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Old 04-20-2013, 02:21 PM   #1
Type2
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Default Fuel pressure raises then tapers under boost WOT?

Issue is pretty simple: At WOT/boost my fuel pressure rises initially, then starts to descend and my AFR's go lean. I also am hitting 1600* EGT at cruise under light load.

On the stock FPR my fuel pressure was about 30psi at idle. My tuner (Mikey) increased the fueling but the AFR's stayed the same so he told me to get another FPR, so I picked up a Fuelab. Installed today, set it to 50psi at idle, and did some logs for my Mikey.

Now, fuel pressure is 50 psi+ at idle, but it seems to exhibit the same problem. At WOT, running 10lb boost I start to run lean (mid 12's AFR). Initially it dips into the low 10's / high 11's. I have a couple videos of the last two logs I sent to Mikey.

Any ideas? Fuel pump? I replaced the fuel filter in the engine bay about 8 months ago.

Log 1

Log 2

Mod list:

Engine:
1. 05 STi heads, stock cams, valves refreshed, bowl blend, gasket matched to intake and exhaust
2. STi short block, new OEM STi nitrided crank, CP forged pistons (99.5mm, 8.2:1 CR), King bearings, reconditioned STi rods, ARP rod bolts (built by Jeremy at DJ's Performance)
3. Killer B oil pickup
4. 11mm STi oil pump
5. 06/07 STi oil pan
6. P&L AVCS / Turbo SS oil line kit

Power:
1. Borg Warner / AGP S200sx_RS_56 Turbocharger .63, A/R (55lbs/min)

Intake Specific Mods:
1. Ported & gasket matched intake manifold
2. Grimmspeed 8mm phenolic spacers
3. TGV Deletes
4. Custom 3" CAI - deleted MAF (built by morrocco88)
5. Crawford AOS v2 universal
6. Relocated IAT sensor to intake manifold
7. STi TMIC

Exhaust Specific Mods:
1. Custom rotated up pipe (built by morrocco88)
2. Custom 3 inch v-band downpipe (built by morrocco88)
3. Cobb 3 inch Forester Catback
4. Ported exhaust manifolds, tapped for EGT probe at 2/4 cylinder button

Tuning / Boost Control:
1. Open source speed density - Mikey @ Phatbotti Tuning
2. Wideband O2 Sensor
3. Hallman Pro RX MBC
4. Tactrix Openport 2.0
5. TiAL MV-R 44mm wastegate (set to 1.0 bar)
6. SuperTrapp EWG muffler
7. Omni Power 4 Bar Map Sensor

Fuel:
1. Toyota Supra (Denso) Turbo Fuel pump
2. DW 850cc side feed injectors
3. Perrin side feed fuel rail kit

Cooling:
1. Mishimoto Radiator
2. TCI large, front-mounted Tranny cooler
3. DEI Titanium lava heat wrap on up pipe & down pipe
4. PTP Lava turbo blanket
5. DEI Reflect-A-Gold tape on TMIC

Gauges:
1. Greddy Oil Pressure
2. Greddy Boost
3. Prosport EGT
4. Prosport Oil Temp
5. AEM UEGO Digital Gauge O2 Air Fuel Wideband Controller (30-4100)
6. Prosport sandwich plate for oil pressure gauge
7. Fuel Pressure gauge (off Perrin fuel rail)
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Old 04-20-2013, 02:50 PM   #2
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Not sure about the flow rate of a stock supra fuel pump, or since it is probably use if it has a problem, but usually when the fuel pressure drops as as the injector duty cycle increases it's a pump problem. Maybe you have a high resistance joint that is causing a voltage drop at the pump or maybe the pump is no good or the flow rate is to low. Also Pro sport gauges are not the best gauges in the world I had a peak hold boost gauge from them and wiring was always a problem, as it would flake out from time to time and not read enough vacuum. Also 1600 F is way to high for a cylinder temp at any point, WOT it should run no hotter than 1400-1475F, and cool off after the throttle is closed. At 1600F pistons start to melt.

