5.3L Tuning -- MAF Removed and Runs Better?

[Swiss922]

Newbie tuner here, but tuning a 5.3L with a Elgin stage 2 sloppy cam for my father. Motor is completely fresh but basically all stock other than the cam and springs. Have made some progress with the tuning but I seem to take 2 steps forward, then 1 back each time.

I can actually drive the truck now but seems to have no power when you step into it. The bigger issue I have is that when it begins to warm in temp and try to start it back up, it wont. Now if I remove the mass airflow sensor from the cold air intake, it fires right up and almost seems to run better. This is a manual 5 speed trans as well, all trans info has been deleted.

Really trying to understand why and if its even possibly to delete the MAF? Attached is the tune file that is currently flashed. Really hoping to maybe chat with someone who is more of a expert in tuning! It seems lean and the next step would be to dial in the timing.

Thanks for all the help!

-Scott

[kevin87turbot]

Here's a revision that will help get it going. It's in SD mode, so it shouldn't require the MAF, but it does require the IAT that is built into your MAF.

If you want to completely eliminate the MAF, then you can just wire a separate IAT like the Camaros and Vettes had in that same era.


Tune1 with kw mods.hpt

[Swiss922]

Here's a revision that will help get it going. It's in SD mode, so it shouldn't require the MAF, but it does require the IAT that is built into your MAF.

If you want to completely eliminate the MAF, then you can just wire a separate IAT like the Camaros and Vettes had in that same era.


Tune1 with kw mods.hpt

Thank you so much!! I will flash it tonight after work and see how it runs.

I would like to leave the MAF if possible to keep it as easy I can but I am far from a tuner expert here so I don't know which would be the best route? Sorry for my question here, but I am not sure what you mean by SD mode?

[kevin87turbot]

Thank you so much!! I will flash it tonight after work and see how it runs.

I would like to leave the MAF if possible to keep it as easy I can but I am far from a tuner expert here so I don't know which would be the best route? Sorry for my question here, but I am not sure what you mean by SD mode?

Speed Density mode.

Since it runs better with the MAF disconnected, that tells me that there could be a problem with the MAF or the MAF location.

[Swiss922]

Speed Density mode.

Since it runs better with the MAF disconnected, that tells me that there could be a problem with the MAF or the MAF location.

That makes sense now and thank you for that information. Thats the part I never could understand is how it actually runs better with it unplugged.

I will apply the tune tonight and see how it goes, again, thank you very much for your time! Not sure if you are into tuning on the side, but I would be interested in paying you for your time to do email tunes if that is something you do?

[blindsquirrel]

MAF is a pain in the ass, pure SD works better and is easier.

[Swiss922]

MAF is a pain in the ass, pure SD works better and is easier.

I agree!! Newer to this and I'd love to keep this is as simple as possible for tuning.

[Fast4.7]

MAF is a pain in the ass, pure SD works better and is easier.

I disagree. Pure MAF works better than Pure SD ever thought about working. The MAF is literally a simple 1-line table as well. Fueling is smoother, less drift with weather changes, and the engine just flat runs better. Get the VE table dialed in, get the MAF curve dialed in, and it will run as good as it gets. Speed Density only is a JOKE when the MAF is capable of handling the airflow of the combination. I am tuning in speed density right now. My VEs were near perfect yesterday, good trims across the board. Today after a weather shift, they are 5-7% lean. On startup tunes I am working on, I actually disable speed density and get it running right with the MAF. I pull data in the tune to form a VE table from the MAF. I use the calculated and filtered VE data as a starting point for the VE table.

[blindsquirrel]

I disagree. Pure MAF works better than Pure SD ever thought about working. The MAF is literally a simple 1-line table as well. Fueling is smoother, less drift with weather changes, and the engine just flat runs better. Get the VE table dialed in, get the MAF curve dialed in, and it will run as good as it gets. Speed Density only is a JOKE when the MAF is capable of handling the airflow of the combination. I am tuning in speed density right now. My VEs were near perfect yesterday, good trims across the board. Today after a weather shift, they are 5-7% lean. On startup tunes I am working on, I actually disable speed density and get it running right with the MAF. I pull data in the tune to form a VE table from the MAF. I use the calculated and filtered VE data as a starting point for the VE table.

