Walbro 450 on stock fuel system?

[vtraudt]

Anybody running the large Walbro 450 on stock fuel system?
Is the stock return system capable of handling the high flow without creating back pressure (high fuel pressure) problems?

[CJ_]

Im running the walbro 450 with 630cc injectors and a 4 bar fpr, stock everything else. My inline fuel pressure gauge says around 60-65psi at idle. So there is some back pressure from the stock return line but not much.

[MetalMan]

Are you considering the version with higher-pressure relief valve?
F90000274

From what I've read it seems like the FPR and/or stock return line cannot handle the flow, and therefore fuel pressure (at idle, part throttle?) is elevated above the typical 4bar minus intake manifold pressure.

[vtraudt]

Im running the walbro 450 with 630cc injectors and a 4 bar fpr, stock everything else. My inline fuel pressure gauge says around 60-65psi at idle. So there is some back pressure from the stock return line but not much.

Is that with vac line to FPR disconnected?
Forgot: is 4 bar (58 psi) stock FPR on 2.7T?

I have a hint of rough idle (small hickups once in a while) and also some hickup in the transition from vac to boost part throttle. Not MAF, TB, N75 (all swapped as test to rule out). 550cc Bosch EV14.

[vtraudt]

Are you considering the version with higher-pressure relief valve?
F90000274

I ordered/installed Walbro TIA485-2 450 LPH Fuel Pump Kit

Mentioned/answered by seller: part number F90000267
(question was: Does this come with pump part number F90000267 or F90000274 (higher pressure version)?)
so 274 seems to be the higher pressure version, 267 the lower pressure?

[CJ_]

I believe 3-bar is stock (~43.5psi) and 4 bar is about 58psi. My 60-65 psi is with vac line connected, can't remember what its at with it disconnected off the top of my head, I can check later today though.

You are correct:
267 = lower pressure relief (~90psi iirc)
274 = higher pressure relief (~110psi iirc)


EDIT:

I have a hint of rough idle (small hickups once in a while) and also some hickup in the transition from vac to boost part throttle. Not MAF, TB, N75 (all swapped as test to rule out). 550cc Bosch EV14.

I actually have this exact same problem, but I have quite a bit going on with my car right now, figured it was due to a combination of things. Following this thread anyways..

[slow ride]

Im running the walbro 450 with 630cc injectors and a 4 bar fpr, stock everything else. My inline fuel pressure gauge says around 60-65psi at idle. So there is some back pressure from the stock return line but not much.

Do you run your own power line with a relay or is this powered by the stock wiring? 4 bar is stock also.

[vtraudt]

Do you run your own power line with a relay or is this powered by the stock wiring? 4 bar is stock also.

I run stock wires (in the hopes that the additional voltage drop caused by stock wire will 'slow down' the pump a bit and mitigate the overpowering of the return flow system.

A quick worst case:
58 psi stock, back pressure 70 psi. square root of pressure ration = 10% higher flow.

[slow ride]

You and I have the same reasoning Volker as I figured I was within the limits of needed flow for my setup using the stock wiring and didn't want to overrun the regulator. I have never measured my base pressure though, but you should see it in idle trim.

[CJ_]

Do you run your own power line with a relay or is this powered by the stock wiring? 4 bar is stock also.

I've run it both ways. I have my hard wiring and relay done with quick connects under the seat so I can swap back and forth easy. Had it like that cause I was diagnosing fuel trim issues awhile back.

Hard wiring gives you about 14v and and the stock wiring provides 12.5v. I have it hard wired now and my tuner just tuned it for the higher fuel pressure I believe.

If I remember correctly, hard wiring it added about 4-5 psi to idle pressure.

[ianwpb]

Is that with vac line to FPR disconnected?
Forgot: is 4 bar (58 psi) stock FPR on 2.7T?

I have a hint of rough idle (small hickups once in a while) and also some hickup in the transition from vac to boost part throttle. Not MAF, TB, N75 (all swapped as test to rule out). 550cc Bosch EV14.

Look into your MAP sensor.. I had a 3 bar MAP go out on me causing hiccups in low vacuum into boost, like what you are describing.

