[Cattledog]

Originally Posted by sleeoffroad

Rick, the reason there is a vacuum line on the fuel pressure regulator is that Toyota wants the pressure differential between the intake manifold pressure and the fuel rail pressure to stay constant. At idle there is vacuum in the intake manifold, thus you need to decrease the fuel pressure, to keep the pressure differential the same. Disconnecting the line is causing excessive fuel pressure at idle. They did not install the pressure regulator because their sensor reads the air flow incorrectly idle. That is documented in the Toyota tech manuals.

Christo, read the data logs. Rick and Turbocruiser had them at one point, Rick and I did most of the testing on my truck and then his. The rail pressure is conected to the vacuum in the intake on a stock truck. The change in pressure in the rail is not linear to the change vacuum in the manifold. Most of the pressure on the rail is with in a couple of psi off idle. If I recall correctly there are two readings for the rail pressure one for idle and one for higher rpm. I will look at the manual tonight.

Originally Posted by sleeoffroad

if your MAF is causing high long term fuel trim at idle with the pressure regulator connected to vacuum, then it is measuring the air incorrectly and the truck is trying to adapt to that. You are telling the truck there is less air that what there is and the truck is trying to make up when it sees a lean condition. By disconnecting the fuel pressure regulator you are increasing the fuel rail pressure and it causes more fuel to be injected for a given duty cycle, so therefore the long term fuel trim goes down.

Read the data... Long term trim is adjusted in intervals by several variables. The short term trim is adjusted VERY quickly.

Originally Posted by sleeoffroad

In a stock truck you will note in the data logs that the short term fuel trim is adjusted a huge amount down when you com off rpm onto idle and way up when you leave idle to upper rpm's. This is due to the poor resolution of the MAF and drop in fuel pressue on the rail. Rick's MAF has none of these issue's due to a contant fuel rail pressure and more accurate sampling of the air flow by the MAF sensor. We have been through this many times with Sumotoy...

Originally Posted by sleeoffroad

I don't understand why this is hard to understand the sensor is smaller and flows better at all rpm just look at the sensors and design..... Toyota didn't design a new sensor so that is would sample less accuratly! And read the data logs

This is a sequntial port fuel injection for OBD-II trucks. The ecu is calculating and adjusting the injector pulse on every injector cycle. More air that the MAF can measure means larger/longer injector pulse. The only problem that could happen would be maxing out the injectors due to their size.

Christo why did you not bring this up two years ago in the original development?

[Cattledog]

Originally Posted by sleeoffroad

On another note, what is your long term fuel trim in closed loop under most driving conditions? Have you ever had a truck measure on a gas analyzer to make sure it is not running lean by checking the NOX readings? You can still be running lean, without tripping codes or having check engine lights.

If my truck was running lean It would have shown up in the o2 sensor reading in the datalogs and my mileage would be better.

I still get only 12 mpg....

[nicholas]

Originally Posted by sleeoffroad

Also, how are you compensating for the increase in pressure in the manifold on boosted trucks if the fuel pressure regulator is not connected. If you don't leave the pressure regulator connected, the extra pressure in the manifold (due to the boost) is not compensated for and the pressure differential will not be constant again. If you leave the regulator connected, the possitive pressure on it will raise the fuel pressure in the rail, thus overcoming the extra pressure in the manifold.

Pardon my ignorance, but what positive or negative effects will a non-constant fuel pressure differential that you describe have on a boosted truck long term?

[sleeoffroad]

Originally Posted by landtank

you'll have an idle LTFT% that is way out of the norm during idle and could possibly throw a code. If you were to do a reset on the ECU, like removing the battery for a long enough period of time, you would be running very lean until the truck got hot enough to enter closed loop and start adjusting for that condition.

So that means the sensor is reading the incorrect amount of air. How did you determine it is correct? Did you flow bench it?

How did you determine that your sensor reads better or more accurate than the stock one, other than your conclusion about the fuel trim that increased when you disconnected the FPR?