I'm glad it works for you, and I know I am one of the chumps who only works with their own one vehicle. But on mine I found after tuning MAF and VE separately, when compared to blended mode straight SD was not only about 0.9 sec quicker 0-60 but also saw 1.5 MPG improvement in city driving. All stock Gen4 5.3, only change being failing the MAF in the tune.

[Fast4.7]

I'm glad it works for you, and I know I am one of the chumps who only works with their own one vehicle. But on mine I found after tuning MAF and VE separately, when compared to blended mode straight SD was not only about 0.9 sec quicker 0-60 but also saw 1.5 MPG improvement in city driving. All stock Gen4 5.3, only change being failing the MAF in the tune.

GenIV is not a GenIII for starters.

I do not see how you could gain that unless you had a bad MAF.

[kingtal0n]

Ah ye olde maf debate

Background
I've tuned hundreds of turbo MAF cars from 02-12 we imported around a thousand engines I volunteered (I was helping wire and tune vehicles we swapped in exchange for parts and cars)

most were sr20 derivations like this swapped S15 engine to 240sx S14 stateside


This was one I put together from the spare free parts


Heres an example of the engines all set out for cleaning, each high cube container brought I think around 90 engines? Or was it 44? I forgot



We would pressure clean and inspect, I tagged them and determined which are the most well cared for, looking for intact OEM air filters and PCV


This was my recent maf sr20 car from a few years ago. Another heap of unwanted parts I painted with walmart $1 paints to make artistic impression.
Attachment 128408


Annnyways. After learning what a maf wants and how useful it can be sometimes, I list pros and cons and procedures.
First setup,
To get the maf to work properly on a turbo vehicle we always need something like this


Which directs bypass airflow back to the post-maf pre compressor tube. Because the slightest leaking causes a major issue with maf output reading. It will see a leak as either too much or too little airflow, of course. Tuners intuitively understand that but novices tend to overlook this simple idea.

This is why anybody that uses a maf NEEDS to pressure test their engine, and/or turbo plumbing, for leaking. Leaking in the tube anywhere after a maf, including intake manifold and throttle body and so forth- will induce error to the maf signal.
Here is a video of pressure testing maf and engine for examples to follow.
Engine only
https://www.youtube.com/watch?v=rYZmZqn3-x0
Entire plumbing system
https://www.youtube.com/watch?v=w1sb5Y1J068

Once there is assured no leaking the next step is proper maf placement. Generally, as far from the turbo or engine as possible, after or near an air filter where air is going to smooth out. Avoid transitions, bends, reducers, anything that will affect flow which can induce or variable turbulence.
Compressor wheels tend to create 'chopping' pressure waves or signals which when near a maf will disrupt maf signal.
Similarly throttle bodies when shut quickly create water hammer 'acoustic pressure wave' which travels upstream and may influence a maf.
Bends, rough pipe, transitions, may create turbulence but more important they disorganize airflow which prevents a maf from producing a linear signal flow.
In other words, a maf can work in a turbulent environment if the flow is consistent, it is quite typical to find consistent turbulent flow in plumbing. However if the flow is being disrupted in a way which produces pressure variations or stagnant/eddies or basically any non-linear flow differential (rate of change over time) the rapid rise or fall of the maf signal is going to alter the fueling properties in a similar fashion- sudden rise in maf signal = sudden rise in engine fueling = sudden spike in rich condition = engine inefficient/waste of fuel/poor running condition for an instant.

These are likely why so much variation in economy and performance is noted when using a maf over SD. The SD can produce a smooth transitional linear voltage signal as engine pressure changes over time because it isn't influenced by the nature of airflow, such perturbations and swirl character. The MAF on the other hand must have a consistent flow exchange in and out over time which gradually increases or decreases in signal strength for a smooth engine running operation.


