return fuel system on a b6

[20vturbo]

ok so I made this thread for all of us to address the issues with the fuel system...
One of the questions I had is where was the 4th line from the fuel filter fpr going.. I know the answer now, it is going back to the tank but on the driver's side....It has some kind of mechanism inside the tank to distribute fuel even to both sides of the tank since i can't see a second pump in there
So this makes my life a little more complicated
So the little skinny line going to the pass side next to the feed line is most likely vacuum vent from the fpr and the return is on the driver's side
FUel tank comes out now

[20vturbo]

correction fuel tank does not come down...You have to remove the whole rear suspension to take that bitch out...I will have to pass the new lines withthe tank on

[AudiA4_20T]

I have an idea of how I'm going to do my return, I'm going to try and come out with a little kit for AZers when its done

[20vturbo]

ok I have pictures but later and now I figured out how the whole thing works...THE RETURN HAS A Y SPLIT INSIDE THE TANK THAT SENDs THE FUEL TO BOTH SIDES...Further they use a phisics principle ( 2 comunicating recipients should maintain same level etc ring a bell) so there is another pipe inside with a spring wich makes sure it bottoms going from one side to the other
Having the return on the driver side makes things easyer for me as \i intend to run both lines on the driver's side
The worst thing is to pass the lines from on top of the fuel tank under the car

[A4 TSCHUSS]

That sounded like a bunch of giberish. "pipe inside with a spring to make sure it bottoms" what the hell does that mean.

[20vturbo]

That sounded like a bunch of giberish. "pipe inside with a spring to make sure it bottoms" what the hell does that mean.

The spring makes sure the hose is always pressed against the bottom of the tank...That hose runs from left to right inside the fuel tank to make sure both sides have the same level of fuel

[A4 TSCHUSS]

Gotcha. I dont see why it would matter if the hose was at the very bottom though if it is just dumping fuel back to the tank.

[20vturbo]

[QUOTE=A4 TSCHUSS;3127340]Gotcha. I dont see why it would matter if the hose was at the very bottom though if it is just dumping fuel back to the tank.[/QUOTE

no that is the hose that makes sure both sides have the same level It has to stay on the bottom I'll post picture when I have some time

[20vturbo]

I finnished the return line yesterday..I am now waiting for some more parts..Some things didn't turn my way, first I need more line and second I could not find a banjo to 6 an line that fits on the 040 check valve...So I have to remove the original check valve and Install an inline check valve..Thanks to summit I will have everything I need by friday next week, and I will post pictures and a parts list of what is needed to do a similar set up.

[diagnosticator]

The return from the filter regulator, does divide to both sides of the tank. The side opposite the fuel pump, uses a suction jet pump to lift fuel to the pump side. The SJP, uses part of the output of the fuel pump to power the SJP in the other side of the tank.

[dirtybrd]

This should work and help with the fuel line size issue. Our FP regs. are set at 3.76bar. This is my idea, run the stock feed line and your choice of aftermarket pumps. Add a return line and a B5.5Passat fuel filter. Install a aftermarket FP reg. and with a return and add a guage. Instead of adding a larger feed line just crank up the fuel pressure to say 4bar. The o2 sensor will adjust the inj. pulse width to compensate for the running rich due to higher FP. Or am I off my rocker? But then again, what's one more fuel line.

[dirtybrd]

I guess you could do the same thing w/ a B5 fuel rail and 4bar reg. Just don't run a signal line to it.

[20vturbo]

This should work and help with the fuel line size issue. Our FP regs. are set at 3.76bar. This is my idea, run the stock feed line and your choice of aftermarket pumps. Add a return line and a B5.5Passat fuel filter. Install a aftermarket FP reg. and with a return and add a guage. Instead of adding a larger feed line just crank up the fuel pressure to say 4bar. The o2 sensor will adjust the inj. pulse width to compensate for the running rich due to higher FP. Or am I off my rocker? But then again, what's one more fuel line.

you mean keep the stock regulator filter and add another fpr..That is like complicating things...This is very easy feed line on pass side return on the driver side, remove filter regulator and all assoc lines that are outside of the tank and install a feed line...I went the extra leg because I wanted racing connections etc...you can also hook the return line from the filter regulator to the actual ffed line that is on the car and run that as return and then install a feed line

[dirtybrd]

No, just the aftermarket reg and a non-return non-regulated filter. After I read it again, it's just easier to run a new feed and a return line with and adjustable reg.

