Struggling to get accurate readings
Thread Starter
Joined: Jun 2014
Posts: 1,241
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From: Noblesville, IN
Struggling to get accurate readings So I've been trying to get my MAF dialed in, but I am getting wildly different readings based on when I drive. I know heatsoak and ambient temps will affect the MAF, but I'm at a loss as to what to do.
I've got two logs attached. Log 1 was this morning, about 55-60 degrees, didn't run into too much traffic and got a couple of chances to open the taps.
Log 2 was in the afternoon/evening. Temps reached roughly 85 today and were close to that when I left. Ended up sitting in a lot of traffic (relatively) so I know things under the hood got pretty hot. (just look at the iat's).
What concerns me is in the morning when I reached redline the MAF spiked super lean, whereas in the afternoon when I hit the rev limiter it was rich by a few points. I'm filtering out 5% throttle transients over 100mS, and my cell count is around 15.
Thoughts? Advice?
I've got two logs attached. Log 1 was this morning, about 55-60 degrees, didn't run into too much traffic and got a couple of chances to open the taps.
Log 2 was in the afternoon/evening. Temps reached roughly 85 today and were close to that when I left. Ended up sitting in a lot of traffic (relatively) so I know things under the hood got pretty hot. (just look at the iat's).
What concerns me is in the morning when I reached redline the MAF spiked super lean, whereas in the afternoon when I hit the rev limiter it was rich by a few points. I'm filtering out 5% throttle transients over 100mS, and my cell count is around 15.
Thoughts? Advice?
Last edited by HappySalesman; Aug 24, 2022 at 10:02 PM. Reason: Helps to actually post the logs lol
Thread Starter
Joined: Jun 2014
Posts: 1,241
Likes: 47
From: Noblesville, IN
Intake tract is an FPT 100mm lid, straight to the MAF housing which is the card style in a TSP 100mm housing (I put a honeycomb in it to help straighten the airflow) to a NW 102 and a Fast 102.
Thread Starter
Joined: Jun 2014
Posts: 1,241
Likes: 47
From: Noblesville, IN
My only problem with a higher cell count is maintaining it. As it is my counts at the rev limiter are only about 15 or so. As I'm only able to do this on the street I can't maintain 6700 long enough to get really good average readings.
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From: Virginia
You're not going to get high cell counts unless you use the maximum refresh/update rate in the tune. A lot of parameters on a lot of PIDs allow higher refresh rates. Set it as high as possible. Minimum count should be 50 for cell hits, ALWAYS. For MAF, consider turbulence your mortal enemy. What does your VE table look like? It’s job is to serve as transient and backup. A good MAF tune starts with a good VE tune. That, or disable dynamic completely if you’re looking for a half way solution. Did you tune the VE first?
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From: Virginia
Another note, because of the way MAF operates, temperature shouldn’t even be a factor. It’s accounted for by the MAF’s operating principles, speaking strictly physics. What’s not is your VE. That doesn’t account for heat, like at all. It’s also the table in use when doing “stomps” as I’m assuming may be the case. When tuning either model, smooth throttle is the key. Keep transients out of the equation as much as possible.
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Thread Starter
Joined: Jun 2014
Posts: 1,241
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From: Noblesville, IN
Since my car is a manual, I figured smooth throttle went out the window due to all of the shifting. It's why I have a filter set up to eliminate data 100ms before and after a throttle change greater than 5%.
Right now the VE table is stock. I have the tune set up to where it should read from the MAF only, so the VE table shouldn't be coming into the equation. I plan on tuning the VE table, but the person who "tuned" my car previously had set it up to run MAF only before and I figured I would just continue where they left off.
Curious that the MAF heatsoaking doesn't affect it's accuracy. I would've thought that since the wires are resistance based (and therefore heat based) that the housing/air getting hot would skew the readings.
Right now the VE table is stock. I have the tune set up to where it should read from the MAF only, so the VE table shouldn't be coming into the equation. I plan on tuning the VE table, but the person who "tuned" my car previously had set it up to run MAF only before and I figured I would just continue where they left off.
