Volvo S70 2.5T
Does anyone know if, when the accelerator is floored, the volvo ECU increases the fuel pressure to the injectors and thus increases the amount of fuel entering the engine for the time the injector is open. This is as opposed to just opening the injevtors for longer...
ie is fuel pressure at all dependant on revs etc.....
Sean
No, fuel pressure in dependant on intake manifold pressure. So under light load when there's lots of vacuum the fuel pressure is lower than high load when there's turbo boost. However, the fuel pressure is kept at a constant amount above intake manifold pressure, so the amount of injected fuel is determined only by injector opening time.
The fuel pressure reg on the injector rail is connected to the inlet manifold where it can sense manifold pressure so that fuel pressure is kept at a constant value above intake pressure. Therefore for the same injector duration fuel delivered will be the same irelevant to intake pressure.
The ECU merely fires the injectors for different time periods depending on engine speed and operating conditions to vary the fuelling.
During certain circumstances the ecu will halve the firing time but double the number of shots per cycle, typically during cranking, and at this time it also ignores the CPS and fires all the injectors once per crankshaft revolution.
Tim..
On Tue, 15 Jul 2003 08:17:25 -0400, Mike F wibbled about:
So - I was wrong about the ECU - but right about the effect which would explain the problem I have.
I have an LPG system on the car that takes the petrol injector pulse, ups it by a % to account for the gas and then squirts gas for that time into the cylinder. However it ignores the manifold pressure - the gas pressure remains constant.
Sean
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