I reread the whole development thread and I saw your reasoning behind disconnecting the FPR and I believe it is simply not the correct thing to do. I can see that a newer sensor can have a better dynamic range, but if you cannot get the truck to idle correctly with all the fuel pressure systems hooked up, then something is wrong. If the sensor is reading the amount of air wrong at idle it is most probably wrong during driving as well.

How did you match the diameter of the housing to the sensor, other than monitor fuel trims?

I know everyone might now say, hey but the truck runs better. You might be experiencing a lean condition and not know it. Without putting the truck on a gas analyzer (to measure NOC) you would not know. Toyota traditionally tune trucks rich for safety. The truck will run better when leaned out, but that is not necessarily a good thing for the motor.

We have seen trucks fail emissions test (high NOX due to running lean) with no check engine lights or codes. The indicator was that it was running at 20% LTFT at idle.

In my testing the only time that the vacuum line influenced the FT% was during idle and it accounted for a shift of about 18% from what I remember.

Was this long term or short term you were measuring? What is the long term fuel trims on normal drive cycles?

[sleeoffroad]

Originally Posted by Cattledog

Christo, read the data logs. Rick and Turbocruiser had them at one point, Rick and I did most of the testing on my truck and then his. The rail pressure is conected to the vacuum in the intake on a stock truck. The change in pressure in the rail is not linear to the change vacuum in the manifold. Most of the pressure on the rail is with in a couple of psi off idle. If I recall correctly there are two readings for the rail pressure one for idle and one for higher rpm. I will look at the manual tonight.

I don't have the logs, but I would like to see what the LTFT is. See my comments on NOX. In this document is a good section on how the fuel pressure regulator work and how it keeps the pressure constant.

[I]Read the data... Long term trim is adjusted in intervals by several variables. The short term trim is adjusted VERY quickly.

I know, but what is it?

[sleeoffroad]

Originally Posted by nicholas

Pardon my ignorance, but what positive or negative effects will a non-constant fuel pressure differential that you describe have on a boosted truck long term?

Either running lean or rich, depending on what situation the truck is in. Everyone thinks that the O2 sensor feedback is enough to keep the truck in line, but that is not so. See comments about emissions and NOX measurements without throwing codes.

Also see document I quoted earlier. Toyota designed the system to operate with a constant pressure differential between the fuel rail and the manifold. The injector size and maps in the computer is designed to work with that. If you mess with that, you are relying on the feedback systems to keep things in check. Well sometimes they will not be able to.

[sleeoffroad]

Originally Posted by Cattledog

If my truck was running lean It would have shown up in the o2 sensor reading in the datalogs and my mileage would be better.
I still get only 12 mpg....

Do you have a datalog that you can post?

[nicholas]

Originally Posted by sleeoffroad

Either running lean or rich, depending on what situation the truck is in. Everyone thinks that the O2 sensor feedback is enough to keep the truck in line, but that is not so. See comments about emissions and NOX measurements without throwing codes.

Also see document I quoted earlier. Toyota designed the system to operate with a constant pressure differential between the fuel rail and the manifold. The injector size and maps in the computer is designed to work with that. If you mess with that, you are relying on the feedback systems to keep things in check. Well sometimes they will not be able to.

Yikes, I read the NOX comments. Also, I have not done an emissions test for almost three years.

[sleeoffroad]

Originally Posted by sleeoffroad View Post
In a stock truck you will note in the data logs that the short term fuel trim is adjusted a huge amount down when you com off rpm onto idle and way up when you leave idle to upper rpm's. This is due to the poor resolution of the MAF and drop in fuel pressue on the rail. Rick's MAF has none of these issue's due to a contant fuel rail pressure and more accurate sampling of the air flow by the MAF sensor. We have been through this many times with Sumotoy...

How do you know that it samples better? It is an anolog device with a response curve. How does that produce better resolution? It can have a broader dynamic range and need a smaller sample to measure, but where is the documentation that says it is more accurate or better resolution?