[killerkali]

I dont remeber the specifics, but my 267 walbro 450 , relayed on e85 had lots of excessive pressure at idle on my stock fuel system -injectors. I drilled out the stock 4 bar orifice and slightly helped, but it needs a better solution, my idle trims are weird i would assume due to this excess pressure.

[vtraudt]

[QUOTE=ianwpb;12010099]Look into your MAP sensor.. I had a 3 bar MAP go out on me causing hiccups in low vacuum into boost, like what you are describing.[/QUOTE
Will do. Easy enough.

[slow ride]

I dont remeber the specifics, but my 267 walbro 450 , relayed on e85 had lots of excessive pressure at idle on my stock fuel system -injectors. I drilled out the stock 4 bar orifice and slightly helped, but it needs a better solution, my idle trims are weird i would assume due to this excess pressure.

When you say weird what do you mean? Like bank to bank offset, etc?

[vtraudt]

Like bank to bank offset, etc?

I had bank to bank offset in the fuel trims. Changed one upper O2 sensor to fix it. Offset was 2-3% in the the trims. Now within 1%.

[julex]

http://www.audizine.com/forum/showth...=1#post9080791

Stock wiring will get quite a massive voltage drop with this pump. I am registering notable idle fuel pressure increase and I already have everything back to return line (which remained factory sized) custom build with dual-rail billet set up with dual return and largest orifice installed in adjustable FPR. I can only imagine how much pressure increase there must be in stock FPR with its pinhole sized FPR orifice..

[killerkali]

When you say weird what do you mean? Like bank to bank offset, etc?

Yes bank to bank offset but very minor, bigger issue was the excess pressure at idle. Not weird i guess lol

I've been thinking about trying this FPR out as it supposedly has a much larger orifice to return through. http://www.usrallyteam.com/index.php...roducts_id=673

[NOTORIOUS VR]

Pretty sure you can get a block off for the Bosch style FPR and then you can just run any aftermarket FPR. That should solve most issues @ idle.

But really, most people who have the big 450 and have been tuned on it should be ok. It's not perfect, but it's close enough when tuned not to cause any major issues.

[vtraudt]

Pretty sure you can get a block off for the Bosch style FPR and then you can just run any aftermarket FPR. That should solve most issues @ idle.
But really, most people who have the big 450 and have been tuned on it should be ok. It's not perfect, but it's close enough when tuned not to cause any major issues.

Currently still in the process of tuning. Wonder if idle hiccups and part throttle transition (vacuum to boost) are caused by high fuel pressure from the 450 pump; and if those issues can be 'tuned out' easily if done properly.

[1thenaton1]

bumping this with a similar issue, hoping OP or others might chime in.

I switched from a Bosch 044 pump setup that I had when tuning my car (stage 3 F21 550cc EV14) to the Walbro 450 after the 044 failed multiple times. I started noticing wacky negative fuel trims and searched for quite some time for a boost leak with no luck. Measured fuel pressure to find out it was similarly elevated to OP, 65 psi with line attached 70psi detached.

One thing i find odd is that my WOT fueling is spot on, according to logs with wideband O2. But the part throttle fuel trims are in the -10 to -15 range, sometimes as bad as -20. I replaced both primary O2 sensors with new to be sure they were not causing the problem, behavior remains the same.

[NOTORIOUS VR]

bumping this with a similar issue, hoping OP or others might chime in.

I switched from a Bosch 044 pump setup that I had when tuning my car (stage 3 F21 550cc EV14) to the Walbro 450 after the 044 failed multiple times. I started noticing wacky negative fuel trims and searched for quite some time for a boost leak with no luck. Measured fuel pressure to find out it was similarly elevated to OP, 65 psi with line attached 70psi detached.

One thing i find odd is that my WOT fueling is spot on, according to logs with wideband O2. But the part throttle fuel trims are in the -10 to -15 range, sometimes as bad as -20. I replaced both primary O2 sensors with new to be sure they were not causing the problem, behavior remains the same.

This isn't an uncommon issue on most stock fuel system cars (not just the B5 S4), the big Walbro's simply over power the regulator/return part of the system and you end up with higher than normal fuel pressure at idle/low load/vac situations.

