Huge AFR difference between banks after 5600rpm, what gives?

[Toni]

Well went to the 1/8 track to try and figure out a better tune. It was good on the street but tough to string together a hard 1/2/3 pull safely. It was good with no knock but my first run here had a ton, forgot to turn on knock alarm... Need to get that figured out. BUT for some reason my rear bank is quite a bit leaner than the front. We are talking .3 to 2.2 afr. Any ideas?

(Boost was actually 15 psi my 0-5v scaling is off)

http://primaryboost.com/store/rt/logs/skyview061011_session_4a.png

2nd gear zoomed in a bit

http://primaryboost.com/store/rt/logs/skyview061011_session_4b.png

btw, best 1/8 was 8.17 @83 with 1.79 60ft

Thanks
Antoni

[UTRacerX9]

Hmm. You can do a few things. Check your O-rings on the rear bank and see if they are leaking under boost. Also, swap injectors from front to rear, and see if the AFR continues to do that, but on the opposite bank. If that's the case, you probably need to clean your injectors.

[Toni]

Well I swapped the rears for the fronts and layed down a fun run pass at the NG. It's still doing it. Seems weird that I would need a dual feed setup. Something else must be going on.

[IPD]

are you running a fuel rail loop, or do you have parallel feed? if it's a fuel rail loop, i'd say that's a good potential problem right there. the fix is either parallel lines or cranking up the pressure/ adding another pump.

[Hans@GZP]

We talked about it a bit last night. No need for a crazy fuel setup on a 15g car. Toni us going to checkout his fuel filter and try to find a replacement element. It looks to me like there is a flow shortage. Could be the filter or a dying walbro pump.

[Toni]

Well the fuel filter was definitely dirty because I had to turn down my base pressure after replacing it. It seems to have helped but the pressure still drops and my IDCs are still higher than the dyno pull. I'm guessing the new filter is just a small bandaid but the pump is the real problem. We'll see next week.

[Toni]

Well, I replaced the fuel pump and it didn't seem to have any effect. Here is the latest log. I have less correction but I am still about -15 and I'm only running 550ccs. Compared when I was on the dyno in may this is much more. Before I was only running like -27 to -30 which made way more sense.

Fuel pressure drop is still high like 14 psi between 4000 and 6200 rpm with no change in boost. I installed a new walbro pump same as before. I did notice this one did not whine as my old one did so I thought that was going to be a good thing. Apparently not. Voltage at the pump is about 13volts. I used a new oring. I checked the afpr diaphram for leaks and there were none visually. I might try and replace it since I have a new one around anyway.

Any other ideas? This is weird as I have changed nothing fuel wise since the dyno. Actually I haven't changed much at all. The one thing I did notice was the fuel pump hat positive wire was warm after running the car. Is this normal?

(I start to get 6 counts of knock around 5800rpm, right where the rear starts to go lean on me)

horizontal guide lines : red line is 12 afr, blue is 10.5.

http://primaryboost.com/store/rt/logs/afterpump070511.png

[AdamVR4]

Process of elimination... Is there a leak or blockage in the vacuum hose / nipple of the AFPR? Any way you can swap out the AFPR?

[mb3000]

We talked about it a bit last night. No need for a crazy fuel setup on a 15g car. Toni us going to checkout his fuel filter and try to find a replacement element. It looks to me like there is a flow shortage. Could be the filter or a dying walbro pump.

This. Don't end up like me.

[Toni]

Process of elimination... Is there a leak or blockage in the vacuum hose / nipple of the AFPR? Any way you can swap out the AFPR?

That is going to be my next test I guess. It's an aem afpr with the rail adapter. I checked the diaphragm for tears but maybe there is another issue with it that passes visual inspection. I have another diaphragm around that I'll swap in to see and check the vacuum lines/fittings.

[i3igpete]

if it's a leaky air port on the FPR (i think adam said that on 3st), then the fuel pressure during idle will be higher than normal as well (or your fuel trims will be lower at low cruise). Did you see anything with that?

[Toni]

if it's a leaky air port on the FPR (i think adam said that on 3st), then the fuel pressure during idle will be higher than normal as well (or your fuel trims will be lower at low cruise). Did you see anything with that?

Hmm I'll have to see if my trims have moved. I normally just glance at my afrs to see if they are still at 14.7 and haven't seen them change. I was getting 27 mpg on the way to and back from the ng so if they have moved it hasn't been off the scale.

[GTwizard]

Electricity is always in a "come here" mode. So if your wires are a tad warm, the pump is trying to pull more than what is available to it. Thats what gets wires hot. Your wires could be way too small for the pump. Everything to the pump needs to be 10 gage including the ground. I run a full fuel loop with IPS fuel rails and airomotive FPR. I only run 360 injectors and not even boosted and found the 2 banks are much more even with this set up over stock. The stock fuel system sucked when running the ram air. Rear bank was lean under ram.

