Landtank MAF surprising scangauge results

[sleeoffroad]

You continue to ask for proof on Toyota's purpose for the FPR. Someone has commented on the probability of FSM language acknowledging the same FPR being used on a 93-94 truck to compensate for poor idle (offline throttle response).

I am asking for proof that the 95-97 mass air flow sensor reads incorrectly at low idle as stated by Rick.

You have not produced anything that supports your assertion that higher pressure in the fuel rail will cause a lean condition.

You don't understand what is happening in the fuel rail.

You have not produced anything that confirms that an OBDII truck is at risk of running lean over extended periods of time without throwing a lean error code.

How many google links do you want me to post?

You have produced no proof that original sensors cannot deal properly with the new MAF. Anyone can say that is not how it came from the factory. Most of the people in this community have trucks that are different than how they came from the factory.

I did not say the sensor can not detect change or manage it. I am saying you also changed the criteria on which it chooses things.

Field testing is the ultimate test for any design. Have you heard of any blown motors due to lean operation caused by too much fuel pressure in the fuel rail???

Again, you don't understand what is happening.

Frankly, I don't trust your explanations on how things work 100%. You told me wrong on the need for castor plates with Js. My truck handles like a dream with 2 degree cc bushings.

What the hell has that do to with this discussion?

Telling me that too much pressure in the fuel rail will cause lean operation does nothing but also send flags up.

Ditto

All the while offering scenarios that lack proof like you'll blow your engine up from lean operation. The difference is that LTs design works based on real data regardless of any possible mistaken statements. The only hint of lean operation is what you are saying. No where else has this even been raised as an issue. Your only proof is that you are not satisfied with the mounds of data that prove there is no lean operation. "It could be running lean just under the radar of the ECU"

If you do not understand what I am asking then I am sorry, there is very little more I can post or explain.

 

[sleeoffroad]

If needed one could restrict the return to tank line which could drive fuel rail pressure up beyond the 80% value inherent to the stock FPR.

Like hooking up the reference line.

 

[jamisobe]

It has a wider response range to measure oxygen content in the airstream vs a narrow band 02 like the the ones installed in our truck.

So turbocruiser was able to monitor for lean operation even at WOT or idle?

When did I say this?

I'm not about to go back. Being fair, you may have meant a risk of lean operation on highly boosted trucks at WOT or at high altitudes, but I don't buy it.

I am thinking that the FPR isn't even capable of providing 100% fuel rail pressure. There will always be blow by which means, if you are correct, that you are probably realisitically looking at maybe another 15% pressure (beyond what is available from the disconnected FPR) in the extreme situation you are describing. But, the occurence hasn't happened during testing or with any users of the MAF. I think your pants are too tight.

 

[jamisobe]

If you do not understand what I am asking then I am sorry, there is very little more I can post or explain.

I now understand what you are saying about being able to theoretically exceed 80% pressure in the fuel rail. But the idea is still coming from left field. If LT's development thread still existed we could go look for the data they shared about A/F mixture under boost, but its gone.

 

[jamisobe]

Like hooking up the reference line.

Except with less horsepower, less driveability, and the need for folks who want or have forced induction to spend more money with you to develop an alternative fuel delivery system.

 

[sleeoffroad]

I now understand what you are saying about being able to theoretically exceed 80% pressure in the fuel rail. But the idea is still coming from left field. If LT's development thread still existed we could go look for the data they shared about A/F mixture under boost, but its gone.

We have known this all along that is why I started looking into why the line was disconnected when we had to do a supercharger on a truck with Rick's MAF installed. That is what prompted all this.

That is also why I started looking at turbocruisers comments, comments re: air flow number etc. That is when I discovered all these statements that did not make sense.

 

[sleeoffroad]

Except with less horsepower, less driveability, and the need for folks who want or have forced induction to spend more money with you to develop an alternative fuel delivery system.

I am not selling anything in this thread.

 

[e9999]

well, amazingly enough, as nerdish as I am and as generally likely as I am to dig through annoyingly detailed technical discussions, I still have given up on this thread a long time ago...

Will somebody please summarize the consensus -if any is ever reached- for us more mundane folks...?



