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Discussion Starter · #1 ·
if the EEC will just compensate the injector pulse to lean out a car if a AFPR is installed and a higher pressure is dialed in with it- thus getting the car back to the same amount of fuel being fired even though the pressure in the line is higher- how the hell would you adjust the A/F ratio if you install higher flowing heads, intake, TH, MAF etc so you are not running too lean?


thx!
 

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You disconnect your battery. Then reconnect after the install. The computer will adjust everything automatically for you. In other words, your computer will adjust until it hits 14.7 a/f at part throttle conditions and add those changes to long term memory. Computer assumes than if your car needed more fuel at part throttle then your car needs more fuel at WOT as well and will add it accordingly.

This will not be true if the fuel your combo needs exceeds the amount of fuel the stock injectors can supply. In that case, a bump in fuel pressure will make up for the difference until an upgrade to the next injector size can be made.
 

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Generally increasing the injector size and using an aftermarket MAF will help the most if you jumped from say 250 to 350 hp. I never could get my EFI combo to run rich enough. I think your best bet is to get a custom tune. An AFPR will only benefit you if the engine is lean anyways. When you increase the fuel pressure, reset the computer, the O2s will see normal as opposed to lean. It's honestly one of those things where you're better off fixing the problem (custom tune/chip) than trying to mask the problem which doesn't always work and generally causes other problems.
 

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Discussion Starter · #4 · (Edited)
ok, the reason why I ask is because I was all set to get kirban until today's discussion about them being waste of time-

my setup this spring with be GT40P's 76 MM MAF, 65mm TB, headers etc... I am going to have 24# injectors installed to complement the heads- so when the car first fires up, I assume that I will be lean with all the extra air so the EEC will increase the pulse width of each injector to get my A/F ration back up to 14.7? and since I will have the larger injectors the higher then stock pulse (needed since there is more air thus more fuel needs to be added) will not over load the higher capacity injector like it would if i had the stock 19#-

is this correct- sounds good to me- almost makes me feel like I know what I am talking about!! LOL- can some one just confirm my logic here is accurate?
 

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You explained it a little funky, Lxpony, but I think ya got it...

• During initial start up, you are actually in open loop (ignoring O2 sensors) for around 90 seconds and running off of fuel tables. By nature, these start up tables are way rich to promote quick warm up. You will be OK there.

• After the 90 seconds or so, your computer switches to closed loop. As soon as it does so, it begins looking at the a/f mixture with the O2's. It is preprogrammed to hit 14.7 a/f, so it will continually target that ratio. Simple as that.

• Since you aren't chipping your car to let it know it has 24# injectors, your properly matched mass air flow meter "tricks" the computer by telling it there is less air coming into the motor than there really is (I suggest using Pro-M). This is not the ideal way, but is usually considered the best way besides a chip or a tuner.

• You will be just fine with your above combo. There is the possiblity of some drivability/idle issues with aftermarket mass air meter/different cam, but those can usually be solved by rotating (clocking) the mass air sensor around a few degrees at a time until optimum postion is found (much like indexing a driveshaft).
 

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Discussion Starter · #6 ·
thanks for your explantion- i have been running a C&L meter for some time now with the 19# flow tube and no drivability issues and that is with a cone filter and my cam is and will remain stock-

thx!
 

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Lxpony said:
thanks for your explantion- i have been running a C&L meter for some time now with the 19# flow tube and no drivability issues and that is with a cone filter and my cam is and will remain stock-

thx!
Just for info--with my C&L and 19lb injectors my combo was fine. However, with the addition of HCI and 24lb injectors (with the appropriate sample tube) I had alot of hot start surging and hunting for idle.

With the addition of the supercharger and 42lb injectors (and appropriate sample tube) it still idled pretty rough with some surging.

Adding a decent Tweecer tune to it fixed the hunting idle and elminated hot start issues. The car drives and idles *almost* as well as it did stock.

If like the rest of us you will constantly crave additional horsepower you might as well buy a tuner now and learn to use it. :)
 

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Discussion Starter · #8 ·
Well, the cam is staying stock so I hope not to have any of your issues.......
 

