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Fuel calculation


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Hi everyone!

Do Anyone ever mind how Vipec calculate how much fuel to inject?

As I can see and estimate calculation pretty simple and shitty. Because vipec isn't calculate how much air have been consumpted! And then take a look at AFR Target table/fuel table/latency/other corrections to calculate injector pulsewidth. We just operating some kind of "numbers" in fuel table to take desired (afr table)result.

Also as we can see in help file vipec do not reccomend to change afr for more than 0.5 afr due to fact we don't get desired afr.

So all we do in fuel table - just try to get our AFRs by the changing pulsewidth which we see not in ms. That's why we often have very shitty 3D graphs.

Also vipec don't take in account IAT to determine air density. Just simple IAT correction table which can just add/subtract percent from injector pulsewidth! NOT calculated air mass!

Can Anyone explain to me how it's possible to have stable AFR each day in any place with such kind of calculator?

Guys Can I ask you to create normal speed density strategy to calculate mass of air and just then injector pulsewidth?

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The ViPEC ECU uses a full speed density calculation with the exception of intake temperature. The master fuel setting takes into consideration the factors for engine displacement, injector size, equations constants and so on. The fuel table is the VE number in the equation. MAP is the pressure used in the equation. The open loop AFR target table is used as the lambda element in the equation. If you do the maths you will find that it is not necessary to completely calculate and display the calculated air mass to determine the injector pulse width exactly. The same result can be achieved.

However, the next release of firmware for iXX ECUs will include a charge temperature correction option to also consider an estimated port temperature in the fuel equation. A full non linear injector characterisation will aso be included in this firmware.

If you are having trouble getting stable AFR on a day to day basis, the problem may be your setup or tune and may be able to be resolved easily.

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Is there an equation available for fuel calculations, or is this proprietary?

Can I also have a response on how critical or integral an engine model is within the Vi-PEC v series product, and subsequently what provisions for advancement and improvement can we look forward to with the newer i series products can we look forward to with respect to the fuel calculations?

From what I've been able to understand thus far, the Vi-PEC brand has a consistently reliable approach to fuel calculations with respect to engine management duties and I'm willing to take the time attain a comprehensive and equally competent understanding of how things work.

Going forward based on previous work experiences a firm understanding on fuel calculations is critical for effective and competent product experience. Not all products on the market can implement the ideal or the gold standard for many reasons, however, manufacturers understand this openly and have made exceptional provisions to ensure that acceptable levels performance can be attained if specific steps have been followed or trained personnel take care of product installations and engine calibrations duties.

As previous stated my aim here is to learn as best as I can the correct techniques in which to extract the best possible product experience so any productive feedback will be greatly appreciated in a big way.

Quick question, does anyone think that there's any merit to completing the Link G4+ course offered by Andre Simon at the High Performance Acadamy to learn some insight about the Vi-PEC brand based on some common similarities between the platforms?


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The exact fuel equation in full detail is proprietary. However, it is not overly complex and is based on the ideal gas law http://en.wikipedia.org/wiki/Ideal_gas_law. Nearly all aftermarket ECUs use the same or a very similar fuel equation. It takes into consideration all of the measurements available to the ECU in the absence of a Mass Air Flow meter. No after market ECUs fully model the engine as OEM ECUs do as this process is extremely complex and not practical from a tuners point of view. OEMs spend millions characterising one engine exactly and mathematically (and empirically) model it in their ECUs.

A good understanding of the exact maths f injector pulse width calculation is not critical for a tuner but a firm understanding of the requirements to change fuel delivered with the changes in measured variables is extremely useful. A good understanding of injector characterisation and the effects of incorrect injector information is also very important.

Andre's course would be very valuable if you have not been exposed to the ideal gas law and exactly how injector pulse width can be estimated from it taking all the factors into consideration. Andre offers two courses, one on basic tuning and one on using PCLink software. The tuning one is what you want.

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