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[quote][i]Algselt postitas: prj[/i] [quote][i]Algselt postitas: ranz[/i] Väike täpsustus, N75 wastgate ei sulge, seda teeb WG vedru. N75 saab ainult WG avada, lastes boosti vedrutaldriku alla. [/quote] Nõus, oleksin võinud ennast paremini väljendada. Üks väga hea PDF boost controli ning võimalike ümberehituste kohta on siin: [url]http://www.s2forum.com/forum/showthread.php?t=33383[/url] Toggle re˛iimis on ta jah siis, kui ta boosti piirab, sest vastasel juhul oleks boost kas liiga kõrge või liiga madal. Muidu on asi ilusti paigal... Samuti natuke vale sõnade valik, "alati, kui aju parajasti juhib rõhku" oleks parem. Natuke rohkem sellest, kuidas MAF-ga ECU töötab nissani ECU-de põhjal (Motronic peaaegu täpselt samamoodi... kas neil on omavahel seos?): [quote]Firstly - Background (If you object to me using Horse Power (hp) as a measurement of airflow, simply substitute in CFM or whatever you're happier with...) Air Flow Meters (AFM), a.k.a Mass Airflow Meters (MAF): The basic function of any ECU is simple. Calculate the correct amount of fuel and ignition advance required by the engine at any time. To make these calculations it needs to sense how much "load' the engine is under. The primary load sensor on the Nissan ECCS ECUs is the Air Flow Meter. It is the ECUs biggest asset and also it's achilles heel (from a performance viewpoint). The AFM measures the true mass of air entering the engine. Since mass of air entering the engine is known, determining the mass of fuel required for an appropriate Air Fuel Ratio is a straight forward calculation. This also means the majority of modifications will not require a retune, unlike MAP based systems. Unfortunately the standard AFM can be a considerable restriction in the intake. A 50mm diameter is not a large area for a turbo to draw through. AFMs also have a set operating range from 0-5V, representing a flow of air from 0 to their max rating. 5V on a CA1ET AFM is equivalent to enough air to make around 200hp. 5V on a 300ZX TT AFM is enough for over 500hp. Fortunately, retuning for a larger, less restrictive AFM is possible. Once the CA18 ECU senses the AFM is at its limit (ie at or close to 5V), it will cut fuel to protect the engine. The dreaded boost cut. Or more accurately, Air Flow Cut. Once the Airflow meter is at 5v, any increase in flow will still result in a reading of 5v, as the sensor is at its limit. The ECU can no longer calculate the correct amount of fuel, so it shuts down the engine to prevent a lean out. Once the AFM reads below 5v, the ECU will inject fuel once again. -- ECU Injection Calculation - Overview Ok, we need to know about a few of the ECU's basic variables first. K Required Number: This constant is the basic injector pulsewidth time. All calculations of injector pulsewidth start here. If you make it larger, all injector pulsewidths will get longer. If you make it smaller, all injector pulsewidths will get shorter. This is a very powerful tool when it comes to changing injectors, AFMs etc. VQ Map: The VQ Map is used to translate the AFMs non-linear voltage response, into a linear load reading. Confused? Don't worry too much. For the moment just think of the VQ Map as a "filter" that the AFM voltage goes through, and gives a load percentage as a result. Eg, 5v = 100%, 4v = 75% etc... Fuel Maps: The ECU has two fuel maps, High Octane and Low Octane. It will always run on the High Octane Map unless it senses a problem. The Fuel Maps have 3 components, the RPM scale, the Flow scale and the AFR correction Map itself. All Maps are 16x16, giving 256 load points. The scales must match the sides of the map so are 16 entries each. Flow Scale a.k.a TP Scale: (labelled 'Boost' in Rom Edit) The Flow scale (as I call it) gives a basic injector pulsewidth(K constant) multiplyer, depending on the load sensed by the AFM. RPM Scale: This scale determines what RPM each axis of the AFR correction map is plotted against. Stock is from 500 rpm to 6800 rpm, in (mostly) 400 rpm increments. AFR Correction Map: This is the business end of tuning. Full mapping of your AFRs across load and RPM. Putting it all together: Ok, go through a quick example to see how all the above works together in determining an injectors pulsewidth for a given load and RPM. For the example lets suppose: K constant = 0.125 Milliseconds AFM reading = 5 Volts RPM = 6800. 