A look at fuel systems (Returnless vs. Return) and how to convert the OEM way...

[AudiA4_20T]

Things required to convert:

1. B6 3.0 fuel return line (that goes from engine bay to joint)
2. B5 1.8T fuel rail (if 1.8T)
3. Fuel pressure regulator (if not included with rail)
4. New fuel hoses and clamps

Optional piece, not needed but more "OEM" like. It can be added later:
1. B6 3.0 fuel return line (that goes from the joint to the driver's side of the tank)

A fellow AZ'er Kodymfk has done an awesome write-up for a -6AN returnless conversion also. Very clean

http://www.audizine.com/forum/showth...system-for-E85

[IVRINGS]

Can't wait for the update... ;) I hope the B6 body's keep soming at that yard. I hope I get the next one.

[dubgli]

so, what if my B6 doesn't have that purple line coming out of the fuel filter? I believe my purple line just goes from the second gas tank to the main gas tank. Im not sure about my second statement, but i know forsure my fuel filter has 2 inlets and only 1 outlet.


With the conversion to the return fuel system, i assume our new type of fuel filters will not have a built in fuel pressure regulator since there is one by the rail now?

[vortexjunkie]

i have the 1.8t fuel rail from a B5 in my attic if someone wants to attempt this

[AudiA4_20T]

so, what if my B6 doesn't have that purple line coming out of the fuel filter? I believe my purple line just goes from the second gas tank to the main gas tank. Im not sure about my second statement, but i know forsure my fuel filter has 2 inlets and only 1 outlet.


With the conversion to the return fuel system, i assume our new type of fuel filters will not have a built in fuel pressure regulator since there is one by the rail now?

what year/motor is your car? All of the B6 1.8Ts I've seen have the purple line. If you don't than that's great since it's fairly useless. You would just need the 3.0 return line.

You are correct in your assumption that you lose the FPR in the fuel filter when you convert. This is why I said you either need a B5 rail or a V6 with an FPR on the rail

[MmmBoost]

Keep in mind that your ECU will need adjusting if you hook up the FPR to the intake manifold.

.......just general information. Not directing that comment at anyone.


oh......and BTW, Clint.....your evap line and return line are backwards on the top diagram which is what dubgli is talking about. Not all B6's have the evap line. <=======now corrected

[Dirty]

so, what if my B6 doesn't have that purple line coming out of the fuel filter? I believe my purple line just goes from the second gas tank to the main gas tank. Im not sure about my second statement, but i know forsure my fuel filter has 2 inlets and only 1 outlet.


With the conversion to the return fuel system, i assume our new type of fuel filters will not have a built in fuel pressure regulator since there is one by the rail now?

what year/motor is your car? All of the B6 1.8Ts I've seen have the purple line. If you don't than that's great since it's fairly useless. You would just need the 3.0 return line.

You are correct in your assumption that you lose the FPR in the fuel filter when you convert. This is why I said you either need a B5 rail or a V6 with an FPR on the rail

Same here, I have an 05 AMB 1.8t and don't have the purple/blue line. I have the 2>1 fuel filter not the 2>2.

[MmmBoost]

oh......and BTW, Clint.....your evap line and return line are backwards on the top diagram which is what dubgli is talking about. Not all B6's have the evap line.

again

[AudiA4_20T]

Keep in mind that your ECU will need adjusting if you hook up the FPR to the intake manifold.

.......just general information. Not directing that comment at anyone.


oh......and BTW, Clint.....your evap line and return line are backwards on the top diagram which is what dubgli is talking about. Not all B6's have the evap line.

You mean the return line comes out from the left? That could be a problem...

[dubgli]

Same here, I have an 05 AMB 1.8t and don't have the purple/blue line. I have the 2>1 fuel filter not the 2>2.

yes, same here, 05 1.8t.. Our fuel pumps are also different as the 034 High Output Fuel Pump DOES not drop in.. I found this out as i was installing the pump, but i sacrificed the gas full/empty feature to make it work..

[MmmBoost]

Motor and Evap are on the same side.

VL (Supply) and RL (Return) are on the same side.

[AudiA4_20T]

How's that?

[MmmBoost]

Fuel goes in the supply port, through the filter material and then to the FPR, whatever fuel flow is left over after the pressure upstream at the rail is at 4bar comes back through the FPR.....down the white plastic tube.......and then out the return port.

