So, say you’re calibrating the MAF airflow vs frequency table (open loop, dfco off, ve disabled, STFT and LTFT off). I want to dial in as much of the MAF curve as possible without entering PE mode. So I raise PE say to 90% throttle. I dialed in my MAF to hit stoich in idle AC on, idle AC off, and cruising (steady accel, steady speed, light pedal) under as much of the cruising steady speed range as possible and it’s consistently stoich. Then I calibrate slightly higher MAF frequencies to stoich by accelerating a little more while keeping a steady throttle. We keep on going until there is a point that in order to calibrate higher frequency values (say above 5k Hz) I have to then subject to higher loads/ higher throttle values while trying to be steady on throttle % as to avoid getting into transient conditions that would pull from VE/dynamic airflow. This is fine for relatively low acceleration, but to access and calibrate higher MAF frequencies to stoich, I have to accelerate and dig into the pedal deeper.

So here are my questions:
1. Until how far should I have to dig into the MAF frequencies to dial them at stoich, because there is a point it becomes very difficult to get clean data with steady accel position as I dig deeper into the gas pedal (faster accelerations) while trying not to hit dynamic airflow changes, especially on the street.
2. How do I know its not “blending” with the VE or compensating for transient conditions under these higher accelerations?
3. Until how far should I bring stoich values up in the MAF curve? Sorry for the long post, but hopefully I’m clear in my questions. Thanks.

 

"but to access and calibrate higher MAF frequencies to stoich, I have to accelerate and dig into the pedal deeper."

After you put PE table back to normal the engine will never meet that condition(90%TPS@stoich) because the engine goes into PE mode at between 35-60% TPS depending on how table is setup.

When in PE mode use wide band air fuel ratio to correct the MAF by comparing to commanded PE ratio (table), adding/subtracting to MAF freq (table) until wide band O2 AFR equals PE commanded AFR

 

With my cars I would drive around like I normally do. Get to about 7000Hz and call it a day. Left PE stock. Just pulled 4 degrees from the whole timing table so you don't get knock to throw off data.

 

Yep yep, that’s about what I ended up doing. I got up to as far as I could which was 7000hz, and called it a day. Car drives really really good now with MAF only tune and under PE wot the aft matches the commanded PE AFR pretty steady , which is great. I still have so much work left to do if I calibrate the VE tables. I started yesterday since I had some time, just to try to calibrate idle and no load RPM sweep with speed density only (MAF fail) and once I dialed in the VE only idle, then as soon as I switched back to MAF only again my idle and no load sweep we’re super lean again. Chasing my tail on it so I decided to call it a day and I loaded back the MAF only tune and leave it for now like this, until I have loads of time to redo VE and then redo MAF. It makes sense now why TurboLX recommended the tuning steps in that specific order.

 

Logging (Actual lambda)/(Commanded Lambda) solves most of your problems. Doesn't matter what the PE or OL target is, just the math is simpler when it's dividing by 1.00, but it still works fine off stoich.

Steady state measurements minimize the influence of VE blending. If you're really worried about it, complete all your steady state VE work first before doing the MAF curve.

 

I don't agree with pulling timing as that's not how the engine is going to be running after your done tuning. (How you actually drive the car) If your engine starts to knock it's telling you you're done tuning without going into PE mode. The engine is cooled by the richer mixture and will combat knock and provide the optimal enrichment needed. If you drive around at 4k+RPM steady state then you're just a fool wasting gas. Think about how you actually drive and tuning will become easier.

 

Typically you can try to dial in your P/T fueling to achieve Stoich But only up to 4000 RPM;s This is one of the trigger points
If using a wideband to read acual AFR readings at P/T try to get your fuel trims at "0" or slightly negative--If you disbale the fuel trims sort them out before turning them OFF
When going to WOT your fuel trims if POSITIVE will be carried over to WOT when they are "just before going to WOT"
A negative fuel trim will never subtract fuel when going to WOT However a positive fuel trim will carry that % at WOT as a lean safety
During "rapid changes in aiflow" below 4000 RPM the ECM will use several sensors to set the final fueling By taking the commanded AFR PE ratio----The VE table--and the MAF table and use an average of all three to set the fueing

PS Once above 4000 RPM's the ECM uses at a steady state the PE table for fueling--However is your VE table is NOT spot on the commanded fueling may not equal the ACTUAL AFR rate from your data logger
Not really a big deal as you can trick your ECM to get your desired AFR
Say if with a wideband you are recordong during PE an AFR of 12.0 --BUT you are commanding in your tune an AFR of
12.6 Then you simply trick the ECM by commanding a leaner AFR trying to achieve 12.6 to something leaner and recheck the wideband until you see the AFR you want
The more accurate your VE table is the closer the Commanded AFR is to your Acual AFR reading---all this does is make your engine easier to tune as long as you get the AFR at WOT you want it does not matter how you get it
ALSO remember REAL AFR readings at WOT are only relevant in the gear ratio closets to !:1 on an auto trans this is 3rd gear on a 6 speed it may be 4th gear
( lower under driven gears always show a RICHER AFR as the eng is NOT at full load----

 

Tuning will become even easier if you get into the habit of creating the conditions to acquire data about the effects of specific regions of specific tables on demand - even if those conditions are rarely encountered in ordinary driving.

Steady-state 4k RPM is perfectly normal if you're going around a corner with intent to accelerate hard as you exit that corner. So you want your spark and fuel to be dialed in for that. And there's no need have an actual corner, you can get the data you need to tune those tables on a straight road too.

Tuning isn't just about how you actually drive, it's about dialing in every table as thoroughly as possible, and that requires data, and sometimes you can get more of the data you need by driving abnormally.

 

"Tuning isn't just about how you actually drive, it's about dialing in every table as thoroughly as possible, and that requires data, and sometimes you can get more of the data you need by driving abnormally."


NO

 

The MAF doesn't know if you are in PE or not. It just knows airflow.
My C5 has been MAF only since day one. It's a 2000 and when in SD, uses an abbreviated VE table which sucks and is a pain in the *** to tune.
The goal with MAF tuning is to have it follow commanded fueling period.
OL tuning is a place to start and mandatory when in PE.

So when driving, don't be whacking the throttle all over the place. Drive smooth, lean on it hard when you want data up high in the maf hz.
Lather rinse repeat.

Get it happy then turn on STFT. See how they look. Might match OL might not. Unless you wish to run OL all the time, call it good. But I like the trims. I final tune it with them as gee, that's how it runs every day.
I leave LTFT off. I drag race my pile and I don't need the trims adding to the final fueling.

After 5 years of running a dyno, tuning mostly Mopigs, I got my C5 on the dyno today. Tune was my street/drag tune which I haven't logged forever. Was decently close, but rich in areas so cleaned that up. I'm an A4 car, hard to tune areas below converter stall. But locked it up and fixed all that.

Good for me to see folks tuning their own cars. I learned on my C5 and now tune professionally.

FWIW, I gained maybe 10hp, found good TQ below converter stall and the turd made 500 (in dyno jet terms) we have a Dyno Dynamics.

Keep at it!

Ron