NefMoto

So I'm starting to read thru the S4 wiki and the tuning guide as I prepare to reflash my 1.8T back to stock and have a shot at tuning it myself.  I'm trying to tackle the fueling section first and I'm a little confused and have some questions...

How exactly does the Motronic system calculate fueling?  From my reading, everything looks like it refers to AFRs and multiplicative increments/decrements.  This makes sense, but has me curious: if you start with a base tune, so you're running base boost.... does the fueling that you dial in at "low" boost" carry over when you increase boost?  My guess is "yes" since you're dealing with AFRs and fuel trims in a way that is agnostic from actual airflow/boost... but I just wanted to make sure.

Also, I will have an uprated FPR and uprated injectors.  From my reading, I know I will have to increase primary fueling, and most likely play with injector timing and latency to get STFTs/LTFTs due to the uprated injectors... but assuming the MAF is stock should I need to touch any MAF-related maps at all?

Also, the section regarding desired AFR and EGT enrichment tables... can anybody explain in slightly simpler terms what that section is explaining?  My basic understanding is that there is a basic map for desired lambda and then maps that deal with fuel enrichment based on EGT.  I know Unisettings has a setting for adjusting the "fuel on increasing load" adaption channel... is EGT the method by which the ECU determines load or does spec load come into at all?

Thanks! :)

Very roughly:
Load * KRKTE * req_lambda = injector on time, where load=MAF/RPM


In most turbo applications the FPR uses the manifold pressure as a "reference", so fuel pressure is constant with respect to boost.


Nope. You can leave all of that alone.


In short: ME7 will run lambda=1 pretty much all of the time. There is a built in enrichment mechanism which is based on an EGT threshold. When calculated EGTs go over that threshold, ME7 switches to the "BTS" map. If req_lambda!=1, ME7 goes "open loop" and no longer uses narrow band O2 sensor feedback to adjust fueling; rather, it relies entirely on MAF readings.

There is some debate whether or not this is the "right" way to do lambda!=1 enrich, since there are other ways of accomplishing basically the same thing (i.e. LAMFA).

Hope this helps.

So if i wanted to just change injectors i would modify only KRKTE?

And tvub.
It is injector latency.

So say I'm starting with a stock 1.8T and stock turbo.  I want to switch to 630cc injectors and a 4bar FPR so I that have some overhead for E85 in the future.

If I tackle the fueling aspect first... what is my "main" goal?  Simply to hit low 13s/high 12s for my WOT AFRs and let ME7 manage lambda=1 situations?

afr of 11.8 to 12.0 would be good for wot.  safe but not too rich.

Ok, so shoot for flat 12s.  Simple enough.

What about part throttle situations?  If I get WOT to run flat 12s, and very light throttle cruising to chill around 14.7, will the ECU properly handle part-throttle fueling or is that another area that has to be tuned for specifically?

the ecu will take care of that for you as long as you let it. after you get your wot afr set,  tweak kfkhfm to get your part throttle fuel triims +/- 3 or so and everything will be slick.

So to get part throttle fuel trims dialed in... do I just literally log them along with throttle angle to find where the bad spots are and make the appropriate adjustments to KFKHFM?

I look at rpm and load... then after that is set u can adjust max desired throttle map if u like... kfwdksmx

kfwdksmx  will allow you to open the throttle sooner on wot

Hmm, I'm gonna have to flash back to stock and start tinkering to digest all of this.  ;D

that's how u learn my friend. good luck.