[mike-2ptzero]

If you guys are running a new feed line why aren't you just using the stock feed line as a return line? Isn't it pointless to put in 2 new lines when there is already one running from the tank to the fuel rail?

[HIERLEVELZ]

Please enlighten me guys as to why we are doing this mod?

[7speed]

everyone seems to believe that the returnless system in our cars limits the max HP output, although I dont think that anyone has created enough power yet to max out the stock system. (huge run-on)

[diagnosticator]

everyone seems to believe that the returnless system in our cars limits the max HP output, although I dont think that anyone has created enough power yet to max out the stock system. (huge run-on)

Okay, maybe a summery review will be helpful.
There is direct evidence, (in the case of Winston's fuel pressure measurements on the dyno,) as well as indirect indications of excessive peak combustion temperatures, and associated detonation damage from lean air/fuel mixtures at full load, (as related to the head gasket failure and associated detonation damage that occurred with the OP's new BAT setup here,) is caused by the fuel pressure dropping below the regulated fuel pressure set-point and is associated with the several symptoms that are related to engine failures and dyno results below expected values. The measured drop of full load fuel rail pressure, and the logged injector duty cycle values exceeding the maximum D.C.%, despite using injectors that are sized according to the mass air flow rate and target air/fuel ratios to achieve the target torque value @ max rpm, implicates the common causative factor is low fuel pressure related.
As logged by several BAT owners, showing actual injector D.C.% values exceeding the maximum specified D.C.% at full load, is indirect evidence that the fuel pressure and associated fuel flow rate is insufficient to maintain the required air/fuel ratios at full load. (This conclusion is based on the expectation that the injectors are otherwise sized appropriately for the mass air flow rate provided by the specific turbo installed.)
Regardless of the above, the measured drop of fuel pressure below the regulated set-point pressure, during full load conditions on the dyno clearly reveals that the "returnless" fuel system is unable to reliably deliver enough fuel for advanced BAT setups, using the stock system configuration.

(Note that my comments exhibit longer run-on sentences than yours, confirming my reputation as the ace of run-on sentences! )

[mike-2ptzero]

everyone seems to believe that the returnless system in our cars limits the max HP output, although I dont think that anyone has created enough power yet to max out the stock system. (huge run-on)

Well we might find that out very soon since 034 should be getting ready to tuning a B6 built 2 liter GT3076r with -6 feed line and 040 pump very soon.

[20vturbo]

Okay, maybe a summery review will be helpful.
There is direct evidence, (in the case of Winston's fuel pressure measurements on the dyno,) as well as indirect indications of excessive peak combustion temperatures, and associated detonation damage from lean air/fuel mixtures at full load, (as related to the head gasket failure and associated detonation damage that occurred with the OP's new BAT setup here,) is caused by the fuel pressure dropping below the regulated fuel pressure set-point and is associated with the several symptoms that are related to engine failures and dyno results below expected values. The measured drop of full load fuel rail pressure, and the logged injector duty cycle values exceeding the maximum D.C.%, despite using injectors that are sized according to the mass air flow rate and target air/fuel ratios to achieve the target torque value @ max rpm, implicates the common causative factor is low fuel pressure related.
As logged by several BAT owners, showing actual injector D.C.% values exceeding the maximum specified D.C.% at full load, is indirect evidence that the fuel pressure and associated fuel flow rate is insufficient to maintain the required air/fuel ratios at full load. (This conclusion is based on the expectation that the injectors are otherwise sized appropriately for the mass air flow rate provided by the specific turbo installed.)
Regardless of the above, the measured drop of fuel pressure below the regulated set-point pressure, during full load conditions on the dyno clearly reveals that the "returnless" fuel system is unable to reliably deliver enough fuel for advanced BAT setups, using the stock system configuration.