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Discussion Starter · #9 ·
I am going to install the injecotrs and sampling tube first , verify it runs fine, then do the heads- that way I will know what would be causing any drivability issues....
 

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Meter by itself might not cause any problems. Heads by themselves might not cause any problems. Cam by itself might not cause any problems. But, any combination of the above might cause problems. When I added ported intakes to my combo, by drivability got a lot worse.

After I got my tweecer r/t, the bulk of my drivability issues were fixed by inputting the correct maf transfer curve. In other words, I told the computer how much air was actually going into the motor. This fixed 85% of my bucking/trailer hitching problems.
 

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Discussion Starter · #11 ·
No, I understand what you are saying- thanks for the input- that just supports my thinking though that doing parts one at a time will allow me to know what causes drivability issues and which do not-

currently my unported Cobra intake, stock heads, 76mm C&L and stock 19# injectors produces a rock solid idle.... hopefully that will remain once the larger injectors and heads are on - AND OF COURSE- I WILL KEEP MY NON ADJUSTABLE FRP ON INSTEAD OF A KIRBAN!!!!
 

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:D
 

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okay so for us guys without chip/tuner, and say I go dyno tune with a WBO2. Does that mean a month later (after driving) my computer will have adapted and my WOT tune would be different?? What air fuel ratio is the computer aiming for during WOT.

This worries me as I've read many guys just tune with super FMU's or air bleeds in conjunction with the regulator. Or even just 42 lb's/MAF/AFPR and no chip. I'm just wondering if maybe I should bother to invest in a chip even though I don't have driveablity problems.
 

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ChewyR said:
okay so for us guys without chip/tuner, and say I go dyno tune with a WBO2. Does that mean a month later (after driving) my computer will have adapted and my WOT tune would be different?? What air fuel ratio is the computer aiming for during WOT.
Yes. It could be different, especially if you have tuned with an adjustable AFPR. The WOT target a/f ratio varies according to the computer you are running. Usually in the 12-12.5 range. This is done by fuel tables and completely ignores O2 sensors.

ChewyR said:
This worries me as I've read many guys just tune with super FMU's or air bleeds in conjunction with the regulator. Or even just 42 lb's/MAF/AFPR and no chip. I'm just wondering if maybe I should bother to invest in a chip even though I don't have driveablity problems.
Tuning with FMU's is a little different. FMU's will increase pressure directly proportional with the amount of boost (referenced from the intake). Usually, that boost only starts coming on in higher rpms. By that time, you are already in WOT. So, the computer doesn't know that the fp has been jacked up at that time. It just follows it's OL tables like it is supposed to. The extra fuel gets thrown in to compensate for the extra air from the blower. FMU's will add the fuel, but they are a lot of times not as precise as needed to provide a smooth a/f ratio across the entire rpm range. Plus, they can be a little slow to react, causing lean/rich spikes during operation.

With your blown combo, I would recommend a dyno tune to make sure everything is OK. Your results might scare you just a little, but hopefully not.
 

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When a chip or custom tune is done, the tuner is able to program the chip to make the EEC look for any AFR (air-fuel ratio) that he wants, so the EEC will not learn around this, but it is true that it will "compensate" some for the added fuel from an adjustable fuel pressure reg, but at WOT-where you need the extra fuel- the computer will NOT make any corrections, it simply runs off of a pre-programmed table, in the A9L (fox body cars) it strives for 11.7 or around that. So in an essence, the adjustable fuel reg is a good idea, and is not useless. It will allow you to richen or lean your combo to where it makes most power at WOT and it will remain that way. Why would you want anything other than a 14.7 AFR at cruise and idle?? it done need it and it will just burn gas...you only need the fuel at WOT....

Sorry so long...just wanted to clarify some things.
 

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There is a good reason why AFPR are sold. The Kirban one is very good. I have one on my car and it's never failed me. As a few guys have stated above normal driving is completely controlled by the computers readings of O2 sensors, but WOT is not. With your setup you may need to put an extra 5lbs in or take 5lbs out... you never know.
A close friend of mine was running a TFS head setup on a custom lower end. He had nothing but problems. We looked at it together and he was running way lean... with 40lbs of fuel pressure on 30lb injectors. I think we ended up with him just over 50lbs to make his popping go away. Plugs started turning brown.

