Hella SSR Relay fuel pump control issue.

[Adamw]

As has already been mentioned, you are not going to be able to control this with a standalone device.  It needs peak and hold control and either the start or finish of the spill event needs to be synchronous with the crankshaft and its pulse with will be decided by the ecu based on feedback from the pressure sensor and the calculated injector PW based on the operating conditions at that instant.  You cant just intercept the output as that effectively disconnects the feedback system from the closed loop algorithm.  You are probably better to look at something like manipulating the fuel pressure sensor signal so the ECU thinks pressure is lower and increases it on its own.

[Stevieturbo]

Although OEM may appear to operate it in sync with crank events....would it actually be critical ?

I'd be surprised if a solenoid that large could actually keep up in such a manner ? It'd probably be worth scoping it to see how it is behaving at present, or if the ecu is in place and is capable of logging fast enough...log it. Although it probably wont be fast enough

Also record it with a current clamp, to see how much current it is actually pulling.

Even injection events, OEM will run multiple very accurately timed events per cycle, but pretty sure most aftermarket ecu's that do direct injection, do not follow this same strategy with far fewer injection events per cycle.

 

In order to run a P&H for high current, something like this with maybe a pair of channels used might suffice ?

https://www.fueltech.net/products/peak-and-hold-8a-2a-driver

But it will all be trial and error.

[Mike D]

I believe the bottom picture shows the peak and hold waveform? 

[Adamw]

7 hours ago, Stevieturbo said:

Although OEM may appear to operate it in sync with crank events....would it actually be critical ?

Yes, it is even more critical than fuel injector control.  Spill valves are controlled just like injectors - they usually have battery voltage deadtime compensation and other PW compensations based on solenoid characteristics as part of the control strategy.  Because fuel is not compressible and the HP pump is a mechanically driven piston pump, to keep the fuel pressure near target the spill valve needs to add exactly the same amount of fuel to the rail as the injectors let out.  The only way it can know how much fuel the pump is capable of delivering at any instant is by knowing camshaft position (i.e how where the pump piston is on its cam lobe).   Say if the ecu calculates it needs 0.2cc of fuel added to the rail and it knows the pump capacity is 0.4cc per stroke, then it needs to close the spill valve when the piston is exactly half way up the cam lobe.

 

45 minutes ago, Mike D said:

I believe the bottom picture shows the peak and hold waveform? 

The graph at the top right of the russian picture is a better representation of what P&H looks like.  So a short patch of 0V (this is the "peak" current), then the rest of the opening time is just short pulses to 0V (typically about 25%DC).