Walbro 255 = 10psi
05-28-2004, 11:49 PM
#1
Walbro 255 = 10psi
The strangest thing happened on the way to 10psi...... 
I've been running 7psi for some time now on the stock fuel pump. Since the injectors are at 100% duty cycle at about 5500rpm, I was starting to run lean into the 12:1 range at exactly 6200rpm.
I've been closely following the fuel pump/FPR/rail mods that many folks are doing...with great interest.
Anyways, today I got the urge to install the Walbro 255 without the FPR. I have the Aeromotive FPR sitting in my garage, but dont have an easy and fast way to run a return line. So I planned on installing the pump myself, and then have Street Image do the FPR and return. From what many people have told me, if you just change the fuel pump, and nothing else, you end up pretty rich at idle...and a sorta backwards fuel curve...rich at idle..and then progressively getting leaner..but always richer than stock.
Well, I installed the pump and fired up the car. Noticed my AEM wideband was still hovering around 14.7:1 at idle, just as before...with the car warm. Hmmm..interesting....so I drove it around to warm thing up further.....still at 14.7:1. Notice...I havent touched anything with the eManage...no injector scalling changes...no IWP changes..nothing at all.
So I began my ritual of doing 2nd gear WOT pulls down Union St in downtown Pasadena...the neighbors and cops love this.
And at 7psi....while dataloggin A/F to my profec...my A/F stayed glued to 10.8-11.0:1...all way to redline! I did this several times to confirm the readings.
Then I increased boost to 8psi...and even accidently to 10psi! My A/F was still hovering right around 11:1 all the way to redline. I did not add any fuel via eManage on these runs....WTF?
What is going on here? Is the 2004 ECU and fuel system totally different than the 2003? Is the 2004 ECU running that much leaner....to actually properly run with just a fuel pump upgrade?
I am totally flabberagasting..but happy...becuase I dont think I even need an FPR for the timebeing. I plan on reducing IPW slightly throughout...to get the A/F close to 11.5:1....but overall, I am pleased.
On June12, we're doing the group dyno day thing...so I'll post new numbers then.
I am running a progressive build to 8 degrees of ignition retard at redline.
One last note, Nissan changed the Fuel pump assembly o-ring gasket to a blue colored material (ACP's was black). The blue one doesn't exand on removal..so I just reused it. I have a couple extra 0-rings if anyone wants them! (I think 350now has dibs on one).
PS: The car pulls like a freaken F-16.....!
Good luck!
Hth,
Sharif
I've been running 7psi for some time now on the stock fuel pump. Since the injectors are at 100% duty cycle at about 5500rpm, I was starting to run lean into the 12:1 range at exactly 6200rpm.
I've been closely following the fuel pump/FPR/rail mods that many folks are doing...with great interest.
Anyways, today I got the urge to install the Walbro 255 without the FPR. I have the Aeromotive FPR sitting in my garage, but dont have an easy and fast way to run a return line. So I planned on installing the pump myself, and then have Street Image do the FPR and return. From what many people have told me, if you just change the fuel pump, and nothing else, you end up pretty rich at idle...and a sorta backwards fuel curve...rich at idle..and then progressively getting leaner..but always richer than stock.
Well, I installed the pump and fired up the car. Noticed my AEM wideband was still hovering around 14.7:1 at idle, just as before...with the car warm. Hmmm..interesting....so I drove it around to warm thing up further.....still at 14.7:1. Notice...I havent touched anything with the eManage...no injector scalling changes...no IWP changes..nothing at all.
So I began my ritual of doing 2nd gear WOT pulls down Union St in downtown Pasadena...the neighbors and cops love this.
And at 7psi....while dataloggin A/F to my profec...my A/F stayed glued to 10.8-11.0:1...all way to redline! I did this several times to confirm the readings.Then I increased boost to 8psi...and even accidently to 10psi! My A/F was still hovering right around 11:1 all the way to redline. I did not add any fuel via eManage on these runs....WTF?
What is going on here? Is the 2004 ECU and fuel system totally different than the 2003? Is the 2004 ECU running that much leaner....to actually properly run with just a fuel pump upgrade?