I don't understand why this is hard to understand the sensor is smaller and flows better at all rpm just look at the sensors and design..... Toyota didn't design a new sensor so that is would sample less accuratly! And read the data logs

How do you know that the factory sensor is restrictive for the air needs for a normally aspirated motor? If stand next to a stream and you drop a bucket (sampling device) into the stream for a second you will get a certain amount of water in the bucket based on the flow. You can then calculate how much water flows in the river, based on the size of the river.

If you now leave everything else constant, but you make the river twice the size, then you will have more flow but you will still collect the same amount of water in the bucket per second.

You can change the bucket size (new sensor), but you still have to calibrate it to be able to calculate the water blow.

Also, how are you compensating for the increase in pressure in the manifold on boosted trucks if the fuel pressure regulator is not connected. If you don't leave the pressure regulator connected, the extra pressure in the manifold (due to the boost) is not compensated for and the pressure differential will not be constant again. If you leave the regulator connected, the possitive pressure on it will raise the fuel pressure in the rail, thus overcoming the extra pressure in the manifold.

This is a sequntial port fuel injection for OBD-II trucks. The ecu is calculating and adjusting the injector pulse on every injector cycle. More air that the MAF can measure means larger/longer injector pulse. The only problem that could happen would be maxing out the injectors due to their size.

How do you know the amount of air is correct? Also how do you know the computer maps go beyond what the MAF is designed for. I know turbocruiser reports more airflow as read from the OBD2. How do you know that is correct, ie, when the MAF sends out 3 volts to the ECU, it takes that reading (plus some other ones) and it makes it into a flow measurement. The new sensor sends out 3 volts as well, however the opening is much bigger so more air is entering the motor. The ECU does not know the opening is better. All it know is the 3 volt reading. So it thinks it gets a certain amount of air but it is in fact not.

Christo why did you not bring this up two years ago in the original development?

I asked about the flow testing back then. As I recall he did not do it.

[Riad]

Christo, you are scaring me man.

I get some where from 14.46 to 14.98 mpg these days. I filled up this morning with 15.318 gallons after driving 221.5 miles. I am adopting to the habit of filling up when the tank is more than or equal to half empty. My gas mileage seems to have degraded over time after getting the new sensor. With stock sensor and (oem) exhaust with leak (between cats) I used to get some where between 16.45 to 16.88 mpg. It stayed that way for a little while after getting the new sensor. I have concluded that its my driving habit that caused the mpg degradation. After reading your post, sounds like I might be causing some long term damage to the engine; although I am not clear on what it is yet. I wonder if it would be wise to put the old sensor back with FPR hose.

[nicholas]

Originally Posted by Riad

Christo, you are scaring me man.

I get some where from 14.46 to 14.98 mpg these days. I filled up this morning with 15.318 gallons after driving 221.5 miles. I am adopting to the habit of filling up when the tank is more than or equal to half empty. My gas mileage seems to have degraded over time after getting the new sensor. With stock sensor and (oem) exhaust with leak (between cats) I used to get some where between 16.45 to 16.88 mpg. It stayed that way for a little while after getting the new sensor. I have concluded that its my driving habit that caused the mpg degradation. After reading your post, sounds like I might be causing some long term damage to the engine; although I am not clear on what it is yet. I wonder if it would be wise to put the old sensor back with FPR hose.

Too late for me, I sold my original sensor last week. I'm still going to wait for some more feedback anyway. I don't drive my rig very often these days.

[aclos3]

Originally Posted by sleeoffroad

Correct,



The sensor is analog and sends out a voltage. The ECU is the one that makes that into a number. What you mentioned above is simply not correct. Here is some info on how the system works.
http://www.autoshop101.com/forms/h34.pdf

The sensor might be more sensitive to air flow changes, but the analog to digital is still done by the ECU.

Just to be clear, I am not knocking this mod, just don't like it when info is posted that is not correct.

