Landtank MAF surprising scangauge results (1 Viewer)

[sleeoffroad]

It doesn't look like anyone with this mod are having any issues, but the thing that bothers me is Toyota is pretty specific about having it's fuel pressure lowered under certain conditions and not having one range of pressure, rather two ranges. But they don't go into detail as to why this is important.

Because their ECU programming assumes a constant fuel pressure differential. Also, they do vary fuel pressure to improve driveability, starting issues, emmisions at starting etc etc.

I would think a constant pressure system would be simplier. Maybe one reason for the lower pressure at idle and lower speeds could be to relieve the ECU from having to make major adjustments. Many engines spend a significant amount of time idling or at low rpm, so if you lower the fuel pressure during those times and the ECU is expecting that, you don't have to make a major compensation based on other sensors.

I think a constant fuel pressure vs a constant fuel pressure differential is purely how they chose to do it and have programming to match both situations. We are not privy to why they would use one system in one car, and another on another motor.

One of the questions I have is that if the rig does go into limp mode due to sensor failures, with higher fuel pressure than it's expecting, would that cause a major overrich condition, if the vehicle is expecting a lower fuel pressure at idle and low rpm. I don't know how much LTFT would override the computer's base map in an open loop, limp mode situation. But I wonder if this could be a potential problem if 02 sensors failed or multiple sensors failed.

In general any limp mode is exactly that. The ECU will put the truck in such a state that it can limp home without danger. It will do what it can to save the motor.

Has anyone come up with a specific reason as to why the new sensor won’t accurate meter the air at idle? If it’s in the development threat, I guess that gone, so I can’t check. Is it because the ECM is not expecting good readings at low rpm and bases it’s idle qualities on other sensors and now the new sensor is throwing the ECM off with it’s accurate readings at low rpm? This is the part that confuses me the most.

it is not that it is not accurate. It is that it reports a voltage that means a certain lbs of airflow to the computer. The size and bore of the housing has changes, so that lbs of air reported is not what is really entering the motor.

The ECU does not know what an accurate airflow reading is, except when it is out of range as to what is expected.

The sensor “appears” to read accurate throughout the rpm range, but not at idle. Why would this be?

The sensor and housing is not calibrated to what the ECU is expecting.

If there was just another way to get this sensor to work in perfect harmony with the ECM at idle so the computer wouldn't have to be tricked by removing the FPR line, this mod would be a no brainer.

Therein lies the rub, if sensor is chosen right, and calibrated to the flow of the new housing and what the stock MAF was, it can be done.

In short, if the ECU reads the MAF and it interprets 10 lbs of air, it must be 10lbs of actuall air flow. That way if we do increase boost, 33lbs will actually be 33lbs. Now if the ECU knows what to do with 33lbs of air is a totally different matter.

If all that is done, then you can start messing with different sensor's and injector sizes for boosted trucks.

 

[LC80Ducati996]

Yes, here is a good read on it. http://www.autoshop101.com/forms/h37.pdf

It is important for people to know that O2 sensors does NOT read air fuel ratio. They only read oxygen in the exhaust gasses. No other gas. That is why it does not know about high NOx or any of the other gasses. It is also not very sensitive. If you read the above you will see that the 02 sensor is termed a switch for LEAN or RICH (ie, below or above 14.7). It does not know a little bit rich, or a little bit lean. Or more lean or how lean the truck is running.


That is why wide band O2's are recommended when you really start playing.

As for turbocruiser, thanks for the kind words, but just a point I want to make. We advised the wide band because we did not know anything about the calibration of the sensor. We did not ignore it at that time.

Yep..

Since the only accurate reading is at 14.7:1 it is not usefull for times when the engine is going to be needed to make power. The AFR for best power is richer than the AFR for best fuel efficiency. So unless it has a wideband o2 OEM it will never use the o2 when you have the skinny pedal floored.

 

[Brian894X4]

I'm coming from the perspective that I need a rig that can operate reliably from below sea level to well over 10,000 feet, with ambient temps will below zero to well over 110 degrees, driving endless for hours in any of those conditions at either 70-80 mph or only 7-8 mph or less, while carrying a load that exceeds GVW, on any kind of pump gas that could range from 87 (or lower) octane to 93 octane, while as much as several hundred miles from the nearest civilization, while the motor as 100K miles (like it does now) or 300K miles (like it will later hopefully).

