AudiWorld Forums - What is the idle fuel pressure?

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What is the idle fuel pressure?

Doing some trouble shooting on the fuel system, and I noticed the pressure at the rail is well over 50psi at idle.

That's considerably higher than my other cars-- is it correct?
Or do I have a regulator problem?

I believe we have a 4.0 Bar Fuel Pressure Regulator, which is ~58 psi, so that sounds normal.

Quote:

Originally Posted by GoHeels (Post 24427302)

I believe we have a 4.0 Bar Fuel Pressure Regulator, which is ~58 psi, so that sounds normal.

That is true at zero boost/zero vacuum. Assuming a warm idle gets you about 14 inches of Mercury (Hg) vacuum, that is about -6.876 psig so idle fuel pressure should be about 51.2 psig.

Often more importantly, under boost, fuel pressure at the rail needs to be 4 Bar (58 psi)plus the boost pressure, e.g. 22 psig boost = fuel rail pressure of 80 psig. Less than 80 psig, the injectors will run lean and you might have pinging issues.