DIY 535 LPFP Discussion/Tester Thread

PFS

Corporal
Nov 19, 2018
102
E6X Team,

I've been asked by a few persistent guys when I'm going to stop goofing off and spending my time chasing the wife around, and come up with a solution for those of you who want some more fuel for your N54 powered 5 series without spending a ton of cash.

Ok ok, I'm on it. Or at least I've started the process. I picked up a brand new bosch pump and after a thorough disassembly, began testing on the bench. Initial results are surprising to me.

Anyone here interested in trying out some solutions? If so, let me know what your setup is, turbos, boost, dyno is good, if you have a LPFP upgrade -which one and did it help your logs/etc.

This is a longer burn project, looking for experienced DIY guys. I understand it's winter in most of the country, that's fine, but I want to get this rolling starting with gathering more info and possibly identifying a tester.

Chris
 

nitemare

Private
Nov 5, 2016
37
Jax, FL
Thanks guys, I'll do some more testing this weekend. đź‘Ť
There are a couple vendors who have solutions already and also a few custom one off ones. Having one 450 run off the EKP and the second triggered via Hobbs or the like is probably the #2 best solution. #1 is using the BPM4 EKP controller to power and run both fuel pumps......but that option is expensive.

I have a custom dual 450 one off....plus all new feed, return, FPR.
 

JuniorB

Sergeant
May 9, 2017
336
Rhode Island
Im in process of doing twin AEM 340 pumps in a M5 bucket. I went out of the norm with running the 450 Walbro, with its high amp rating, and found the AEM right behind that pump at 65-75psi. Although it takes fine to put the bigger pumps in, they’ll work with the stock screen. It’s still way under a DW400 bucket.
 

iitsD

New Member
Apr 19, 2019
6
California
I'm in for more fueling options. It'd be awesome if there was something similar to Radium's FHST. Seems like a really clean solution but sadly no love for the E60.

VTT stage 2 turbos @ 26-27psi
Fuel-it Stage 2 kit running E40 mix
also using 50/50 water/meth injection
 
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PFS

Corporal
Nov 19, 2018
102
Hey guys, thought I'd post a couple of the findings so far.

First, a little background. Normally when testing pumps I test the assembly, meaning the electrical pump itself in the bucket/assy as per the factory, with factory or upgraded venturi's etc. The reason why is end use assembly matters more than pc/part comparisons, BUT... we need pc/part comparisons to make good decisions on building that final assembly.

Before we get to that point though, let's take a look at what we're working with internally, pump wise on the 5 series. I grabbed a new Bosch 5 series pump assembly, and first things first, pulled 'er apart to see what the guts were like. Pretty stout! Tossed her in the 'ole reliable portable pump test bench (made 'er on a shop cart) and this is what I got.

535 flow.jpg


You could call that 1.25 GPM minus a little. Voltage was 13.5V, current draw was about 16 Amps. Remember this is the pump itself, straight connection directly off the pump (-6 line on the OEM pump hose barbs).

There are normal fluctuations with pumps, you'll see some run a touch stronger than others. Some of this is wear in, some of it is unit-to-unit inconsistencies. By and large they all fall within a fairly tight performance window, but this is one of the reasons why we validate pump assembly performance on every single pump, before anything is shipped -no exceptions.

So let's take a look at the venerable Walbro 450. Commonly used as an OEM pump upgrade on the BMW platforms, we know on the 3 series N54 (and some N55) powered vehicles the 450 outflows the stock pump by a massive amount. Seems like a shoe-in for an upgrade on the 5 series too -let's compare it pump-to-pump and see what a brand new 450 puts down -remember, this is -6 line attached directly to the hose barbs on the pump outlet, no fittings, no goofiness, just pure pump output on our test stand:


450.jpg


I'd still call that 1.25 GPM, only I wouldn't say "minus a little". Voltage was 13.5V, current draw was about 19 Amps.

The competition markets the 450 as an upgrade on a 5 series, but I don't see it. Less than 0.1 GPM difference, draws 3 Amps more, and a complete package out the door (with no core) is close to $900 for the mods done to a pump you can pick up new from FCP for under $200 shipped. The 450 does, however, slightly outflow the stock pump, and remember the stock pump isn't "officially rated for E85 use". Personally? Not impressed and neither should you be. Not many people have test stands to validate performance on; I spent a large part of my career as a test engineer, so while I'm comfortable with some seat-of-the-pants engineering, it's all a bunch of bullshit if you don't get real world performance out of it. The 450, god love it, comes up short -not because the 450 isn't a great pump, but because the 5 series pump is so much better than expected.

The 5 series pump assembly is a bit of a pain in the ass to take apart. Granted, I've only done one (and it IS doable) but for the guys who want a reasonable LPFP upgrade, a 450 is absolutely NOT the key to victory; save your money, it's a TERRIBLE value to put a 450 in a 5 series. Don't despair though, we have plenty of great options to keep you guys happy with fuel.

