URS6 Build

[coultl]

I'm started my URS6 build and I've been getting great info from this forum. I'm learning a lot as I'm going and I figured it would be good to write some of it down in case it helps anyone else. I'd also REALLY appreciate feedback and tips.

I'm a ME who started my career in car tuning. Mostly designing upgrade parts for Mercedes and Porsche cars. Brake kits, intakes, headers, intercoolers, lots of carbon stuff, etc. I've only dabbled in engine tuning so I have a lot to learn there. I've owned many Audis (1990 V8, 2004 A4 Ultrasport upgraded, 2008 S4 Avant) but I've always loved the URS cars. I just finished the timing chain on my B7 S4 so I can finally get the S6 project going!

I'm starting with a 1995 S6 that already has some great upgrades including:
- 2Bennett big brakes front and rear
- 2Bennett 3" down tube and 3" exhaust
- RS2 ex manifold
- Upgraded / lowered shocks and springs. Not sure exactly what's in there but they feel great.
- 2Bennett upper strut mounts

The goal for this build is to hit 400whp with a GTX 3071 Gen2. I know that's pushing it but hopefully I can get there. The planned upgrades are:

- GTX 3071 Gen2
- Apikol FMIC
- ID 1050x injectors
- Integrated engineering rods
- ST valves and springs
- 7A cams
- Meth injection
- Stage 4 Ringer Racing clutch
- ECU Master EMU Black
- FULL PARTS LIST HERE: https://www.dropbox.com/s/exlch5adck...vice.xlsx?dl=0

I have most parts in hand now, but I am going to start by getting the ECU setup and getting a basemap working. I'm only upgrading the injectors and fuel pump and then working on the tune. After that is in a good spot I'll pull the engine out.

Build details HERE: https://www.dropbox.com/s/exlch5adck...vice.xlsx?dl=0

Thanks in advance for any and all suggestions!

[K Simmonds]

You should be able to make 400whp with that set up, are you getting a K26 turbine housing for the Garret so it fits the RS2 manifold?

Injectors seem to be a bit on the large side, though mapped properly they'll be fine and give you future head room should you decide to go for a larger turbo down the line.

Oh yeah,

[coultl]

Good to hear! Yes, got the K26 housing. I went with the 1050 injectors and Walbro 450 so I have the option to run E85. I have limited access to E85 so I’ll probably stick to pump gas.

[coultl]

I'm running into an issue with air/vapor in the fuel return line. The Walbro 450 is in and car is running on the standalone EMU. I have a fuel pressure sensor installed and setup as well. I have tried two fuel pressure regulators, one is a new Bosch FPR, the other is OEM Audi.

Video here: https://youtu.be/dtREBtpOdu8

Runs great, everything seems perfect, except if it's been running for a little while (long enough to get fully warmed up) the fuel pump get's loud and the fuel pressure drops down from 4.1 bar to about 3.8 bar. I put a scope in the tank and found a ton of air that's coming from the return line (which is connected to the fuel pump basket). There's so much air that the pump seems to be pulling some of it in...creating the noise. I drained the fuel and return line is setup correctly. No issue there.

It seems like the fuel vapor is forming when the fuel exits the regulator (I can feel bubbles in the return line connected to the fuel rail if I pinch it). When I remove the cap while the car is running I get a woosh of air out of the tank, so the vapor seems to be too much more the evap system to handle. It only happens when the engine is fully hot...and the fuel is presumably hot too.

Any ideas?! I don't see anyone outside of diesels having this issue. Anyone else out there running a high flow pump like the 450 with the stock regulator?

Also, I designed and 3D printed a tool to remove the fuel pump carrier. Works great. Files here: https://www.dropbox.com/sh/bf2ltf0u8...oQx2E6nWa?dl=0

[K Simmonds]

I ran a Bosch 044 pump in my RS2+ spec 3B with a 7A 4 bar FPR and never encountered a problem like this. However I completely did away with EVAP system before I put the car on the road, I vented my fuel tank to the atmosphere via a ball valve in case the car ever ended up on it's roof.

I know it's a bit dodgy but could you try it with a fuel tank cap loose briefly and see if it still does it? Though I doubt it's the EVAP getting overwhelmed, plenty of people on here have retained it with high power set up's.

I like your fuel basket tool, very nicely done.

[newsh]

I’m running a 450 on my B5 RS4, no issues.

Have you tried it with a full tank of fuel, is the pump deep enough in the tank?

[K Simmonds]

Good idea John. Try it with more fuel.

[coultl]

Good to hear your 450 is working in your RS4. That uses the same fuel pressure regulator so that gives me confidence.

The pump is mounted low enough in the basket. It's just right. I have not run a full tank. That will help some but I'd like to figure it out at 1/2 tank first. The entire basket if fully submerged.

Here's what I think is happening. The fuel heats up over time and eventually gets hot enough to boil in the return line. It will not boil in the feed line due to the pressure. I think the hot fuel picks up a few more degrees in the rail and then once it's through the regulator it boils off some of that heat. That boiled off petrol vapor then travels back into the tank.

