markruffryder

hi guys,
i was wondering if there was any significance on whether i connected or disconnected the vacuum/boost reference pipe off the manifold to my adjustable fuel reg.

hope sum1 can be of help. cheers

silent running

What, you mean whether you should connect it or not? Yes you should connect it.

markruffryder

wt does it actually do to the regulator?

it is disconnected at the moment and seems to run ok. it was recommended to leave it disconnected, but for what reason i'm not sure about.

markruffryder

anyone know what it does?

Slowboy Racing

Generally When the engine is on vacuum it will open the fuel return valve on the reg wider allowing more fuel to return to the tank

silent running

The vacuum line feeds the regulator with vacuum or boost to allow it to adjust its fuel pressure in line with the situation in the manifold and thus the injectors. E.g. it's set to run 3bar fuel at atmospheric pressure i.e. with the vacuum pipe disconnected. With it connected and the engine idling it will run somewhere in the 2 bar range, on a bar of boost, it'll be running 4 bar fuel pressure. This is what the ECU is expecting it to do, so if you run your fuel regulator vacuum hose disconnected it will simply revert to a fixed 3 bar which will be close enough on some half throttle driving, but on full throttle and light throttle the fuelling will be either too lean or too rich.

markruffryder

thanks guys i understand it thoroughly now.

cheers.