[Toni]

Did some testing today...

First checked the fuel system to see if it will hold pressure to make sure the pump oring is sound. It was kinda tough because my aem afpr loses pressure immediately. Has always been like that even after swapping orifices and diaphragm. I hear this is common. I ended up clamping the return line and blipping the pump.

Seems good here. Takes a long time for the pressure to drop off.

http://primaryboost.com/store/rt/logs/pumporingcheck.png

Then I checked the regulator's operation at different psi. I used the same boost line to the regulator to my regulated compressor. Here are some boost levels:

(boost sloping is from my compressor's regulator, takes a while for it to get steady unless I put a lot of load on it)

http://primaryboost.com/store/rt/logs/regcheck7psi.png

http://primaryboost.com/store/rt/logs/regcheck14psi.png

http://primaryboost.com/store/rt/logs/regcheck21psi.png

I did the same tests before and after swapping the regulator diaphragm and there was no difference. Obviously this is not a real world test since there are no injector "leaks", battery voltage only, and the car is off. This is on a cold car as well.

Tomorrow I'm going to do some more tests and see what happens after the pump has been running for a while. I also plan to rig a voltage tester so I can log it while driving. I will figure this shit out!

[Toni]

Alright did some more things. I removed the left over stock wire (5") going to the fuel hat. I pried the terminal apart and soldered my 10awg wire directly to it. Tested with meter and there is "no" resistance measured. I also removed the ground log and grinded it down and added my own 10awg ground. Wiring should be solid now. I also added 16awg jumper wires to my logger to log voltage. I adjusted for voltage drop with my added test leads.

Here is the log. I forgot to hook up my boost sensor after testing the regulator but my gauges peaked at 14.5psi.

http://primaryboost.com/store/rt/logs/070811pumpvoltagetest.png

I extended the left scale (I usually forget) for the legend.

Voltage does not drop. However, when I logged the voltage on mmcd/palm, it drops to 12.5 from 13.6. That's weird... Is that common?

So at this point in summary:

I have solid 10awg hot wiring to the pump
new fuel pump (walbro 255)
new fuel filter
new afpr regulator
voltage at pump does not change
pump oring holds 75psi+

One thing I thought about is maybe it's something right from the start. The filter on the end of the pump. It looks a little grey. Maybe I got a tank of shitty ass gas and it is the one that is clogged? Cheap enough to replace I might as well do it anyway.

[J. Fast]

Just throwing a few ideas out there... Have you tried swapping the O2 sensors and wiring from each bank? Swap the front to rear leaving the current wiring intact and see if you still get the same reading? Maybe try reversing how you're feeding the fuel rail? Switch the feed and return lines at the rails to see if there's some kind of obstruction in the rail or the loop? It's a pain but maybe it's worth a shot.

[Toni]

Just throwing a few ideas out there... Have you tried swapping the O2 sensors and wiring from each bank? Swap the front to rear leaving the current wiring intact and see if you still get the same reading? Maybe try reversing how you're feeding the fuel rail? Switch the feed and return lines at the rails to see if there's some kind of obstruction in the rail or the loop? It's a pain but maybe it's worth a shot.

Well after I started logging fuel pressure and thinking about the fact that I've been adding a ton of fuel compared to the dyno earlier this Spring it seems that it's a global issue at this point. Initially, I only saw the discrepancy between the two banks because it was dead obvious. Now it all came together to reveal some sort of flow/fueling issue. I don't have many explanations left I feel. I'll find it :)

[mb3000]

This is just a wild guess, but do you still have your charcoal canister?

[Toni]

This is just a wild guess, but do you still have your charcoal canister?

Nope, that has long since been removed by the previous owner.

[mb3000]

Is the line capped or open?

[Toni]

I believe it's open. If this is the line referring to the gas tank. I forget but it goes tank -> can -> vacuum to filter out gas take fuels?

[mb3000]

IIRC if the line is capped it makes the pump work harder because of the vapors in the tank. The hot temp's affect the expansion of the vapors & such.

Probably nothing, but if you've tried everything else it might be worth an inspection.

[Toni]

I should be good with that because I haven't changed anything since the dyno so I'm guessing it wouldn't have all of a sudden become clogged.

[Toni]

Well, did some more debugging. I removed the pump input filter and clamped on a larger opening stainless mesh filter. No changes. I tried to make the hotwire extra *hot. No relay involved just battery -> fuse(different one) -> terminal -> pump. I manual connect the terminal to power the pump. This also did not help. I put another map sensor close to the afpr reference port and logged the system.