[AudiA4_20T]

good stuff!

[vtraudt]

What large fuel pumps are true 'drop in' for the B6 AMB, including matching filter/sock?
Sources for kit?

First thing on the list for return style E85 conversion (to handle the massive flow/pressure; 4 bar base plus 2 bar boost = 6 bar 90 psi fuel pressure).

[AudiA4_20T]

What large fuel pumps are true 'drop in' for the B6 AMB, including matching filter/sock?
Sources for kit?

First thing on the list for return style E85 conversion (to handle the massive flow/pressure; 4 bar base plus 2 bar boost = 6 bar 90 psi fuel pressure).

Wet0willy01 sells an 040 drop-in kit.

[vtraudt]

Wet0willy01 sells an 040 drop-in kit.

The 040 seems a bit small for 1000cc at 90 psi or?

[AudiA4_20T]

The 040 seems a bit small for 1000cc at 90 psi or?

I apologize it's the Aeromotive.

[vtraudt]

Wet0willy01 sells an 040 drop-in kit.

So Wet0willy01 drop in kit is using Aeromotive 340? Not sure how the 340 holds up on E85. And flow at 90 psi is lower than my design goal of 200-225 lph.
The Walbro E85 (some call it 450, Walbro says 430 and 450 with *) would be the right pump, just concerned about 'drop in' fit.

And then: upgraded lines needed? or at least upgraded return line (instead of using the evap line as return).

[Wet0willy01]

AEM makes a pump that will work with my adapters that are e85 rated.

[vtraudt]

AEM makes a pump that will work with my adapters that are e85 rated.

This one? If numbers are true, may be borderline for my needs. Would like to see 225 lph at 90 psi. Walbro 430/450 E85 fits the bill, but have no confirmed 'drop in' setup/fit.

[vtraudt]

Probably similar to the aeromotive:

[Kodymfk]

Would it be alright to let evap (mini line that connected to E) vent to atmosphere? Doing this conversion and am curious. Or should I block it off?

[AudiA4_20T]

Would it be alright to let evap (mini line that connected to E) vent to atmosphere? Doing this conversion and am curious. Or should I block it off?

Your car will smell like gas and it'll drip everywhere. Ask me how I know lol. I cut the line about 1" out, washed it out with water (so it wouldn't light), used a lighter to seal it closed, and put it back.

[Kodymfk]

Good to know lol.did you experience any run out of fuel at a quarter tank issues?

[Kodymfk]

I used this thread to switch my return-less system to return last weekend. It turned out great! Thanks for this info!

[AudiA4_20T]

I used this thread to switch my return-less system to return last weekend. It turned out great! Thanks for this info!

glad I could help. Cross posting your thread in the top post for reference.

[BerNur]

Good to know lol.did you experience any run out of fuel at a quarter tank issues?

i have this issue, how did you fix it? or someone else can chime in

[f1torrents]

I have mine done the way outlined in the second picture.
I used the factory manual to see how it was assembled and came to the same conclusions as the OP.
I have gone as far down as 1/16 of a tank of gas and it was still running fine.

With the stock 1.8T I used to go to empty and then 20Km more on occasion.

[Kodymfk]

glad I could help. Cross posting your thread in the top post for reference.

Good deal :)

[Kodymfk]

i have this issue, how did you fix it? or someone else can chime in

Nope. Have been testing this issue as well. I've only ran it down to 45 miles and the second red line from E so far. But I plan to run it all the way to confirm. Did you measure the distance from your stock fuel pump setup?

[elRey]

Since the 3.0 line still requires a hose from engine end of hard line to rail (not 100% solution from filter to rail), has anyone tried a B5 line or passat line? Are they the correct lengths from filter to bay? They also have the added benefit of routing the bay portions further away from turbo. So, may be even use the feed line aswell.

Thoughts?

[vtraudt]

Who has completed a E85 return style conversion to the B6 A4 1.8T?
How?
Maybe schematic?
Of particular interest: how are both halfs of the tank kept full? Stock is using a syphon system with. Filter return goes to one side of the tank, suction Y pumps fuel to other side of tank.
Simply running the (new) return line to the existing (right from filter) IMO does not work well, since return line has flow reduction orifice (causing way too high return flow back pressure). Eliminating the reduction kills the 'suction' effect (and only 2 side of the tank is filled).

