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Old 03-14-2016, 12:52 AM   #1
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Fuel Pump Duty Cycle questions

Can someone help me understand Fuel Pump Duty cycle?

I have Fuel Pump Duty Cycle and Fuel Pump Percentage logging when using my SCTX4. If my FPDC reads 60 and my FPP reads 116, does this mean I am maxed out?

The pump duty cycle is anywhere from 58.x to 60.x throughout the pull. What gives?
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Old 03-14-2016, 08:28 AM   #2
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What are your mods and intentions? You shouldn't be maxed out unless you are FI at higher boost without a BAP or are trying to go E85.
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Old 03-14-2016, 01:19 PM   #3
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What are your mods and intentions? You shouldn't be maxed out unless you are FI at higher boost without a BAP or are trying to go E85.
I am running 10lbs of boost and already have a Roush plug-n-play fuel pump regulator.

The logs do not make sense to me if at 960 RPM my duty cycle is 58.6 and percentage is 120 and at 6200 RPM my duty cycle is 60.3 and percentage is 0.195.

What is this telling me?
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Old 03-14-2016, 10:03 PM   #4
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Nothing, I'd say. If you are looking to see if you are maxed out, look at your afr, bank one and two and stft. If it's pushing hard here, something is up. The system is returnless, so the ecm would normally bemonkeying around with duty cycle and pressure all the time. Your BAP is messing with that a bit.
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Old 03-14-2016, 11:56 PM   #5
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Nothing, I'd say. If you are looking to see if you are maxed out, look at your afr, bank one and two and stft. If it's pushing hard here, something is up. The system is returnless, so the ecm would normally bemonkeying around with duty cycle and pressure all the time. Your BAP is messing with that a bit.
I am asking the question because it ties into my power loss at high RPM from my other thread.

It turns out I was logging Fuel Pump Module Duty Cycle instead of Fuel Pump Duty Cycle. After a conversation with SCT, 0.5 is max and I see that before WOT.

So here are some questions from a frustrated first time booster:

1) What AFR should I see at boost? I hear ~11 is good, but LiveLink doesn't show these numbers. I get a lambda, so what's the calculation?
2) The goal is 600 RWHP, so a stock fuel pump with a BAP is enough, proof positive?
3) If 0.5 represents the pump at max duty cycle, and since I have a returnless fuel system, why isn't this cause for concern? My understanding is that in a return style system then the pump would be at 100% all the time.
2)
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Old 03-15-2016, 09:44 AM   #6
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1. An AFR in the 11 could be more fuel than needed. A WOT Lambse near the low .8s is fine.
2. You should be fine but, 600 wheel is definitely when people start to push stock stuff and not all stock stuff is created equal.
3. Returnless systems work by deadhead pressure against the fuel rail and having the ecm command the amount of push required to meet the engines needs in real time. I'm not sure you can draw too many conclusions from this data, or maybe I just don't know enough. Your BAP running all the time at full voltage, which is the way the ecm contols the pump, is messing up how much you can draw conclusions from the data here, I think.

Any time I see high pm power loss on a blower car, I don't think fuel, I think spark. Do you have any misfire events recorded? What plugs are in there, how old are they and what are they gapped at?
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Old 03-15-2016, 12:28 PM   #7
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1. An AFR in the 11 could be more fuel than needed. A WOT Lambse near the low .8s is fine.
I plotted my data to look at the AFR for bank1 and bank2. During the WOT pull, the AFRs roughly track each other (not dead nuts, but I understand that to be normal) and range from 11.9 to 12.1 at 6300 RPM. The AFRs trend lower to 11.1 at 6700 RPM.

If I understand what you are saying about the BAP is that since it's in circuit the duty cycle is invalid. If so, I'll shelve the concern for now.

Quote:
Any time I see high pm power loss on a blower car, I don't think fuel, I think spark. Do you have any misfire events recorded? What plugs are in there, how old are they and what are they gapped at?
I also plotted spark advance1 and spark advance 2, and during the WOT pull they both average 14 with a dip to 10.75 at 4400 RPM. The current data logs show zero misfires during the WOT.

Interestingly enough, I have had problems with the plugs since day 1 (6 months ago was the install). I am the second owner and I presume the plugs used were the original plugs. The instructions call for a gap to 0.03 and I presume those were followed. However, since the initial install the car would just bog down like a dog at 5500 RPM and you could hear the knock.
The plugs where replaced with Iridium plugs gapped to 0.03 and the power loss was pushed up higher into the RPM band near 6200 RPM.

