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mgrover



Member Since: 17 Oct 2019
Location: Leeds
Posts: 393

United Kingdom 2006 Range Rover Sport Supercharged Java Black
4.2 supercharger vacuum side vs plenum side?

anyone know which is which?

the quote am taking this from is

Quote:
The installer had made the mistake of using a common vac pipe for both the vacuum operated lube system and LPG system (reducer vac connection and pressure sensor connection) and the mistake of connecting this common vac pipe to the vacuum side of the supercharger rather than to the plenum side. I could already see in software that the LPG map was wrong, wrong in a way (rising map numbers toward higher engine load conditions) which pointed to the vac pipe being connected to the wrong side of the supercharger... this in itself would mean the LPG system would have no chance of fuelling the engine properly under boost conditions because A. with the reducer set at 1.5 bar above reference pressure there would only be 1 bar of relative pressure at best under boost conditions instead of the necessary 1.5 bar (1.5 bar necessary with spec of injectors fitted). B. It would be impossible to map correctly with actual reducer relative pressure following pre-supercharger pressure.


if you ignore all the LPG jargon, and the pressure stuff the writer of the quote mentions the two sides, my lpg system uses the vac pipe that goes into the fuel pressure sensor, is that from the vacuum side or plenum side? also i assume its just left/right sides?

cheers
martin

Post #604616 Thu Sep 17 2020 1:50pm
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Andy K



Member Since: 18 Sep 2015
Location: GL
Posts: 4754

England 2005 Range Rover Sport TDV6 HSE Rimini Red

is this referring to your car? Are you finally getting to the bottom of your problems ?

They are talking about either side of the throttle butterfly I think.
Though you also have a supercharger (so that has an inlet and outlet as well)

So I think the fuel pressure regulator should be connect to the engine side.

So at idle it will see a lot of vacuum
And cruise speed it will be near normal pressure.

But to see the pressure created by the supercharger, it would need to be after the supercharger

Basically the lower the pipe connection on the throttle assembly, the better. AKAIK

Post #604622 Thu Sep 17 2020 5:43pm
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mgrover



Member Since: 17 Oct 2019
Location: Leeds
Posts: 393

United Kingdom 2006 Range Rover Sport Supercharged Java Black

The quote refers to a different 4.2sc.

But my car am chasing the high long term fuel trims. Think its time to start taking things apart tbh cause am out of ideas whats causing them. I must of smoke tested the car a good 10-15 times with no leaks. The engines compression is strong and fuel system doesn't seem to be having any problems.

And no mechanic will touch the car because its lpged so am on my own

Post #604627 Thu Sep 17 2020 8:24pm
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