Last edited by gfx2043; 04-20-2013 at 03:03 PM.
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Old 04-20-2013, 03:05 PM   #3
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Is the FPR reference hose attached? Does it fit snug, and have it's own vacuum/boost source on the intake manifold? Make sure it is not plugged.

I know this is a silly question, but your build has been a long one, and things like this can be easily forgotten.

EDIT: reread your thread and it looks like you have this squared away. Doesn't hurt to check tho

Could be the fuel pump I suppose...do you have a walbro or even OEM pump to swap in for a test?

Last edited by aboothman; 04-20-2013 at 03:21 PM.
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Old 04-20-2013, 03:54 PM   #4
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Quote:
Originally Posted by gfx2043 View Post
Not sure about the flow rate of a stock supra fuel pump, or since it is probably use if it has a problem, but usually when the fuel pressure drops as as the injector duty cycle increases it's a pump problem. Maybe you have a high resistance joint that is causing a voltage drop at the pump or maybe the pump is no good or the flow rate is to low. Also Pro sport gauges are not the best gauges in the world I had a peak hold boost gauge from them and wiring was always a problem, as it would flake out from time to time and not read enough vacuum. Also 1600 F is way to high for a cylinder temp at any point, WOT it should run no hotter than 1400-1475F, and cool off after the throttle is closed. At 1600F pistons start to melt.
Honestly, I don't know what the flow rate is either. The PO told me it flows more than a Walbro 255 and is quieter. My guess is they are about the same.

The 1600* temp does worry me. After installing the Fuelab FPR at cruise I'm seeing about 1540* right now, but any extra load it climbs. Keeping an eye on my AFR's make me think it's leaning out a bit, but I'm not sure.

Quote:
Originally Posted by aboothman View Post
Is the FPR reference hose attached? Does it fit snug, and have it's own vacuum/boost source on the intake manifold? Make sure it is not plugged.

I know this is a silly question, but your build has been a long one, and things like this can be easily forgotten.

EDIT: reread your thread and it looks like you have this squared away. Doesn't hurt to check tho

Could be the fuel pump I suppose...do you have a walbro or even OEM pump to swap in for a test?
Yeah, I got the FPR reference hose attached correctly, but it certainly helps to double check.

I don't have a spare pump hanging around. I'm assuming a 255 should be more than enough pump for my purposes. I tossed around the idea of going E85 and putting bigger injectors on, etc, but I think I'm going to abandon that pipe dream and just run 91 for simplicity sake. I hear 255's are pretty cheap and simple drop in's... The pump I am using I have no idea how old it is, but it has at the very least seen 65k miles.

I should be clear that I have NOT received a new map from Mikey based on the 50 psi baseline. I'm assuming my fueling tables could be screwed up now that my injectors are seeing over 20 lbs more psi at idle on this new FPR. Maybe this is why the fuel doesn't hold pressure?

Also, I notice when at cruise putting a little bit of foot into the throttle makes the fuel pressure jump from about 50 psi to 60 psi. Kind of strange.

Check out this video:
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Old 04-20-2013, 05:36 PM   #5
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#1 Get that pump out of there iirc the supra pumps pull a lot of amps and your fp circuit may not be able to power it properly(go to apeusa.com and get a walbro and any needed hardware from there.)Also its funny that when you bumped the base that high the car didn't go pig rich like it should have which points to a fuel delivery issue. good luck
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Old 04-20-2013, 05:41 PM   #6
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^^ Good info there.

Your video is what made me think that there was an issue with the FPR pressure source...especially considering the issue remained consistent across FPR. The pump does seem like the other logical candidate though.

I am sure that by now you are aware of how these FPR work, so I will put it out there for future readers . They are a rising rate FPR, which means once you are in boost the fuel pressure should be your base + manifold PSI, and should rise proportionally with your boost.
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Old 04-20-2013, 05:55 PM   #7
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Quote:
Originally Posted by john 1badSTI View Post
#1 Get that pump out of there iirc the supra pumps pull a lot of amps and your fp circuit may not be able to power it properly(go to apeusa.com and get a walbro and any needed hardware from there.)Also its funny that when you bumped the base that high the car didn't go pig rich like it should have which points to a fuel delivery issue. good luck
Going to pick up a Walbro 255. They are cheap and should hold me at 91 octane no problem up to 400 whp. I doubt I make any more than that. Re: not going pig rich -- I was kinda thinking the same thing. I was expecting my AFR's at idle to be in the 10-12 range, but it's at 14.7 no problem.