Currently, my plugs are NGK TR6 gapped to 0.028 and I installed the BAP to eliminate this power loss. I almost want to say this power loss comes and goes meaning that I can actually feel it under WOT, but not all the time. It's weird.

A local tuner took this data on a Mustang dyno and stated that in his opinion there is nothing in the data that would explain the power loss. He was just as confused as I am. AFR, throttle angle, spark, lambse, etc. all looked kosher. This is why I am getting frustrated, because what else could it be? No evidence of belt slip either.

If there was an exhaust restriction or engine damage, wouldn't this throw other parameters off (AFR, spark advance, etc)?

I appreciate the free help and time. This is more than I have been getting over the last couple of months.
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Old 03-15-2016, 12:38 PM   #8
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That spark pull at 4400 is pretty common on Coyotes. I think it has to do with vvt adjustment.

You still have cats in the car?
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Old 03-15-2016, 03:11 PM   #9
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That spark pull at 4400 is pretty common on Coyotes. I think it has to do with vvt adjustment.

You still have cats in the car?
Yes, I still have the stock cats. I have another data log and with the cat temperature banks logged and the temps get up to 1750 F.

The other results from this data are fairly much the same during WOT:
Lambse Bank1: 0.79
Lambse Bank2: 0.79
Measured AFR1: 0.79 to 0.84
Measures AFR2: 0.79 to 0.83
Cylinder Head Temp: 89C
Intake Air Temp2: 114F
Spark Advance v2: 7 up through 14. Probably due to the knock sensor when first getting on the throttle.

The only thing out of the ordinary is knock which initially is a +3 and goes down to -2 during the pull. This knock behavior has always been there even before the blower install.
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Old 03-15-2016, 03:14 PM   #10
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I think you should pull the cats and retune.

Cat + FI = weirdness at the 10 psi level.
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Old 03-15-2016, 04:42 PM   #11
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I think you should pull the cats and retune.

Cat + FI = weirdness at the 10 psi level.
You are not the first person to tell me to remove the cats. I might go down the road of a test pipe first before spending the cash on a set of Kooks long tubes.
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Old 03-15-2016, 04:55 PM   #12
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Test pipes are 80% of a full length header anyway. FI will fix any flow issues.

The cat temps are fairly high and it's indicating they are working hard here. Keep pushing, you'll melt them. High cat temps can cause the computer to freak, pulling timing, inducing cat overtemp which will mess up your fueling or triggering knock ******.
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Old 03-16-2016, 01:10 PM   #13
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Test pipes are 80% of a full length header anyway. FI will fix any flow issues.

The cat temps are fairly high and it's indicating they are working hard here. Keep pushing, you'll melt them. High cat temps can cause the computer to freak, pulling timing, inducing cat overtemp which will mess up your fueling or triggering knock ******.
This, tune by afr, drive by EGT. The .79 -.84 lambda is pretty standard. You're typically going to make the best torque at ~.85 but with FI you'd want a bit richer otherwise you may not have the best cooling across all the cylinders. To much or to little fuel can cause temperature issues, so there is no way to tell if fueling is an issue with your EGT's without logging and testing.

As for the spark pull, without knowing more about your tune we can only speculate. Assuming the knock threshold and spark tables were not zeroed out /built from scratch and or not using proper correction(s) and are being used to evaluate one or more table(s) region and not target a single cell you'll see spark being pulled and added regularly.
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Old 03-16-2016, 01:22 PM   #14
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Test pipes are 80% of a full length header anyway. FI will fix any flow issues.

The cat temps are fairly high and it's indicating they are working hard here. Keep pushing, you'll melt them. High cat temps can cause the computer to freak, pulling timing, inducing cat overtemp which will mess up your fueling or triggering knock ******.
I started to log the cat temps because I wanted to know if there was a problem. During dyno pulls, these PIDs are never logged. From my reading, 1750F is on the highside.

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This, tune by afr, drive by EGT. The .79 -.84 lambda is pretty standard. You're typically going to make the best torque at ~.85 but with FI you'd want a bit richer otherwise you may not have the best cooling across all the cylinders. To much or to little fuel can cause temperature issues, so there is no way to tell if fueling is an issue with your EGT's without logging and testing.
Stupid question, what is EGT? Something with the throttle?

