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Walbro 255 vs DW301 on factory fuel pump wiring

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Old Nov 25, 2011, 05:46 PM
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Walbro 255 vs DW301 on factory fuel pump wiring

Cliff Notes of the Cliff Notes:
- Based on my testing, the DW301 and Aeromotive 340 provide no advantage over a Walbro 255 when using factory fuel pump wiring.
- A fuel pump rewire substantially improves the performance of a Walbro 255.
- With my rewire, I see no difference between a Walbro 255 and a DW301.

Cliff Notes:
On factory fuel pump wiring...
- DW301 flows about the same as a Walbro 255 without the pressure relief mod
- Aeromotive 340 flowed substantilly less than a Walbro 255 without the pressure relief mod

With a good quality rewire....
- A Walbro 255 does substantially better than on factory wiring. Fuel pressure at peak fuel demand went from 33 psi of pressure across the fuel injector with the factory fuel pump wiring to 40 psi pressure across the fuel injector with my rewire. AFRs went from 12.8:1 down to 11.4:1. That's a substantial improvement.
- I see no difference between a Walbro 255 and a DW301. In both cases, fuel pressure holds a steady 43-44 psi to about 6250 rpm, and then fuel pressure drops to about 40 psi by 7500 rpm.

Details:
This is a comparison between my three year old Walbro 255 (without the fuel pressure relief mod) and a new DW301. My Walbro 255 is no longer keeping up with fuel demands now that I've turned up the boost on my recently fortified motor, so I borrowed a uvambo's DW301 to do a head-to-head comparison on factory fuel pump wiring.

For the comparison, I did WOT 3rd gear runs on the same day within about 2 hours of each other. All I changed was the fuel pump. The fuel system is stock with the exception of the fuel pump, a Wilson fuel rail (monster ID), and FIC1100 injectors. I logged a bunch of items during the runs, but most importantly, I logged WB AFR, IDC, boost, and net fuel pressure across the injectors. This last item was made possible by having a Kavlico pressure sensor tapped into my Wilson fuel rail and running the pressure data into a spare ADC input on the ECU. The net fuel pressure across the injectors is the fuel rail pressure minus the boost pressure. With a factory fpr, the net fuel pressure across the injectors should be 43.5 psi at all times if the fuel system can supply enough fuel. This is my gauge for determining whether the fuel system can keep up with demand.

Onto the results. A plot of the Walbro data log is first, and the DW301 is shown second. Looking at the Walbro first, at about 4500 rpm the net fuel pressure starts drifting below 43.5 psi, and by 7000 rpm, the net fuel pressure is down to ~33 psi. The fuel pressure falling off like this means the fuel pump cannot keep up with demand. A result of this lack of fuel flow is the AFR drifting up into the high 12s.

Next plot is the DW301. As can be seen, the net fuel pressure, boost, and AFR curves are identical to that of the Walbro, so I see absolutely no fuel flow gain over the Walbro on stock fuel pump wiring.

December 11, 2011 Update
Chad at CBRD sent me an Aeromotive 340 to try. I had high hopes that it would do well, but it did substantially worse than both the Walbro and DW301. The car felt a bit funny getting into the throttle and misfired a few times, so I lifted at 6000 rpm. For some reason, there was a substantial amount of knock during spool that pulled a bunch of timing. AFR was fine at that point, so I'll chalk it up to the occasional wierd knock response. After that, the fuel pressure across the injectors dropped so quickly that AFR went north of 13:1 by 5000 rpm. I felt a bit freaked about that afterward, but hopefully E85 will live up to its reputation of being forgiving. The thought crossed my mind that the seal at the pump outlet was leaking, so I logged fuel pressure after shutdown, and it held just fine. Anyhow, it did so much worse than the other pumps, I half wonder whether I got a defective pump. After installing it, I had to prime it to get it to start flowing. Never had to do that before.

January 2, 2012 Update
Rewire is finished. The basis of my rewire is the STM rewire kit. Very nice kit. So far, I've only had a chance to test out my Walbro 255. What a difference a rewire makes. Fuel pressure at peak fuel demand went from 33 psi of pressure across the fuel injector with the factory fuel pump wiring to 40 psi pressure across the fuel injector with my rewire. AFRs went from 12.8:1 down to 11.4:1. That's a substantial improvement. Result is shown below. Next up (in a week or two) will be a DW301 and a Walbro 400.

January 8, 2012 Update
Finally got around to doing back-to-back testing of a Walbro 255 and DW301 with my fuel pump rewire. To make sure things were as 1-to-1 as possible, I redid the Walbro 255 test this weekend (and am using that data and plot for the comparison). Interestingly, I lost a few psi of pressure at the injector during the Walbro 255 retest this weekend. Perhaps my relays are breaking-in. Anyhow, the results of the testing with my rewire are again that the Walbro 255 and DW301 have nearly the same performance. Fuel pressure holds a steady 43-44 psi until about 6250 rpm, and then fuel pressure tapers to about 40 psi. Plots are shown below.

Wish I could say something better for the DW301. The only thing I haven't addressed in this study are the fuel pump sock and in-housing filter. The sock is black in color, but I see no sign of clogging when pulling the pump from the tank. Perhaps I'll make one last comparison between these pumps using a fresh sock. After that, I'll be testing the Walbro 400.