Quote:
Originally Posted by aboothman View Post
^^ Good info there.

Your video is what made me think that there was an issue with the FPR pressure source...especially considering the issue remained consistent across FPR. The pump does seem like the other logical candidate though.

I am sure that by now you are aware of how these FPR work, so I will put it out there for future readers . They are a rising rate FPR, which means once you are in boost the fuel pressure should be your base + manifold PSI, and should rise proportionally with your boost.
(For future readers): My Fuelab FPR is a 1:1 which means for every pound of boost it should increase fuel pressure by 1 psi. I believe the Aeromotive is the same as well.

I can't think of anything else at this point that might be causing my fuel pressure issues, so new fuel pump it is.

Thank you both for your help.
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Old 04-20-2013, 06:03 PM   #8
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you're welcome keep us posted as to how it goes with the new pump.
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Old 04-20-2013, 06:49 PM   #9
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Quote:
Originally Posted by Type2 View Post

Going to pick up a Walbro 255. They are cheap and should hold me at 91 octane no problem up to 400 whp. I doubt I make any more than that. Re: not going pig rich -- I was kinda thinking the same thing. I was expecting my AFR's at idle to be in the 10-12 range, but it's at 14.7 no problem.

(For future readers): My Fuelab FPR is a 1:1 which means for every pound of boost it should increase fuel pressure by 1 psi. I believe the Aeromotive is the same as well.

I can't think of anything else at this point that might be causing my fuel pressure issues, so new fuel pump it is.

Thank you both for your help.
Need to increase the gauge on the wiring for the pump.

And ditch that supra pump, the walbro F90000267 will keep up no problem, just go to heavier gauge wire so when it pulls more voltage it can keep up.

-Phil
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Old 04-20-2013, 06:51 PM   #10
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Quote:
Originally Posted by Flat 4 Motorsport View Post

Need to increase the gauge on the wiring for the pump.

And ditch that supra pump, the walbro F90000267 will keep up no problem, just go to heavier gauge wire so when it pulls more voltage it can keep up.

-Phil
I picked up a 255. Should I run thicker wire for that. Is it necessary?
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Old 04-20-2013, 11:34 PM   #11
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OEM wiring will be enough for testing purposes. I have yet to rewire mine for the same reasons you mentioned earlier; the FPC has to be bypassed to donit right and I still drive my car on the street, so I am not comfortable doing so.

Of course a lot of people have done so with no issue...I am just paranoid at times
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Old 04-21-2013, 09:24 PM   #12
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Is the fuel pressure gauge referenced to atmosphere or to manifold pressure?
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Old 04-21-2013, 09:33 PM   #13
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Is the fuel pressure gauge referenced to atmosphere or to manifold pressure?
Not sure. How do I check? The fpr takes vacuum from the manifold.
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Old 04-21-2013, 10:01 PM   #14
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My Defi set has an electronic setting that will automatically subtract manifold pressure from the fuel pressure to display the pressure differential across the injector. That differential pressure is what governs injector flow.

Unless your fuel pressure gauge has a controller that is referenced to manifold pressure (by a vacuum line or from another gauge), you would expect to see the fuel pressure gauge moving all over the place as you move between vacuum and boost. My Defi in differential pressure mode starts about 3.5 bar at idle but will stablize pretty quickly at 3 bar (my fuel pumps are overrunning the regulator at idle).

If you have 50 psi at idle referenced to atmosphere, that is really 60+ psi differential pressure. Lower that so that you have 43-44 psi differential across the injector (ask your tuner about this first and get a map for it or you will go really lean and pop the motor for sure!). Your pump may have more stable delivery at a lower delivery pressure. Walbro's fall off at high delivery pressure and Denso's might do the same.
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Old 04-22-2013, 10:32 AM   #15
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Originally Posted by junebugfareast View Post
My Defi set has an electronic setting that will automatically subtract manifold pressure from the fuel pressure to display the pressure differential across the injector. That differential pressure is what governs injector flow.