1) ECU reads AFM - 5v. 2) 5v is "filtered" by the VQ Map - 100% load. 3) Flow scale at 100% load is consulted (column 16) = 83. 4) Basic Pulsewidth = K constant x Flow scale Basic Pulsewidth = 0.125 x 83 Basic Pulsewidth = 10.375ms 5) ECU consults RPM Scale, 6800 rpm corresponds with row 16 of the RPM scale. (We have already calculated column 16 for the Flow scale.) 6) Entry in the AFR correction Map: row 16, col 16 = 1.6. 7) Injection Calculation = Basic Pulsewidth x AFR Correction Injection Calculation = 10.375 x 1.6 Injection Calculation = 16.6ms There you have it. In our imaginary ECU, at 5 volts on the AFM, 6800 rpm, it will pulse the injectors for 16.6ms or around 95% duty cycle. If you followed all that, then you're now prepared for the good stuff. The next section will give you all the specifics about the above variables, where and what the values are in the ROM image, how to interpret them into meaningful values, and how to use them in tuning your ECU. -- ECU Injection Calculation - Detailed Analysis K Required Number: (Nice and simple, some unknowns though) CA Rom Address: 3F80 - 3F81. 2x 8bit Values. Quanta: 00 B7 seems to equal 0.125ms(!) SR Rom Address: 000A - 000B. 2x 8bit Values. Quanta: ? ms As said before, the K required number is the basic injector pulsewidth. On a stock CA1ET map it appears to be 0.125ms. For now that is all you need to remember. You'll see how it fits in the "Putting it all together 2" sections. How do I know that the K Constant in a CA1ET (00 B7) = 0.125ms? Well to be honest, I don't. I received this vital piece of info from a Japanese CA tuner. Sceptical (as I am) I deconstructed all the maps on my CA1ET to calculate Duty Cycle and AFR with the 0.125 ms value and it fits perfectly. So, I'll continue with this assertion until I can be proven wrong/right. VQ Map: (This could take a while) CA Rom Address: 3E18 - 3E74. 52 x 16bit Values. Resolution: 0.1Volt. Quanta: 16bit Precision Quotient SR Rom Address: 0700 - 077F. 64 x 16bit Values. Resolution: 0.8Volt. Quanta: 16bit Precision Quotient If you know nothing about AFMs, or Math, I might confuse you here. I've made this as simple as I can, but if I confuse you, or you disagree, email me. If you already know lots about AFMs, you could probably just skip to the "* So how do I read a VQ Map? *" paragraph. Where do I start. As I've stated before an AFM doesn't have a linear response. If it did, we wouldn't need a VQ Map. Therefore we need a mechanism that will convert this non-linear Voltage into a linear Quotient (or percentage) of the AFM's maximum flow. Hrmm... Voltage... Quotient... Map... VQ Map? What do I mean by non-linear? Ok, lets say we have an ACME AFM, good for about 500hp and 0-5v. At 0v we know its flowing 0hp worth of air. At 5v its flowing about 500hp worth of air. But what about inbetween? If it was linear, 1v might equal 100hp worth of air. So: 1v = 100hp 2v = 200hp 3v = 300hp and so on. So if you read 2.48v at the AFM you'd know you were flowing 248hp worth of air. But that would make this section far too easy to write. The response of the AFM is non-linear in that, its voltage gradient decreases as the flow increases. Gradient means 'rate of change'. In other words "it takes more air flow to increase the voltage, as the air flow increases". I'll try and explain a little clearer. Lets take our ACME AFM, and give it a non-linear response. 