SAFC2 question

[Puscifer]

Alright, the research I've done has lead me to asking this question. I always look around and stew over stuff before I actually step out and ask - Because most answers are right under the nose.

The situation at hand is that I have a big 16g, 550cc RC Injectors, upgraded + rewired pump, AEM Fuel Rail - (was under the impression I do not need an AM FPR with this setup so I'm on stock) good bit of other mods but I'm only listing the post sensitives.

So.. w/ the tuning guide and such I have understood that the trims need to be within 5% for low/hi and the base that should be started out is -18% and lean out from there. When I perform a test pull in 2nd gear @ WOT to around 7k|rpms I am running waaaay lean. Now for the last month or two I've managed to work my way into the +% in order to obtain proper fuel trims. Is this normal? averaging about 12mpg and it's ugh.

Boost Leak Test has shown there's a small BoV leak and I've replaced the other one near the TB, was missing the gasket on the piping side. My GReddy boost gauge is showing I'm hitting about 1 bar (14.38psi iirc)

I can't quite afford a wide band ATM due to yet another hellion on the way but as useless as a narrowband is it's reporting I'm stoich until about 3800rpm then it says I'm rich, but, it is actually leaned out to -26% from there and beyond. Any clue's at all?

Thanks in advance,
Dosage

 

[spyderturbo007]

How do you know you're running lean? You don't want to tune using front O2 since it's really only good for generalizations. With a 2g, you want to tune using airflow and timing advance.

Can you post a log at idle / light cruise along with one of your 2nd gear pulls?

For the idle log, just select front O2, STFT, LTFT, RPM and airflow. Before you do the 2nd gear pull, go WOT for a second or two and verify that the TPS on the logger reads around 100%. After that, log airflow, timing, front O2 and RPM only which will maximize your samples per second on the logger.

 

[mikelv]

Based upon what you posted I would also ask why you would need that much correction factor on the AFC? Last time I checked 550 injectors are ripe right around a 10% correction factor. You are trying to use a formula that coincides with your Global Fuel Setting Correction factor with DSMLink.

DSMLink Fuel sliders work differently than the AFC; they actually work in conjunction with the injector pulse width, as where the SAFC uses your Karman MAF Senor Signal coming into the ECU (which in turn affects injector pulse). Based on the value (measured in Hz) the ECU determines values such as ignition timing and injector pulse width. The major down side to using an AFC is you cannot control dead time. With larger injectors, you don't only get more fuel, but slower response. The injectors will spray more or less based on the MAF signal, but will still react slower.

DSMLink Formula: (450cc/ Inj. Size) -1 = (% of compensation)

Here are a few quotes and excerpts on how to calculate a start point correction factor. Also, and most of the time, (-10%) is a decent place to start with 550's.

Definitive Piggyback Tuning Guide: KPT 4321

STEP 1: Setting up the car and the SAFC.

Before we begin the guide on how to tune with a SAFC, you must make sure the car is set up correctly to do so. Make sure all the fuel components are in good condition, and make sure you have no boost or vacuum leaks. Also, if you have a 255 lph or larger fuel pump with no adjustable regulator, then either get a new reg or don't try to use the fuel trim techniques outlined below.

Second of all, setting up the SAFC. At this point, I will assume that you have it wired in properly, if you do not, there are plenty of directions in the VFAQ. Also, may I suggest that you DO NOT do the "blue wire mod", it has been proven to degenerate the O2 sensor's signal.

In the Th-Point section of the SAFC, set the low trigger at 30%, and the high trigger around 80-85%.

In the NePoint section, set them to: 1k, 2k, 3k, 4k, 4.5k, 5k, 6k, and 7k,.

Now, you want to use baseline corrections for fuel injectors. If you have 450's, leave both tables at zero. If you have 550's, put them around -10%. If you have 660's, usually around -18% would be a fine starting point. If you have a hacked MAS, then you will want to use about 5% MORE than these values.

The next section will cover fuel trims, and how to set the low throttle table.



