Walbro 525 wiring

fmorelli

Colonel
Staff member
Aug 11, 2017
2,146
Virginia
Hey guys ... some folks are starting to run the Walbro 525 which I believe is the Hellcat pump. Looking at the E89 Z4 TIS, it looks like a 20A fuse feeds the EKPS on a 2.5mm cross-section line (14AWG) and the EKPS then feeds the LPFP with a corresponding 2.5mm line. If my reading of the TIS is correct, 14AWG is generally a 15A line that, in short runs, some run it at 20A. So that would max that line out. Correspondingly, the Walbro 525 diagram below seems to indicate that the pump loves to draw as much as 24A and full hump. The quandary is self-evident - does one need a 25A feed on both wires (to EKPS and to LPFP) or ... ?

Did I get something wrong? Thanks!

Filippo

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InnovativeAuto

Specialist
Mar 14, 2018
56
With a pump like that I think it’s best to just hardwire it IMO. 10 gauge from the battery with a 25-amp fuse. Stock wiring to activate the relay. Nice to see an OEM pump flow that much

What kind of power are you looking at? I’ve heard the Z4 pump is good for some high hp. I’m hoping with upgraded turbos I won’t have to mess with it but will see...
 

Erichale77

Lieutenant
Nov 14, 2016
773
Clearwater, FL
On my set up I was instructed to wire my 525's , one to a hobs and the other to an ignition and my 450 to the EKP because it draws less amps. Not sure on wire gauge or relay type but I will ask.
 

fmorelli

Colonel
Staff member
Aug 11, 2017
2,146
Virginia
With a pump like that I think it’s best to just hardwire it IMO. 10 gauge from the battery with a 25-amp fuse. Stock wiring to activate the relay. Nice to see an OEM pump flow that much

What kind of power are you looking at? I’ve heard the Z4 pump is good for some high hp. I’m hoping with upgraded turbos I won’t have to mess with it but will see...
I'm not running that but two buddies are - Fuel-It is now supplying the 525 as I understand it. One Z4 friend is on Pure's the other just installed GC Lite 2.0's. Z4 stock runs a different LPFP logic. The crappy part is the LPFP install is underneath the car (I could say more but I won't).

People say you can get by with a Z4 stock LPFP and E mix (eg E50).

Thanks for the feedback ... seems to confirm what research I did. Bigger wire direct, relay to switch on. Z4 guys reading this thread - there is often a spare opening in the power distribution block to do a nice, clean power install. See the first half of this post on my build thread. I suggest 10AWG and 30 amp fuse for a smidge of headroom given the Walbro 525 specs ... which happens to be exactly what I did in that build thread for different use.

Filippo
 
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JimmyNeutron

Lurker
Feb 11, 2018
20
I definitely wouldn't try to run a 525 off the EKP as the current draw under transient conditions would likely overload/damage the controller... the 450 can already push the EKP to the limit. I used 10AWG Tefzel wire sheathed in Raychem RW-200 for my Hobbs triggered second 450 - no issues so far.

I'd like to run twin 525s but I'm waiting for Torqbyte to release their new CANBus controller before I install them. From what I understand, the main advantage of their controller is that it doesn't require your second pump to be triggered by a Hobbs switch but instead it controls both pumps at the same time. On their Instagram, they say they've been running twin 525s without any issues but they have a few more tweaks to be made to the controller's CAN protocol. From the photos they've posted, it looks like a larger fuse and heavier wiring harness are included. No solid ETA on the release, as it's been "a few weeks away" since March of this year. They just released the VW version of the controller so hopefully it won't be much longer.
 
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jts1981

Private
Jan 29, 2018
29
NYC
With a pump like that I think it’s best to just hardwire it IMO. 10 gauge from the battery with a 25-amp fuse. Stock wiring to activate the relay. Nice to see an OEM pump flow that much

What kind of power are you looking at? I’ve heard the Z4 pump is good for some high hp. I’m hoping with upgraded turbos I won’t have to mess with it but will see...
I'm one of the buddies Filippo mentioned.

A little background. We installed the 525 pump during our GC Lite install a few weeks ago, not knowing of the amperage issue. At that time I only pulled a code when getting into boost, but not during regular driving. The code at the time was just to be careful and see dealer right away.

After the wiring upgrade + relay + fuse as you mentioned we received an instant code warning of fuel pump failure and potential cutting power.

Turns out the ekp needs to see variable load to adjust fuel. The relay was not sending the info it needed. Sorry for my lame description, I'm not versed at all at electrical stuff so I'm trying regurgitate what my mechanic said.

After some discussion with our other buddy, the other Z4 with a 525 pump we decided to just run the 10 gauge wire from the pump directly to the ekp, and swap the oem fuse with a 30a instead of running the relay. He's running his 525 feeding a PI and Pure stage 2 turbos at 28+ psi and I think he only blew a fuse once.

Its not ideal but at least its a hair safer that before.

We feel the only real solution after this is a better ekp unit, or some how reprogram it to accept a high load.

I attached some pics of the from the install, which was pretty straight fwd (I should have realized at this point we would be fucked...NOTHING for the z4 goes according to plan...fucking hell...), and pics of the codes from the scanner.

Anyways just wanted to let the forum know whats up, and also thank you for the advice. It was a great idea. Unfortunately BMW likes to make our lives hell.
 