I believe the ECU is able to make more numbers out of the signal it recieves from the newer sensor. I remember reading in the development thread that they were seeing something like 2 updates per second with the old sensor and 32 updates per second with the new one. I don't recall how they knew this, and I don't feel like reading the 200 post thread again.

[aclos3]

Originally Posted by TrickyT

I disagree about the more data points per second. That's a function of the ECU, not the sensor. What is superior about the new style sensor is that it has more dynamic range and, I believe, is more linear at the low and high ends of its dynamic range.

I should have been more careful with my words. I said "data stream," which implies it is a digital signal. I did not mean to imply this. The fact does remain, however, that the computer effectively operates smoother and more efficiently because it is able to turn the signal into more usable data.

[landtank]

this sensor has been evaluated by several people running a wide band sensor and it showed vertually no difference with the exception of during boost where it actually corrected some of the extremely rich conditions that were present with the stock setup.

[nicholas]

Originally Posted by landtank

this sensor has been evaluated by several people running a wide band sensor and it showed vertually no difference with the exception of during boost where it actually corrected some of the extremely rich conditions that were present with the stock setup.

I thought this was the case and it was my primary reason for doing this mod.

[aclos3]

Nicholas. Same here! At the same time, I also appreciate people opening up discussions like this for the sake of helping out the community. Its conversations like this where we really learn things.

[nicholas]

Originally Posted by aclos3

Nicholas. Same here! At the same time, I also appreciate people opening up discussions like this for the sake of helping out the community. Its conversations like this where we really learn things.

I haven't lost faith in the LT MAF, but I agree it is nice to read these sorts of discussions to learn more about the vehicle. I am always amazed at the intelligent people on this board. I learn something new almost every time I log on.

[sleeoffroad]

Originally Posted by aclos3

I believe the ECU is able to make more numbers out of the signal it recieves from the newer sensor. I remember reading in the development thread that they were seeing something like 2 updates per second with the old sensor and 32 updates per second with the new one. I don't recall how they knew this, and I don't feel like reading the 200 post thread again.

The ECU did not change, so that is impossible for it to get "more numbers". The refresh rate on a OBDII scanner depends on the scanner and the amount of data parameters the particular software is tracking at any one point. No-one knows what the ECU is doing with the readings, or how fast it processes it, other than Toyota.

[sleeoffroad]

Originally Posted by landtank

this sensor has been evaluated by several people running a wide band sensor and it showed vertually no difference with the exception of during boost where it actually corrected some of the extremely rich conditions that were present with the stock setup.

Rick, I understand that. But we did a SC on a truck with one of your MAF's install and we saw the FPR hose removed. That is when I started looking into it and reading what you wrote on it.

So I am trying to understand what you did and how you came to the sensor and design that you did.

However I would think that just evaluating with a wide band O2 might not be enough to conclude that everything is a-ok. Do you still have any of those logs? I am sure you do not want to rehash the whole design thread again, but do you mind to answer some of the questions I had or share some of the references you used.

[Brian894X4]

Well, I'm pretty confused now.

I have a few questions for anyone willing to answer them. Christo, Rick or anyone else.

What sensors does Toyota use and how do they determine fuel pressure on 1998 and newer engines, which, as shown, does not use the same MAF sensor as our 1995-1997 engines.

It appears to, if I'm reading the diagrams right that Toyota uses the same fuel pressure regulator with the same vac lines hooked up on 1998 and later models that do not use the older "inferior sensor". If the vac line that we disconnect for this mod is mainly to compensate for the inferior sensor, why would Toyota leave it hooked up in later models where this sensor doesn't exist?

How does TRD or Toyota compensate for the added air flow of a supercharger with their stock unmodified kit? How do they prevent a lean condition when adding all that airflow that the system was never originally designed for or expecting? Do they rely on the computer to make all adjustements or are there additional parts and sensor modifications made?

If we're relying on the 02 sensors more than Toyota intended (assuming I'm reading this right) then what happens when one or both 02 sensors fail or get old and produce false readings?