Every combo is different... With the setup you have, if it's running good, don't change the injectors. Try your 19s with your MAF on the setup and see what happens... I would get the AFPR and add about 10 to 15lbs (stock is something like 38), but stock injectors will go way past stock HP/TQ combos. I also had 19lb injectors with a C&L 73, it ran great... when I changed to 24lb injectors and the sample tube my idle never was the same... Hell it ran better with the 19lb tube and the 24lb injectors... until I got a Pro M and some 30s (along with heads and a cam, I already had a Vortech). Since the Pro M went on I have never had any idle problems... I even loaned out my Pro M to solve a couple friends idle problems.... who turned around and bought a Pro M themselves.
 

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One other thing to realize about FPR is that spray pattern is altered also. Back when I had a 305 powered TPI camaro I did some reasearch in moding it. Lingfelter actually found 5 hp in adjusting the pressure for spray pattern, not additional fuel. It also stated that this wasn't as effective on the Fords as the two companies use different types of injectors. Just stating what I learned, I don't know why. So in essence if you do bump fuel pressure and pulse widith is altered, the spray pattern may provide better atomization, thus helping power and gas mileage.

Edit. FWIW When I bought my car last spring it had the exhaust and gears done to it. My first pass was a [email protected] With the addition of the UPR(kirban) FPR, BBK pulleys(wp and crank only), the cheapy CAI, and MSD box and coil I improved to my now best ET and MPH. So that was almost 1 full second in Et and almost 6mph through mostly tuning with the AFPR.
 

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SSKiller said:
When a chip or custom tune is done, the tuner is able to program the chip to make the EEC look for any AFR (air-fuel ratio) that he wants, so the EEC will not learn around this,
The tuner is only able to target a specific a/f ratio in "Open Loop" (WOT or at Start Up). Targeting a/f ratio at part throttle "Closed Loop" is almost impossible to do. It can be done but is usually a last ditch resort.

Originally posted by SSKiller but it is true that it will "compensate" some for the added fuel from an adjustable fuel pressure reg,[/B]
It will compensate the necessary amount to reach 14.7 a/f. If it runs out of adjustment range (+ or - ~25%), you will get a check engine light.


Originally posted by SSKiller but at WOT-where you need the extra fuel- the computer will NOT make any corrections, it simply runs off of a pre-programmed table, in the A9L (fox body cars) it strives for 11.7 or around that. [/B]
You are correct in saying that it does not make any corrections (based off of O2 sensors at WOT/Open Loop). The corrections are implied from the short term corrections (KAMRF) to long term adaptive memory. These corrections are then added to the WOT fuel tables. The EEC does use fuel tables for WOT/Open Loop conditions with specific targeted values. However, the actual values almost never match up with the targeted values (using a wideband O2). This happens because adaptive has modified those values to match what the EEC has seen at part throttle/Closed Loop conditions. In effect, the EEC assumes that since you are rich at part throttle conditions, then you will be rich at WOT conditions and makes the appropriate changes.


Originally posted by SSKiller Why would you want anything other than a 14.7 AFR at cruise and idle?? it done need it and it will just burn gas...you only need the fuel at WOT.... [/B]
I agree wholeheartedly.

In slo5oh's case, his friend was running lean consistently. So in that case, by upping his fp, he was able to fix the problem all across the board.

I never meant to insinuate that AFPR was useless, there are some cases where they have been used with great success to make up for a deficiency in injector size, etc. :D
 

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93Cobra#2771 said:
I never meant to insinuate that AFPR was useless, there are some cases where they have been used with great success to make up for a deficiency in injector size, etc. :D
You just hit the nail on the head. Excellent explanation by the way, but that statement is really all anyone needs to know.
 

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but that statement is really all anyone needs to know.
True, would have saved me a lot of typing and thinking about how I needed to word it. I get a little long winded some times... :D :D
 
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