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Old 05-22-2006, 10:13 PM   #1
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Default Adjustible FPR topic w/ afc stuff too. (this is a long one)

Alright let me set the mood.
This comment in the other thread:
Quote:
Originally Posted by 95naSTA
Bill, I'd have to see your fuel trims to believe it.
Wasn't ment as a jab at Bill or implying that he is wrong/lying.
To me it just seems pretty amazing.
The internet is a wonderful place to have comments taken the wrong way.
In my mind there is a possibility that it can work.
But there would only be a select few applications where it would. I trust Bill enough to assume he fits this criteria.
So heres whats going on in my head:

Bill'* general situation from what I've read:
(expecting some correction as I probably don't know everything)
LIM porting done, gen 3 blower swap, and flow matched injectors.
From these mods the engine should be flowing more at all times and more importantly each cylinder should be getting the same amount of air and fuel.
PEMs and some exhaust work.
Also, making the engine flow more air in general.
Jet stage 2 chip
Slightly more timing? higher shifts, and modified fueling. This could have the potential to yeild more KR if my ASSumption about the timing is correct. But the modified fueling could also help in meeting the demands of the engine flowing more.

Now on the the adjustible FPR.
I'm relating it to my adjustible trans modulator since there both vacuum controled diaphragms.
I've noticed that if I tighten the center pin too much, the trans will bang into gear but it will shift hard at WOT. When I loosen it, the banging into gear will stop but the WOT shifts will be softer. I have also seen cut away views of diaphragms so I understand how they work mechanically. So, thats where I'm coming from in my understanding.

Now with Bills setup I'm assuming that it flows more in general but I would also assume that it flows significantly more at WOT. With that said I would think that would be much more fuel needed up top as well.

So, Now back to the adjustible FPR. If your increasing the fuel rail pressure at WOT, the pressure must also be raised at idle. At least slightly. This would initially create a rich condition.
But.... Wait Wait Wait!!!
I also understand how these comupters manage the fuel. It has an initial fuel curve (in this case it'* Jet'*)for any given condition. These conditions are a combination of many sensor outputs such as MAF, MAP, Crank Sensor, IAT, etc.
Control feedback for the fueling is taken from the O2 once the car warms up. And Integrators (INT) are generated. INTs will over time adjust the Block Learn Memory which is a modification of the original fuel curve. The initial BLM will be at 128.
When fully learned, if the BLM is higher than 128 at a certian situation more fuel was added. And if it is lower, then the car was originally running rich at that certian situation.
Although the computer can adjust it is always best the have your BLMs as close to 128 as possible. From what I understand the pcm is designed to work efficiently at or close to that condition. So, the further you move away from BLMs of 128, the less efficient your fueling becomes.

Back to increasing the fuel pressure at WOT and also having an increase at Idle. The computer can adjust for a rich condition creaded by the increased fuel pressure at idle over time but unless you have the right mix of conditions your BLMs are going to be off somewhere. And if they are too far off the fueling won't be as efficient.

Now another point that Bill has made is the higher pressure (to a point) leading to better fuel atomization especially at WOT. With better fuel atomization there is less fuel wasted since it burns easier. That would also lead to less overall fuel. This also means that, up top, it'* easier to get the fuel needed. And the change in pressure increase dosen't have to be as drastic.

So, Bill I do understand cetian things that could make it work but the window of opportunity for having this work seems to be narrow to me.

I'm not trying to call you out Bill but could you post your highest and lowest BLMs after you have considered the computer to have learned the setup? Not a recording since you cant do that just the #* you have observed.

And lastly about the AFC, specifically the 2.0. IMO this is a great tool. I have been using it for over a year and a half now so I have plenty of experience with it. I recognize it'* draw backs and limitations and also realize that it isn't the end all solution for fueling but it has been working great for me. With this tool and changes within +- 8% of the current fuel table I am able to maintain very good Long Term Fuel Trims (BLMs). This is not just for one condition either. When cruising on the highway, accelerating, etc., the LT Fuel Trims do not stray far from 128. Ultimately, I will have the fueling programed to eliminate the use of the AFC. Then the curve will then not be limited to 12 linear segments associated with maf frequency but an actual curve.
Another advantage to programing out the AFC is different conditions will be suited better that have the same MAF flow rate. For instance you could be cruising and the MAF sensor will be picking up 40 gm/sec and sure enough at some point during acceleration you will also be flowing the same amount. Adjusting with the AFC changes both conditions while you may have only needed to adjust one. THAT is the major draw back of the tool.
But even so, from my experience with it on my car, I am able to suceed in getting my fuel trims to be correct.