Here is a quote from my article:

Apex SAFC:

Before we get started, we must first understand the concept of the Air Flow Converter.
Basically, (and without getting into complicated detail) the AFC "intercepts" the MAS Airflow Signal coming into the ECU (Hz) and "fools" the computer into thinking less air is entering the engine. Since fuel delivery is primarily based upon Airflow, this will allow you to compensate for larger injectors, by reducing injector pulsewidth.
When you run larger injectors, the ECU doesn't have a "sixth-sense". It doesn't automatically know you have larger injectors, so it won't adjust injector pulsewidth. Basically, this means if your running 550cc injectors, the ECU will spray them as if they were 450's causing you to run rich, (but we'll get to that later). For the most part, when you upgrade fuel injectors, all it means is you have an injector with bigger holes in the end of them that allow more fuel to spray for a given amount of time. (Hint: that's why for the most part injector prices are pretty close regardless of size) And no kiddies, THAT DOESN'T MEAN YOU CAN PORT YOUR INJECTORS!!!

Basic Concept of Operation:

Okay, let's talk about basic AFC operation. As I stated before the SAFC intercepts the frequency signal from the MAS and converts it to a set value based on your settings. How it does this is the AFC has a set of maps based by engine load and rpm. The percentage correction is exactly what it says: it will compensate the percentage you enter at each RPM and Throttle Position, off the actual value measured at the MAS.

For example, if the actual signal coming into the ECU is 500 Hz, and you have a correction factor of (-10%) the new value the ECU will calculate is 450 Hz. Make sense?

So if you have a larger injector, and your car is running rich or sluggish, you must make the correction factor in order to compensate. Ideally, after the correction the injector pulsewidth will be reduced, and the car should operate as though it were stock. Now there is a benefit to this regarding Open Loop Conditions, but we'll get to that a little later on.

The next correction factor you must take into account when tuning with the AFC is Throttle Position Compensation. There are two TP setting included with the AFC, Hi, and Low. Although it seems simple, you need to understand that it's not as straight forward as it looks. Below the low setting, the car will calculate airflow from the tables from your low throttle point settings. Above the high setting, the ECU will calculate airflow based upon the high throttle point settings.

Okay, now from there you need to log as suggested.
For WOT (Hi map): Front O2, Timing, RPM, TPS, Aiflow (MAS), and Knock (if available).
For Cruise (Lo map): STFT, LTFT, RPM, TPS, Airflow (MAS) .


Cruise: Once you get your Fuel Trims close to 0, or at least within 5%, then you can make some pulls.

WOT: Look for a nice smooth timing curve that doesn't seem to keep "backing off" throughout the pull. If you can measure knock, .04 or .07 degrees of knock is usually just engine vibration, but and more than that is a no-no. The 2G knock sensor is very sensitive, which is a good thing. You're looking for a timing curve that will run smooth and steadily all the way up. I wouldn't want to put a number on it, but your setup should run 15 or 16 degrees of total timing pretty well.

Your Front O2, if it's in good working order will be around .96v or .98v under WOT. Any less than that and you're too lean. Old school tuning, I would usually run a little rich for pump gas giving you around 1.00v on the front O2. This worked well with an EGT plug before Widebands were easily accessible. Now for 200 bucks, you can save yourself a lot of headaches.


A side note regarding tuning with the AFC, which is pointed out in most technical articles, is the affect it will have on your total timing. Since the AFC doesn't have an ingnition timing feature built in, there is no way for the computer to compensate, or overcompensate for changes in airflow signal. Simply said, when you hack your MAS, and change things, the computer doesn't know the difference. It's not like it can read your mind; it's programmed do work a certain way and that's that. If you decrease the airflow signal to compensate for larger injectors, think about it.? Lower airflow levels get more timing advance, because the ECU thinks you are pulling in less air, this will continue to happen until the engine detonates and the knock sensor retards the timing curve. As long as you keep an eye on things you shouldn't have a problem.

Use the guidelines outlined in the tech articles on here, some good judgment, and you'll be fine.

 

[No_Skillz]

You need an aftermarket FPR. An adjustable one is best, like the Aeromotive. Your stock one is not allowing enough to return to the tank, so at higher RPMs in boost you are running extremely rich. Any fuel pump upgrade from stock should have one. (What made you think you didn't need one?)

 

[mikelv]

No sure but I never heard of that. Nice catch, I missed that one.

I've never heard of your fuel rail allowing enough to eixt. It still has to go through the regulator.

 

[spyderturbo007]

so at higher RPMs in boost you are running extremely rich. Any fuel pump upgrade from stock should have one. (What made you think you didn't need one?)