Unless your fuel pressure gauge has a controller that is referenced to manifold pressure (by a vacuum line or from another gauge), you would expect to see the fuel pressure gauge moving all over the place as you move between vacuum and boost. My Defi in differential pressure mode starts about 3.5 bar at idle but will stablize pretty quickly at 3 bar (my fuel pumps are overrunning the regulator at idle).

If you have 50 psi at idle referenced to atmosphere, that is really 60+ psi differential pressure. Lower that so that you have 43-44 psi differential across the injector (ask your tuner about this first and get a map for it or you will go really lean and pop the motor for sure!). Your pump may have more stable delivery at a lower delivery pressure. Walbro's fall off at high delivery pressure and Denso's might do the same.
Good grief. I had no idea there was more to it that simply checking the fuel pressure on the rail.

Regarding fluctuating while going between vacuum and boost - is that why my needle jumped 10psi immediately when I was at cruise and gave it a little gas? It isn't really going "all over the place" but it sure jumps.

Before I replaced the stock FPR with the Fuelab my pressure was 30 psi at idle and under throttle would go up to 50 psi. Now with the Fuelab FPR, my idle is 50, but it won't hold pressure under heavy throttle. It will make it to 60+ psi but will fall back. Regarding my new baseline fuel pressure (going from 30psi base to 50 psi base) -- oddly enough I'm not driving around pig rich right now. Maybe it's because I'm speed density tuned? Not sure.

Re: placement of fuel pressure sender -- should I tap the FPR to measure fuel pressure? Right now I'm just tapping the rail. Would the FPR provide more accurate measurements?

Thanks
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Old 04-22-2013, 03:04 PM   #16
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Check out the differential fuel pressure thread Cobb started a while ago. I had a problem with my setup using the stock FP speed controller set points. Normally the pump switches to medium speed @ 33% IDC and full speed @ 66% IDC. When I changed out the stock injectors for 1150CC injectors the fuel flow @ 30% IDC was more than the pump could supply at low speed so I had to change the speed controller set points to 8% and 20% IDC for medium and fast speed. A quick fix for you could get to just hard-wire the pump and bypass the controller all together.

Do you see a change in pressure when the fuel pump changes speed?


NOTE: When setting base fuel pressure you need to do it with the vacuum line disconnected. It should be 43 psi stock. The 30 psi you saw was probably with the vacuum line hooked up at idle which is not base fuel pressure.
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Old 04-22-2013, 03:18 PM   #17
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Originally Posted by kellygnsd View Post
Check out the differential fuel pressure thread Cobb started a while ago. I had a problem with my setup using the stock FP speed controller set points. Normally the pump switches to medium speed @ 33% IDC and full speed @ 66% IDC. When I changed out the stock injectors for 1150CC injectors the fuel flow @ 30% IDC was more than the pump could supply at low speed so I had to change the speed controller set points to 8% and 20% IDC for medium and fast speed. A quick fix for you could get to just hard-wire the pump and bypass the controller all together.
Is there anything wrong with the fuel pump operating at 100%? I'm assuming the pump would wear out faster, and it would be constantly overflowing and passing back into the fuel tank, which I guess isn't that big of a deal. I've read a few threads on the topic and I have not got a definitive answer on this point. Regarding the wiring, I found two kits:
Summit Racing Kit
STM Kit
Any preference?

Quote:
Originally Posted by kellygnsd View Post
Do you see a change in pressure when the fuel pump changes speed?
Maybe that is the wild jump I am getting when at cruise I start to tip the throttle in and it jumps about 10psi in the blink of an eye (see post #4).

Quote:
Originally Posted by kellygnsd View Post
NOTE: When setting base fuel pressure you need to do it with the vacuum line disconnected. It should be 43 psi stock. The 30 psi you saw was probably with the vacuum line hooked up at idle which is not base fuel pressure.
That is great to know. When I get the Walbro 255 I will make sure to set it with the vacuum line disconnected. Mikey wanted me to set the pressure to 50-52 psi. I wonder what his rationale is for that...