Curious that the MAF heatsoaking doesn't affect it's accuracy. I would've thought that since the wires are resistance based (and therefore heat based) that the housing/air getting hot would skew the readings.
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Verdad Gallardo TECH Fanatic
Joined: Oct 2014
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From: Virginia
Since my car is a manual, I figured smooth throttle went out the window due to all of the shifting. It's why I have a filter set up to eliminate data 100ms before and after a throttle change greater than 5%.
Right now the VE table is stock. I have the tune set up to where it should read from the MAF only, so the VE table shouldn't be coming into the equation. I plan on tuning the VE table, but the person who "tuned" my car previously had set it up to run MAF only before and I figured I would just continue where they left off.
Curious that the MAF heatsoaking doesn't affect it's accuracy. I would've thought that since the wires are resistance based (and therefore heat based) that the housing/air getting hot would skew the readings.
Right now the VE table is stock. I have the tune set up to where it should read from the MAF only, so the VE table shouldn't be coming into the equation. I plan on tuning the VE table, but the person who "tuned" my car previously had set it up to run MAF only before and I figured I would just continue where they left off.
Curious that the MAF heatsoaking doesn't affect it's accuracy. I would've thought that since the wires are resistance based (and therefore heat based) that the housing/air getting hot would skew the readings.
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Joined: Oct 2014
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From: Virginia
I’ll also bet that tuning the VE will not hurt a thing except help you. If that’s not it, and your VE is truly disabled, then it sounds like fuel transients are off a tad. The MAF is meant for steady state operation. Without a predictive VE, then hopefully you addressed this with the transient tables too, to account for rapid throttle transitions. MAF only tunes are what many would call a “lazy tune” or something I’ve only done when I had the car for like an hour and I was pressed for time. Customer knew full well it wasn’t a “full” tune, but yes it can be done. Even on those with a disabled VE I didn’t see wild AFR swings as described. Even later when readdressing those tunes for other issues, but otherwise they ran fine.
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From: Virginia
One more thing, what is your filter equation to determine throttle % greater than 5%? If it’s not a derivative function using time, it may also be contributing to skewed data.
To get a good derivative, watch my acceleration rate video on how to do that. It’s based on rate of change, aka, derivative, in the case of that video it’s using speed. That can be applied to literally any PID in the tune if you’re crazy enough to log all of that.
Essentially it’s (PID - 1000ms) - (PID + 1000ms)
The period of time is up to you, and I’m also not sure if this will work as an actual filter. Filters are great for a lot of reasons, but I’m highly curious what your math is for determining what 5% is, unless you mean literal, which is probably why you are restricted on data.
To get a good derivative, watch my acceleration rate video on how to do that. It’s based on rate of change, aka, derivative, in the case of that video it’s using speed. That can be applied to literally any PID in the tune if you’re crazy enough to log all of that.
Essentially it’s (PID - 1000ms) - (PID + 1000ms)
The period of time is up to you, and I’m also not sure if this will work as an actual filter. Filters are great for a lot of reasons, but I’m highly curious what your math is for determining what 5% is, unless you mean literal, which is probably why you are restricted on data.
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From: Virginia
Another question here (my apologies since I’ve asked a lot already) is do you have LTFTs disabled?
LTFTs will remember whatever number they had last at the moment you enter PE. So if at that point they are lean, they stay lean through PE and do affect it. Same for rich. You do have trims off for tuning, correct?
I don’t know why you didn’t respond to my other questions. I’m here to help like everyone else is. Don’t be scared to answer. This is the place to ask before you blow something up. Knowledge is free here brother, don’t be a stranger.
LTFTs will remember whatever number they had last at the moment you enter PE. So if at that point they are lean, they stay lean through PE and do affect it. Same for rich. You do have trims off for tuning, correct?
I don’t know why you didn’t respond to my other questions. I’m here to help like everyone else is. Don’t be scared to answer. This is the place to ask before you blow something up. Knowledge is free here brother, don’t be a stranger.