What is the real danger here in Christo's mind, just so I understand. That the sensor itself may not be reading properly to the computer and that we are running lean all the time, or is the real problem the disconnected vac hose and how that affects fuel pressure both at idle and at speed?

By the way, read this thread I started in the 70 series section. Someone was kind enough to post some nice detailed picturs of a 2008 (yes 2008) 1FZ-FE engine. Note the following. That there is no MAF sensor in the air hose at all. And that the vac hose that we capped off on this mod is still very much in place just like on our rigs. As far as what Toyota uses for a MAF sensor, the EPC indicates that they have a temp sensor (temp sensor only) in the air pipe somewhere. (I don't see it in these pictures.) So, unless this temp sensor happens to replace the MAF sensor of old, I don't know how else they measure air pressure.

http://forum.ih8mud.com/70-series-te...questions.html

At this point, being admittedly very ignorant on this issue and the testing results, my concerns are that Toyota continued using that vac hose on models that have nothing to do with our 1995-1997 sensor. So what does that mean and how does that affect those of us that have removed and capped off that hose?

[turbocruiser]

I wish all the naysayers would simply swap one of these terrific MAF's in and analyze all their doubts themselves; those that have swapped have all loved the mod and many have offered overwhelming evidence that the thing works without worry. Some points we've posted ad-nauseum...

1. Idle is much much smoother with the LT MAF and the FPR capped off.
2. AFR's in closed loop are almost the same with more "micro-adjustments" made. IOW, with the Stock MAF, AFR in closed loop averages 14.7 but it bounces between 14.3 and 15.3. With the LT MAF, AFR in closed loop averages 14.7 but it adjusts alot btwn 14.7, 14.8, 14.6, etc. It "appears" that the sensor limits the range of adjustment and makes many more "micro-adjustments" as opposed to the .4 to .8 AFR range with the Stock MAF.
3. Not only open loop in general but WOT in specific shows MUCH better AFR's. With the Stock MAF, the transition to open loop was similar but WOT was much much much richer - my Wideband A/F Gauge measured all the way to 10.0 (max richness it reads - probably even richer) almost instantly with the Stock MAF - with the LT MAF the transition to WOT would start at 12.6 then drop to 12.4, 12.2, etc and after holding WOT past the point of reason wouldn't reach anything lower than 10.8. That is significant improvement.
4. I see no lean conditions whatsoever measured with a wideband.

Remember that the wideband has no hint that the MAF is different; it is simply measuring the AFR. The ONLY thing I would wonder is what pressure is the fuel rail running with in open loop in general and with WOT in specific. Other than attaching a fuel pressure gauge directly to the fuel rail and then taping it to the hood, I cannot help here, maybe one of the naysayers will step up to that task?

[sleeoffroad]

Originally Posted by Brian894X4

How does TRD or Toyota compensate for the added air flow of a supercharger with their stock unmodified kit? How do they prevent a lean condition when adding all that airflow that the system was never originally designed for or expecting? Do they rely on the computer to make all adjustements or are there additional parts and sensor modifications made?

If the line is connected to the manifold, the FPR will see the boost and up the fuel pressure in the rail. The pressure in the rail minus the boost pressure will then still yield the constant fuel pressure differential. It is important to note they don't want constant pressure in the fuel rail, but a constant pressure differential.

If we're relying on the 02 sensors more than Toyota intended (assuming I'm reading this right) then what happens when one or both 02 sensors fail or get old and produce false readings?

If the O2's fail outside spec, it will throw a check engine light. Search on "failed emissions due to high NOX" ans see how many cases that can happen (truck running lean) without throwing codes. On later trucks, a Air Fuel sensor is used and not a 02, which makes things more accurate.

What is the real danger here in Christo's mind, just so I understand. That the sensor itself may not be reading properly to the computer and that we are running lean all the time, or is the real problem the disconnected vac hose and how that affects fuel pressure both at idle and at speed?

The danger is for both boosted trucks and normally aspeirated that the truck is running lean, but not lean enough to cause codes.

