencies on some of the PWM outputs. In case you're keeping a running tab... LOL

Currently, I still need to run Jean's PWM multiplier board to control the fuel pump. I might be going to a cable-driven setup soon enough but for now it does limit some of my I/O options.

[ashford]

i have been using jeans pwm multiplier for similar usage, the unit also works for a frequency multiplier.