I still get 10-12 psi pressure drop on the fuel pressure. Boost signals are nice and level during the pull. I forgot to scale them for today's atmosphere, subtract 13.78psi if you are interested in actual boost gauge numbers. The two sensors are a bit different but I have them split from different devices with slightly different wiring etc so there is some error involved between them.

There isn't much left to test...I ordered another current sensor so I'll try to log that to see if the current supply to the pump is dropping for some reason. Perhaps the electrical system can't handle the load when rpm ramps up? I dunno. This is getting ridiculous.

http://primaryboost.com/store/rt/logs/071111_hotpump.png

[Toni]

I ended up doing some liter/hr calculations tonight. I figure, if it's the fuel pressure regulator then this test should pass.

So the basic idea is to connect the return line to a gas can and time how long it takes to get a certain amount. I was unsure of the accuracy of the can lines so I decided to do this by weight. I used my postal scale and measured 1 liter of fuel and compared that with "gasoline" numbers online. All was well.

So basically, I placed the hose in the can, start my logger and run the pump. Logger has boost (simulated by my compressor), volts, and fuel pressure. Once turned off, I can measure how long the pump was running and then calculate liters/hour.

So I end up with x kg of fuel + tank, subtract the tank weight. That gives me fuel weight. Divide by kg/liter of fuel to get liters. Then convert liters / min to liters/hour.

I'm spelling this out in case someone notices something wrong.

A problem I first realized is voltage. It was at 11.75 to 11.9. So I ended up hooking my charger which gave me a little over 12 v at the pump. This matched up to values I can compare to online.

Here are the numbers:
11.9volt @ 45psi = 200.41l/hr
12.1volt @ 63.5psi = 166l/hr
12.3volt @ 62.6psi = 167l/hr

http://www.stealth316.com/images/flowtest-walbro.gif

So at 63psi fuel pressure and 12v it shows about 184l/hr. Compared to my data, I'm roughly flowing less with more voltage at the pump. Given my operating voltage of 13.1 I'm flowing 205-210 l/hr according to the graph. Assuming my measured values are linear with voltage. That puts me under 200l/hr, about as low as 188 to 193 l/hr.

Yeah, making a lot of assumptions and it seems odd that I would have issues at under 60% idc. At that point I would think that I still have enough fuel even with the measured flow numbers.

It would be nice if I can run the pump at operating voltage somehow.

[Toni]

Well a couple of you guys might be right. I think it's the afpr. Even though I changed the diaphragm and ball I didn't throughly inspect the orifice seat. After rigging up both my pumps for a band-aid just to see the car working again I was playing around with the larger orifices and noticed the wear on the old one I had removed. It's not confirmed but basically what I think was happening is once the injectors got opened up the fpr should have closed tighter, however the wear prevented that so the pump didn't have enough juice to overcome this extra leak to the return. After looking at this I would be a little worried with a walbro 255 and 550ccs. Basically after all the bends, filter, voltage drop, older alternator I just don't think it has enough to be safe for my car. I may move to an aeromotive stealth pump to get that little extra. First, I'll get a new seat and see if that is really the problem.

http://primaryboost.com/store/rt/afprwear/afpr_ball_seat_wear.jpg

[Toni]

Problem solved!!! it was that stupid orifice. So basically that still means I'm on the end of what the walbro can handle with 550s with my car because the fpr needs to be completely shut to hold pressure. I've heard other cars can handle more but maybe they are just tuning it out. Funny how that little jet opening can cause so many problems... I will be calling aem, this part is only two years old and less than 10kmiles.


I basically let off once I saw 9s on the wideband gauge. Fuel pressure holds steady now.

http://primaryboost.com/store/rt/logs/072011afterjetchange.png

[Hans@GZP]

I just had a turbo integra come in with the same problem (dropping fuel pressure at high rpms) with the AEM FPR and twin walbros (car makes almost 500 fwhp). I just sold him a bolt on Aeromotive unit and told him about your problem with the orifice. I'm willing to bet he has the same problem. I may order up another Aeromotive FPR and see if I can get it to fit on our fuel rail with the adapter. If so, it would be a far better option.

[Toni]

I would be curious to know how many miles were on it. The problem might be that the aem afprs wear too much if you are on the end of the pumps capacity. That means there is more contact between the ball and seat over time. It wouldn't surprise me if other people are having the same problem and just tune it out, or go to a dual feed system which ultimately changes their fpr.

[Hans@GZP]

I doubt he has many miles on it. It's not the type of car you drive every day LOL. He thought the pumps were pulling too much current, so he ran a separate 30 amp circuit for each walbro. Ended up with the same problem. So, even with dual walbros, he was dropping pressure. I guess it doesn't take much for that to happen if it's slightly worn. I'll have to ask him how many miles are on that FPR.