Quote:
As for the spark pull, without knowing more about your tune we can only speculate. Assuming the knock threshold and spark tables were not zeroed out /built from scratch and or not using proper correction(s) and are being used to evaluate one or more table(s) region and not target a single cell you'll see spark being pulled and added regularly.
I have to go back to my tuner anyway. At 2000 RPM there is this god awful oscillation. I looked at the data and the throttle blade angle, AFR, spark advance all move up and down. It looks like the AFR is VASTLY different from bank1 to bank2 during this time. This happens at cruise or after a pull and coasting and then getting back on the gas ever so slightly.

I am not sure if these behaviors are related or not.
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Old 03-16-2016, 02:52 PM   #15
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EGT = Exhaust Gas temp. We can only infer this from cat temp but, you need to get those cats out quick because they are coming apart and are going to screw things up and make your problem indistinguishable from all the weird symptoms. Do that, then retune.

Oscillation at part throttle could be caused by many things. I'd look first for a post maf vacuum leak.
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Old 03-16-2016, 04:51 PM   #16
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I started to log the cat temps because I wanted to know if there was a problem. During dyno pulls, these PIDs are never logged. From my reading, 1750F is on the highside.

If your car was dyno tuned, typically AFRs are concentrated on at first. However EGTs should have been logged for the already stated reason(s)


Stupid question, what is EGT? Something with the throttle?

5LHO got it

I have to go back to my tuner anyway. At 2000 RPM there is this god awful oscillation. I looked at the data and the throttle blade angle, AFR, spark advance all move up and down. It looks like the AFR is VASTLY different from bank1 to bank2 during this time. This happens at cruise or after a pull and coasting and then getting back on the gas ever so slightly.

I am not sure if these behaviors are related or not.

At low engine loads, cruising, off throttle you really do not need to worry about small variations. You will see leaner numbers under all of those conditions and with little to no load it really doesn't matter what the spark is doing. Unless for some crazy reason the knock and knock threshold tables have been seriously altered

I very highly recommend you get an AFR gauge, that way you have a known good sensor you can compare with the one on your car

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EGT = Exhaust Gas temp. We can only infer this from cat temp but, you need to get those cats out quick because they are coming apart and are going to screw things up and make your problem indistinguishable from all the weird symptoms. Do that, then retune.

At this point, because we don't know time elapsed this is a must

Oscillation at part throttle could be caused by many things. I'd look first for a post maf vacuum leak.

This is also good info. There are just too many variables we don't know yet for your situation. The tune being the big one.
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Old 03-17-2016, 07:24 PM   #17
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Well, the general consensus is to eliminate the cats. I heard back from Justin @ VMP, and the tuner who took the dyno data both recommended the cats to come out. One clue is the "one time it's good" another run "it's bad" leads people to believe it is a latent failure in the cats.

I'll will be looking for a deal for a set of Kooks headers with a non-catted x-pipe. This will be over the next couple of months.

I'll keep this thread updated as the time comes.
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Old 03-18-2016, 01:13 AM   #18
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Well, the general consensus is to eliminate the cats. I heard back from Justin @ VMP, and the tuner who took the dyno data both recommended the cats to come out. One clue is the "one time it's good" another run "it's bad" leads people to believe it is a latent failure in the cats.

I'll will be looking for a deal for a set of Kooks headers with a non-catted x-pipe. This will be over the next couple of months.

I'll keep this thread updated as the time comes.
I could agree if they took the runs in the same day and close in time together. Did they recommend you remove the cats at any time before or during the dyno runs? Or did they recommend that after you went back and asked? IMO they should have mentioned it at the beginning.
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Old 03-18-2016, 09:13 AM   #19
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It's straight up obvious from the datalogs the cats are way too hot, signifying potentially a couple things.

Either the heat of the boosted exhaust is too high and it's cooking them, or the ecm is seeing the temps too high and is dumping raw fuel in to try to cool them and it's combusting in the cat itself and melting them.

This is why the tune and power are all over the place and this will likely mess something up soon.