0v = 0hp 1v = 25hp 2v = 75hp 3v = 175hp 4v = 300hp 5v = 500hp So it takes 25hp worth of air to progress from 0-1v 50hp 1-2v 100hp 2-3v 125hp 3-4v 200hp 4-5v thus "it takes more air flow to increase the voltage, as the air flow increases" Lets plot this little map out with some bad ascii art to further demonstrate. See how the marks are further spread out as you go right along the axis... Vertical Scale is Voltage Horizontal is Airflow V 5 * o 4 * l 3 * t 2 * s 1 * 0 1 2 3 4 5 Air Flow So if you read 2.48v at the AFM, how much air are you flowing now? Somewhere between 75 and 175hp is all we really know! We could (linearly) interpolate between 2v and 3v and calculate 123hp (2-3 = 1v, 75-175 = 100hp -> .48v = 48hp, 75hp + 48hp = 123hp) But thats guess. Quite a big guess. And you don't want your ECU making big guesses. So what is the solution? An accurate VQ Map. See our little maps above that say 1v = 25hp and so on? Well that is a crude VQ map. To make it useful, we need more precision. Much more precision. The CA ECU's VQ Map has 52 points, mapping the airflow at 0.1v intervals. The SR's has 64 points, mapping the airflow at 0.8v intervals. Sounds simple? Well to make things harder, the VQ map doesn't (directly) give you a hp reading. It gives you a quotient. Think of it as "Percentage of Maximum Flow". If you know how to read a VQ Map, you could look at the point for 2.48v, and say - the AFM is flowing 32% of its maximum at this point. If you happened to know that your AFM was good for 500hp, then its flowing about 160hp at 2.48v. Simple. * So how do I read a VQ Map? * This might be easiest to explain using ROM Editor. Go onto the VQ Map Tab and you'll see a list of 52 or 64 numbers depending on what type of map you're looking at. If you look at a lot of different cars VQ Maps, you might notice that all the values range from 0 - 65535. 65535 just happens to be the largest value possible with 16 bit unsigned integers. This is handy to know, as the VQ map uses 16 bit unsigned integers to store it's val ues. I still haven't told you how to read a VQ Map have I. I'm sorry that you didn't find a tuning website written by someone more to the point, and you are stuck reading mine, but eh, what're you gonna do? Ok - Take a value in the VQ Map - any value. Divide it by 65535. What do you get? Well that's your quotient. Multiply that by 100 and you've got your "Percentage of Maximum Flow". At what AFM voltage is that % value for? Well if its on a CA map, the first value is for 0.1v, the second for 0.2 v and so on. For an SR (and most others) the first value is for 0.08v, the second for 0.16v and so on... Want an example? Yes? Well you'll have to wait till I give you one. But I will put one here soon. RPM Scale: CA Rom Address: 3BD0 - 3BDF. 16 x 8 bit Values. Quanta: 50 rpm SR Rom Address: 00E0 - 00EF. 16 x 8 bit Values. Quanta: 50 rpm The Vertical Scale of the AFR Correction Map is RPM. The stock range is 500 - 6800 rpm. If you built a de-stroked screamer that revs to 12000 rpm you might get a bit worried about what the ECU will do above 6800rpm. Fortunately Nissan thought of this, and allows you to modify this scale and specify the operating rev range of your motor. The stock Nissan specified values are fine for me, as I have my redline set at 7500rpm. Keeping them the same also means you don't have to recalibrate the AFR Map, and extrapolate values for the new rev ranges. If you do decide to make changes here, this is what you need to know. The ROM image contains 16 values that makes up the scale. To decode these into RPM simply multiply them by 50. Open a Map in ROM Editor, and modify some of the RPM values - you'll notice they increment and decrement 50 rpm intervals. Flow Scale: CA Rom Address: 3BC0 - 3BCF. 16 x 8 bit Values. Quanta: None - Multiplication Factor SR Rom Address: 00F0 - 00FF. 16 x 8 bit Values. Quanta: None - Multiplication Factor The Horizontal Scale of the AFR Correction Map is what I call Flow, and it is important because its the primary load axis. You already know the AFM is the primary load sensor, so it makes sense that these two are closely linked. When the AFM is flowing close to