R33 Fuel Pump Wiring , Better Feed Retaining Fpcm ?

[GTSBoy]

1 hour ago, Dose Pipe Sutututu said:

From what I gather I should just bin the whole fuel pumps running on PWM and just have them full noise with a massive fuel cooler to manage heat.

No, I have no problem with PWMing the pump. It's just the PWM motor controllers usually use big transistors as the switching units, without the optocouplers and other shenanigans that go into making an SSR. SSRs are black boxes,  but they shouldn't just be treated as black boxes when you push them outside of their design intent.

Fuel Lab, etc, pump controllers would just be a normal MOSFET switched PWM circuit. I'm sure you could find something workable on the net with some searching. You don't need a PWM circuit that generates it's own pulses and has a pot or anything else to adjust the PW. You only need the back half of the circuit that takes the pulses into the input of the big switch and lets the angry pixies flow. The main difference is that the PWM input and the main switched circuit end up having to share some things (like, at the very least, the earth side, I'm guessing) because the circuit would not be completely decoupled the way that and SSR does for you.

[Ben C34]

i gave this a shot with an SSR, and aborted. WHen you put a scope on the output it makes no sense, and the shape is wrong. weird buzzing that shouldnt happen and just generally misbehaving. 

as mentioned the proper way to do it is with MOSFETS, which i have not done yet. 

[Ben C34]

i havent watched yet, this is what you theoretically want, assuming it isnt a piece of shit.

[Ben C34]

ok, just watched it, 12v 30 amps max.    which makes sense now that  i read the title as 3000W. so ok for a Walbro bro. turns out i have already bought one so i will see how shit it is or isnt in real life. 

was planning on just using a switched output to control pump either flat out, or PWM'ing. 

[Dose Pipe Sutututu]

Great info guys - I might buy a moderately cheap oscilloscope to actually see what's happening. Great if someone wants to donate me a lab grade one I used at uni (I did a whole semester of introduction to electrical engineering for fun as an elective, I was the only student from IT) lol

The car has gone through 3x tanks of fuel so far, and the SSRs haven't died yet - but let's see, if they do then I'll fast track the mosfet idea.

[GTSBoy]

What sort of heatsinking do you have on the SSR? It should be bolted to something reasonably big and steel/alloy just based on what the datasheet says.

[GTSBoy]

42 minutes ago, Ben C34 said:

i have already bought one so i will see how shit it is or isnt in real life.

Are you saying that you've bought one of these motor controllers? Keep in mind what I posted to Johnny. The control input to those controllers is a potentiometer, controlling the pulse widthe coming out of the onboard pulse generator. You don't need that part of it. You need the PWM output from the ECU to drive the output stage of the motor controller directly. If they don't provide you with an easy way to interface with that (and disable the onboard pulse generator) you're going to have trouble using it.

[Ben C34]

46 minutes ago, GTSBoy said:

Are you saying that you've bought one of these motor controllers? Keep in mind what I posted to Johnny. The control input to those controllers is a potentiometer, controlling the pulse widthe coming out of the onboard pulse generator. You don't need that part of it. You need the PWM output from the ECU to drive the output stage of the motor controller directly. If they don't provide you with an easy way to interface with that (and disable the onboard pulse generator) you're going to have trouble using it.

Yep. One of them.

I wasnt particularly clear before, however I think I will just use a 2 stage setup with a switched output commanding full speed , so the rough idea is figure out where I want the pot set for enough fuel for general use, then replace pot with resistor. Output from ecu to short out resistor for full speed.

 

[Dose Pipe Sutututu]

1 hour ago, GTSBoy said:

What sort of heatsinking do you have on the SSR? It should be bolted to something reasonably big and steel/alloy just based on what the datasheet says.

At the moment none, but I do have the correct heatsinks for them sitting on a shelf, just need a way to fit it all nicely (which hasn't been done, heatsinks were bought as an after thought).

Funny enough, they don't get too hot.

WIP photo (old) but you get the idea.

 

[zoomzoom]

MOSFETs are great and perfectly acceptable in an automotive environment - if properly protected. The gates must be protected against transient spikes. A few tens of volts can be all it takes to destroy the oxide layer and short the device. Unfortunately cars are terrible with transient spikes. So you'll have to trust that whatever device youre using has been designed by an automotive minded electrical engineer.

Not to mention that high currents controlled by PWM are probably going to create transients of their own. Those kinds of MOSFET controllers are going to switch hard and create a lot of high frequency transients.

I'd be cautious about those devices which are probably just someone's side project - which isn't intended to be a slight, but creating a rugged device for automotive use is going to take a lot of testing.

[Ben C34]

20 minutes ago, zoomzoom said:

MOSFETs are great and perfectly acceptable in an automotive environment - if properly protected. The gates must be protected against transient spikes. A few tens of volts can be all it takes to destroy the oxide layer and short the device. Unfortunately cars are terrible with transient spikes. So you'll have to trust that whatever device youre using has been designed by an automotive minded electrical engineer.

Not to mention that high currents controlled by PWM are probably going to create transients of their own. Those kinds of MOSFET controllers are going to switch hard and create a lot of high frequency transients.

I'd be cautious about those devices which are probably just someone's side project - which isn't intended to be a slight, but creating a rugged device for automotive use is going to take a lot of testing.

agreed. Which is pretty much why I have not installed it yet.

I would prefer to try out a fan controller from a VF commodore (or heaps of other options). They pwm the cooling fans so must be capable of a fair bit of current.

I'll start hunting for one of them again.... 

[Ben C34]

Actually this looks like the go.

Chinese versions available, 600w mentioned somewhere. No special plugs required cos you can chop off the existing plugs . Google this part number people  8K0959501G

 

[tridentt150v]

Before everyone jumps on a train that they can't get off, has anyone actually measured the heat changes in the fuel at the tank?

I'd be interested in quantifying just how much heat we are talking about?  What pump type? And under what conditions?

Maybe what is needed for a dedicated track car isn't necessary for a road going version?

I didn't see this data anywhere in the thread BTW.  

 

[Dose Pipe Sutututu]

I log fuel data, comes from the flex sensor.

Driving around the streets for about 45 minutes brings up the temps to about 35 degrees. Considering the outside air was about 18 degrees (data inside the Temp, Pressure, Fuel) table.

I suspect this will climb quite quickly on the track.

Mind you, the pumps are running on PWM and duty set quite low off boost.

To prove a point, I'll set both pumps to full noise and see what temps we get.

 

[Dose Pipe Sutututu]

I should also provide context, I have 1 DW300 lift pump (full noise) and 2x Wallahbros 450L in a surge tank running PWM.