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Target AFR

Understanding AFR

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Discussion and questions related to the course Understanding AFR

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I'm new at tuning and it is my first time to think of tuning my car and i just made an AFR TARGET before i start tuning .

I made the table of AFR Target as the fuel table at my AEM FIC6.

I just did it as a guesses and with your help i hope to get it better

Note : My Car 4 Cylinder NA With High lift Cam

Kindly check the attachment file .

Attached Files

I'd only suggest a couple of changes. You may find that the engine will benefit from a slightly richer AFR at WOT and high rpm. This isn't always the case, but particularly with engines that are knock limited the additional cooling from a richer mixture can allow a little more timing and hence a little more power. I'd experiment to see what your engine wants but it's not uncommon to run as rich as 12.5-12.7:1 at WOT and high rpm.

You're targeting 15.0:1 at high rpm and low load, as well as in the over run areas. If you're doing this for economy then you'd be better to focus your efforts in the cruise areas which are typically lower in the rpm range. I prefer a richer mixture at mid load and high rpm to help with combustion cooling as we only tend to operate in these areas when the engine is being driven hard.

Thank you Andre for your reply .

i'll try to get as close as 12.7 and see how the engine will behave .

im only going to tune fuel map and maf map and o2 map as AEM FIC6 does not support Ignition timing for NA

That's was i was thinking of making the afr around 13.0.1 .

For high rpm and low load i wasn't thinking of doing it for economy .

So do you think i'd better go richer around 13.5 ?

I'm not familiar with the FIC6 but with a piggyback controller you'll only be able to affect changes in air fuel ratio when the factory ECU is running in open loop mode, otherwise the closed loop fuel trims will just fight your changes and remove them.

How can i figure out the open loop and the close loop from the rpm axis ?

sorry for my question but im new at tuning and this will be my first time and i want to tune my own car .

as i learned and searched around close loop at lower rpm and open loop at wot but what i need to know where does each of them start and where it end.

Note : For Fuel Table im going to use MAP LOAD and for MAF TABLE im going to use Voltage

Without the ability to scan the factory ECU and see when it transitions into open loop mode, it's essentially impossible to tell. To make matters worse, some ECUs such as those used in late model Porsches run continuously in closed loop meaning a piggy back won't be able to affect the air fuel ratio.

Generally with a piggyback ECU we are only going to make changes at full throttle when in most applications we can be certain the factory ECU is operating in open loop. If you want to make more thorough changes to the fuel delivery then a full replacement ECU or a reflash solution is probably a better option.

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