That's probably a different requirement than the guys who go nuts on their motors to get as much power out of them as they can...i.e. the 1300 h.p. supra motor.

The one question nobody has answered in my mind is why the ECU and sensor won't mesh properly at idle without other modifications. At least I missed it if they did. I think that's a critical question for me personally considering the above requirement. Had the sensor been a direct swap with no mods and giving the same apparent perfermance gains, it would have been a no brainer, but the apparent fact that ECU doesn't like the sensor readings at idle are hard to ignore. For some this doesn't matter and that's perfectly fine. For others, it makes the mod questionable and makes me wonder if there's some other way to fix this one issue. This is just a matter of personal preference and it doesn't mean either side is right or wrong in my view. I'm still debating in my own mind.

This discussion to me has been one of the most valuable threads ever. I've learned more about the Toyota EFI systems that I ever thought possible. Which could really help me later for diagnosing a problem in the field. If you haven't already, everyone really needs to read through the SAE papers that Christo posted earlier in the thread. It has a lot of value well beyond this one project.

 

[Kernal]

newb here again; still lurking and reading; had a couple of thoughts; is there any way to reprogram the ECU to make it all work "correctly" with the modified MAF? How about some vacuum switch that would automatically disconnect the vacuum to the FPR when it doesn't need vacuum (if ever), and then resupply the vacuum when it needs vacuum? I've read some posts about a ?wideband O2 sensor; is one available and fittable to our rigs, and would it help a stock engine?

 

[SeanAndHis80]

No reprogramming the stock ECU. They make piggyback computers to essentially do just that. A piggyback will modify the input, output or both signals to map out fuel delivery/ignition timing different than the stock unit.

A wideband sensor would work with a piggyback - or a replacement ECU - but the stock ECU would not know what to do with the signal.

 

[jasonmt]

My point is that the values you are looking at is a calculated value from a voltage reading. The calculation assumes a certain response and bore size of MAF housing. If you change either, the calculation does not know this. So you can not compare the values. Without knowing that 3 volt from your sensor means 20 lbs (or whatever), you can not use the airflow numbers as shows on the OBD2 interface. Making any interpretation from those values are not correct. They might be, by pure luck, but that is what needs to be verified.

I think people do, and strange as it might seem, I am actually trying to help you. Have you ever looked at what these people do?
Abaco Performance, LLC

If your car is not included in our library of mass air transfer, you may still use the DBX mass air meter by using the mass air transfer table from your factory ECU, or by sending us your meter, air piping and air box for us to flow, ($50.00 fee) and then installing those transfers into the DBX with Abaco software.

Not having a horse in the race as my 80 series runs on diesel the website Christo linked to raises a few points:

1. It seems like the main point of contention vis a vis the response curves could be solved by sending $100 and a air box, piping and both the oem sensor/housing and Rick's housing/sensor to these guys.
2. Those Abaco sensors seem to be a pretty impressive piece of kit with the "tuneability" built into the meter, the 85mm meter looks to go for ~$380 which seems like a great deal for the forced induction guys.

 

[Ebag333]

A suggestion to compare the voltage outputs of the two MAFs for a given airflow is to hook them up in series to a variable speed blower. If they are series they must see the same airflow. You could swap positions to verify they still read consistant, otherwise add more length between the fan and between the sensors to reduce turbulance. Then you could get a feel for the voltage outputs.

Seems that all this debate could be easily solved by someone doing this (though as Christo said, not with a house fan ).

Hook up a volt meter to the sensor, run the truck through it's paces noting down the voltage at various circumstances (IE: at 2.5k RPM cruising, climbing a hill, idle, etc).

Swap out Landtank's MAF for the OEM one. Repeat your tests.

If the voltage is significantly different, the numbers could be used to figure out what the ECU is seeing, and possibly why the different issues occur.



I think Christo's concerns on disconnecting the FPR is valid. I think that there's a valid point that you're unlikely to damage the truck by blocking it off, but I'd like to at least know the reason as to why blocking it off is needed, and the possible effects of doing so. As far as I can see it right now, the reason is basically "because that's what makes it work."

 

[sleeoffroad]

You also have to take the bore and design of the housing into account. Not just the voltages.