By the way, read this thread I started in the 70 series section. Someone was kind enough to post some nice detailed picturs of a 2008 (yes 2008) 1FZ-FE engine. Note the following. That there is no MAF sensor in the air hose at all. And that the vac hose that we capped off on this mod is still very much in place just like on our rigs. As far as what Toyota uses for a MAF sensor, the EPC indicates that they have a temp sensor (temp sensor only) in the air pipe somewhere. (I don't see it in these pictures.) So, unless this temp sensor happens to replace the MAF sensor of old, I don't know how else they measure air pressure.

http://forum.ih8mud.com/70-series-te...questions.html

It appears on that picture that they have a MAP sensor in the intake manifold. (Manifold Absolute Pressure).

[aclos3]

Originally Posted by sleeoffroad

The ECU did not change, so that is impossible for it to get "more numbers". The refresh rate on a OBDII scanner depends on the scanner and the amount of data parameters the particular software is tracking at any one point. No-one knows what the ECU is doing with the readings, or how fast it processes it, other than Toyota.

What do you mean by "changed?" Of course the ECU hasn't been physically swapped, reprogrammed, or otherwise modified. I never implied that, not even close!

The ECU does not have to be "changed" to take advantage of a cleaner signal from one of its sensors. The software adapts to this and a computer can indeed create "more numbers" or perhaps more accurately a better data curve from a cleaner signal.

After reading about the forced induction rigs, it became very clear that this MAF housing / sensor combo is able to provide better signal, further into the rpm range than the stock one. I don't think anyone can argue that.

It sounds like you're hinting that the ECU is not able to take advantage of the better sensor and the gains we're are seeing are from a lean condition that we have created by performing these mods. The fact that the forced induction trucks are able to operate in closed loop further into the power band suggests that the ECU is indeed able to do something magical with the better sensor and that our gains are not simply from a lean condition.

[sleeoffroad]

Originally Posted by turbocruiser

I wish all the naysayers would simply swap one of these terrific MAF's in and analyze all their doubts themselves; those that have swapped have all loved the mod and many have offered overwhelming evidence that the thing works without worry. Some points we've posted ad-nauseum...

Sure, but Rick posted why Toyota used the vacuum line on the FPR and it was simply incorrect. From his development thread

"The vacuum line removal addresses the fact that the new sensor you now have has a broader range of accuracy and can read the lower air flows accurately at idle. Because of this we need to remove the vacuum line so we have a constant fuel rail pressure."

All I am asking is where is the info coming from re: the accuracy and dynamic range of the sensor. I don't think that is out of line to ask from someone that sell this mod.

1. Idle is much much smoother with the LT MAF and the FPR capped off.

That might simply be due to the rise in fuel pressure. Why is the sensor causing high LTFT with the Toyota designed fuel system (that is still used today) hooked up?

2. AFR's in closed loop are almost the same with more "micro-adjustments" made. IOW, with the Stock MAF, AFR in closed loop averages 14.7 but it bounces between 14.3 and 15.3. With the LT MAF, AFR in closed loop averages 14.7 but it adjusts alot btwn 14.7, 14.8, 14.6, etc. It "appears" that the sensor limits the range of adjustment and makes many more "micro-adjustments" as opposed to the .4 to .8 AFR range with the Stock MAF.

The ECU has not changed. How can it result in more adjustments? The AFM is anolog. All A to D is done inside the computer.

3. Not only open loop in general but WOT in specific shows MUCH better AFR's. With the Stock MAF, the transition to open loop was similar but WOT was much much much richer - my Wideband A/F Gauge measured all the way to 10.0 (max richness it reads - probably even richer) almost instantly with the Stock MAF - with the LT MAF the transition to WOT would start at 12.6 then drop to 12.4, 12.2, etc and after holding WOT past the point of reason wouldn't reach anything lower than 10.8. That is significant improvement.

Have you had it on a analyzer / dyno and actually verified that it is OK?