Actually, this only applies at idle, cruise and the first couple psi of boost. After that, you're using enough fuel that it won't cause any problems. Let's say for example, your fuel pressure at the rail is 7psi over base. In that case, once you hit 7psi of boost, things will even out.

As for the pump, I didn't see anything other than "upgraded fuel pump" so I had no idea which pump he was running.

 

[No_Skillz]

Actually, this only applies at idle, cruise and the first couple psi of boost. After that, you're using enough fuel that it won't cause any problems. Let's say for example, your fuel pressure at the rail is 7psi over base. In that case, once you hit 7psi of boost, things will even out.

As for the pump, I didn't see anything other than "upgraded fuel pump" so I had no idea which pump he was running.

From my understanding, the stock FPR regulates pressure by release. When a fuel pump is upgraded, it doesn't release enough, so pressures are higher. This only gets worse as PSI rises since the vacuum line connected to the FPR creates higher pressures in the regulator. Also, if the regulator isn't allowing enough fuel to flow past at vacuum, there's no way it'll let enough go by under higher pressure. The flow rate of the injectors also shouldn't come anywhere near the capabilities of the pump, so fuel pressure at the rail should remain unaffected by higher RPM. Let me know if I'm totally off the mark here.

 

[spyderturbo007]

Here you go, just to save a little time since Kevin explains it very well and believe me, he knows what he's talking about. I trust his knowledge 1000%

The stock FPR will raise fuel pressure, not drop it. It also won't have any effect at WOT (or anything over about 10 psi). So your leaning out on top is probably caused by something else. The stock FPR will also bollix fuel pressure in a very predictable and repeatable fashion, but it will not be a linear change. That's what makes it tough to tune around, though it can be done. I'm a big fan of giving the ECU what it expects, and that's 43 psi across the injector at all times.

To provide a quick illustration of what is going on, simply check your base pressure and compare it to expected base pressure. For example, if the stock reg and 255 is giving you a base pressure of 50 psi, that is 7 psi over what the regulator is trying to achieve. At everything up to 7 psi of boost, fuel pressure will remain at 50 psi. Once you get to 8 psi, it will start to rise 1:1. So everything from 7 psi and under is banjaxed, and anything over 7 psi is normal. You can see the non-linear relationship as boost pressure rises. At 2 psi you are 5 psi too high, and at 6 psi boost you are only 1 psi too high. At 20" of vacuum, fuel pressure is 17 psi too high. And that makes it pretty obvious why this is a much bigger problem at idle/cruise.

 

[jrohner]

I've never seen even a hint of fpr overrun on the 3 cars I've tuned with 255hp pumps. I'm not convinced that it's anything more than a myth.

 

[Demon33]

Here you go, just to save a little time since Kevin explains it very well and believe me, he knows what he's talking about. I trust his knowledge 1000%

Quote:
Originally Posted by 95GSXRacer
The stock FPR will raise fuel pressure, not drop it. It also won't have any effect at WOT (or anything over about 10 psi). So your leaning out on top is probably caused by something else. The stock FPR will also bollix fuel pressure in a very predictable and repeatable fashion, but it will not be a linear change. That's what makes it tough to tune around, though it can be done. I'm a big fan of giving the ECU what it expects, and that's 43 psi across the injector at all times.

To provide a quick illustration of what is going on, simply check your base pressure and compare it to expected base pressure. For example, if the stock reg and 255 is giving you a base pressure of 50 psi, that is 7 psi over what the regulator is trying to achieve. At everything up to 7 psi of boost, fuel pressure will remain at 50 psi. Once you get to 8 psi, it will start to rise 1:1. So everything from 7 psi and under is banjaxed, and anything over 7 psi is normal. You can see the non-linear relationship as boost pressure rises. At 2 psi you are 5 psi too high, and at 6 psi boost you are only 1 psi too high. At 20" of vacuum, fuel pressure is 17 psi too high. And that makes it pretty obvious why this is a much bigger problem at idle/cruise.

The purpose of the FPR is to maintain a consistent (base) pressure between the fuel rail/injectors and the intake manifold to allow for consistent fuel delivery.

