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 Post subject: Stock Fuel Pump Limits - Feedback welcome....
PostPosted: Wed Aug 30, 2017 11:16 pm 
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I Say: Plan for tomorrow,Live for TODAY!
Vehicle: MY12 XT

Posts: 30
Location: Sydney
Hi There,
I have been struggling with working out when to upgrade my fuel pump (Subaru Forester XT 2012) 20psi Tune. There are quite a few supporting mods: VF52 with Blanket, UEL Headers, Uppipe with blanket, 3"TBE, 3"Racing CAI, PSR Intake, Company 23 Anti-surge 3 Port EBC, large TMIC, GFB Recirc BOV, AOS. Stock Fuel Pump and Injectors.

Everything I have read, says that they should be fine for my set up, but the logs say different......

Sadly I had noticed the Injector Duty Cycle hitting 100% on a recent log..... So I needed to determine why. So I tried googling ( a lot) to determine whether I was fuel starved, with no answers to be found. Especially that if I had an upgraded fuel pump, the IDC would reduce, as the correct fuel to target the correct AFR. As IPW would reduce to meet the target AFR.

Sooooo I thought I would model fuel flows, so basing a BIG assumption that the stock fuel pump 155lph, has the same dynamics as a DW65c (265lph), same dynamics but lower flow. That is they decrease in performance as flow requirements and fuel pressure needs to be maintained with increased manifold pressure.
So some basic parameters: Stock injectors flowing at 100% require 136lph - So initially this looks OK - right ? But No - this is where I would like some feedback. Constructive of course ! So be nice.

So I put together some numbers, these are model to a similar dynamic to the DW65c - As manifold pressure increases, flow rate needs to increase to support the maximum flow and battle the manifold pressure pushing back! Simple right.
I added some intermediate columns to get a more granular calculations.

This is what I have found, I hope it makes sense. I have attached a picture of the spreadsheet and supporting data to show what I have found.

The calculations are based around hitting limits, there are a large number of variables involved, but I was looking to determine what limits would be hit.

I have included the DW65c data to see whether it would support my targets. Please note - I was trying to work out the flow needed to MAX out my injectors (yes - I know you should only target 80%, I am looking at limits and working back)

Please note that this is a best case scenario, in that the DW65c I would expect be engineered better and would degrade better that stock, so the stock line is definitely best case, especially in high load situations.

Remember that the calculations assume no other limitations that would inhibit maxing out the injectors - whether it is the right thing to do or not.

Conclusion:
So the data and associated graph shows that if I was driving the injectors to 100%, anything over 14psi, the fuel pump would struggle to keep up. Therefore an upgraded fuel pump, theoretically reduce my IDC. Since the FPR can be sustained at the correct level as flow and manifold pressure increases, it clearly shows that the stock can not support the flow rates needed for a 100% IDC (if I want to go that high).

Thoughts or feedback would be appreciated.


Attachments:
Fuel Pump Graph.jpeg
Fuel Pump Graph.jpeg [ 178.06 KiB | Viewed 41 times ]
File comment: Data & Graphs.
fuel pump calcs.jpeg
fuel pump calcs.jpeg [ 278.22 KiB | Viewed 50 times ]

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Silver Fox !
VF-52 with Lava turbo blanket, 11psi Wastegate Spring, 3 port Company23 Anti-Surge BCS, 3" Mishimoto CAI, PSR Intake, Headers & Up-pipe in Lava wrap, Large TMIC, GFB BOV, Grimmspeed AOS, 3" TBE, Front & Rear Whiteline Heavy Duty Anti-Sway bars, KiddoRacing 18psi Tune for 98, Short shifter - 200kw atw
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 Post subject: Re: Stock Fuel Pump Limits - Feedback welcome....
PostPosted: Wed Aug 30, 2017 11:50 pm 
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I Say: Car mods are like OddBodz, you got to collect them all! -------------------------------------
Vehicle: MY05 STi swapped sled

Posts: 17175
Location: Spearwood Perth WA
Really. Its not like a fuel pump is a high value item. Certainly cheaper than replacing melted pistons. If there is any doubt its not upto tast then i wouldnt hesitate to fit something bigger.

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 Post subject: Re: Stock Fuel Pump Limits - Feedback welcome....
PostPosted: Thu Aug 31, 2017 12:12 am 
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Vehicle: MY08 XT (SH)

Posts: 743
Location: Brisbane
I have a spare low-km AEM 320-E fuel pump (E85 compatible) sitting around if you want to experiment.