At the end of the day the two MAF and MAP achieve the same goal. They both produce some final air fuel ratio value for the engine at some airflow theoretically measured (Virtual or theoretical VE compared with pseudo-measured mass). Because the maf would be easier to disrupt and encounter difficulty- why would anybody ever use it when they have MAP?

Because MAF tuning is incredibly easy, and fast. It saves time. Its like a shortcut method for tuning an engine. I can tune a MAF turbo car in an hour or less. A MAP car might take ten or fifty times longer if you really want to flush out every square inch of the map area in contrast. I could spend years going over a MAP tune and simply minutes on a MAF tune. The MAF takes the effort out of tuning a vehicle when and only IF when the MAF is setup in the plumbing properly. And this is the biggest challenge to using a maf- it isn't the tuning, which is simple. It is the placement and setup of the maf, ensuring there are no leaks and performing a complete analysis and diagnostic of the engine to ensure proper running ensues at some given maf placement given the application.

MAF pros:
Fast & easy to tune compared to MAP
Easy to identify changes in airflow mass due to a sudden leak or change in plumbing

MAF cons:
Difficult to position on some engines, sometimes it has no useful or reliable place at all
Hard for novices to emphasize and understand the flow through issues related to output signal
A leak in the plumbing may cause the driver to become broken down somewhere
Slight restriction caused by maf hot-wire (& screen sometimes) always in the way of flow somewhere

MAP pros:
Ignores flow conditions for the most part, not affected by buffeting
Leaking plumbing doesn't render the vehicle inoperative or cause poor fuel conditions (N/A engines)
Linear signal rate of changing output with changing pressure is easy to achieve
Doesn't restrict the tube or interfere with flow due to a hot-wire in the tube
Allows more elaborate plumbing, tighter bends, more options for tube placement, shorter tubes some places

MAP cons:
Difficult to fully tune, or simply time consuming
Relies somewhat heavily on appropriate Intake Air Temperature reading

Personally I will never use a maf whenever possible, for my own vehicles. However because a MAF is so simple a device and effective tuning solution, if the engine already has one and no reason not to use it properly I will always keep the MAF, and ensure it is setup properly to trouble free operation. If given the option of BOTH like with GM vehicles I always ditch the MAF in favor of the more potentially reliable, less restrictive, but difficult to tune MAP system. This also helps with custom plumbing as all of my vehicles are turbo and keeping a maf on a turbo vehicle when MAP is an option is sort of silly IMO

[Alvin]

I favor SD on most builds. Reversion is the main reason.


I don't get the saving time argument.. The car must be either tuned in both SD and MAF or SD for best results. If your talking about shortcuts that just gets the car out the door sure MAF only might save time but it might also cost more in come backs.


MAF sensor fouling or degradation is something almost never brought up. Had a 2010 camaro dropped off last week that was around 13.7:1 with 30 degrees of timing because the MAF was degraded/dirty/fouled, not reporting as much air as actual, and at a lower airmass for the timing table.

[Fast4.7]

I favor SD on most builds. Reversion is the main reason.


I don't get the saving time argument.. The car must be either tuned in both SD and MAF or SD for best results. If your talking about shortcuts that just gets the car out the door sure MAF only might save time but it might also cost more in come backs.


MAF sensor fouling or degradation is something almost never brought up. Had a 2010 camaro dropped off last week that was around 13.7:1 with 30 degrees of timing because the MAF was degraded/dirty/fouled, not reporting as much air as actual, and at a lower airmass for the timing table.