With the vacuum line disconnected from the FPR, zero intake pressure is in essence simulated at the FPR and base FP is 43 psi, for example. Think of it this way, with a 1:1 FPR Fuel rail pressure=base FP+intake pressure. Connect the vacuum line to the FPR and you'll see the fuel pressure drop about 1 psi for every 2" of applied vacuum to the FPR. The conversion from vacuum to pressure is actually: PSI=vacuum * -0.491 PSI. Using 20" of vacuum in this example and the above formula we get: Fuel rail pressure = 43 psi + (-10 psi) or 33 psi. This also applies to boost, but instead of converting vacuum to pressure, we simply use the boost pressure. For example, with 17 psi of boost we will see fuel pressure rise to 60 psi (FP=base FP+intake pressure)

Essentially, what is happening is that the fuel rail pressure is being adjusted by the FPR based on the intake pressure so that the injectors will always be operating at a net pressure of 43 psi thus, allowing for a more consistent fuel delivery.


Can you please explain how a 1:1 ratio is not linear? In the example above- "At 2 psi you are 5 psi too high, and at 6 psi boost you are only 1 psi too high. At 20" of vacuum, fuel pressure is 17 psi too high. " isn't that a linear progression from 5 psi to 1 psi?

2 psi boost = 5 psi over base FP
3 psi boost = 4 psi over base FP
4 psi boost = 3 psi over base FP
5 psi boost = 2 psi over base FP
6 psi boost = 1 psi over base FP


"For example, if the stock reg and 255 is giving you a base pressure of 50 psi, that is 7 psi over what the regulator is trying to achieve. At everything up to 7 psi of boost, fuel pressure will remain at 50 psi. Once you get to 8 psi, it will start to rise 1:1. So everything from 7 psi and under is banjaxed, and anything over 7 psi is normal. "

I don't think this is correct. The FPR is simply a differential pressure regulator designed to maintain a pressure difference between the input and output. So if there is a rise in input pressure the output will rise by the same amount. This differential setting is fixed on the stock FPR but is adjustable on an AFPR which is needed when FPR overrun is encountered like when using a 255 lph fuel pump.

Also, can you explain how the stock FPR does not have an effect at WOT or above 10 psi as your quote indicates?

 

[spyderturbo007]

I don't think this is correct. The FPR is simply a differential pressure regulator designed to maintain a pressure difference between the input and output. So if there is a rise in input pressure the output will rise by the same amount. This differential setting is fixed on the stock FPR but is adjustable on an AFPR which is needed when FPR overrun is encountered like when using a 255 lph fuel pump.

Also, can you explain how the stock FPR does not have an effect at WOT or above 10 psi as your quote indicates?

Inside the FPR is basically a diaphragm and a spring. The spring has a constant rate based on the manufacturers' specifications. In our case, with no vacuum or boost signal, the spring is designed to hold the pressure at 43.5psi. If you apply vacuum, more fuel is allowed to return to the tank and during boost applications, less is allowed which creates more of a restriction and thereby increases fuel pressure.

Kevin wasn't saying that the stock FPR doesn't have any effect above 10psi, but that the overrun regulator will no longer be overrun after you pass the 10psi of boost mark.

 

[Puscifer]

Wow. Thanks for the extended amount of knowledge base there. I had been up for a good 32 hours when I made that post. Well rested and such now. I fully understand what you guys mean by the tuning difference via SAFC / DSMLink, Sadly the pulls I'm talking about are via PocketLogger and tuned w/ SAFC2. I'd notice the range when I was leaned out floating from .48-.62v, couldn't never really get in the .8 range. I richened it up and was finally able to get to .82v *sometimes* & I'm not really sure why I started out with -18% I now realize it should be -10% - I think I may've (mis)read somewhere or something.

I replaced the O2 Sensor and I've got the 190LPH FP (sorry i didn't post that) which is why i stated i read i didn't need an AF FPR but if you guys directly say i do, then, yeah.. I'll get on those logs in the morning when I can. In the mean time i'm going to soak all that info in. Thanks again!

 

[Kevin Jewer]

My post turned into a big long mess, let me try again. My quote above was in response to a specific case, not a general over view of how the system works. So I will attempt to clear things up. We actually agree on how the system should work.

The purpose of the FPR is to maintain a consistent (base) pressure between the fuel rail/injectors and the intake manifold to allow for consistent fuel delivery.

Correct. Pressure across the injector should remain constant regardless of manifold pressure to provide predictable fueling, so we adjust fuel pressure relative to manifold pressure to keep the differential equal.