To make it worse, fuel pressure will not follow a linear increase because of the regulator/return not able to deal with the volume. This makes tuning VERY difficult. It can be done but it's not easy and certainly you cannot use an off the shelf tune (or a tune that was made for a fuel system setup that doesn't have this issue) and expect good results. The tune will have to be made (tuned around) this inconsistency. Or you need to upgrade the regulator and return line to handle the volume and then everything should work properly again.

[1thenaton1]

Thanks for the reply. What would be a reasonable way to upgrade the FPR / return line?

and you end up with higher than normal fuel pressure at idle/low load/vac situations.

This is in line with my observation that fuel trims are more negative in daily/city/commute driving and closer to normal in "fun" driving.

I guess at .5 bar boost and above the fueling would be correct, and below that it would be increased.

[NOTORIOUS VR]

Thanks for the reply. What would be a reasonable way to upgrade the FPR / return line?

It is just as it reads really... delete the stock FPR, run an external FPR and increase the diameter of the return line to the tank.

[vavJETTAw36]

It is just as it reads really... delete the stock FPR, run an external FPR and increase the diameter of the return line to the tank.

+ new tank lid (or modify the stock) + Fuel injector rails

[julex]

Choke point #1 is stock regulator diaphragm nozzle seat/tube which is about 1/16"... not joking. You can drill it out to ~1/8 as the upper part it already 1/8"... for some reason they decided to make it is a shape of a funnel.

The return lines are adequate provided the FPR is not choking your system. I have zero fuel drift at idle with Walbro 450 wire directly to battery with 8AWG wire - so the worst case scenario for this particular problem - although I must say that I have aftermarket FPR which can flow buckets of fuel without any issues... But if you modify FPR the way I described above, you will alleviate the worst of the problems with stock FPR.


Left factory, right drilled out:



Size of factory hole...:

[CELison]

With an aftermarket FPR, I don't feel you need to increase the size of the return to the tank. I've seen guys have to do this, but only with twin pumps that are both running all the time. I have a 450, wired directly to the battery and don't have any issues on the stock fuel lines. A1000 FPR, 034 Rails, but stock lines from the firewall to the tank. The issue seems to be the factory fpr being the bottleneck.

[jaychen]

Choke point #1 is stock regulator diaphragm nozzle seat/tube which is about 1/16"... not joking. You can drill it out to ~1/8 as the upper part it already 1/8"... for some reason they decided to make it is a shape of a funnel.

The return lines are adequate provided the FPR is not choking your system. I have zero fuel drift at idle with Walbro 450 wire directly to battery with 8AWG wire - so the worst case scenario for this particular problem - although I must say that I have aftermarket FPR which can flow buckets of fuel without any issues... But if you modify FPR the way I described above, you will alleviate the worst of the problems with stock FPR.


Left factory, right drilled out:



Size of factory hole...:

I havent pulled a stock FPR apart. Can you remove that piece easily to drill it out?

[julex]

I havent pulled a stock FPR apart. Can you remove that piece easily to drill it out?

No. You'll need a drill press so that you can set up plunge depth on the bit to prevent hitting the diaphragm.

Somewhere at 1/2 to 3/4 of max depth the neck widens and that's why you don't have to drill all the way down to diaphragm seat to remove this obtrusion.

[jaychen]

No. You'll need a drill press so that you can set up plunge depth on the bit to prevent hitting the diaphragm.

Somewhere at 1/2 to 3/4 of max depth the neck widens and that's why you don't have to drill all the way down to diaphragm seat to remove this obtrusion.

Ok. I might cut my spare in half on the band saw first to verify this.

[rnagy86]

I think i've tried drilling the regulator already and that did not help much. Since then I am using a radium adjustable FPR and that can do the job properly.
I had a fuel pressure sensor with the oem FPR as well and the worst was really light load, pressure did not even go below 4.2 bars.
This fucks everything up tuning wise, as your dead times will be completely different depending on if you are at idle or light cruise.

If you cut an oem FPR you can try to make the orifice bigger, maybe i did not do it all the way, I can't really recall, but make sure you have a *digital* pressure
sensor so you can compare MAP and fuel pressure.