I will add to something nobody talks about. SD has a fueling drift. I am tuning here in Texas where it can be 28F on a cold start and a few hours later 75F. I have tried adjusting the IAT contribution numerous times as it is mostly related to IAT. I tried the stock values for my engine and they were way off. I used newer values from the same engine in a GMT800 truck. I tried newer values out of the same chassis with a 6.0L, still a large error that is entirely caused by the IAT swings. Finally turned of Complex Air Temp modeling that uses only the IAT and does not try to model manifold temp. That made the fueling as tight as it has been, but there is still a ~10% fueling swing in SD between 28F and 170F IAT. When it is 75F outside my factory air box has IATs ranging between 80F and 170F depending on speed and load. I have considered moving the IAT to the Bosch T-Map in the manifold plenum in an attempt to calm sone of that swing even more. With a cast iron lower intake and aluminum upper lid, I feel the IAT will be more stable and thus less of a fueling swing after warmup. With the MAF enabled the fueling does not experience these dramatic swings.

The other thing nobody mentions is that GM calibrated the line pressures and torque based stuff around a properly functioning and calibrated MAF.

[kingtal0n]

I favor SD on most builds. Reversion is the main reason.


I don't get the saving time argument.. The car must be either tuned in both SD and MAF or SD for best results. If your talking about shortcuts that just gets the car out the door sure MAF only might save time but it might also cost more in come backs.

You are thinking too narrow. Some vehicles like Nissan Silvia and Nissan Skyline come with only MAF sensor, no MAP. So the MAP is an option but not factory. People bring me that car and ask if they should buy MAP or MAF stand-alone power FC units for it... I tell them simply the MAF I can tune easily in a couple hours for 1/4 the price and thats the way to go if they can setup the plumbing the way I tell them to. After I tuned around a hundred of them I probably saved 200 or 300 hours and lots of money for lots of people. MAF is perfectly reliable and acceptable if you know what you are doing, and very fast to tune, and a factory only setup for many cars that never had MAP.

SD has a fueling drift.

Yes it was annoying at first but then I put a 1000OHM Variable resistor inline with my IAT and simply dial it up or down as needed when heat soaking in traffic to maintain a desired A/F ratio.

[Fast4.7]

You are thinking too narrow. Some vehicles like Nissan Silvia and Nissan Skyline come with only MAF sensor, no MAP. So the MAP is an option but not factory. People bring me that car and ask if they should buy MAP or MAF stand-alone power FC units for it... I tell them simply the MAF I can tune easily in a couple hours for 1/4 the price and thats the way to go if they can setup the plumbing the way I tell them to. After I tuned around a hundred of them I probably saved 200 or 300 hours and lots of money for lots of people. MAF is perfectly reliable and acceptable if you know what you are doing, and very fast to tune, and a factory only setup for many cars that never had MAP.





Yes it was annoying at first but then I put a 1000OHM Variable resistor inline with my IAT and simply dial it up or down as needed when heat soaking in traffic to maintain a desired A/F ratio.

Good old Nissan. I tuned all 3 of my VK56s both of my Titans, my M56S, my VQ35HR G35 Sedan and my Pathfinder with the 4.0L. MAF and factory widebands on the newer stuff. The G35 and M56S both had dual MAFs. The G35 has ~270K on it and it still has both OEM MAFs despite having had K&N filters for years now.

I need to poke around at how a P01 or P59 uses the IAT to compensate for fueling. I feel like some table or value somewhere is missing that cannot currently be adjusted that is jacking with the fueling. I have literally tuned SD TBIs with wet manifolds that did not have the air/fuel ratio drift that a P01 or P59 has in SD. The old TBIs were pretty bad too. I used to set them up with VEs increased enough to give BLM readings of about 120-124 when they were heat soaked so that they were overly rich when the manifold was atomizing the most fuel and that prevented them from being crazy lean when they were cold. I also added fuel to open loop and held closed loop off until a higher temperature to prevent it from running extremely lean on a cold manifold. Its hard to believe a P01 or P59 can be worse than that in SD, but they are.

[kevin87turbot]

I favor SD on most builds. Reversion is the main reason.


I don't get the saving time argument.. The car must be either tuned in both SD and MAF or SD for best results. If your talking about shortcuts that just gets the car out the door sure MAF only might save time but it might also cost more in come backs.