With the vacuum line disconnected from the FPR, zero intake pressure is in essence simulated at the FPR and base FP is 43 psi, for example. Think of it this way, with a 1:1 FPR Fuel rail pressure=base FP+intake pressure. Connect the vacuum line to the FPR and you'll see the fuel pressure drop about 1 psi for every 2" of applied vacuum to the FPR. The conversion from vacuum to pressure is actually: PSI=vacuum * -0.491 PSI. Using 20" of vacuum in this example and the above formula we get: Fuel rail pressure = 43 psi + (-10 psi) or 33 psi. This also applies to boost, but instead of converting vacuum to pressure, we simply use the boost pressure. For example, with 17 psi of boost we will see fuel pressure rise to 60 psi (FP=base FP+intake pressure)

Essentially, what is happening is that the fuel rail pressure is being adjusted by the FPR based on the intake pressure so that the injectors will always be operating at a net pressure of 43 psi thus, allowing for a more consistent fuel delivery.

All correct.

Can you please explain how a 1:1 ratio is not linear? In the example above- "At 2 psi you are 5 psi too high, and at 6 psi boost you are only 1 psi too high. At 20" of vacuum, fuel pressure is 17 psi too high. " isn't that a linear progression from 5 psi to 1 psi?

2 psi boost = 5 psi over base FP
3 psi boost = 4 psi over base FP
4 psi boost = 3 psi over base FP
5 psi boost = 2 psi over base FP
6 psi boost = 1 psi over base FP

Now this is where the confusion begins. You're listing how far the pressure is off from "target" and calling the progression linear. And it is, but only because mnaifold pressure is linear. Fuel pressure across the injector however, which is what we care about, is NOT linear. This chart will illustrate my point, and I don't think you'll see anything you didn't already know. We are just looking at two different functions.

"For example, if the stock reg and 255 is giving you a base pressure of 50 psi, that is 7 psi over what the regulator is trying to achieve. At everything up to 7 psi of boost, fuel pressure will remain at 50 psi. Once you get to 8 psi, it will start to rise 1:1. So everything from 7 psi and under is banjaxed, and anything over 7 psi is normal. "

I don't think this is correct. The FPR is simply a differential pressure regulator designed to maintain a pressure difference between the input and output. So if there is a rise in input pressure the output will rise by the same amount. This differential setting is fixed on the stock FPR but is adjustable on an AFPR which is needed when FPR overrun is encountered like when using a 255 lph fuel pump.

It is correct, but only in its original context which was regarding the example of fuel pressure over run at 50 psi minimum pressure. This is the same scenario the chart above describes.

Your description is mostly correct, assuming "input" really means manifold pressure reference and not the actual FPR input. I'm sure this is what you meant. The last statement about an adjustable FPR being needed when over run is present isn't entirely correct. A bigger fixed or adjustable FPR will help to eliminate over run, but the fact that it's adustable is irrelevant. Once you can't flow enough fuel back to the tank you can no longer adjust pressure down (manually or via the manifold reference port), which is the definition of fuel pressure over run. It's the same thing as saying that in a case where a fixed stock wastegate causes boost creep, an adjustable stock sized wastegate would allow you to adjust the creep down. You can consider fuel pressure over run "fuel pressure creep," and you could call boost creep "boost pressure over run" or "wastegate over run." To get back to the point, the only thing the adjustable factor in an FPR gives you is base pressure adjustability. You can't go any lower than the system will allow. When I say system, I mean regulator, lines, fittings, 2g AWD saddle tank siphon, etc. In fact I don't even like the term "FPR over-run" because it implies the FPR is always the cause, when in fact it can be any of the above. I'd rather call it fuel pressure over run and leave the diagnosis of the cause up to the user.

Also, can you explain how the stock FPR does not have an effect at WOT or above 10 psi as your quote indicates?

Again, in its original context that statement is correct. "Effect" meaning "negative effect," or fuel pressure over run.


Again, we seem to be in agreement. Hopefully this post clears things up.

 

[Kevin Jewer]

I've never seen even a hint of fpr overrun on the 3 cars I've tuned with 255hp pumps. I'm not convinced that it's anything more than a myth.

Anyone that says it's a myth has either never had it, doesn't have the tools to measure it, or doesn't know what he is looking for. Now, I'm not saying any of this is the case with you, I have no way to know. So I would ask for more information regarding those three setups, tools at your disposal to measure it/log it, and what you've done to try to find it.