Looking for simplest working solution.

[elRey]

... since return line has flow reduction orifice (causing way too high return flow back pressure). Eliminating the reduction kills the 'suction' effect

Where exactly is this orifice located ? I've seen a thread about restriction in the filter. Is there one
elsewhere?

Which side does the B5 / passat 4motion return to?

[Rogue A4]

Where exactly is this orifice located ? I've seen a thread about restriction in the filter. Is there one
elsewhere?

Could this be the restriction, from this thread.

As you see at the top when I finished this setup, I was at 80psi pressure. This was due to the return hat having a much smaller hole in the elbow of the return. This created back pressure (bottle neck). It's suppose to be at 4 bar at idle (58ish psi) and the very small hole with a rubber diaphragm internally cause a good amount of back pressure. I decided to have fun and stock up fuel hats etc and try a hand full of different routes. I went as far as creating an out of fuel tank system to test different routes I was curious about.

[Rogue A4]

Who has completed a E85 return style conversion to the B6 A4 1.8T?
How?
Maybe schematic?
Of particular interest: how are both halfs of the tank kept full? Stock is using a syphon system with. Filter return goes to one side of the tank, suction Y pumps fuel to other side of tank.
Simply running the (new) return line to the existing (right from filter) IMO does not work well, since return line has flow reduction orifice (causing way too high return flow back pressure). Eliminating the reduction kills the 'suction' effect (and only 2 side of the tank is filled).

Looking for simplest working solution.

blitz2190 posted this awhile back, looks interesting, click.


https://www.radiumauto.com/Venturi-J...-Kit-P760.aspx

[elRey]

So, I've just read their posts and I still have not seen definitive evidence that more flow thru siphon/suction pump prevents it from working.

I see some inference and pressure issue, but not a direct link with boring oriface and siphon issue without other varibles in play. Or did I miss something?

Eliminating the reduction kills the 'suction' effect (and only 2 side of the tank is filled).

Thanks for the references to the oriface/pressure. Now where are the post about the siphon issues with more flow?
What's different with B5s? Did they have same issues?

[AudiA4_20T]

Since the 3.0 line still requires a hose from engine end of hard line to rail (not 100% solution from filter to rail), has anyone tried a B5 line or passat line? Are they the correct lengths from filter to bay? They also have the added benefit of routing the bay portions further away from turbo. So, may be even use the feed line aswell.

Thoughts?

They don't fit. Why is it not 100% solution from filter to rail? Go to the hardware store and get a couple feet of 5/16" fuel hose and some clamps. Looks OEM

Who has completed a E85 return style conversion to the B6 A4 1.8T?
How?
Maybe schematic?
Of particular interest: how are both halfs of the tank kept full? Stock is using a syphon system with. Filter return goes to one side of the tank, suction Y pumps fuel to other side of tank.
Simply running the (new) return line to the existing (right from filter) IMO does not work well, since return line has flow reduction orifice (causing way too high return flow back pressure). Eliminating the reduction kills the 'suction' effect (and only 2 side of the tank is filled).

Looking for simplest working solution.

Have you measured the pressure at the return line? I never had issues with mine.

[vtraudt]

Running walbro 450 and dash 6 supply and return, we saw 80 psi. May be lower with small pump. But defeats purpose of a conversion = big flow.

Sent from my Nexus 7 using Tapatalk

[vtraudt]

I have mine done the way outlined in the second picture.
I used the factory manual to see how it was assembled and came to the same conclusions as the OP.
I have gone as far down as 1/16 of a tank of gas and it was still running fine.

With the stock 1.8T I used to go to empty and then 20Km more on occasion.

I assume 2nd picture setup works with smaller pumps/flows. But causing very high fuel pressure at rail for big pump setups. Restrictions in return to tank cause backpressure. FPR can only control down to back pressure level.

so, what if my B6 doesn't have that purple line coming out of the fuel filter? I believe my purple line just goes from the second gas tank to the main gas tank. Im not sure about my second statement, but i know forsure my fuel filter has 2 inlets and only 1 outlet.


With the conversion to the return fuel system, i assume our new type of fuel filters will not have a built in fuel pressure regulator since there is one by the rail now?

Sent from my Nexus 7 using Tapatalk