(Note that my comments exhibit longer run-on sentences than yours, confirming my reputation as the ace of run-on sentences! )

You are dead on...BUt to complete your statement, my worry is not the actual b6 set up but the size of the connectors, and not the line since that has a fair size...If you look at the fuel pump check the nipple that connects the pump to the line, about 3mm diam, and then the connector itself is very small inside...And yes the feed line could be used as return, I wasn't happy with where it was and that is why I choose to remove it....It's the inside of the connector that made me go with those hardcore AN fittings..TO explain more about those connectors, they maintain same diam as the hose inside, there is no reduction in size where they atach to the line, they are designed for flow, more they are the army/navy standard and they are widely used in the aircraft industry...After this I will not be worried about the fuel system

[HIERLEVELZ]

So in Laymans terms there is evidence than the returnless system show a drop in fuel pressure despite using the appropriately sized injectors and upgraded fuel pumps? And this has lead to injectors running at near 100% duty cycle. In turn causing detonation, lean conditions and blown headgaskets in one or several members' BAT euipped Audis.

Okay, maybe a summery review will be helpful.
There is direct evidence, (in the case of Winston's fuel pressure measurements on the dyno,) as well as indirect indications of excessive peak combustion temperatures, and associated detonation damage from lean air/fuel mixtures at full load, (as related to the head gasket failure and associated detonation damage that occurred with the OP's new BAT setup here,) is caused by the fuel pressure dropping below the regulated fuel pressure set-point and is associated with the several symptoms that are related to engine failures and dyno results below expected values. The measured drop of full load fuel rail pressure, and the logged injector duty cycle values exceeding the maximum D.C.%, despite using injectors that are sized according to the mass air flow rate and target air/fuel ratios to achieve the target torque value @ max rpm, implicates the common causative factor is low fuel pressure related.
As logged by several BAT owners, showing actual injector D.C.% values exceeding the maximum specified D.C.% at full load, is indirect evidence that the fuel pressure and associated fuel flow rate is insufficient to maintain the required air/fuel ratios at full load. (This conclusion is based on the expectation that the injectors are otherwise sized appropriately for the mass air flow rate provided by the specific turbo installed.)
Regardless of the above, the measured drop of fuel pressure below the regulated set-point pressure, during full load conditions on the dyno clearly reveals that the "returnless" fuel system is unable to reliably deliver enough fuel for advanced BAT setups, using the stock system configuration.

(Note that my comments exhibit longer run-on sentences than yours, confirming my reputation as the ace of run-on sentences! )

[dirtybrd]

Yes that line will only flow "X" amount of fuel without a increase in pressure. Being as the fuel pressure is fixed the easiest option is the increase the size of the line.

[20vturbo]

Yes that line will only flow "X" amount of fuel without a increase in pressure. Being as the fuel pressure is fixed the easiest option is the increase the size of the line.

there is not much diff in size between the line on the car and a 6 an line..The critical point is the feed from the pump to the regulator....You can add a bigger line but if you have a restrictor before that what's the use

Scrap the fixed pressure regulator..After all the money we put into those cars what's another 130$

[dirtybrd]

I agree on the reg. No more buying bigger injs.

[AudiA4_20T]

I agree on the reg. No more buying bigger injs.

yea but the pump doesn't like being pushed to more pressure... The best scenario would be to run 3 bar with some big ass injectors. The pump wouldn't have to work as hard. And we could turn it up if it wasnt flowing enough and let the ME7 adapt

[dirtybrd]

yea but the pump doesn't like being pushed to more pressure... The best scenario would be to run 3 bar with some big ass injectors. The pump wouldn't have to work as hard. And we could turn it up if it wasnt flowing enough and let the ME7 adapt

I was saying with the proper pump, sorry I should have specified. But yes, the ECU will adapt to the extra pressure by adjusting inj. pulse width.