10 psi on this setup is right at the edge for cats in.
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Old 03-18-2016, 11:47 AM   #20
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Everything will be coming together towards the end of April. I ordered Kooks headers with an off-road x-pipe from MarylandSpeed for $1250. I am on vacation for a couple of weeks in April so, by the end of the month install and tune should be done.
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Old 05-11-2016, 12:55 PM   #21
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It's almost been 2 months, but my Kooks long tubes and non-catted x-pipe are being installed over the next couple of days. I will post back after the installation and tune revision.
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Old 03-12-2017, 10:35 AM   #22
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Fuel Pump Duty Cycle questions

what happened after the install & tune revision? did the hesitation/stalling under boost stop? I am having the same issue with stalling (current diagnosis is double digit long term fuel trim readings indicating a lean condition) and am down to 3 last potential mechanical causes (after all the other vac related issues were ruled out) before I take it back to the tuner:
1. Fuel Delivery issue (I have stock fuel pump with a Roush BAP)
2. Bad MAF sensor (I am getting MAF lb/min readings, but not sure if they are correct)
3. Overheating cats (+1600F) - I have kooks ultra high flow green cats in my kooks setup, but when I give it gas they overheat
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Old 03-12-2017, 05:12 PM   #23
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what happened after the install & tune revision? did the hesitation/stalling under boost stop? I am having the same issue with stalling (current diagnosis is double digit long term fuel trim readings indicating a lean condition) and am down to 3 last potential mechanical causes (after all the other vac related issues were ruled out) before I take it back to the tuner:
1. Fuel Delivery issue (I have stock fuel pump with a Roush BAP)
2. Bad MAF sensor (I am getting MAF lb/hr readings, but not sure if they are correct)
3. Overheating cats (+1600F) - I have kooks ultra high flow green cats in my kooks setup, but when I give it gas they overheat
Ah, I am glad that you posted to remind me to update.

The stock catalytic converters were damaged, meaning that the honeycomb was melted in both cats. This could have been an existing condition before I had the VMP installed, because the first owner had a tune, and "didn't like how it drove." Possible pre-existing condition and then the VMP tune simply exacerbated it.

Removing the damaged stock cats, and installing the Kooks longtubes, offroad x-pipe and retune solved everything. Before the Kooks and tune, I was at 475 peak RWHP. After install and tune I was at 614 RWHP and no hesitation or feeling like it is falling on its face at WOT.

1) I also have the stock fuel pump with a Roush BAP.
2) Not sure about the MAF. I think poster Voltwings may be able to help you with the readings.
3) If your Kooks high flow cats are that hot (same as mine) they may be damaged. I am not an expert, but poster 5LHO flagged the extreme temps as an issue. I also had feedback from a local tuner to be wary of the stock cats with Superchargers and rich mixture.

There was never a *definitive* flag to say, "Yep, it was the cats", but enough feedback for me to take the risk and purchase. I am glad I did.

EDIT:

I thought about using borescope to look at the cats before taking them off. The rear of the cats were fine; there was nothing wrong with the honeycomb there. The front of the cats is were the melting of the honeycomb was happening. With your Kooks high flows, it may be easier to disconnect the exhaust and simply look.
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Old 03-12-2017, 05:59 PM   #24
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Do you know the fuel capacity of your Roush BAP system? What size injectors are you running?
My Roush is putting out 640RWHP with the 98lb injectors and the same BAP as you



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Old 03-12-2017, 08:40 PM   #25
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Do you know the fuel capacity of your Roush BAP system? What size injectors are you running?
My Roush is putting out 640RWHP with the 98lb injectors and the same BAP as you



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Off the top of my head I don't know the fuel capacity of the BAP. I am running 47lb injectors, 10 lbs of boost.
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Old 03-12-2017, 08:43 PM   #26
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Thanks


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Old 03-13-2017, 07:36 AM   #27
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what happened after the install & tune revision? did the hesitation/stalling under boost stop? I am having the same issue with stalling (current diagnosis is double digit long term fuel trim readings indicating a lean condition) and am down to 3 last potential mechanical causes (after all the other vac related issues were ruled out) before I take it back to the tuner:
1. Fuel Delivery issue (I have stock fuel pump with a Roush BAP)
2. Bad MAF sensor (I am getting MAF lb/min readings, but not sure if they are correct)
3. Overheating cats (+1600F) - I have kooks ultra high flow green cats in my kooks setup, but when I give it gas they overheat
What makes you think the readings are wrong?
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Old 03-13-2017, 07:46 AM   #28
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I don't. I don't know how to interpret them. I am looking to validate whether or not the MAF Sensor is lying to the computer based on all the intake upgrades I have done and my tuner is not really savvy in this particular area


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Old 03-13-2017, 09:43 AM   #29
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AHH. Well, typical rule of thumb - and this is very much an "on paper" thing with lots of room for variation - is 10 horsepower at the crank for every 1 lb/min. Now, that's "horsepower worth of airflow" if you want to be super technical, but the car will also make power with timing, compression, etc... So its not like you will expect a car that makes 600 at the crank to flow 60 lb/min, but you would expect to be at least in that ball park.