Here's the test that I think proves this theory. When I shut the hot engine off, let it sit for 5 ish minutes and then cycle the fuel pump the bubbled in the tank are so big that they are easily audible in the car. In that condition the fuel in the rail gets very very hot. (back seat is out and fuel pump access cover is off so it's a little easier to hear what's going on inside the tank)

The question is, is this normal? I would think so. Maybe I'm just overly worried about it and it's mostly normal. Maybe the high flow pump makes it more likely for those bubbles to reach the pump inlet, but the vapor bubbles must be there with a stock setup too.

Up Next:
- I am going to modify the fuel pump basket to eliminate or reduce the amount of return line fuel that is directed at the pump inlet. The return fuel path is a pretty interesting / highly engineered thing. I'd share photos but there's no way to get the assembly out of the tank.
- I am going to wrap the fuel rail (and maybe the filter too) to insulate it somewhat from the engine heat.

I'm tired of smelling like gas but hope to wrap up the fuel system soon!

[coultl]

Oh, quick PSA. After I set everything up I had a small leak in the factory fitting connecting the rubber fuel line to the rail. It was just due to the line being old, but I wanted to mention it because it's not a great spot for a fuel leak. Something to double check.

I replaced both lines with Earls 5/16" vapor guard hose.

[coultl]

While I'm sorting out the fuel issue I'll share a few things I've come across while setting the the ECUMaster EMU Black. The AAN base config is just a base... Also the AAN wiring harness takes a little work to get it right.

I ponied up for the classes at https://www.evans-tuning.com/ and they are awesome. Feels like I'm learning an entire new profession but it's great to have a teacher who knows their s$#t.

Base config:
- The trigger angle is set at 70 degrees. Not correct. Using a timing light I landed at 58 degrees. Sound right?
- The spark table looked way too aggressive to me. I backed the timing down a lot...like more than 10 degrees. Once I get some time on it I'll see where it needs to be.
- The knock engine noise table was way off.
- The IAT sensor calibration was off and I couldn't get it setup properly. I ended up pulling the thermistor out of a GM 25036751 and soldering it into the G42 sensor. Forgot to get a photo of this but I just snipped out the old thermistor and soldered in the new one. Getting the new one out of the sensor without damaging it took a little care. The metal on the G42 didn't want to take solder but adding some flux worked.
- Mostly, the base config has the triggers setup and a few other sensors. Everything else needs to be gone through.

AAN adapter:
- The AC clutch signal isn't wired so I added a jumper shown below. Pin 41 on the motronic to pin 35 the ECU Black. This allows the ECU to up the idle valve PWM when the AC clutch is engaged. I couldn't get the idle to work without this. Not sure why they didn't just do this in the adapter. (FOLLOW UP: this seems to be a 12V signal so I need to add a voltage divider as the ECU wants to see 5V)
- You need to wire in the wideband. There's good instructions so that's easy...except the wire colors were not correct with my sensor and I almost fried it. I should have double checked.
- The constant 12V power is also not wiring in through the adapter. This is strange bc there is constant 12V available on the motronic plug. I assumed this was because that's on a 5A fuse and the ECU needs more power? I ended up wiring the constant 12V power to the jumpstart post under the hood with a 15A fuse.

I will share my ECU config file, once it's in better shape.

NOTE: This ended up driving a +12V signal and the ECU only accepts up to a +5V input. I need to add a voltage divider to bring the voltage down.

[Tractor Dave]

Trying to puzzle this out
If the fuel lines have been replaced did someone delete the third line? Have you still got your carbon canister and is it blocked? There is a filter at the bottom that gets full of muck.

[K Simmonds]

Trying to puzzle this out
If the fuel lines have been replaced did someone delete the third line? Have you still got your carbon canister and is it blocked? There is a filter at the bottom that gets full of muck.

That's a good suggestion Dave, there's something funny going here and it's probably something very simple, he shouldn't be getting the symptoms he's experiencing.

[coultl]

The vent system is all there and operating correctly. I did some tests on it and all seems to be working correctly. The issue is still there when I remove the fuel cap so it’s not a issue with pressure in the tank.

When I have installed the pump I removed the original bump holder and filter. The new pump has the proper pump pre filter installed. The tank is very clean and even the filter I removed was clean. No issue with a clogged filter in the tank.

I’m trying a new option. The Walbro 450 outflows the oem FPR and I’m thinking that maybe there’s some kind of cavitation happening in the FPR. I’m going to install an Aeromotive FPR which is made for this kind of flow. I really doubt it’s going to make a big difference but it’s probably good to have a FPR that can properly regulate the pump anyway.

[Tractor Dave]

Interesting
I think you must have a leak somewhere. You pump is somehow pulling air into the system.
I know Newsh had issues with the connector pipe on his when he fitted one of these. Double check the connections between the cap and pump again. Apparently the one that came with the pump was very poor quality and had split.

[newsh]

Interesting
I think you must have a leak somewhere. You pump is somehow pulling air into the system.
I know Newsh had issues with the connector pipe on his when he fitted one of these. Double check the connections between the cap and pump again. Apparently the one that came with the pump was very poor quality and had split.

Yes the piece of hose they supplied with the Walbro was rubbish and split within a couple of days but that meant I had no pressure at the fuel rail and the car wouldn’t start.