4. I see no lean conditions whatsoever measured with a wideband.

Yes, I can see that. But what I believe you are seeing is that in general the sensor is causing the truck to run lean accross the board. Which in your case, might be a good thing since you have extra air coming in and the stock map might be really rich on the top end.

Remember that the wideband has no hint that the MAF is different; it is simply measuring the AFR. The ONLY thing I would wonder is what pressure is the fuel rail running with in open loop in general and with WOT in specific. Other than attaching a fuel pressure gauge directly to the fuel rail and then taping it to the hood, I cannot help here, maybe one of the naysayers will step up to that task?

I am not a naysayer. I am simply asking questions. I have asked some in the past, but since we did not have to deal with the mod, I let it go. Now we have to deal with it and I want to see what is up.

[sleeoffroad]

Originally Posted by aclos3

What do you mean by "changed?" Of course the ECU hasn't been physically swapped, reprogrammed, or otherwise modified. I never implied that, not even close!

The ECU does not have to be "changed" to take advantage of a cleaner signal from one of its sensors. The software adapts to this and a computer can indeed create "more numbers" or perhaps more accurately a better data curve from a cleaner signal.

How can it create more numbers? It samples a certain analog input on a certain time and then converts that into a digital number for it to use. What would make it sample the sensor more often?

The sensor can be more sensitive to small air flow changes but the sampling of the voltage from the sensor is still constant. The A to D that happens inside the ECU is that same as is the resulution at which this is happening, as well as the resulting digital number.

After reading about the forced induction rigs, it became very clear that this MAF housing / sensor combo is able to provide better signal, further into the rpm range than the stock one. I don't think anyone can argue that.

The response range of the sensor might be wider, however there is also still no evidence that the stock ECU know what to do with that number. Does the stock fuel map extend beyond 26 lbs of air / 30 lbs of air?

It sounds like you're hinting that the ECU is not able to take advantage of the better sensor and the gains we're are seeing are from a lean condition that we have created by performing these mods.

I am sorry, but yes, that is my gut feeling.

The fact that the forced induction trucks are able to operate in closed loop further into the power band suggests that the ECU is indeed able to do something magical with the better sensor and that our gains are not simply from a lean condition.

This was based on trubocruiser and Ricks assesment that the o2 sensors went off-line. The OBD2 scanner they use(Autoengenuity), does not show the actuall CLOSED LOOP/ OPEN LOOP flag. Since we have a SC'ed truck here with Ricks MAF we will check and see if that is really the case.

[Brian894X4]

Well, I for one am glad Christo is chiming in. Although I'd rather be ignorant on the issue have nothing to worry about. I'm not saying anyone here is right or wrong, but Christo obviously has direct experience with Toyotas in general and specificly this engine, unlike some of the armchair naysayers in the past threads who were making a lot of guesses.

As far as beating a dead horse, there's a lot of new info here in this thread. For one thing, in the hundreds of prior posts, unless I missed it, I did not see one word mentioned about what Toyota did on the 1998 to current 1FZ-FE engines to replace the old MAF sensor. I would think researching that information would be critical and yield incredibly valuable information on this project.

I mean seriously. What could be more important than what Toyota chose to do on the future 1FZ-FEs after they had developed the new sensor. One thing we know for sure is that they didn't continue with the 1995-1997 MAF sensor. We also know they appear to have kept that vac line in place all the way through today's models. Why? If the vac line is only to compensate for the inaccurate older senor, why leave it in place now? I would think this would be a critical question to have answered.

Furthermore, running lean is not something to be sluffed off. From my understanding, one of the reasons for having a slightly rich engine is to keep the engine cooler and to increase longevity of the engine. Not to mention to be able run safely in a variety of conditions that these engines are expected to run under, fom extreme cold to extreme heat.