I am totally flabberagasting..but happy...becuase I dont think I even need an FPR for the timebeing. I plan on reducing IPW slightly throughout...to get the A/F close to 11.5:1....but overall, I am pleased.
On June12, we're doing the group dyno day thing...so I'll post new numbers then.
I am running a progressive build to 8 degrees of ignition retard at redline.
One last note, Nissan changed the Fuel pump assembly o-ring gasket to a blue colored material (ACP's was black). The blue one doesn't exand on removal..so I just reused it. I have a couple extra 0-rings if anyone wants them! (I think 350now has dibs on one).
PS: The car pulls like a freaken F-16.....!
Good luck!
Hth,
Sharif
Last edited by Sharif@Forged; 05-28-2004 at 11:52 PM.
05-29-2004, 12:04 AM
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Re: Walbro 255 = 10psi
ahhhh HA! 10 PSI EH????? he he he, its like having a loded gun!
hmmmmmm i wonder how much hp you could make on june 12th @10PSI ....hmmmmmmm.......i wonder.......
hmmmmmm i wonder how much hp you could make on june 12th @10PSI ....hmmmmmmm.......i wonder.......
05-29-2004, 03:53 PM
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it would be really cool to get a bunch of us '04 guys to start doing some datalogging and try to draw some correlations (or differences) between the '03 and '04's.
Adam
Adam
05-29-2004, 07:30 PM
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Thanks for the great info. I have a question though. Did the A/F increase at all at higher rpms or was it pretty flat?
Also do you notice if it gets rich for a bit after throttle changes then goes back to the steady state for cruising. That would show it was the factory O2 triming the extra fuel. We appreciate you giving us hard data like this, it helps us all.
I was looking at the 255 related threads and came across this one:https://my350z.com/forum/showthread....ght=walbro+255
In it Guru states you can just drop in the pump no problems. They did it to Yancy's car if I remember correctly and his was a 2003. So we have two people that did it no problem and a few that had the higher pressures. Did the people with higher pressures also measure A/F?
Gary
Also do you notice if it gets rich for a bit after throttle changes then goes back to the steady state for cruising. That would show it was the factory O2 triming the extra fuel. We appreciate you giving us hard data like this, it helps us all.
I was looking at the 255 related threads and came across this one:https://my350z.com/forum/showthread....ght=walbro+255
In it Guru states you can just drop in the pump no problems. They did it to Yancy's car if I remember correctly and his was a 2003. So we have two people that did it no problem and a few that had the higher pressures. Did the people with higher pressures also measure A/F?
Gary
Last edited by 7 eleven; 05-29-2004 at 07:48 PM.
05-29-2004, 09:13 PM
#7
Tim, no...i dont have a pressure guage...i think i will get one soon.
A/F was very steady through the range....about 10.8 at the richest...and 11.2 at the leanest...and this was at 8.5psi
7-Eleven, when I go from cruise to WOT, it immediately will to the sub 11.0:1 range....and stay pretty stable throughout.
At idle...it is totally stockish....14.7-15.0....
one other thing...I had to grind away almost everything on that pump to get it to fit...and I had to grind the clip. I had to literally grind everything in sight. But i got a bit overexuberant with the dremel on the base of the pump, and actualliy grinded right through the plastic bottom of the pump...maybe a 1mm hole at the largest. I figure it wouldnt make a difference since the bottom of the pump is totally submerged in the fuel bucket.
Who knows...maybe that little hole is relieving some pressure...but if my high school physics serves me correctly, it would make no difference since the bottom part of the pump is completely submerged in fuel.
Any ideas?
A/F was very steady through the range....about 10.8 at the richest...and 11.2 at the leanest...and this was at 8.5psi
7-Eleven, when I go from cruise to WOT, it immediately will to the sub 11.0:1 range....and stay pretty stable throughout.
