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  1. #1
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    Question for Tune Developers... Flash vs. Piggy

    There has been a "feud" for the longest time regarding piggybacks vs flashes and target af ratios.
    A flash has been prooven to add more fuel down low and in the mid range of the power band.

    Some piggy backs claim they can already, or will be able to do the same.
    Now I know how piggys adjust fuel, the manipulate the wide bands and fuel pressure to achieve the desired af ratio.

    I am not very good with electronics, but I understand what they do, just not how they actually do it.
    What limits how much fuel we can inject down low assuming we have enough flow to achieve it.

    The jb3 uses different resistors to get richer, the procede uses the same resistor as the "original" jb3 and claims it could add fuel down low, but its not needed. Weather its needed or not, I don't care. I want to know how these resistors limit af targets. Whats the point of these resistors anyway? Is there another way to change the voltage to whatever we want without using resistors?

    Other piggys claim that there is no limit with the way they control fuel. They ramp up fuel pressure and also change the wide band voltage so the target does not go back to a stock like af ratio.

    Here is my question to the tune developers. Who is full $#@! and why?

  2. #2
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    This has the potential to get very interesting, good topic.
    Chrome Space Bar Issue: http://www.boostaddict.com/showthrea...338#post738338


    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

  3. #3
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    Bump for this thread...

    Jake seems busy correcting speds on e9*, Sniv is to cheap to pay to be a sponsor here, hopefully, Terry will help this topic out.

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    I look forward to hearing what BrenM3 has to say.
    Chrome Space Bar Issue: http://www.boostaddict.com/showthrea...338#post738338


    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

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    It's just simple electronics and ohms law. The ECU reads the wideband sensor by measuring how much current moves through it. The more current you bias the richer the air/fuel targets go. Voltage is fixed at 2.25v so to bias more current you need smaller fueling resistors.

    Here's what everyone is running:

    CPE 500ohm
    JB3 G4 and PRO 1000ohm
    JB3 G3 18 ohm 3300ohm
    PROcede 4700ohm
    JB3 G3 5100ohm

    With 4700ohm you can bias up to ~.47 ma. Which is around 13.5 in the midrange 12.0 up top. To go richer you need to pull more current. With the G3 18 ohm we can bias up to ~.68ma. That lets us go to around 13.0 in the mid and 11.8 up top. Of course these numbers are all relative based on how the wideband you're using is reading. There is a lot of dyno to dyno variance on them as you would expect given the various amounts of abuse they receive.

    With the G4 we went to 1000ohm and are currently working on a more sophisticated control mechanism. This dyno is before that mechanism and is running around 1.5ma peak. The 1000ohm let us bias up to 2.25ma which works out to 10.5:1 in the midrange and 10:1 up top. Richer than you'd ever want to go but then we can control it all on the software side.

    PS. All the piggys now control fuel pressure which we did first BTW in early 2008. It extends the maximum fueling range and lets us avoid the tuner detection codes. But has no impact on air/fuel targets.

    Click here to enlarge

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    Good info

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    Adjusting fuel pressure has no impact on af? How is this possible?

    I don't see how these resistors even mean anything. Hear me out.

    Say your are using a 4.7 or 500 like the procede and cpe. Say you adjust the wideband signal by the maximum amount available and once that is dialed in, you up the fuel pressure by 20-30 percent, how will that not richen up the curve?

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    Good point

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    Laloosh just a note on the Flash AFR. GIAC for example does not touch the AFR under 3000 rpm. is stock like. After than it gets fatter and fatter.
    07 335i AT - MOTIV 750 - MHD BMS E85 - BMS PI - JB4G5 - Okada Coils - NGK 5992 Plugs - Helix IC - Stett CP - Custom midpipes with 100 HJS Cats - Bastuck Quad - PSS10 - QUAIFE LSD - BMS OCC - Forge DVs - AR OC - ALCON BBK - M3 Chassi - Dinan CP - Velocity M rear Toe arms - Advan RZ-DF - LUX H8 - Level 10 AT upgrade
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  10. #10
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    Click here to enlarge Originally Posted by Laloosh Click here to enlarge
    Adjusting fuel pressure has no impact on af? How is this possible?

    I don't see how these resistors even mean anything. Hear me out.

    Say your are using a 4.7 or 500 like the procede and cpe. Say you adjust the wideband signal by the maximum amount available and once that is dialed in, you up the fuel pressure by 20-30 percent, how will that not richen up the curve?
    It's closed loop so you have an air/fuel target. If you raise the fuel pressure more fuel goes in, the o2 sensor reports a richer signal, and IPW goes down. You need the resistors to change that target and fool the closed loop system in to targeting your richer (or leaner) air/fuel ratio.

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    Click here to enlarge Originally Posted by Terry@BMS Click here to enlarge
    It's closed loop so you have an air/fuel target. If you raise the fuel pressure more fuel goes in, the o2 sensor reports a richer signal, and IPW goes down. You need the resistors to change that target and fool the closed loop system in to targeting your richer (or leaner) air/fuel ratio.
    Terry does the change that the resistor causes linear through out the range. i.e. it will follow the AFR map of the stock fueling but at a different value or is there another parameter that you make a change through increments of the range?