So, I'm not critisizing anyone and I'm not supporting anyone's idea. Not knowing anyone here personally, I consider myself neutral, but I hope that these concerns are not just ignored and are addressed specificly as best they can be. Don't be afraid to say, we're not sure, if you're not sure. After all, I don't think anyone would disagree that the increased performance is there and the idea behind the mod is pure genious. But if anyone thinks it really isn't an issue with these concerns, let's hear some detailed explainations. And if there are, maybe further research is needed? Not that the mod should not be done, but maybe some additional steps need to be taken. Maybe disconnecting that vac line isn't such a good idea.

I don't know.....

[aclos3]

Because it samples that analog stream at a frequency. It is easy to see why the original MAF design creates more turbulence and it is also not hard to believe that the older sensor is more sensitive to turbulence. The new MAF obviously provides more laminar flow and the new sensor is likely able provide a meaningful signal even in more turbulent air (compared to OEM).

When the computer samples the signal from this modified sensor setup it does not have to throw out nearly as many data points as noise because the sensor is not washing out in turbulence as often. This should allow the computer to better control the engine. I can't seem to find the part where they noticed an increase in sampling frequency, so maybe I was mistaken on this point. Even if the computer does not increase sampling frequency, many more of its samples are accurate; which is better than simply an increased sample rate anyway.

I haven't heard of anyone failing an emissions sniff test or having engine problems because of this mod. I'm not sure how many of these things Landtank has sold, but I'd think that after a year and a half problems would have cropped up and been well documented on this forum.

[Riad]

I need to find a place where I can do a dyno.

[sleeoffroad]

Originally Posted by Brian894X4

Well, I for one am glad Christo is chiming in. Although I'd rather be ignorant on the issue have nothing to worry about. I'm not saying anyone here is right or wrong, but Christo obviously has direct experience with Toyotas in general and specificly this engine, unlike some of the armchair naysayers in the past threads who were making a lot of guesses.

Brian, yes, I am not trying to shoot this mod down, or discredit the work Rick did. However there are some assumptions that were made, and statement made that just did not make sense or was incorrect. All I am trying to do it get to the bottom of it. There is no doubt that technology advances and if we can all benefit from it, that is great, but we have to be realistic and take some time to think about the mods.

Yes, we are in a fortunate position that we have Toyota and Lexus trained people on staff. They have a whole different understanding of how these things work (and access to way more documentation that normally available to the public) and how Toyota designed it. I do discuss these items with them and we normally hash them out pretty good. Probably more so that what we should.

This is one of those cases where we all started asking questions.

I mean seriously. What could be more important than what Toyota chose to do on the future 1FZ-FEs after they had developed the new sensor. One thing we know for sure is that they didn't continue with the 1995-1997 MAF sensor. We also know they appear to have kept that vac line in place all the way through today's models. Why? If the vac line is only to compensate for the inaccurate older senor, why leave it in place now? I would think this would be a critical question to have answered.

Toyota did not do the pressure regulator on the truck just because they always did. You are doing great research on this and it is a good thing to ask questions.

Furthermore, running lean is not something to be sluffed off. From my understanding, one of the reasons for having a slightly rich engine is to keep the engine cooler and to increase longevity of the engine. Not to mention to be able run safely in a variety of conditions that these engines are expected to run under, fom extreme cold to extreme heat.

[/quote]

Exactly, I am not saying everyones motor is going blow up. However it is not something to ignore if we change one of the major input to the fuel management system and then disconnect Toyota engineered systems to get the desired results.

[aclos3]

Brian, I absolutely agree and your concerns echo mine! I'm not trying to attack or blindly defend something to make myself feel better about what I've done to my truck. I am genuinely interested in the answers to these questions, but I believe they may be tough to find.

As for the later model 1FZs with improved sensors and FPR vac lines, it's a guess to me! The potential variables of this system are: low flow readings or lack thereof, injector duty cycles, fuel pressure rail, throttle position and the programming of the ECU. If the computer is programmed differently, it could use a different combination of parameters to determine how it handles idling in the newer engines. I could invision a scenario where it is able to read low flow air, yet still monitors throttle position to determine injector duty cycles/fuel pressure. This is pure conjecture though.