At idle...it is totally stockish....14.7-15.0....
one other thing...I had to grind away almost everything on that pump to get it to fit...and I had to grind the clip. I had to literally grind everything in sight. But i got a bit overexuberant with the dremel on the base of the pump, and actualliy grinded right through the plastic bottom of the pump...maybe a 1mm hole at the largest. I figure it wouldnt make a difference since the bottom of the pump is totally submerged in the fuel bucket.
Who knows...maybe that little hole is relieving some pressure...but if my high school physics serves me correctly, it would make no difference since the bottom part of the pump is completely submerged in fuel.
Any ideas?
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05-29-2004, 10:49 PM
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Sharif:
The only thing I can think of is that the 04 Z's have a better internal FPR in that plastic housing and can maintain the 52 psi at idle and now at WOT the fuel pressure is not droping so your getting the fuel you wanted. If this is the case I will be buying a new 04 pump housing. Great job. CJ
The only thing I can think of is that the 04 Z's have a better internal FPR in that plastic housing and can maintain the 52 psi at idle and now at WOT the fuel pressure is not droping so your getting the fuel you wanted. If this is the case I will be buying a new 04 pump housing. Great job. CJ
05-30-2004, 01:50 AM
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Originally posted by gq_626
Tim, no...i dont have a pressure guage...i think i will get one soon.
Any ideas?
Tim, no...i dont have a pressure guage...i think i will get one soon.
Any ideas?
05-30-2004, 08:12 AM
#11
Originally posted by ACP
1st thing is get a fuel pressure gauge and see if there is a drop in pressure.
1st thing is get a fuel pressure gauge and see if there is a drop in pressure.
I will start searching for one this week......can you PM me with a price?
05-30-2004, 08:27 AM
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one other thing...I had to grind away almost everything on that pump to get it to fit...and I had to grind the clip. I had to literally grind everything in sight. But i got a bit overexuberant with the dremel on the base of the pump, and actualliy grinded right through the plastic bottom of the pump...maybe a 1mm hole at the largest. I figure it wouldnt make a difference since the bottom of the pump is totally submerged in the fuel bucket.
The only thing I can think of is that the 04 Z's have a better internal FPR in that plastic housing and can maintain the 52 psi at idle and now at WOT the fuel pressure is not droping so your getting the fuel you wanted. If this is the case I will be buying a new 04 pump housing. Great job. CJ
Gary
05-30-2004, 11:21 AM
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Maybe we can ask Performance Nissan if they can get the part# for the fuel pump assembly? The stock FPR between 03 and 04 in particular.
I'll send this link to Jason @ Performance to see if he can look it up for us.
I'll send this link to Jason @ Performance to see if he can look it up for us.
Last edited by 350Now; 05-30-2004 at 11:26 AM.
05-30-2004, 11:51 AM
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GQ,
That's cool that your car runs rich through out the rpm range. I have the Walbro 255 with the stock regulator and 380 cc injectors with the ATI porcharger. I do have a fuel pressure gauge for those wondering and at idle it is at 74psi. At WOT 6600rpms (9lbs boost) the pressure drops to 50psi and the A/F is lean at 13.0 on a dynojet.
I have my car jacked up currently for the return line install from the engine bay. I will be installing the SARD type R regulator on monday and should have some results by mid to end of week. This should lower pressure at idle to what I select and should raise pressure based upon boost. Can't wait.
MIKE
That's cool that your car runs rich through out the rpm range. I have the Walbro 255 with the stock regulator and 380 cc injectors with the ATI porcharger. I do have a fuel pressure gauge for those wondering and at idle it is at 74psi. At WOT 6600rpms (9lbs boost) the pressure drops to 50psi and the A/F is lean at 13.0 on a dynojet.
I have my car jacked up currently for the return line install from the engine bay. I will be installing the SARD type R regulator on monday and should have some results by mid to end of week. This should lower pressure at idle to what I select and should raise pressure based upon boost. Can't wait.
MIKE
05-30-2004, 09:09 PM
#17
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I'm no expert regarding the Z's fuel system, but here's a thought.
I do know that the Z's fuel system runs @ a fixed pressure (I think it is 55 psi or so).
