Setting up injectors/ stock air box or CAI when doing so?

Spamby

Meat Product Toy
So I'm digging into tuning again via ATR and I've got a question. Cobb suggests or basically states that you must use the factory air intake to set up your injectors properly. Is this the case or is there a workaround? I can understand this from a "starting froma known variable" aspect, but there has to be a workaround for those that have a CAI installed prior to tuning, correct?
 

HolyCrapItsFast

Drinks beer!
If you do not have the stock MAF then just use theoretical values to start with including the manufacturers latency values. Unfortunately this is going to be a hunt and kill process because nothing is known. You have to find the values for scale and latency on your own. There is a process for that but it is involved and time consuming

One process would be to install stock injectors at stock fuel pressure and scale the MAF and Load Comps till fuel trims are near zero. Then install the new injectors and simply scale and adjust latency accordingly.

Another process would have you install your new injectors with theoretical values and manufacturers latency and scale them for WOT. So you would make your WOT AFR's match your fuel table and then adjust your latency till fuel trims are the same across the board. Then do the rest with MAF scaling and calibration.

What I usually wind up doing is I start with theoretical values first and do some normal driving logs plus some highway cruise. Then I just take a look at what I see and determine how to proceed. For instance if my fuel trim errors are high in the idle region of the MAF but low in the upper region of the MAF, then I know to add to latency. If the opposite is true then I reduce latency. If the error is the same across the entire MAF then the latency is good and all you would have to do is scale it to bring the trims closer to zero. You can adjust scale at this point by either adjusting the injector scale or the MAF scale or a combination of the both but be careful with adjusting MAF scale to much because this effects the calculated load value reported by the ECU.

Then I will do a WOT run and see how the AFR's out of the tail pipe match up with the AFR table +/- any compensation (Commanded Fuel) and then adjust MAF scale to bring those close to each other usually with in 1%. Then your done and now you can probably go back and calibrate the C/L MAF region better.

Your going of have to do allot of logging and you will need a wide band.

For greater details you should have a look at my tuning guide.
 

HolyCrapItsFast

Drinks beer!
Also note that when you are doing any kind of C/L tuning/calibration, you will be referencing the stock AFR sensor and adjusting according to A/F correction #1 and A/F Learned #1 together. Any WOT tuning/calibration will be done by referencing the Wide Band AFR and comparing that with Commanded Fuel.
 

Spamby

Meat Product Toy
Yes, I do still have the stock MAF so that should be a bit easier. I can throw it back on if/when I decide to jump off of the cliff.
Still just reading and reading.
Speaking of tuning guides, bad noodles link sends you to some foreign shit site.
Many thanks to you, as always.
 
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