S6 timing

[twoqu]

Yep but that wouldn't solve the issue IF the battery itself is not receiving a good 14V+ when running.
If I have calculated properly the delivery drop for the pump at 13.5V rather than 14V is in the 6% range also which could be a conincidence!
There is potential for voltage drop due to the position of the battery in the C4.

[UrS4boy]

There is potential for voltage drop due to the position of the battery in the C4.

This is why you relay the C4 UrS fuel pump to the battery - about 1V less drop than the OE voltage routing system.

[twoqu]

Yep I understand that!
But it does not magically add more voltage. It only prevents voltage from being lost.
If the cars battery does not receive the correct voltage in the first place from the alternator, i.e. over 14V at idle then I think there is an issue. From the screen shots of VCDS I saw it under 14V at idle and in the mid 13V in the mid range. It should be over 14V at idle and nearer 14V in the mid range.

[HMS-S6]

Even if this was the case I'm sure Dmitri on his lean running thread said that 12.5 is pleanty for these pumps.

[twoqu]

Just an observation!
If I knew definitively what the problem was, believe me I would tell you.
Hopefully you are a liittle bit nearer the solution than before.

[UrS6 - IamS6]

Rich,

Keeping up to date with your progress, Educational for me.

My tuppence, go to a decent Bosch dealer and order a 15 volt regulator for your alternator. It's a good idea for everything on the car, dash lights, wipers, etc..

Can do your car no harm, and is not too expensive.

Best wishes.

[HMS-S6]

Thank you all for your suggestions. If possible if but you all a round when this is all over!

[twoqu]

Going back to Dmitri's lean thread he also invested in a superior non OE pump!

[UrS4boy]

Even if this was the case I'm sure Dmitri on his lean running thread said that 12.5 is pleanty for these pumps.

More voltage, to a point, is better than less voltage. That said, I am running fuel RS2 hardware with Stage 3 MRC software that makes 1.8 Bar (26 psig) boost (over atmospheric) with a relayed Bosch "091G" equivalent pump relayed off a battery that sees a maximum of 13.7 V and I have no issues.

IF the fuel pump is fine (nagging doubt on that issue), THEN I think there is some form of restriction in the fuel lines from pump to the fuel rail.

[newsh]

As long as we're 100% sure there is no leak or blockage in the vac/boost line to the FPR... Then it has to be a bad pump, low voltage at the pump terminals, blocked filter or other restriction in the fuel supply to the fuel rail.

[AndyP]

Even if this was the case I'm sure Dmitri on his lean running thread said that 12.5 is pleanty for these pumps.

Pretty certain you'd want 13.5v minimum to reach factory quoted flow rates.

[HMS-S6]

It was a while ago now but I drove the car with a DMM in the back of the pump plug and I'm sure it had over that but I can double check.

[HMS-S6]

I know its been mentioned that the pump itself is in doubt however this would be a tall order surely since the new one came from Audi as a genuine part and didn't change the charictoristics of the fault at all.
In saying this, because of my future plans for the car I wouldn't mind popping an 044 in there.

[HMS-S6]

I have driven the car today (as I've HAD to with the snow!) with my 1:1 adjustable FPR on it. Now I must stress before anyone shouts at me that it's only for diagnosis purposes. I have no intention of leaving it plumbed in.
To make the fuel pressure 5 bar at 1 bar boost I've had to wind the AFRP to 4.2 bar at idle (-0.5 bar). The car isn't perfect on WOT but much better and with a 12.7/8:1 AFR showing. Looking like fuel delivery. Wonder if it has a feed leak INSIDE the tank?

[newsh]

I guess it could be a split in the rubber hose between the pump and the hatch.