The way the system maintains this pressure is to pump it up to some greater pressure, and then send it through the regulator (maybe part of the stock pump) to maintain a correct pressure on the fuel lines to the injectors. Now, there will be a limit to the flow rate of the stock pump, so that as the engine requires more and more fuel, that flow rate will be exceeded and the pressure will begin to drop. Eventually, the pump will not be able to maintain the stock pressure level, and the pressure in the lines to the injectors will drop as well.
If you use a higher flow pump, you will not necessarily change the pressure (since you will still be using the stock regulator to maintian the pressure) but now you will not have the pressure drop at the higher RPMs. To me, it makes sense that if you keep your line pressures the same as they were before, you won't be flowing more fuel at lower RPMs, since your fuel flow is based on injector pulse and pressure and your pressure hasn't changed at the low end.
Anyhow, maybe I'm off about the regulator thing, but I see nothing strange about your results.
EDIT for a couple more points:
First, I guess you would only see your fuel pressure dropping when you approach a high injector duty cycle. So, if the new pump is now maintaining your pressure, you would tend to get richer @ when you reach whatever that duty cycle was. So, if you used to lose pressure when you were reaching 80% injector duty cycle (but didn't realize it and kept increasing duty cycle in the hopes of getting more fuel) then when you upgrade the pump you will get more fuel in all the places you are above 80%. With this in mind, your results would definitely be based on your initial tuning and when you started losing pressure.
Anyhow, just some theory that may be completely wrong depending on how the fuel system actually works.
-D'oh!
I do know that the Z's fuel system runs @ a fixed pressure (I think it is 55 psi or so).
The way the system maintains this pressure is to pump it up to some greater pressure, and then send it through the regulator (maybe part of the stock pump) to maintain a correct pressure on the fuel lines to the injectors. Now, there will be a limit to the flow rate of the stock pump, so that as the engine requires more and more fuel, that flow rate will be exceeded and the pressure will begin to drop. Eventually, the pump will not be able to maintain the stock pressure level, and the pressure in the lines to the injectors will drop as well.
If you use a higher flow pump, you will not necessarily change the pressure (since you will still be using the stock regulator to maintian the pressure) but now you will not have the pressure drop at the higher RPMs. To me, it makes sense that if you keep your line pressures the same as they were before, you won't be flowing more fuel at lower RPMs, since your fuel flow is based on injector pulse and pressure and your pressure hasn't changed at the low end.
Anyhow, maybe I'm off about the regulator thing, but I see nothing strange about your results.
EDIT for a couple more points:
First, I guess you would only see your fuel pressure dropping when you approach a high injector duty cycle. So, if the new pump is now maintaining your pressure, you would tend to get richer @ when you reach whatever that duty cycle was. So, if you used to lose pressure when you were reaching 80% injector duty cycle (but didn't realize it and kept increasing duty cycle in the hopes of getting more fuel) then when you upgrade the pump you will get more fuel in all the places you are above 80%. With this in mind, your results would definitely be based on your initial tuning and when you started losing pressure.
Anyhow, just some theory that may be completely wrong depending on how the fuel system actually works.
-D'oh!
Last edited by D'oh; 05-30-2004 at 09:16 PM.
05-30-2004, 10:12 PM
#18
D.oh, the issue that has occured with some folks and the Walrbos 255 is that the stock intank FPR cannot physically keep up with the high flow and pressure of the Walbro 255. So at idle...the stock pressure was about 70psi...essentially, the cheezy stock intank FPR cannot vent enough fuel. Then as RPM and fuel demands increase, now the stock FPR starts to keep up, and at redline, you are all the way back to 50psi.
Now, as mentioned, with my car..and apparently a couple of others, we were able just to drop in the 255 and have relatively steady A/F ratios...even at idle, where I was expecting to be quite rich.
Until I get a fuel pressure guage, I cant really confirm what my pressures are...but I know that at idle, my A/F is the same as stock...so I am assuming the pressure should be near stock.