I'll find that Cobb thread and read through it.
Again, T H A N K S!
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Old 04-22-2013, 05:48 PM   #18
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http://forums.nasioc.com/forums/show....php?t=2474303

Here is a link to the thread I mentioned.

If you data log you should be able to log fuel pump speed and temperature if you are worried about running it 100% full time. Lots of people do it and I probably will too eventually but since I was able to change when my pump changed speeds I figured I'd try that first. Nothing will last as long when run 100% compared to running it at reduced speed but its not like its going to fail in 3000 miles either.
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Old 04-22-2013, 05:51 PM   #19
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The Summit kit doens't mention what gauge wire it uses. 10 gauge is a good side for the STM kit wiring.
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Old 04-22-2013, 07:47 PM   #20
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Quote:
Originally Posted by kellygnsd View Post
http://forums.nasioc.com/forums/show....php?t=2474303

Here is a link to the thread I mentioned.

If you data log you should be able to log fuel pump speed and temperature if you are worried about running it 100% full time. Lots of people do it and I probably will too eventually but since I was able to change when my pump changed speeds I figured I'd try that first. Nothing will last as long when run 100% compared to running it at reduced speed but its not like its going to fail in 3000 miles either.
I just finished reading that thread. SUPER interesting stuff! I also saw where you were able to adjust the variable pump control. What program were you using to log and alter those parameters? Is that something I can do myself, or my tuner can do? (I have a Cobb AP and software, as well as RomRaider). I really need to learn how to tune, since waiting days and days to hear back from Mikey is a pain. I feel a bit helpless. Anyway, I am probably just going to go to 100% duty cycle for simplicity sake, but your idea is a much better and more elegant solution.

Quote:
Originally Posted by kellygnsd View Post
The Summit kit doens't mention what gauge wire it uses. 10 gauge is a good side for the STM kit wiring.
I picked up the STM kit. Also, the STM kit had an in-line fuse for the power wire. A little piece of mind. I will probably hard wire up the pump at the same time this weekend. If the pump craps out every 3 years, that's fine with me. I'm just concerned about noise.

I think I may reinstall the pressure gauge in the engine bay to see if it is holding pressure after turning the key off. I really want to make 100% all the fuel system components are working perfect. I wonder if it makes any difference if I am reading directly from the port on the Fuelab FPR or on the fuel rail. I assume they read the same.

Again, thanks for your help.
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Old 04-22-2013, 10:25 PM   #21
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I'm running a Link G4 standalone so I can log and change almost anything. I also have my fuel pressure sensor directly treaded into my Fuelab FPR. When setting base fuel pressure that's the pressure port the tell you to use.
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Old 04-25-2013, 01:31 PM   #22
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Got the W255 in yesterday. I'll probably install it this weekend. One thing I've noticed since I installed the Fuelab FPR is that when I turn the key on, the pressure goes up, then slowly fades until the low pressure warning goes off. I took a video of it this morning. I was under the belief that once the pressure gets to say, 45 psi, it should stay there even if I turn the key off or the pump stops cycling. Could my FPR be not holding pressure, or does this look like the fuel pump still? Or the gauge?

I have yet to put a gauge back on the fuel rail in the engine bay. But before I took it off (when I had the stock FPR on - i.e. prior to installing the Fuelab FPR) - I would have zero fuel pressure after shutting the car off.

Thanks
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Old 04-25-2013, 01:49 PM   #23
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might be a faulty gauge. fuellab fpr may not be holding, or a fuel leak in any line
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Old 04-25-2013, 01:55 PM   #24
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^^^^^^^^^^^leakin injectors too maybe.......
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Old 04-25-2013, 01:57 PM   #25
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Originally Posted by Blackout713 View Post
might be a faulty gauge. fuellab fpr may not be holding, or a fuel leak in any line
Definitely no fuel leak unless it's in the tank. Unfortunately there's really no way to check the gauge without sending it back. Same with the FPR. Hell, maybe the new fuel pump I bought will be bad as well!

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Originally Posted by Paidfor View Post
^^^^^^^^^^^leakin injectors too maybe.......
Any way I can test this without sending them to Witchunters?
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