I could provide tons of personal examples of fuel pressure over run regarding the FPR, the 2g return line, and the siphon from my personal 2g and EVO, but there's no need for me to do that. There is an overwhelming abundance of data available on the internet to prove its existance, even if I haven't dealt with it personaly for so many years.

 

[mikelv]

Wow. Thanks for the extended amount of knowledge base there. I had been up for a good 32 hours when I made that post. Well rested and such now. I fully understand what you guys mean by the tuning difference via SAFC / DSMLink, Sadly the pulls I'm talking about are via PocketLogger and tuned w/ SAFC2. I'd notice the range when I was leaned out floating from .48-.62v, couldn't never really get in the .8 range. I richened it up and was finally able to get to .82v *sometimes* & I'm not really sure why I started out with -18% I now realize it should be -10% - I think I may've (mis)read somewhere or something.

I replaced the O2 Sensor and I've got the 190LPH FP (sorry i didn't post that) which is why i stated i read i didn't need an AF FPR but if you guys directly say i do, then, yeah.. I'll get on those logs in the morning when I can. In the mean time i'm going to soak all that info in. Thanks again!

Ha, seems the Wiseman have been passing "the force" of knowledge via your thread.

.82v is insanely lean for a front O2 reading. Don’t pull the car like that!! I’m surprised you haven’t fried anything quite yet but be careful until we can get things right.

How long has it been since you’ve changed your front O2? This low of a reading is not good either way.

Let’s start with the tuning guide links I posted for you and see what is going on. I’m sure if you take away some of that correction factor (add % on the AFC) and start with (-10%) you should see thing get a little better. Actually, I want you to go up to about (-7%) or (-8%). Too rich is better than too lean in almost all instances. If we get the tuning dialed in correctly and we still see inconsistant numbers, then we'll raise the red flag.
I mentioned the piece about DSMLink because I knew you were using that correction factor equation. (This is a great formula). However, it’s meant for making corrections in “real time” with injector pulse. The AFC cannot do this. Let me know if you need more explanation on the operation of the AFC.

All the talk about the AFPR is excellent, and do what you can to learn from it. It’s not going to destroy your car to not have one temporarily. You will see better performance and more consistent fuel delivery, but keep the boost down, and you’ll be ok.

 

[Puscifer]

Still waiting for the lot to clear for the log pull, as I agree about the .82v being way to lean and my main concern for having to dip into the +% on the AFC, that's what put me here in the first place. the O2 is about 4 months old, bosch and proprietary plug. I replaced it 4 months ago hoping to fix this very same problem. good thing it's not my DD eh.

 

[mikelv]

Still waiting for the lot to clear for the log pull, as I agree about the .82v being way to lean and my main concern for having to dip into the +% on the AFC, that's what put me here in the first place. the O2 is about 4 months old, bosch and proprietary plug. I replaced it 4 months ago hoping to fix this very same problem. good thing it's not my DD eh.

I hear you on that one.

I'm not thinking you're having a fuel delivery problem physically here then. (Sorry I missed the part in your post about going positive)

Re-check the wiring of the AFC, and possibly the MAS. Basically what I’m thinking is your Air Sensor might be telling the computer only a certain value, which in turn will affect fuel delivery. If the MAS is sending a screwy signal, then the ECU won’t fire the injectors properly.

I say this because when you go positive, (increasing the MAS signal frequency) the injectors richen you back up. So the fuel WILL deliver, but only when you “boost” the MAS signal.

So check the wires, and check the MAS.

What kind of airflow numbers are you logging? Are you using Pocketlogger?

 

[Demon33]

Now this is where the confusion begins. You're listing how far the pressure is off from "target" and calling the progression linear. And it is, but only because mnaifold pressure is linear. Fuel pressure across the injector however, which is what we care about, is NOT linear. This chart will illustrate my point, and I don't think you'll see anything you didn't already know. We are just looking at two different functions.

Truly a picture is worth a thousand words. Seeing it graphically, I instantly knew what you meant and I totally agree with you on this one.