Walbro 255 on factory fuel pump wiring



DW301 on factory fuel pump wiring



Aeromotive 340 on factory fuel pump wiring



Walbro 255 with mrfred fuel pump rewire



DW301 with mrfred fuel pump rewire
Attached Thumbnails Walbro 255 vs DW301 on factory fuel pump wiring-drop-si-intake-m3_run3_walbro255.gif   Walbro 255 vs DW301 on factory fuel pump wiring-drop-si-intake-m3_run4-dw301-factory-wiring.gif   Walbro 255 vs DW301 on factory fuel pump wiring-drop-si-intake-m3_run1-ae340-factory-wiring.gif   Walbro 255 vs DW301 on factory fuel pump wiring-drop-si-intake-m8_run1-walbro-255-em-relay.gif   Walbro 255 vs DW301 on factory fuel pump wiring-drop-si-intake-m8_run2-dw301-em-relay.gif  


Last edited by mrfred; Jan 14, 2012 at 07:37 AM.
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Old Nov 26, 2011, 02:59 PM
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I can send u one. Lmk
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Old Nov 26, 2011, 03:17 PM
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interesting - i immediately ran rich from swapping stock fuel set up + walbro to dw301, but i guess that doesn't necessarily mean it's flowing more?
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Old Nov 26, 2011, 04:00 PM
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Interesting..

Here is my Walboro 255 with relief pushed in vs DW301 OEM wiring.

No tuning changes made, just swapped and logged. FYI the leaner af is with the DW301 pump. And on top of that, weather was 15 F warmer with the DW301



FP HTA Green with FIC Bluemax 1250 injectors .
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Old Nov 26, 2011, 04:08 PM
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Originally Posted by BluEVOIX View Post
Interesting..

Here is my Walboro 255 with relief pushed in vs DW301 OEM wiring.

... FYI the leaner af is with the DW301 pump. And on top of that, weather was 15 F warmer with the DW301 ...

FP HTA Green with FIC Bluemax 1250 injectors .
You're in the exact same power realm as me. So for you, the DW301 flowed less than a modded Walbro?

Last edited by mrfred; Nov 26, 2011 at 04:12 PM.
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Old Nov 26, 2011, 04:14 PM
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Great info MrFred. Not that I would switch between a walbro to a dw300 but it is good to know how the car reacts between the 2 pumps.
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Old Nov 26, 2011, 04:14 PM
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Originally Posted by CBRD View Post
I can send u one. Lmk
Thanks. PM'ed you.
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Old Nov 26, 2011, 04:25 PM
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I expected more out of my dw also. At 27psi boost on e70 I started running lean due to low fuel pressure. I rewired the pump and overran my stock fpr. I bought an aftermarket one. Set it to 45psi and now I'm out of fuel at 30psi. On a dynojet I'm at about 500whp. I'm going to try a walbro 400 pump next. In the long run I will need a double pumper though.
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Old Nov 26, 2011, 05:01 PM
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Originally Posted by mrfred View Post
You're in the exact same power realm as me. So for you, the DW301 flowed less than a modded Walbro?
Correct, DW301 ran leaner than the modded Walbro on my car. I did not do any flow testing just the a/f logging and also I used a multimeter to check the OEM line voltage and it was at a solid 12.5 volts minimum during WOT.

Since you already have a walboro and are willing to test pumps, why not mod it and compare it on your setup?
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Old Nov 26, 2011, 05:06 PM
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Originally Posted by wizzo 8 View Post
I expected more out of my dw also. At 27psi boost on e70 I started running lean due to low fuel pressure. I rewired the pump and overran my stock fpr. I bought an aftermarket one. Set it to 45psi and now I'm out of fuel at 30psi. On a dynojet I'm at about 500whp. I'm going to try a walbro 400 pump next. In the long run I will need a double pumper though.
Here is a 25 psi E85 comparison: Again, the leaner af is the DW301 no tuning changes made just drop in and log.

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Old Nov 27, 2011, 12:41 AM
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Good info right there...
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Old Nov 27, 2011, 06:30 AM
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this is exactly what we have been seeing too. the aeromotive pump on my back to back test showed identical to the DW300 too. when we dropped the buschur double pumper in, the car spit and sputtered it ran so rich
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Old Nov 27, 2011, 09:49 AM
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Originally Posted by BluEVOIX View Post
...

Since you already have a walboro and are willing to test pumps, why not mod it and compare it on your setup?
I guess I'll have to do that. I imagine I'll get the same results as you, but I'll have fuel pressure data. I think Chad is going to send me an Aeromotive 340 to try, so I'll wait until I receive that. Based on KevinD's comment, sounds like the Aeromotive will give the same result as the others. DB is setting me up with a Walbro 400 that I hope will be the final solution.
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Old Dec 11, 2011, 10:38 AM
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As a followup to the original comparison, I stopped by Cobb Tuning Surgeline on Friday, and the topic of fuel pumps came up because they were getting ready to tune a Subie with a custom fuel system that they just installed. I brought up my experience with the DW301, and their experience with DW301's on Subies with factory wiring mirrors what's been posted here - same or lower flow than a Walbro 255. They were quick to point out though that with a rewire, the flow rate of the DW301 improves.

So, I just finished installing an Aeromotive 340 sent to me by CBRD. Still on stock wiring. Should have test data by the end of the day.
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Old Dec 11, 2011, 11:09 AM
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Mrfred, Myles here...

If it means anything, i went from an intank 255 feeding an inline 255 with stock wiring, made 644whp/406tq @ 26psi with a 13.0 AFR out the top... did a rewire and put a 340 intank still feeding the inline 255 and made 660whp/417tq @ 26psi 13.0 AFR out the top... forgot to mention it's on E85

Not quite as good of a test as you though... In the end in my car it was worth about 20whp....

My car is at its extreme though, trying to pull 800hp worth of fuel through 1 fuel pump isnt helping..
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