What you can do is plot maf flow (lb/min) over rpm and i wouldnt be surprised if it is shockingly similar to the dyno curve.

Another thing that makes it tricky, and it would be hard to say for certain without having access to the tune file, is how the fuel trims affect that actual logged MAF reading.
For example, almost all cars show a logged MAF value and a logged fuel trim value, but It is important to know if that logged MAF value you are being shown is before or after the fuel trims were applied, because that can skew hp calculations if you are basing them off airflow. That is how we found out how the computer was calculating fuel on another platform when non of our estimated hp math was checking out.

for example, if you see a logged MAF value of "M" and a logged fuel trim of "+FT" (plus, since fuel trims can be negative), are you assuming the car arrived at the logged AFR by M+FT, OR is the logged MAF value already including "FT" and you would just be concerned with the logged "M" value. This is one of those cases where having access to the tune file helps.

At the end of the day though, you can kind of run the math with and without the fuel trims and still see if you're in the right ball park. Its just something to be aware of.
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Old 03-13-2017, 09:55 AM   #30
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Well if that is true, then there is a ton of unaccounted for air going into the engine causing extreme lean condition (20:1) at any rpm higher than 2000 even causing my ultra high flow kooks cats to overheat
My sensor is showing numbers not even close to that and my intake setup is as follows (imagine how air there is here):
Free flow air filter (2,500 ccfm)
Big JLT 123 mm tube
VMP 67 mm TB
Ported elbow and supercharger inlet
So .....
Either sensor is bad or sensor capacity is maxed out, plus tuner did not do the right thing with MAF tuning



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Old 03-13-2017, 10:54 AM   #31
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It is possible the sensor was not scaled for the larger 123mm housing, That housing is 48% larger than stock. What do your fuel trims look like, they should be pegged at 50% if that were the case?

Are you showing a logged value of 20:1 AFR? Remember that fuel trims are a percentage, not a hard value, meaning if the fuel trim is +7 that is adding 7 percent of the commanded value at that point.
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Old 03-13-2017, 11:27 AM   #32
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Fuel Pump Duty Cycle questions

Long term Fuel trims are positive double digit high. STFT Is positive between 3 and 8%

Fuel delivery:
Fuel pressure at the fuel rail is a constant 55-56 with big 98 lb injectors, stock pump with Roush BAP

A/F over 2,000 RPM fluctuates on the high side peaking at 30:1, but more common 20:1 and car stalls and jerks at steady speed in any gear

I can't tell for sure the lean condition is due to unaccounted air or lack of fuel. I am leaning more to unaccounted air. That is my struggle now to decipher


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Old 03-13-2017, 12:49 PM   #33
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Good lord, if you're really logging that AFR Do NOT run the car any more until you get it sorted. I'm amazed it will even stay running over like 18:1. I think we found your problem.
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Old 03-13-2017, 12:59 PM   #34
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Question is:
What potential mechanical issues are driving this AF ratios up?
Air not accounted for or some kind of issues in the fuel delivery system?
I know the most probable culprit is in the tune, but I need to cross out all potential mechanical issues before I make that trip to the tuner...
So from that perspective I am working on:
1. MAF sensor
2. Fuel pump or BAP or filter
3. My amateur and inexperienced install of the big injectors
4. Clogged cat
Boy, is this fun or what?


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Old 03-13-2017, 01:28 PM   #35
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Since the fueling is off when fuel demand is low, i would cross out everything except the MAF. At least at this point and time. My guess is an oversight on the tuner's part, and the MAF table was not scaled to account for the larger MAF housing.
Now, if the issue was exclusively during high load / WOT conditions, i would consider the fuel pump, but this doesnt look like that to me at least.
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