Your description is mostly correct, assuming "input" really means manifold pressure reference and not the actual FPR input. I'm sure this is what you meant. The last statement about an adjustable FPR being needed when over run is present isn't entirely correct. A bigger fixed or adjustable FPR will help to eliminate over run, but the fact that it's adustable is irrelevant. Once you can't flow enough fuel back to the tank you can no longer adjust pressure down (manually or via the manifold reference port), which is the definition of fuel pressure over run. It's the same thing as saying that in a case where a fixed stock wastegate causes boost creep, an adjustable stock sized wastegate would allow you to adjust the creep down. You can consider fuel pressure over run "fuel pressure creep," and you could call boost creep "boost pressure over run" or "wastegate over run." To get back to the point, the only thing the adjustable factor in an FPR gives you is base pressure adjustability. You can't go any lower than the system will allow. When I say system, I mean regulator, lines, fittings, 2g AWD saddle tank siphon, etc. In fact I don't even like the term "FPR over-run" because it implies the FPR is always the cause, when in fact it can be any of the above. I'd rather call it fuel pressure over run and leave the diagnosis of the cause up to the user.

Again, we seem to be in agreement. Hopefully this post clears things up.

Great analogy. We're all familiar with boost creep and you're right, fuel pressure over run is very similar, if not the same. No confusion or disagreement here. And you're right, a bigger regulator, fixed or adjustable will help eliminate fuel pressure over run but only if it is the bottleneck in the sytem. You could still have over run if any of the other fuel system components are too small and limit the fuel return flow.

Mostly, we do seem to be in agreement. Thanks for taking the time to clear that up.

 

[Puscifer]

http://i607.photobucket.com/albums/tt157/dosage_album/1m-idle.jpg

there's a short idle log, kind of iffy at this point about going WOT

 

[spyderturbo007]

Was the car warmed up completely before you took that log? Your FT's aren't cycling and it looks like your front O2 is on it's way out the door.

Can you post up your current SAFC settings, such as TPS trigger points, Ne points and corresponding correction factors, etc?

 

[Puscifer]

Sure thing. Yeah, I warmed it, turned it off for a few minutes, back on for a couple - then took the log. I replaced my old bosch o2 thinking it was dead as well.. thinking it's like mike suggested and in the wiring. here's what you asked for -

TH-Points 30-85%

NE / Lo / Hi
800 0 -6
1400 0 -6
2000 +4 -6
2600 -1 -6
3200 -4 -7
3800 0 -7
4400 -4 -7
5000 -8 -5
5600 -8 -5
6200 -6 -5
6800 -6 -5
7200 -6 -5


Right around the idle - 2k base is where i'm having the most issues at, obviously. w/o vacuum leaks or anything else i had a naturally high idle as well and the more i leaned it out, the higher it got. With all this out there.. I've never read anything about the "display scale" menus on the AFC, what should they be at as well? thanks and i hope that's what you were looking for.

 

[spyderturbo007]

I see your STFT is updating, but it hasn't moved to the LTFT yet. Was the O2 sensor you swapped in new, or was it used?

Mathematically, your low throttle settings should be in the -15% neighborhood, but typically they are lower. I've never seen a DSM obey the mathematical correction at idle / cruise. I would guess you will end up in the neighborhood of -10% when you are done.

The problem is that we need to get the O2 sensor fixed before you can set the low throttle map since the ECU is seeing a lean condition from the front O2 and adding fuel to compensate. Anything you do right now, is going to get jacked by the ECU because of the problem with the front O2.

 

[Puscifer]

Yeah, I've went outside and checked my connections for the front o2 and they're doing fine, I also used the proprietary plug on it so i didn't have to wire it in.. Yes, they were both brand spanking new bosch o2's. I'm gonna run out and undo the blue wire mod for the AFC in a little bit to see if that's impacting it at all and recheck the wires for the ecu / afc once more.

 

[spyderturbo007]

I'm gonna run out and undo the blue wire mod for the AFC in a little bit to see if that's impacting it at all and recheck the wires for the ecu / afc once more.

It has been "said" that the blue wire mod will degrade the O2 sensor signal on it's way to the ECU, so that could be the problem. Well, at least we will know for sure if that's true once you unhook the wire. After you do that, go ahead and post another log at idle, I'm anxious to know if it's true or not.

 

[Puscifer]

Sorry for the delay. Checked all the wires and now there's nothing piggybacked onto the o2 sensor, direct to the ECU now. here's the newer log

http://i607.photobucket.com/albums/tt157/dosage_album/1m_idle2.jpg

meh. originally it had a o2 dump housing but it was welded to run into the exhaust and i replaced it with the famous megan racing SS recirculated o2 housing but i dont see why that'd impact it's reading. gonna go back to being a wire monkey for a little bit to investigate some more.