 

[wearsabrowncoat]

I'm coming from the perspective that I need a rig that can operate reliably from below sea level to well over 10,000 feet, with ambient temps will below zero to well over 110 degrees, driving endless for hours in any of those conditions at either 70-80 mph or only 7-8 mph or less, while carrying a load that exceeds GVW, on any kind of pump gas that could range from 87 (or lower) octane to 93 octane, while as much as several hundred miles from the nearest civilization, while the motor as 100K miles (like it does now) or 300K miles (like it will later hopefully).

I haven't had mine in that long but I can say it has run smoother since install and I have had absolutely no issues from temp ranging from -55 to 75. I'm at 1600 feet now but will be headed to 6000'+ next month into Colorado. Call me a fool but I won't be bringing the old MAF.

This thread feels like Sumotoy should be involved

 

[SeanAndHis80]

I think if I were to try and test this on the cheap I would rig a way to stick both on a running rig of any sort run it through it's paces and compare the values simultaneously from the two. That way both would always be drawing the same regardless of other factors.

Another interesting point from the Abaco website:

If your car is not included in our library of mass air transfer, you may still
use the DBX mass air meter by using the mass air transfer table from
your factory ECU, or by sending us your meter, air piping and
air box for us to flow, ($50.00 fee) and then installing those transfers
into the DBX with Abaco software.

Which seems to contradict what Christo says:

In the case of a KN, no air filter or whatever before the MAF does not matter. If the stock MAF used (the one the ECU progamming was done for) then 3v from the sensor means the same thing, does not mattter what is in from of it.

In reality even opening up the intake by removing the obstruction is going to change parameters that the ECU is expecting, changing the sensor is another unexpected change. I wonder how Slee does the fuel management on it's 80 turbo implementation - it must use an aftermarket unit as there would be no way the stock ECU could be able to understand all of the changes to the intake - or am I missing something?

I'm coming from the perspective that I need a rig that can operate reliably from below sea level to well over 10,000 feet, with ambient temps will below zero to well over 110 degrees, driving endless for hours in any of those conditions at either 70-80 mph or only 7-8 mph or less, while carrying a load that exceeds GVW, on any kind of pump gas that could range from 87 (or lower) octane to 93 octane, while as much as several hundred miles from the nearest civilization, while the motor as 100K miles (like it does now) or 300K miles (like it will later hopefully).

That's probably a different requirement than the guys who go nuts on their motors to get as much power out of them as they can...i.e. the 1300 h.p. supra motor.

If you want that kind of reliability out of a 13 year old truck with 100K+ miles on it - you should not be playing around with anything but stock parts. Plain and simple.

 

[Brian894X4]

I just started to do some testing between the two sensors and I didn't get very far, before something kind of disturbing happened.

While at idle (with the Landtank sensor installed) I removed the lid of the air filter cover to make an adjustment and stuck my hand inside the air filter. The engine began to stumble and almost died. My first inclination was that my air hose is cracked and I either just broke it or was letting in some air somehow past the sensor.

However, the hose checks out. So I put my hand in the pathway of the intake again and again the engine stumbled and almost died. I have messed with other cars and have found that I could block the airway almost completely and the engine would only die have the air intake was completely blocked. In this case, it wasn't completely blocked at all. Maybe not even halfway blocked. In fact, my hand wasn't sealed against the intake at all, it was only causing a minor disruption of the airflow. All it took to kill the engine was a disturbance in the airflow. That does not seem right to me.

BTW, having the FPR plugged in or not, made no difference.

My test will be to remove the filter canister completely and see how the sensor behaves with no airfilter. Then after that, I'll install the old MAF and see how it reacts. Could be this is perfectly normal, so I'm going to do a few more tests and we'll see what happens.

 

[Ebag333]

You also have to take the bore and design of the housing into account. Not just the voltages.

True. But that'd be at least a start and give some hard data.

I just started to do some testing between the two sensors and I didn't get very far, before something kind of disturbing happened.

While at idle (with the Landtank sensor installed) I removed the lid of the air filter cover to make an adjustment and stuck my hand inside the air filter. The engine began to stumble and almost died. My first inclination was that my air hose is cracked and I either just broke it or was letting in some air somehow past the sensor.

However, the hose checks out. So I put my hand in the pathway of the intake again and again the engine stumbled and almost died. I have messed with other cars and have found that I could block the airway almost completely and the engine would only die have the air intake was completely blocked. In this case, it wasn't completely blocked at all. Maybe not even halfway blocked. In fact, my hand wasn't sealed against the intake at all, it was only causing a minor disruption of the airflow. All it took to kill the engine was a disturbance in the airflow. That does not seem right to me.