I posted this topic to discuss both topics in the title. I'm not trying to stir up any pissing contests or 'one uping'. This is a great oppurtunity to learn more about the subjects at hand from one another. So... CONSTRUCTIVE comments are more than welcome.
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Old 05-22-2006, 10:24 PM   #2
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Mike, forget the vac control for a minute. The trans modulator that you and I have is STRICTLY vacuum controlled like the FPR, but the FPR has backup. It'* called the PCM (and all it'* inputs).

The PCM will do everything within it'* power to maintain the proper AFR at all times if you allow it to.

In my particluar case, with the setup I have, the FPR does wonders for me. My fuel trims (both long and short) are within factory spec (data taken a couple months back), and I have no fueling issues across the band. I am now back to 30+mpg on the freeway as well, and all my power is restored with ZERO KR on a 2.2" pulley.

I know you've been a fan of the AFC for quite some time, and I know you know that my opinion is that it'* an inferior bandaid or tuning aid at best. I went with the FPR based on the data and issues I was observing and expert opinion I sought.

Based on my scan data, it was the right choice and I have absolutely ZERO tuining issues at this point (well, one actually, but it'* not fuel related).

I could really give two ***** if you believe me or not. I have nothing to prove, but at the same time, I've never misled anyone on this Forum, and I think you know it. After Blazin'* crap-fest today in two different topics, I'm done for now. Wanna know more? Go buy one and try it for yourself. You'll be one-up on the FPR expert that never tried one (you know who).

Let'* not forget your PCM is a totally different animal than mine, but at the same time we have a S1 and a S2 L67 running FLAWLESSLY on Adjustable Fuel Pressure Regulators.

If you don't want to run one, and BlazinLo doesn't either, that'* fine. I really don't give a **** right now. I have one in my car, I love it, I have no issues, and I'm willing to discuss it with anyone that actually understands how the PCM lowers the DC of the fuel injectors to maintain proper AFR regardless of fuel pressure (within reason).

I'm done with this subject and topic at this point.
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Old 05-22-2006, 10:45 PM   #3
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Bill, I do understand how Injectors work too.
I don't want you to prove anything to me or the rest of BC. And I'm NOT trying to prove you wrong.
You obiously know more about how your setup is working than I do.
I just want to learn more about it and I'm sure others do too.
I posted everything I could think of pertaning to your situation and my thought precess about it. Where am I missing things? What am I not getting.
If your tired of the crap fest, I can understand.
So, maybe come back to this?
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Old 05-23-2006, 01:11 PM   #4
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Wow! Where to start?

Let me start with the FPR as it relates to Bill'* situation. (The principles will be the same for any modern EFI gas engine)

Pre adjustable FPR Bill had made many changes to up the air flow through the engine.
The PCM can adapt to the changes with in set limits. The reason the factory set these limits (they can't be changed with a chip) is to flag component failures. (something is broken and needs to be fixed)

With the significant rise in air flow the PCM will raise fuel trims to bring A:F back to the correct ratio. If the trims exceed the limits the car will run like doo and will be lean up top and possibly everywhere else.

There are a few possible solutions:
AFC; works well enough for most, (there are some wicked fast cars using them) but if you are at the edge of injector capacity you will still go lean at the top. (BOOM)

Larger injectors and reprogrammed PCM; limited availability of custom chip tuners for the Bonne makes this impractical.

Larger injectors and stand alone engine and transaxle management; expensive (parts, labor, tuning on a dyno) and there is no one that I know of that has interfaced with the 4T60E.

Adjustable FPR; Look at trims calculate change in injector flow required to zero them. Do the math to find the change in fuel pressure to achieve this flow. set FPR. Drive car for awhile. Check trims. Repeat until all is good.

(sqrt(new FP/old FP))*old injector flow=new injector flow

The idea of the adjustable FPR is to tune injector flow rate to work with the duty cycle the PCM wants.

The biggest advantage over an AFC is the AFPR follows the infinite point curve of the fueling maps, an AFC works in linear zones. (it is only perfect at one point in each zone)

I will add to this based on qeustions generated.
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Old 05-23-2006, 02:06 PM   #5
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AFC calibrators are not a true curve. They provide a response curve made of small lines. At one particular 'point' on each line, you are at the proper AFR. You never achieve true efficiency, and should the AFC calibrator fail, you run the risk of BOOM in a forced induction application.