It flowed too much for my use (it couldn't return enough fuel at the 100% setting) but that may not be an issue for you.

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 Post subject: Re: Stock Fuel Pump Limits - Feedback welcome....
PostPosted: Thu Aug 31, 2017 10:12 am 
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I Say: Plan for tomorrow,Live for TODAY!
Vehicle: MY12 XT

Posts: 30
Location: Sydney
Bram - absolutely agree ! I just needed to find the root cause, as there is no real data to show when to upgrade.

Yowie - I do appreciate the offer - I already have a dw65c in transit.

I will update the thread after upgrade to confirm what I believe to have found.

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Silver Fox !
VF-52 with Lava turbo blanket, 11psi Wastegate Spring, 3 port Company23 Anti-Surge BCS, 3" Mishimoto CAI, PSR Intake, Headers & Up-pipe in Lava wrap, Large TMIC, GFB BOV, Grimmspeed AOS, 3" TBE, Front & Rear Whiteline Heavy Duty Anti-Sway bars, KiddoRacing 18psi Tune for 98, Short shifter - 200kw atw


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 Post subject: Re: Stock Fuel Pump Limits - Feedback welcome....
PostPosted: Mon Sep 04, 2017 11:25 am 
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I Say: Plan for tomorrow,Live for TODAY!
Vehicle: MY12 XT

Posts: 30
Location: Sydney
Update:
Sooooooo......... Firstly, while I was in there doing the install of the new fuel pump, I thought I would also change the filter, which is in the tank (the fuel pump plus into it).
I found that there has been a contamination of my fuel, there was a lot of rust in the bottom of the bucket of the fuel pump, the sock that is attached to the fuel pump was also filled with fine rust particles. To say that I was horrified is an under statement. It was due for a filter change in November anyway (5 year service). I have been using BP Ultimate 98 for the last 5 years, so to say that a premium fuel was contaminated was doubly shocking. Since I use only 2 of the local stations since purchasing, I reported it immediately.

On the up side, from 4K to redline has a very good smooth hard pull. So right now very happy with the results of the upgrade. Very happy. My only concern now, is whether the injectors need cleaning........ It stumbles less, compared to before upgrade and new filter, dropping to idle, so I just may need to be a little patient while it flushes out. Still much better response and pull. A slight change in IDC, but I need to wait a little longer to get the crap flushed to know the exact changes.

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VF-52 with Lava turbo blanket, 11psi Wastegate Spring, 3 port Company23 Anti-Surge BCS, 3" Mishimoto CAI, PSR Intake, Headers & Up-pipe in Lava wrap, Large TMIC, GFB BOV, Grimmspeed AOS, 3" TBE, Front & Rear Whiteline Heavy Duty Anti-Sway bars, KiddoRacing 18psi Tune for 98, Short shifter - 200kw atw


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 Post subject: Re: Stock Fuel Pump Limits - Feedback welcome....
PostPosted: Thu Sep 07, 2017 8:03 am 
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Vehicle: MY06 XT

Posts: 579
Location: Sale Vic
With the bigger pump and a clean filter, your MAF scaling at the top end will probably need adjusting. Until then you'll probably find it is running rich now.

This is assuming it was properly scaled for the old pump as the pump was probably always struggling. I saw AFR go about 0.5 richer at the top end for the same MAF scaling when I did mine.


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 Post subject: Re: Stock Fuel Pump Limits - Feedback welcome....
PostPosted: Thu Sep 07, 2017 11:10 am 
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I Say: Plan for tomorrow,Live for TODAY!
Vehicle: MY12 XT

Posts: 30
Location: Sydney
Hi Lach01,

Thanks - Already checked - It is running purposefully rich, high boost at high revs to avoid detonation.

The MAF scaling has already been as well, I have a 3 Inch racing CAI followed by a 3 inch Silicon Intake right uptown the turbo inlet. It makes a great sound too !

I have an internally recirculating BOV, that sounds amazing.

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Silver Fox !
VF-52 with Lava turbo blanket, 11psi Wastegate Spring, 3 port Company23 Anti-Surge BCS, 3" Mishimoto CAI, PSR Intake, Headers & Up-pipe in Lava wrap, Large TMIC, GFB BOV, Grimmspeed AOS, 3" TBE, Front & Rear Whiteline Heavy Duty Anti-Sway bars, KiddoRacing 18psi Tune for 98, Short shifter - 200kw atw


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