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    Click here to enlarge Originally Posted by George Smooth Click here to enlarge
    Terry does the change that the resistor causes linear through out the range. i.e. it will follow the AFR map of the stock fueling but at a different value or is there another parameter that you make a change through increments of the range?
    Strangely it's not a linear relationship. For example .5ma @ peak torque gives you more of an afr delta than .5ma @ peak hp. Not sure why but to compensate we map by RPM and DME observed boost.

    (For those not familiar to dial in the air/fuel between min and max you alter the analog signal voltage from 2.25 to 0. With a 10bit DAC that gives you 460 "steps" of adjustment if you're going all the way to 0v. That signal is normally mapped based off boost, rpm, etc.)
    Last edited by Terry@BMS; 10-27-2010 at 02:24 PM.

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    Ok I was thinking of a different scenario. Say you have the proper resistor and you are targetting 11.0 across the board. The a/f doesn't reach the target because the ipw is maxed out. Adding fuel pressure then would richen the curve. I am simply remembering how tuners claim 450-460 being the limit of the stock fuel system and I remember then saying IPW was maxed out. Is it the injectors that are infact the first to cause the fuel limit? If so adding pressure would raise that limit

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    Click here to enlarge Originally Posted by Laloosh Click here to enlarge
    Ok I was thinking of a different scenario. Say you have the proper resistor and you are targetting 11.0 across the board. The a/f doesn't reach the target because the ipw is maxed out. Adding fuel pressure then would richen the curve. I am simply remembering how tuners claim 450-460 being the limit of the stock fuel system and I remember then saying IPW was maxed out. Is it the injectors that are infact the first to cause the fuel limit? If so adding pressure would raise that limit
    Of course. If you don't have enough fuel to hit the target then raising the fuel pressure will help get you there. So would spraying a ton of meth. But the target itself is set by the fueling resistors. If they are not set properly the DME will simply reduce injector pulsewidth when you throw more fuel at it (via more pressure, meth, etc) to get on target.

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    Ok so in conclusion, as long as your have a resistor that is capable of hitting 10.x, you can dial in 10.x despite you ipw being maxed out by adding pressure. Has anyone who claimed the fuel limits actually tried this? Shiv claimed something around 460 on the asr car, you claimed somewhere around 450ish. Did any of you bother jacking up fuel pressure?

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    The fuel control has a PID system similar to boost control. If you dial in a value that is so rich you can't hit it you'll get the fuel system equivalent to a 30FF code. So you need to set the target properly and then there has to be enough fuel to hit the target for the ECU to stay happy.

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    1 out of 1 members liked this post. Yes Reputation No
    But what I am asking is: If you can hit with pressure, what is the limit.

    Limit # 1: injector pulse width
    Limit # 2: ?

    I am not trying to attack you, I'm glad someone who has the means to try this stuff is sharing his experience, however with all the talks for people building engine, adding big singles or upgraded twins, I feel like this fuel limit has to be revisited and explained a little better.

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    You mean what is the limiting factor in terms of fueling past a certain power level? Much of that has to do with what air/fuel you're comfortable with. When I was dyno testing n2o I could not go richer than 13.5:1 or so in the midrange with everything maxed out + 2000ml/min of meth. If you are OK going leaner you can make 550rw with tons of meth. If you want a safe air/fuel level with no meth probably 440rw. My gut feeling is if we had larger injectors the fuel pump would move plenty more volume (at a lower pressure) but it's just conjecture at this point. The in tank pump may also need to be swapped out which would be easy to do.

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    So assuming safe id 13.5 mid falling to say 12.0, 440 is the limited with the proper resistor and raised fuel pressure?

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    You can hold 13.5:1 down to 12.0:1 @ 440rw on a dynojet with maxed out fuel pressure and ~5k fueling resistors.

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    Ok let me try this another way.

    What is the limit with maxed out fuel pressure (what is maxed out fuel pressure to begin with) and the proper resistor

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    Still not sure if you're grasping what the resistors do. Think of them as boost targets. With a 4.7k resistor you can enter a 13.5:1 midrange target. With a 1k resistor you enter a 10.5:1 midrange target, etc. Just like boost targets you can enter in 25psi if you want but if the turbo hardware only supports 16psi that is all you're going to make. So if you want 13.5:1 and are happy with that (i wouldn't be) then 4.7k ohm is the proper resistor for that maximum target. You could also use 500ohm resistors with less attenuation and also target 13.5:1.

    So then the question becomes how much torque can you support at 13.5:1 @ maxed out fuel pressure with no meth. I think around 450wtq and that is at around 3400psi fuel pressure.

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    Click here to enlargeClick here to enlargeClick here to enlarge
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    [SIGPIC][/SIGPIC]

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    Terry I understand how resistors work now. I think I might be wording my question wrong, so im going to give you a scenario.

    I want to dial 12.5 mid range, and never fall above 12.0 after that. With the proper resistor, and fuel pressure, What kind of power can we hit given the correct turbo before we start seeing the fuel system limits. Once injector pulse width is max out to achieve that 12.5-12.0, how high can we up the pressure before we have trouble reaching that a/f ratio.

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    On the race maps on the JB3 end we're running close to the max fuel pressure (trying maxing out sensor @ 5v and having pump say no way). Maybe there is a touch more in there but the pump starts to freak out if you go much higher than we do now. So whatever power we're making now at those air/fuel ratios is close to the limit.

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