BTW, having the FPR plugged in or not, made no difference.

My test will be to remove the filter canister completely and see how the sensor behaves with no airfilter. Then after that, I'll install the old MAF and see how it reacts. Could be this is perfectly normal, so I'm going to do a few more tests and we'll see what happens.

Very curious. Curious enough that I walked out to my truck and tried it.

I couldn't get it to stall. I blocked the intake to the absolute best of my ability with nothing more than my bare hands, and could get the idle to drop way low, but couldn't get it to stumble, sputter, or die at all.

 

[Brian894X4]

Ebag333, do you have the stock MAF or the Landtank MAF.

What I found after more testing was that the stock MAF performed as you described. I couldn't get it to stall with the filter canister lid still attached, trying to cover the filter canister lid hole. However, with the filter canister lid removed and the stock MAF exposed, I could get it stall by simply putting my hand over the sensor hole...not sealing it, but distrupting airflow. Still it took far more to get it to quit than the Landtank MAF.

The Landtank MAF stumbled and started to die by simply having the filter canister lid hole (while attached to the MAF) just barely covered. Not sealed at all. Once I removed the canister and the Landtank MAF was explosed the engine started to run rough and just waving my hand in front of the MAF caused the engine to almost die. Furthermore, my STFT was in the 20s and my LTFT was 15. I didn't bother to test it any further. The next thing I did was check all my connections, remove my intake and verify that there was no cracks and then install the stock MAF.

The stock MAF performed as I described above.

After running back on the road with the stock MAF, the performance gains of the Landtank MAF were pretty apparent. Testing under the exact same conditions, including weather and temp, I couldn't get the scangauge to indicate anything more than 260 gross h.p. Remember that with the Landtank MAF it was grossing 305 h.p. The stock MAF intake just feels restricted compared to the Landtank MAF and I'm sure that's a significant reason for the power increase.

Baring some fluke like a bad MAF sensor that I used for this mod or something else I missed, my current conclusion is that the Landtank MAF is definately not calibrated for our ECU at idle and that causes some potential issues that even modifying the FPR may not be able to fix. Based on what happened to me, there's a real risk of killing the motor if the intake gets partly clogged or disrupted such as during a water crossing or some other event. However, for whatever reason, be it better sensor readings or less restriction, or a accidental lean condition, the engine definately runs better and has more power. Significantly more power at the upper end. Could be that it's only a calibration issue at idle and not the rest of the powerband. I don't know.

If someone else who has the landtank MAF wants to test out this potential problem to make sure I'm not all washed up, let the engine idling, lift up the filter canister lid, but leave it attached and just partly plug the intake. If it stumbles and dies then you have the same issue I had. The stock MAF will not even stumble under this condition. This would make sure I just don't have a bad MAF or some other problem.

 

[Ebag333]

Ebag333, do you have the stock MAF or the Landtank MAF.

Stock MAF. (Currently. )

Based on what happened to me, there's a real risk of killing the motor if the intake gets partly clogged or disrupted such as during a water crossing or some other event.

That was exactly my thought. Water crossing, storm in the desert plugging up the filter with sand....anything along those lines could cause the truck to die. Not good, IMHO.

 

[jamisobe]

Ebag333, do you have the stock MAF or the Landtank MAF.

What I found after more testing was that the stock MAF performed as you described. I couldn't get it to stall with the filter canister lid still attached, trying to cover the filter canister lid hole. However, with the filter canister lid removed and the stock MAF exposed, I could get it stall by simply putting my hand over the sensor hole...not sealing it, but distrupting airflow. Still it took far more to get it to quit than the Landtank MAF.

The Landtank MAF stumbled and started to die by simply having the filter canister lid hole (while attached to the MAF) just barely covered. Not sealed at all. Once I removed the canister and the Landtank MAF was explosed the engine started to run rough and just waving my hand in front of the MAF caused the engine to almost die. Furthermore, my STFT was in the 20s and my LTFT was 15. I didn't bother to test it any further. The next thing I did was check all my connections, remove my intake and verify that there was no cracks and then install the stock MAF.

The stock MAF performed as I described above.

After running back on the road with the stock MAF, the performance gains of the Landtank MAF were pretty apparent. Testing under the exact same conditions, including weather and temp, I couldn't get the scangauge to indicate anything more than 260 gross h.p. Remember that with the Landtank MAF it was grossing 305 h.p. The stock MAF intake just feels restricted compared to the Landtank MAF and I'm sure that's a significant reason for the power increase.