TESTING UPDATE:
Today, I was doing more thorough road testing with the Walbro 255 at 8.5psi. I noticed two things on todays runs. First of all, my car voltage guage on the dash was significantly below the 14...it looked like maybe 13volts or so of juice. The fuel pump works off the car's voltage, so if you have lower voltage for whatever reason, the pump isnt going to spin as fast....this is a problem.
So anyways...I made my same runs in 2nd gear and I was clearly running leaner than last night...instead of 10.8-11.0, i was in the 11.5-11.7 range. When I did some pulls in 5th gear on the freeway...I was hovering solidly at 12.3:1 (until 5000rpm when I let off)...too lean for me...
So I have a question here. How the heck can I keep my voltage from dropping? Someone said that TS can setup the ECU to peg at 14volts regardless. I really need a solid voltage to get a consistent tune..this is nutty.
I know for sure that the pump slows when voltage drops..becuase at idle, with the car parked, I'll open the windows and hold the button down...i see the voltage drop, and I hear the pump sound slowing as well.
Can this car make things anymore difficult???????
FYI: This voltage issue would not be solved with any of the fuel/FPR/Rail solutions that are out there....you would still have inconsistent fuel pressure and tune throughout....unless the pump was producing high enough pressures before the FPR, in order to offset any decrease in pump pressure due to a voltage drop...maybe there is enough of a cushion there...since the Walbro can easily produce 70psi with the intake FPR screwing thing up.
Now, as mentioned, with my car..and apparently a couple of others, we were able just to drop in the 255 and have relatively steady A/F ratios...even at idle, where I was expecting to be quite rich.
Until I get a fuel pressure guage, I cant really confirm what my pressures are...but I know that at idle, my A/F is the same as stock...so I am assuming the pressure should be near stock.
TESTING UPDATE:
Today, I was doing more thorough road testing with the Walbro 255 at 8.5psi. I noticed two things on todays runs. First of all, my car voltage guage on the dash was significantly below the 14...it looked like maybe 13volts or so of juice. The fuel pump works off the car's voltage, so if you have lower voltage for whatever reason, the pump isnt going to spin as fast....this is a problem.
So anyways...I made my same runs in 2nd gear and I was clearly running leaner than last night...instead of 10.8-11.0, i was in the 11.5-11.7 range. When I did some pulls in 5th gear on the freeway...I was hovering solidly at 12.3:1 (until 5000rpm when I let off)...too lean for me...
So I have a question here. How the heck can I keep my voltage from dropping? Someone said that TS can setup the ECU to peg at 14volts regardless. I really need a solid voltage to get a consistent tune..this is nutty.
I know for sure that the pump slows when voltage drops..becuase at idle, with the car parked, I'll open the windows and hold the button down...i see the voltage drop, and I hear the pump sound slowing as well.
Can this car make things anymore difficult???????
FYI: This voltage issue would not be solved with any of the fuel/FPR/Rail solutions that are out there....you would still have inconsistent fuel pressure and tune throughout....unless the pump was producing high enough pressures before the FPR, in order to offset any decrease in pump pressure due to a voltage drop...maybe there is enough of a cushion there...since the Walbro can easily produce 70psi with the intake FPR screwing thing up.
05-30-2004, 10:38 PM
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The Walbro sucks that much juice?? This seems odd ..well mabye when combined with all the other electric gadgets u got in there.
You get an optima yellow top yet??? if not i would start there.
You get an optima yellow top yet??? if not i would start there.
05-31-2004, 12:32 AM
#20
Squill, the pump isnt causing the voltage change. I dont think this is unique to my car, but even before I had the pump...or my TT, my voltage would fluctuate between maybe 13-15volts....I have idea why it does this...but it is not stable every day....
I was going to get the Yellow Top, but I think there were issues with them...still sorting that out. either way, its not the battery, becuase the alternator and voltage reg are controlling the voltage when the car is running..not the battery...unless it is totally dead and drain a bunch of power from the alternator....it is not dead.
I was going to get the Yellow Top, but I think there were issues with them...still sorting that out. either way, its not the battery, becuase the alternator and voltage reg are controlling the voltage when the car is running..not the battery...unless it is totally dead and drain a bunch of power from the alternator....it is not dead.