RomRaider

So some other things that might use frequency in the ecu.

-fuel pump pwm
-avcs solenoids (we dont want to change this)
-possibly tgv motors (maybe repurpose this somehow)

The fuel pump would be icing on the cake... set to 50hz it could run a solid state relay = high amp pump speed control.

ok so if i measured it correctly, the frequency of the fuel pump duty cycle is 81.2hz. but i have read somewhere is is more like 250hz.

http://www.pickercomponents.com/pdf/Relays/PCS34-DC-Input-80-Amp-SCR-Hockey-Puck-Solid-State-Relay.pdf

these relays only work up to 63hz

Would 81.32726089785296 sound about right?



Can't promise it's the right one, but looks like a frequency based figure, and related to the fuel pump.

Jesus christ!! Thats mental. I can do some testing if you can define it. I have a ssr setup currently. Just a matter of running a temporary wire from the factory controller to the ssr.

Perfect - I'll send you the definition, then you can test it directly.

Cool! You have my e-mail address... im pretty confident it will work.

It f*** works!!!!!

I will post the relay type and settings that worked and wiring diagram.. But this is epic! I just need to tidy it all up. Give me a chance to confirm everything is good.

Yeeha!

ok so the pwm signal wire is marked FPC on the stock fuel pump controller. removing the fuel pump controller will render the in tank pump useless so this needs to be connected to the solid state relay along with your big pump. i am running 50Hz to the ssr. remember the whole purpose of this is to supply large current to the fuel pump but retain the speed control. i have seen alot of guys running resistors on the control side and diodes on the output side and some running just one of or none of. not to sure how that impacts the setup but i am running neither for the time being and its working fine.

my factory pump controller is completely removed. i get 100% duty for prime and a short time after starting it then follows my fuel pump duty setting in the rom.

further to the above. i am going to add a low pass filter to give a nice analog voltage to the pump rather than pwm (13.8v on and off) this should make its operation alot smoother. as we have control over the frequency from the ecu to match the relays rated frequency, the output frequency sounds a little low. i think the easiest way to rectify this would be a simple capacitor and resistor working as a low pass filter taking away the ripple.

Wouldn't the resistor defeat the purpose of using a low impedance/high current solid state relay?

The ssr is just passing through a pwm @ 50hz. By using a low pass filter it would convert the pwm generated by the ssr (passed through from ecu) and convert it to a analog voltage. This would result in a nice almost linear variable 0-13.8v constant voltage to the pump. It works without it. Just sounds a tad choppy at lower voltages.

The low pass would be connected to the pump along with your thicker gauge wire. So the current can still flow through but the low pass filter should remove the pwm effect.

At 100% duty, all current still has to pass through the resistor. Pump current could be 15-20A. How much voltage are you willing to lose to the resistor?

so leaving the + to the pump as per the above diagram but also add the low pass filter. obviously the current supplied by the low pass filter during pwm Off time will be low, but it should go along way in smoothing it out.

i have been doing some searching around and have come across ssr's suitable for higher frequencies. i am going to test the low pass filter idea but ideally using a higher frequency ssr would be easier.


Here is a bad example of low frequency pwm. you can hear its far to slow.
https://www.youtube.com/watch?v=e3Y8Sq2JHj4