[1thenaton1]

A1000 FPR, 034 Rails, but stock lines from the firewall to the tank. The issue seems to be the factory fpr being the bottleneck.

Could you please post a pic of this setup? Not very familiar with aftermarket FPRs - is a fuel rail upgrade required? I am currently just running 91 so stock fuel rails seem fine, but I do want to maintain headroom for running E85 in the future, hence the pump upgrade in the first place.

[vavJETTAw36]

Could you please post a pic of this setup? Not very familiar with aftermarket FPRs - is a fuel rail upgrade required? I am currently just running 91 so stock fuel rails seem fine, but I do want to maintain headroom for running E85 in the future, hence the pump upgrade in the first place.

What are your power goals? Plenty of folks, including myself, making 600+whp on factory fuel system. 1000cc injectors @92% IDC

[CELison]

Could you please post a pic of this setup? Not very familiar with aftermarket FPRs - is a fuel rail upgrade required? I am currently just running 91 so stock fuel rails seem fine, but I do want to maintain headroom for running E85 in the future, hence the pump upgrade in the first place.

Don't have any pics, but I'll describe it. Areoquip line from firewall to the pass side fuel rail (034), then another section to the driver side rail in series, then from the driver side rail to the FPR (A1000) then from the fpr back to the firewall. All stock lines from the firewall back to the tank.

[1thenaton1]

What are your power goals? Plenty of folks, including myself, making 600+whp on factory fuel system. 1000cc injectors @92% IDC

Nothing crazy, just a daily driven stage 3 setup with custom tuning, maybe 400whp. I guess my question was really can you run an external FPR with stock fuel rail. Would gladly take a recommendation on which FPR as well. Thanks

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[christianb5s4]

What are your power goals? Plenty of folks, including myself, making 600+whp on factory fuel system. 1000cc injectors @92% IDC

I'm in that camp. Running EV14 injectors (OEM Porsche GT2 1266cc), stock rails, stock FPR, stock lines, and high pressure relief Walbro 450. I also supplement with methanol injection but the fueling was not maxed out prior to methanol, although I am making more power now.

[vavJETTAw36]

Nothing crazy, just a daily driven stage 3 setup with custom tuning, maybe 400whp. I guess my question was really can you run an external FPR with stock fuel rail. Would gladly take a recommendation on which FPR as well. Thanks

Sent from my SM-G930V using Audizine mobile app

yea theyve got an adapter for lack of better terms that goes in the factory location and then you can run an aftermarket FPR.

https://www.summitracing.com/parts/t...SABEgKoUvD_BwE

Or go with an adjustable factory type. 034 sells that one.

https://store.034motorsport.com/fuel...k-fitment.html

[CELison]

If you do put a factory style fpr in, I would put a gauge on it so you can see your actual fuel pressure. As shown above, there are plenty of guys making good power on stock rails. But I have heard that the factory rails sometimes starve bank 2. I don't have any real world data to back that up, just what my tuner told me.

[1thenaton1]

I'm in that camp. Running EV14 injectors (OEM Porsche GT2 1266cc), stock rails, stock FPR, stock lines, and high pressure relief Walbro 450. I also supplement with methanol injection but the fueling was not maxed out prior to methanol, although I am making more power now.

It would be interesting to see your fuel pressure at idle and also your fuel trims on part throttle if you care to add some addtl data to this discussion

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[vavJETTAw36]

It would be interesting to see your fuel pressure at idle and also your fuel trims on part throttle if you care to add some addtl data to this discussion

Sent from my SM-G930V using Audizine mobile app

It's probably like mine, ~68/61 psi. not an issue since i am custom tuned.

[julex]

yea theyve got an adapter for lack of better terms that goes in the factory location and then you can run an aftermarket FPR.

https://www.summitracing.com/parts/t...SABEgKoUvD_BwE

Or go with an adjustable factory type. 034 sells that one.

https://store.034motorsport.com/fuel...k-fitment.html

Both of these items share the same problem... the adapter looks like a very small port just like stock FPR. The 034 looks a little larger but the bottom line is there simply isn't enough diameter left on the tube that needs to go into a very small port to have the orifice of the size capable of flowing the volume of fuel needed for pressure to not peg at 60psi+.