MAF sensor fouling or degradation is something almost never brought up. Had a 2010 camaro dropped off last week that was around 13.7:1 with 30 degrees of timing because the MAF was degraded/dirty/fouled, not reporting as much air as actual, and at a lower airmass for the timing table.

I agree Alvin. I've seen so many faulty MAF's over the years, I typically prefer SD on many applications. The GEN 3 MAF's were the worst. I'm fine with using MAF on the GEN 4 stuff...but I also clean the customer's MAF's if they don't read correctly. I also give them a lecture on the disadvantages of K&N filter oil on anything that uses a MAF.

[Alvin]

I will add to something nobody talks about. SD has a fueling drift. I am tuning here in Texas where it can be 28F on a cold start and a few hours later 75F. I have tried adjusting the IAT contribution numerous times as it is mostly related to IAT. I tried the stock values for my engine and they were way off. I used newer values from the same engine in a GMT800 truck. I tried newer values out of the same chassis with a 6.0L, still a large error that is entirely caused by the IAT swings. Finally turned of Complex Air Temp modeling that uses only the IAT and does not try to model manifold temp. That made the fueling as tight as it has been, but there is still a ~10% fueling swing in SD between 28F and 170F IAT. When it is 75F outside my factory air box has IATs ranging between 80F and 170F depending on speed and load. I have considered moving the IAT to the Bosch T-Map in the manifold plenum in an attempt to calm sone of that swing even more. With a cast iron lower intake and aluminum upper lid, I feel the IAT will be more stable and thus less of a fueling swing after warmup. With the MAF enabled the fueling does not experience these dramatic swings.

The other thing nobody mentions is that GM calibrated the line pressures and torque based stuff around a properly functioning and calibrated MAF.

I'm not seeing those issues.. Prehaps its how I'm doing things verses how you are.

[Fast4.7]

I agree Alvin. I've seen so many faulty MAF's over the years, I typically prefer SD on many applications. The GEN 3 MAF's were the worst. I'm fine with using MAF on the GEN 4 stuff...but I also clean the customer's MAF's if they don't read correctly. I also give them a lecture on the disadvantages of K&N filter oil on anything that uses a MAF.

I have never had an issue with K&N oil then again I do not clean my filters for like 50K because they generally do not need to be before that.

I also use GenIV MAFs on my personal GenIIIs. The signal is so much cleaner on the new MAFs.

[Fast4.7]

I'm not seeing those issues.. Prehaps its how I'm doing things verses how you are.

I can watch the fueling swing. It is directly related to IATs. Then again my IATs swing from 30F to 170F or more within a short period of time. GM did not make a very efficient air box in relation to intake air temps on my worst offender. Might as well have an open cone filter without any form of heat shield. I have actually even considered cutting a slot in the leading edge of the hood to help eliminate the hot air being drawn into the air box from under the hood because it heat soaks so badly.

[kingtal0n]

I can watch the fueling swing. It is directly related to IATs. Then again my IATs swing from 30F to 170F or more within a short period of time. GM did not make a very efficient air box in relation to intake air temps on my worst offender. Might as well have an open cone filter without any form of heat shield. I have actually even considered cutting a slot in the leading edge of the hood to help eliminate the hot air being drawn into the air box from under the hood because it heat soaks so badly.

I've noticed that not all the a/f walk out is due to IAT because sometimes when heat soaked I can adjust my IAT back to ambient and I am still lean on the wideband.


I think some of it is due to the voltage drop, my alternator output drops maybe 0.5v during a heat soak situation because the exhaust runs nearby the alt.
another issue is heating of the fuel system and injectors. Injector solenoids fire more slowly the hotter they get. Hotter fuel is less dense. Taken together the same pulse duty is less fuel over time during a heat soaking (I am running a DEAD HEAD for simplicity @ 600rwhp), compounded with reduced voltage, ofc I tried adding comp to the injector delay during reduced voltage but that never seems to cover the spread. So now I just keep turning the IAT until I see what I like.