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sleet142

Private
Oct 6, 2018
30
I just did a rewired fuel pump to a MSD solid state relay. The ekp is the power activation (pwm) and a clean 12v source from the battery goes to the fuel pump.
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jts1981

Private
Jan 29, 2018
29
NYC
I just did a rewired fuel pump to a MSD solid state relay. The ekp is the power activation (pwm) and a clean 12v source from the battery goes to the fuel pump.
Is this for primary or secondary? I'm running 525 in bucket as primary. The ekp needs to variable voltage so it can adjust the speed from my understanding.

If primary, how are you not getting codes?
 

sleet142

Private
Oct 6, 2018
30
Primary. I get the typical plausibility code. But the ekp uses pulse width modulation to vary the voltage. So instead of it cycling the fuel pump directly, it now cycles the solid state, which cycles the 12v from the battery.

I have noticed that when idling or crusing around that the pump is at 89 psi, which means the ekp is just about as low in its duty cycle that it can go. But when I am in boost, the car targets 70ish psi like it should.
 
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sleet142

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Oct 6, 2018
30
Oh. And do not use a mechanical relay on the primary unless you want the pump to run at 100%. A mechanical relay cannot be pwm'd reliably.

Another note, with the MSD solid state, there are multiple channels. So if someone wanted to activate a second pump with a hobb switch you would wire it in as the activation, and run a line out to the pump.
 
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fmorelli

Colonel
Staff member
Aug 11, 2017
2,146
Virginia
hopefully its the fuse first. need to keep a philips and extra fuses in the car now. womp womp woooooomp
I'm afraid not. You have to increase the fuse at the fuse box, so the EPK is no longer protected. At least I have that concern for you.

Given the lpfp is handled completely different for the Z4 vs. Any other n54, I'm curious if the issue with wiring has to do with the control approach on the Z4, and doesn't cause a problem for the other n54 platforms?

Filippo
 

jts1981

Private
Jan 29, 2018
29
NYC
yea we used a mechanical waterproof relay from Hella...

interesting about the solid state relay. So it gives the ekp the variable loads it needs, and you attached a higher fuse?
 

sleet142

Private
Oct 6, 2018
30
The fuse for the EKP stays stock. There is a fuse on the wire that goes from the battery to the solid state relay. 30A fuse considering the Walbro can pull up to 24ish amps. (This can also depend on the total current draw from the 4 channels that the solid state has connected). So you could also add a fuse on the wire to the fuel pump from the Solid state.

A mechanical relay, when pulse width modulated, cannot make the physical contact and release that contact at the duty cycle that the EKP runs at, so it will stay closed and run your pump at the full 12v from the battery.

A solid state relay, having no mechanical parts, can be activated and deactivated very quickly. Thus why the EKP can apply a duty cycle to it (12v from ekp on and off quickly), and vary the now 12v from the battery to the fuel pump.

make sense?
 
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fmorelli

Colonel
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Aug 11, 2017
2,146
Virginia
The fuse for the EKP stays stock.
I agree. For two reasons.
  1. EPK innards are designed for no more than 25A service. Increasing the fuse to the EPK puts it in jeopardy.
  2. With auxiliary LPFP power wiring, the EPK no longer feeds ~20A max juice to the LPFP. Instead the EPK LPFP output wire goes to the new auxiliary relay, and turns the relay on/off as needed to all power to go through the relay to the LPFP. In essence the EPK becomes a low amperage device.
There is a fuse on the wire that goes from the battery to the solid state relay. 30A fuse considering the Walbro can pull up to 24ish amps. (This can also depend on the total current draw from the 4 channels that the solid state has connected). So you could also add a fuse on the wire to the fuel pump from the Solid state.
I would say this is a mandatory add - one wants a 30A fuse inline between the battery and the relay.

A mechanical relay, when pulse width modulated, cannot make the physical contact and release that contact at the duty cycle that the EKP runs at, so it will stay closed and run your pump at the full 12v from the battery.

A solid state relay, having no mechanical parts, can be activated and deactivated very quickly. Thus why the EKP can apply a duty cycle to it (12v from ekp on and off quickly), and vary the now 12v from the battery to the fuel pump.
This is where I am lost. Weak on how the PWM electronics are working, and what the EPK is trying to measure (that causes the codes registered in the DME).

Let's go back to what @jts1981 said, "Turns out the ekp needs to see variable load to adjust fuel. The relay was not sending the info it needed. Sorry for my lame description, I'm not versed at all at electrical stuff so I'm trying regurgitate what my mechanic said."

Well as I understand it, the EPK is now just a dumb switch. It will never see LPFP pump load since it no longer provides power to LPFP, it just simply sends signal to a relay. So if the above statement from @jts1981's mechanic is correct, it would seem irrelevant what relay there is as the EPK would never see the LPFP power in either mechanical or solid state case. And again, this is for primary LPFP signal from EPK.

If you could elaborate? I likely misunderstand something or have an incorrect conception. Thanks!

Filippo
 
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jts1981

Private
Jan 29, 2018
29
NYC
please refer to my pics of the scanner for what I mean about the car not reading the fuel pump, and the other pics showing phase c, phase b....

note these were taken when the hella mechanical relay was used.

we decided to abort that as mentioned in my original post...
 
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