It is a TOOL to define what you need for a custom burn, not a long-term solution, and never a power-adder.

In my particular case, I increased the top-end flow across the band on my car. Not just from the larger TB, but from the porting as well. We (those that were involved in the troubleshooting, diagnosis, and planning) surmise that my stock PCM and Jet chip could not quite adjust to the new flow required. It ran like dogmeat with the 93 MAF sensor, and better with the 95.

Rather than potentially limit myself with the 93 MAF sensor, we went big. My injectors themselves were not the limiting factor. The PCM (and the trim tables) were. By mildly bumping my fuel pressure (with the new Walbro to back it up), I was able to get the stock 29lb injectors to flow a little more per pulse, allowing the PCM to fall back into the 'trim range' if you want to think of it in that manner. The adjustment wasn't extreme.

The end result is that I'm currently running around 45-46 PSI (up from 43.5 which is 3.0bar), making my injectors flow at closer to 30lb/hr (310cc/hr vs. 305cc/hr) rather than the stock 29lb/hr rate.

This small increase was all I needed to overcome my fueling/trim issues. I will probably bump my fuel pressure slightly higher this summer for track runs to benefit from the intercooling effect that a richer condition can provide. This has been done before with great success, and is not a new idea in the automotive world.

The current state of my car is perfect fuel trims. I've checked it once since adjusting it initially (about 2 days later) and verified that it'* rock-solid.

Referring to the other topic (now that I've cooled my nerves a bit), it irritated me that someone claimed to know alot more about something than my experience on my own car, regardless of the fact that he'd never tried it himself. I know damn good and well what works on my own car and what doesn't. I don't have what anyone would consider a 'normal' setup, but I made it work without having a custom burn (other than the Jet Stage 2 chip) and without having to use the AFC calibrator to either survive or provide data for another chip. I achieved my ultimate goal of using the Stock 93 PCM and JET chip with a Gen3 top end, even though I didn't think it would work based on the cars that tried before me.

Using an AFC controller beyond the point that you figure out what needs to be done to a custom PCM is like running your space-saver spare tire for longer than it takes you to get to the tire shop.

I had my choice of replacing the tire (adjustable FPR) or running the dinky spare for the short or long-term (AFC Calibrator).

Based on my results, I chose wisely. From a cost standpoint, reliability standpoint, and ease of tuning standpoint.

Many thanks to the following during this fun-fest of getting my fueling right:

Greyhare
2000SilverBullet
John Wikoff
jr's3800
Fuel Injection Enterprises
INTENSE Racing
(all of the above were consulted in some manner before I decided on the FPR.)

The Casper'* adjustable FPR works BEAUTIFULLY in my application, and should in similar applications as well.

Still don't believe my fuel trims are perfect? That'* not my problem. It'* yours.
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Old 05-23-2006, 02:13 PM   #6
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Bill W:

At least from my perspective and I bet for others who have silently followed your progress.. I think we're more interested in how you were able to tune it so perfectly... Your last post was a good explanation.
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Old 05-23-2006, 07:03 PM   #7
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Alright!
This is more of what I was hoping for.
Great info in here.
I definitely do see how it can work for your application.
So, previously, your LT fuel trims were bumped up and just out of factory spec.
Then, with the adj. FPR, you were able to increase the amount of fuel (per given pulse width) enough to bump your LT fuel trims back down in factory spec.
I believe that can work.
What I ment by 'I'd have to see it to believe it' is that I can't beileve your long term fuel trims are at or really close to 128. But I can believe they are within factory spec.
I actually didn't know there is such a thing as a factory spec. for fuel trims..
Like I said, I wanted to learn what I was missing.
Whether I believe you or not was never a problem in my eyes. I usually go with what I know and will change my mind when more facts are brought to the table.

I guess the thing now is to see how the change in season effects the lt fuel trims. Or if it is enough to bump it back out of factory spec. I'm guessing that could just be an adjustment away?
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Old 05-23-2006, 07:05 PM   #8
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Tweak and go. Car runs perfectly in 90 temps so far.

This is why I bought the full kit with the gauge. It takes me 10 seconds to adjust.
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Old 05-23-2006, 09:21 PM   #9
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Very cool. Thanks guys!
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