Maf counts and fuel trim

[02edge_V6Online]

So I'm in the process of tuning my car with email tunes but whàt should my maf counts be at and what could be a reason that they are low also at idle my short term fuel trim is around .96 and 1.03 what could be causing tgat

 

[6 Shooter]

There is no way to answer your question about what the MAF counts should be. Like humans, every car is different particularly so with modifications. The best way to find out though is to set your tune to open loop and use a wideband O2 sensor to provide the actual A/F ratio numbers. Then, you gotta data log read the numbers, and adjust the MAF counts accordingly. For MAF counts, there are some 30+ settings from zero throttle range to 1023 counts. Things that change A/F ratios are injectors, throttle body size, location of the MAF, type of MAF, clocking of the MAF, vacuum leaks, spark plugs, spark plug wires, condition of the coil, any power adders, cam modifications, cam lift, intake mods, valve sizes, head porting, to name a few.

For your bank to bank mis-match, it could be a lazy O2, location of the O2 bung from one side to the other, addition of LTs, or tables in your tune.

There is no details in your signature about your car. Any accurate answer would be just a WAG. Post a data log and I'll take a look.

 

[02edge_V6Online]

not too sure how id post a file like that but car has an intercooled v1 at idle maf counts were around 105 and my tuner says that theres a problem and it can not be tuned if you shoot me your email I can send you the file

 

[JTsStang]

What maf are you using and what count are you seeing at peak rpm? Counts convert to voltage more or less. Like phil said there are about 30 a to d counts the pcm refers to as for fueling. Without proracer you will not have access to the mass/tic used for fueling. What are you seeing for load readings at peak rpm/boost?

As for the swing in o2 readings could be a exhaust leak, different brand o2, etc... lots of reasons. If the difference is too great the pcm will refer to bank one for fueling. +-5% isnt that bad. Once you turn adaptive back on it will take care of that. I only run 1 o2 sensor and have adaptive injector mapping set to bank 1 o2.

You should do a sig of all the mods on your car.

 

[02edge_V6Online]

my tuner has only asked for logs idling in neutral and free rev in neutral so I have not done any under load or at wot he said to start witht his and when its dialed in better we will do those I am running and hpx maf

 

[douglass_V6Online]

my tuner has only asked for logs idling in neutral and free rev in neutral so I have not done any under load or at wot he said to start witht his and when its dialed in better we will do those I am running and hpx maf

Try this log idle, 1500, 2000, 2500, 3000, & 3500 rpm. Hold each one steady for about 20-30 seconds, alowing the fuel trims to stablize. Log the Fuel Short trims for both sides, Maf Counts, ISC duty Cycle, Fuel Pressure, TP absolute, TP relative,spark, spark source, air temp, coolant temp,fuel source, and your wideband if possible. Make sure the engine is at normal runing temp when recording. Do you have the tuning software? Be sure to save the file as an excel File, and post it up.

 

[6 Shooter]

Try this log idle, 1500, 2000, 2500, 3000, & 3500 rpm. Hold each one steady for about 20-30 seconds, alowing the fuel trims to stablize. Log the Fuel Short trims for both sides, Maf Counts, ISC duty Cycle, Fuel Pressure, TP absolute, TP relative,spark, spark source, air temp, coolant temp,fuel source, and your wideband if possible. Make sure the engine is at normal runing temp when recording. Do you have the tuning software? Be sure to save the file as an excel File, and post it up.

Recommend first switching to open loop if you have a wideband O2 and can read the digital A/F ratio numbers in your data logs. If NO wideband O2, the STFTs can be used. Further, hold those RPM settings for 2-3 seconds only. Otherwise, the file size gets so large that you can't post it, and can't email it.

In addition to the items in the above list, you will also need RPM, engine load, gear, vehicle speed, and analog 2 if you have a wideband O2.. Also, the adaptive learning should be turned OFF if any changes to the tune are going to be made. Same holds true if you are data logging. You need to see what the numbers are showing without too many internal computer tweeks altering the tuner programmed in numbers.

 

[JTsStang]

I have found it to be a waste of time free revving on my setup. For fuel adjustment you really need to be crusing at highway speeds. Steady state driving holding each maf count (200-400) for 20sec in forced open loop. A hill works great also because you can keep the engine in higher loads while not climbing in speed as fast. This is why I will be taking mine to the dyno to dial in the mtf at higher load so I can watch the latop and maf counts and not have to worry about what direction the car is going under boost.

 

[douglass_V6Online]

In addition to the items in the above list, you will also need RPM, engine load, gear, vehicle speed, and analog 2 if you have a wideband O2.. Also, the adaptive learning should be turned OFF if any changes to the tune are going to be made. Same holds true if you are data logging. You need to see what the numbers are showing without too many internal computer tweeks altering the tuner programmed in numbers. .

Thank you for adding to the list I knew I was forgetting a couple things to log and was hoping someone would fill in the blanks

 

[6 Shooter]

First off, all my tuning is done in open loop with adaptive tuning turned off and the rear O2s turned off. One of the first things when tuning the MAF is to data log an engine startup without stepping on the gas pedal. When the car starts up without stepping on the gas, goes to 1250-1300 in 3-4 seconds, and then drops down to 900 within 9-10 seconds, the lowest end of the MAF is pretty well tuned.

At idle, engine loads would be ideally around .150-.180. The throttle position sensor should indicate around 180-195 countts. MAF counts around 180 to 220. Voltage around 14.1. Engine timing around 26-28, maybe slightly higher.

Next, in the driveway, car in neutral, coolant temps at 160-170, I look at A/F numbers at idle, 1200, then 1500, then 1800, then 2000, then 2500, then 3000, and last 3500 each time watching A/F ratios at around 14.5 to 15:1. Hold each of the numbers for 3 seconds. Throttle position counts should stay below 300. When the MAF counts show desired A/Fs at each RPM setting, I go drive the car. Downshift to 2nd and find a stop light/stop sign. Accellerate in 2nd slowly from idle to around 4000 RPMs taking about 30 seconds to accomplish the task. Setting A/F numbers will require having a copy of the base fuel table in plain view because the A/F numbers should be more rich above the 300 throttle position counts.

When the MAF is dialed in in 2nd gear to 4000, I ususlly do a 2nd gear WOT from idle to around 4500 watching the A/F numbers. With a blown car, this will happen very quickly, maybe 3 seconds. WPT throttle position counts should read in the 950 counts range, maybe a little more or little less.

Next, is highway driving with the transmission (auto) locked to prevent downshifting from 4-3, 3-2, or 2-1. Leave the car in Drive, turn off O/D, get down to around 1500, and go WOT. Shut the car down when hitting 90 mph OR any A/F numbers higher than 11.5:1.

My goal is to tune the car for the lower 2/3s of the MAF counts. Next, go back to closed loop (EEC and O2s changing A/F ratios) and check to see if the A/F numbers are still at the commanded fuel table numbers.

Now, I am ready for the dyno. Time on the dyno is significantly reduced and so is the cost. 3-4 pulls and done.