minimum, the minimum values on this scale are referenced, when the AFM is flowing close to maximum, the max values are referenced. But what are these values? Well they are a multiplier, that when applied to the K Constant give a basic injector pulsewidth for a given airflow measured by the AFM. Now the clever thing that the Nissan engineers did here, was to set the injector pulsewidth to that required for a Stoich (14.7) AFR. How could they do this? Well that's the beauty of AFMs. Air Fuel Ratio is determined by Mass. An AFM will accurately determine the mass of air entering the engine at any given instant. Now we just need the corresponding mass of fuel to enter the engine to have our 14.7 AFR. Since the Nissan engineers knew the flow rates of the injectors, they could then calculate the required injector pulsewidth. Using the Flow Scale to calculate basic pulsewidth will be covered in depth in "Putting it all Together 2". AFR Correction Map: CA Rom Address: 3D00 - 3DFF. 256 x 8 bit Values. Quanta: None - Multiplication Factor SR Rom Address: 0100 - 01FF. 256 x 8 bit Values. Quanta: None - Multiplication Factor These maps are the business end of tuning. If you've read how the flow scale works, you'd realise that it alone, is enough to calculate an injector pulsewidth that will provide a 14.7 AFR at all loads measured by the AFM. Thing is, we don't want a Stoich AFR at all loads and RPMs. Nice and rich at high loads/rpms to keep the engine together, and lean it out somewhat at light loads for good cruising economy and throttle response. To do this the AFR correction map will provide a(nother) multiplyer that is applied to the basic pulsewidth, to give a final injector pulsewidth. Since the basic pulsewidth provided by the flow scale is a known 14.7 AFR, this multiplyer will also allow us to calculate the new 'corrected' AFR. Lets say we wanted a Stoich AFR at idle (say 800rpm, at minimum load on the map). The basic pulsewidth is already stoich, so to lets keep it the same (Set the multiplyer to 1). Want a Rich AFR? Make the Multiplyer greater than 1. Lets say bulk rich - around 10:1. We'd want a multiplyer of 1.47 (14.7 / 10). And Lean? You guessed it, Multiplyer of less than 1. Targetting an AFR of 16:1? Use a multiplyer of 0.92 (14.7 / 16). Open up ROM Editor again and have a look at the Fuel Maps (hi/lo octane, doesn't matter). Those numbers don't look anything like 1, or 1.47 or 0.92, do they? So how do we read them? I'm glad you asked. Here's the little forula you need. if DATA > 128 then MULTIPLYER = (DATA - 64 / 128) else MULTIPLYER = (DATA + 128 / 128) This formula dictates the range of multiplyers we have access to, ie: 0 = 1x (0 + 128 / 128) 128 = 2x (128 + 128 / 128) & 129 = 0.5x (129 - 64 / 128) 255 = 1.5x (255 - 64 / 128) Thus we can target AFR of 7.35:1 (2x) through to 29.4:1 (0.5x) which should be enough for anyone. Putting it all Together Part 2: Lets repeat the exercise we completed the first time around, but this time use the raw data, and formula we now know. Lets use it on a stock CA1ET Map So - Air Flow Meter is reading 4.9 Volts & Car is revving to 6800rpm. What Injector pulsewidth will the ECU use, and what is the target AFR. For bonus points, what will the dutycycle of the injectors be? Start - Determine Flow Quotient. AFM is reading 4.9 volts. Check the Value of the VQ map at position 49 (0.1v resolution remember). Divide it by 65535. What did you get? Ok, our AFM is measuring X% of it's total flow. Next - Read Flow Scale. The Flow Scale has 16 columns. We need to know which column to read. Multiply your Flow Quotient by 16 and round up. Ok, Column 16 on the Flow Scale is 83 Next - Determine K Constant Pulsewidth. I'm going to lay a new fomrula on here Next - Determine Basic Injection Pulsewidth. Basic Injection Pulsewidth = Flow Scale Multiplyer x K Constant K Constant Pulsewidth = 00 B7 = 0.125ms. Basic Injection Pulsewidth = 83 x[/quote] [/quote]
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