Baring some fluke like a bad MAF sensor that I used for this mod or something else I missed, my current conclusion is that the Landtank MAF is definately not calibrated for our ECU at idle and that causes some potential issues that even modifying the FPR may not be able to fix. Based on what happened to me, there's a real risk of killing the motor if the intake gets partly clogged or disrupted such as during a water crossing or some other event. However, for whatever reason, be it better sensor readings or less restriction, or a accidental lean condition, the engine definately runs better and has more power. Significantly more power at the upper end. Could be that it's only a calibration issue at idle and not the rest of the powerband. I don't know.

If someone else who has the landtank MAF wants to test out this potential problem to make sure I'm not all washed up, let the engine idling, lift up the filter canister lid, but leave it attached and just partly plug the intake. If it stumbles and dies then you have the same issue I had. The stock MAF will not even stumble under this condition. This would make sure I just don't have a bad MAF or some other problem.

You still have turbulence as a variable. To test your hypothesis you really need to restrict flow without disturbing the airflow. The stock MAF appears as if it would be better at cleaning up air flow with the constrictive airfoil design vs the new sensor that takes a much smaller sample from a more specific part of the airflow.

I can't imagine that anyone in the real world would run their truck without the air canister intact. Try putting a piece of paper or something around the air filter and then closing it back up. This would better duplicate a clogged air filter.

 

[sleeoffroad]

You are not making any change to the housing that the sensor is installed in with a K&N or something like that. That is the only thing that matters. Some cares the sensor is installed directly into the intake tube, and that is why they want the tubing. If you did change that tubing size, then you are affecting the calibration.

I wonder how Slee does the fuel management on it's 80 turbo implementation - it must use an aftermarket unit as there would be no way the stock ECU could be able to understand all of the changes to the intake - or am I missing something?

We use a piggyback to add fuel via extra injectors.

 

[turbocruiser]

As for turbocruiser, thanks for the kind words, but just a point I want to make. We advised the wide band because we did not know anything about the calibration of the sensor. We did not ignore it at that time.

That's right, I hope that's how it sounded what I wrote? I was trying to emphasize to everyone that while you advised me about all these potential things way back when, you also advised that the way to monitor the end result is through the wideband. Since it was what I and I alone wanted to do, you helped me do it as safely and as mindfully as possible.

I was also trying to emphasize the two different contexts of occasions here between what I wanted from you then and what the current customer wants from you now. Either scenario I'm saying your service is superb. I never got any of that confused so I'm sorry if what i wrote sounded the other way.

I do think I might have misunderstood the message then about the FPR; I ultimately understood that the wideband would reveal any problem and I realize right now that's not the whole picture but I write that off to what I was understanding then, not what you were trying to tell me then; I do distinctly remember all those thoughts as well ... like I wrote the way I understood it "there were thoughts about those things but no real concerns... (as long as the wideband is working)" and I hope that's how it sounded to everyone. If not, my apologies and attempt at correction here.

We use a piggyback to add fuel via extra injectors.

BTW, are you working with the SMT7 yet for the 80?

 

[semlin]

i wish i could find my 1994 FSM i am 95% sure it tells me that the FPR on the 93-94 compensates for the lack of sensitivity of the VAF at low rpm.

if that is so, then the generic discussion of toyota the purpose of FPR's that christo has attached is not the whole story. if it does the same thing for the stock MAF, this would also potentially explain why the landtank FPR is "conflicting" with the FPR. basically, the ecu may be getting a reading from the newer MAF when it is not expecting one because the stock MAF will normally have dropped out. the FPR "baseline" fuel pressure may be calibrated to compensate for an expected zero "baseline" maf signal to the ecu at or near idle, but the landtank MAF may still be generating a calibrated signal.

 

[semlin]

that would also explain the differing results above from hand blocking the two mafs at idle. on the stock maf at idle the ecu may be getting no maf signal and simply flowing a predetermined baseline fuel flow calibrated for a 700 rpm idle. for the landtank maf, it is still getting a maf signal and so trying to respond to the differing air flows caused by hand blocking.

 

[semlin]

you could maybe fix this "conflict" by leaving the FPR connected, but adjusting the idle lower or higher to find a point where the FPR baseline fuel pressure matches up and there is no fuel trim problem.