RomRaider

I have a few other posts going on tuning for E85. I'm starting to get the upper hand on learning some things, but I'm lost with some reasons for O/L fueling error.

From what I understand DT (latency) effects C/L (low PW) more in either direction then O/L (higher PW). I understand that scaling the injectors higher or lower universally lowers or raises PW.

But I hear everyone talk about scaling the maf. Now from everything I've gathered the MAF is only a reference for load. Based upon that theory scaling the maf would only raise the load, putting the car in a higher load region on the O/L fueling map.

I'm real close on my scaling and latency but under boost I have some ups and downs in my final AFR that is too fine to be tuned out using the O/L map.

Exactly how does the ecu come up with PW, or how does it determine how much PW is needed to reach my target fueling at say 2.7 g/rev at 4k rpms? Say my afr values in O/L are 11.4-1 at all load/rpms regions during the pull, but I see anywhere from 10.9 to 11.6-1 afr's. What is the fine tuning process for this? If I raise my maf, at the same "amount" of air I will see higher loads, which will require the O/L map to be rescaled for the raised load, but I would still target 11.4

I'm not sure what determines total PW. I don't want to raise my load, (scaling the MAF) I think its the appropriate route for tuning in C/L when trims are within 5%, but not O/L.

Last note how does the ECU determine total timing at warm idle? Raising my Base Timing map at the load/rpms cells has no effect on idle timing.

Scaling changes ipw globaly. The fueling map is only an enrichment or enleanment map that lets you modify ipw at different rpm and load ranges. The maf scale is just another avenue that you can use to modify ipw but at different mafv.
Look at it this way. If you watch what cells are being used in a 3rd gear pull on your fueling map. Then you change the maf scale by 10% + or -. Then do another pull. The cells that will be used in the fueling map will be different if you have enough resolution in the area of the fueling map to see the cells that are being used change. The change is caused by how the ecu determines load. It is hard to explain in simple terms. Maybe someone on here can give a simpler explanation.
Scaling, maf and fueling map are all dependent. If you change one it will effect one of the others or both. Other tables will play into this somewhat like comp tables and latency. But that is a different book to read.
There are tables that control timing at idle but they have not been released in the defs yet according to Merch.

The MAF is much more than just a reference for load, it's THE source the ECU uses to determine how much air is coming in, and therefore how much fuel to add.

The fueling logic works [basically] like this
1 - The current air flow through the MAF sensor causes it to read a voltage, that voltage corresponds to the amount of air it's reading
2 - The ECU reads this voltage, looks in the MAF scaling table, and determines the air flow into the engine in g/s
3 - The ECU then reads the RPM, and computes load (MAFg*60 / RPM).
4 - The ECU uses the RPM and load, and looks in the Primary OL fueling table to determine the target AFR
5 - The ECU looks at other tables/inputs and modifies the target AFR as necessary (coolant temp, IAT, etc)
6 - The ECU calculates the necessary amount of fuel to hit the target AFR, given the current air flow rate (g/s) from the MAF, adjusted for AFR Correction and AFR Learning
7 - The ECU looks at the injector scalar to determine the PW necessary to inject this amount of fuel
8 - The ECU adds a certain amount of time to that PW to account for injector latency
9 - The ECU sends the final PW to the injectors, they open, squish, bang, blow
If the ECU is in OL, it ends here, if in CL it continues on to step 10
10 - The ECU looks at the primary O2 sensor, calculates the AFR, and adjusts the AFR Correction as necessary to hit the target AFR

The MAF signal is used both in steps 3 (to calculate load) and 6 (to determine the IPW). If your MAF scaling is off, both your load AND your fueling will be off. The easiest way to scale the MAF in OL is to do a WOT pull, and plot the AFR error vs MAF voltage. Assuming your injector latency/scalar are correct, the AFR error is caused almost entirely by the error in the MAF scaling, so that's how it should be fixed.

thank you!

that was a super awesome reply eggroll.. I wasn't aware of the total importance of the maf vs. total ipw. Ipw sucks balls, as the numbers get confusing.

I've raised the latency with poor results, lowered the latency with poor results, I found where my latency likes to be (back firing or stumbling depending on up or down)

I asked this because I wanted to know the maf's relevance to IPW other than load and referencing the OL fueling map. It makes sense, now whether or not I can make sense of it is a different story

I've tried to read up as much as I can on true latency scaling, and to me having your latency off is worse than having your scaler off. Since the latency is time to open for the injector, this will shift open time/close time further one direction, applying fuel to early or to late in the combustion stroke.

I'm almost in favor of finding what latency the engine likes rather than the ltft/stft because of poor drivability with higher/lower latency's for that particular injector. Therefor tuning your lt/st fuel trims should be done 3 ways (two for cl and 3 for open) injector scalar, maf scaling and finally in OL, OL fueling table to get your correct afr's desired.

It just becomes a pain trying to sort out load calculations once maf scaling is done...

Does anyone know how to reference maf voltage vs. manifold pressure on the stock td04? I've noticed that around 1.0 load is 0psi or about 2.6v. Which makes sense as that would be the end of the ltft's.

Am I right??