One final note about flow numbers; these are similar to dyno numbers in that it's difficult to directly compare one setup to another pump test bench elsewhere, so don't get too bogged down in the direct numbers, just understand that if I put a pump on and it flows X GPM, swap pumps and it flows 2X, that same delta is going to be on any other test bench.

Our pump stand numbers are good; don't bother with a 450 in your 5 series. We'll have more solutions for you soon. :)

Chris

Edit: Someone requested a chart to outline the differences. Using advanced technology, I did such a thing.
IMG_7710.jpg
 
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marseille

Specialist
Jul 1, 2019
53
Any idea what pump is in my Spool Performance Stage 2 LPFP? It's supposed to: "flow more than double compared to the stock pump"
 
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PFS

Corporal
Nov 19, 2018
102
Any idea what pump is in my Spool Performance Stage 2 LPFP? It's supposed to: "flow more than double compared to the stock pump"
No clue, I'd ask them what actual pump they they used and how they came to those flow numbers! I'm sure to be able to state "twice the flow" they have some sort of flow bench to validate that. :)

Remember, anyone can throw a pump in a bucket and consult the manufacture to shout out pump capability numbers, but this isn't pump assembly flow capability. What I mean is, a walbro 450 flows about 450lph at 13.5V and 30psi. This has nothing to do with what you get at the actual engine, after it bleeds off some to a venturi, goes through several fittings, the driver's side regulator & rigamarole, snakes through the lines and makes it to the HPFP inlet. We CAN use it for pump-to-pump comparisons, assembly-to-assembly comparisons, and for ballparking appropriate fuel system capability (ROM, or rough order of magnitude).

All the above niceties being said, if we round the OEM pump down to 1.24 GPM (unfair to the OEM pump, remember this is on my stand), and convert to liters per hour we get about 280 on my test bench (13.5V/72 psi). To give twice the flow, that'd mean that pump has to output 560 liters per hour, which unfortunately per the chart below is going to be a TALLLLLLLLLLL order for any single current pump to do, even the big-mama brushless walbro.

In other words, don't believe the hype, do believe the test results.

(again, my test bench vs. another... so don't get too bogged down in actual flow numbers on different test setups!)

pump_test_flow.jpg


Chris
 

typedRew

Sergeant
Feb 25, 2019
398
These results make sense of why my buddy with FBO and E60 blend can run it just fine on stock fuel pump in his 535 wagon.

Looking forward to seeing what you offer, because hes still trying to get a LPFP for his and a 450 does seem like a waste.
 
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JuniorB

Sergeant
May 9, 2017
336
Rhode Island
I was on my bench playing with my dual pumps in a m5 bucket, and saw this. I’m surprised at the results, seeing that a Walbro flows 450 lph. I didn’t chose it either for the high amps it pulls, so I went with AEM 340. Real street done a huge segment on in take pumps, and what there rated at with pump, and e85. Looking at the psi between 65-70, were these pressures need to be, i wasnt convinced a 450 would dominate for the extra amps it needed to sustain our pressures. I’ve pulled both pumps from the twin m5’s, and a single, and found no info on there flow numbers. I’m also seeing that, these twin 340’s are to big in this bucket, so I’ll go back to a single 340, and go from there.
 

JuniorB

Sergeant
May 9, 2017
336
Rhode Island
I was looking at real oem, the e60 is listed at 200 lph, so if the 450 is rated at, 450 lph, that would be double the flow. The other option that’s never talked about, is a bap.A lot of factory cars run these, the Demon runs, twin baps, with of course twin 525s !
 

PFS

Corporal
Nov 19, 2018
102
These results make sense of why my buddy with FBO and E60 blend can run it just fine on stock fuel pump in his 535 wagon.

Looking forward to seeing what you offer, because hes still trying to get a LPFP for his and a 450 does seem like a waste.
Yep, a new walbro really isn't enough of an upgrade over a new OEM pump to justify it. Now a 295....
 

PFS

Corporal
Nov 19, 2018
102
I was looking at real oem, the e60 is listed at 200 lph, so if the 450 is rated at, 450 lph, that would be double the flow. The other option that’s never talked about, is a bap.A lot of factory cars run these, the Demon runs, twin baps, with of course twin 525s !
The e60 is probably rated at factory fuel pressure. I didn't look up the rating, I just tested instead. The 450 won't do 450 lph unless it's at very low pressures. All I care about is what pumps flow on my test bench with 13.5V and reasonable current draw. It's convenient to use a stock EKP, and it's useful to have significant flow margin available. I think these are reasonable goals. :)

Chris
 

JuniorB

Sergeant
May 9, 2017
336
Rhode Island
Agreed, I just happen to look it up seeing I was into the buckets. I wasn’t thrilled about the 450s amperage, looking at the higher pressures in the 65-70 range, I liked the aem better
 

JuniorB

Sergeant
May 9, 2017
336
Rhode Island
I was searching for an alternative way to piggyback my second fuel pump, came across an idea to use what Fuel It offers for the 335. They offer an adapter for the bucket, and a bracket off that that holds a second pump, so it just ties into a stock pump.I emailed to try and get one, the reply back was no, won’t sell it . Imagine that....
 

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