(oh, and Christo.... Dude, dontcha have some beautiful 100 armor to finish off still ? )

 

[sleeoffroad]

I tried to here,
IH8MUD Forums - View Single Post - Landtank MAF surprising scangauge results

but you are right, I need to get back to work

 

[jamisobe]

We have known this all along that is why I started looking into why the line was disconnected when we had to do a supercharger on a truck with Rick's MAF installed. That is what prompted all this.

That is also why I started looking at turbocruisers comments, comments re: air flow number etc. That is when I discovered all these statements that did not make sense.

Yes, but why go shooting off before you know if its a problem. Rick even said that early in the development he disconnected the FPR and then investigated why it worked.

Being the well connected vendor that you are you should be able to call an engineer up at TRD and ask about how much fuel rail pressure is needed under high boost and how much pressure is available. You don't have enough information to say it doesn't work right. How do you know that 80% fuel rail pressure isn't enough for the most extreme boost situations? At least LT has done the testing and their wideband O2 tracking told them it was ok.

It is almost like you are making accusations because technically you can. When in fact nobody has had any problems with this upgrade. For this installation, I personally think you should have raised the question with Rick offline and then the two of you could have verified whether 80% or more fuel rail pressure is needed for high boost. Doesn't sound to me like more than 80% is needed based on field testing.

 

[semlin]

Yes, obviously that is not documented on a Land Cruiser since it is not a boosted truck from the factory. The regulator on the 80 is a 1:1 regulator. You can also get regulators with different ratio's that increases pressure more than a 1:1 ratio.

It also responds to boost.

Is that one precisely designed for a boosted application, probably not. Does it work and do it, yes. It is designed to be a 1:1 ratio. Yes, it is an accurate spring design.

Yes, hoop up your pressure source to the regulator and measure fuel pressure, you will see it goes up, until you overpower the capacity of the fuel pump.

Because it ensures there is enough pressure on the fuel rail to maintain a constant pressure differential over the boosted pressure in the manifold. There is limits to this, for example it won't keep up with 20lbs of boost, or it won't keep up if the fuel pump is weak, or the fuel supply is compromised due to dirty filters.

ok thanks. and thanks for taking the time to respond in so much detail too.

i am not sure if you are saying the fpr accurately matches fuel pressure to manifold pressure when under boost, but i get that it will produce enough fuel pressure to match up to the manifold pressure from 20lbs of boost. i agree that this is useful and desirable even if the fpr is not precise under boost.

so, just returning to the discussion as a whole for minute, i think you are saying that landtank's maf install procedure clashes with a bonus feature in the FPR that you have found useful for increasing fuel pressure in boosted trucks.

i think you are also saying that you have a hard time believing that landtank's maf can keep up with the fuel requirements for a boosted truck when the truck is seeing lower fuel pressure than in your boosted installations. that skepticism extends over to regular unboosted operation.

however, for regular unboosted operation, disconnecting the FPR is increasing fuel pressure to the maximum unboosted pressure specced by toyota. so there is no increased danger of the engine running lean from this modification in a non-boosted truck. at worst, you are just wasting fuel.

so really your concerns boil down to three issues:

1. you can't understand how the ecu is compensating for the increased air volume from landtank's maf in boosted and unboosted trucks, especially with lower fuel pressure in boosted trucks.

2. you don't understand why the FPR is causing a trim problem only at idle for the landtank maf, and suspect it must be causing the same problem at higher rpms.

3. you do not like landtank's fix of disconnecting the FPR because you think it might be masking a problem with the maf, and because you do not like the idea of losing the bonus fuel pressure bump for boosted trucks that the FPR can give.

Am i missing anything?

 

[Ebag333]

however, for regular unboosted operation, disconnecting the FPR is increasing fuel pressure to the maximum unboosted pressure specced by toyota. so there is no increased danger of the engine running lean from this modification in a non-boosted truck. at worst, you are just wasting fuel.

First, thanks for your explanation on the FPR. I obviously had it backwards.


On this though....didn't LT disconnect the FPR to reduce fuel usage at idle? If disconnecting the FPR increases the fuel rail pressure to maximum (or perhaps more accurately maximum in a non-boosted scenario), then why would the fuel usage go down at idle?

Maybe that was explained, but it seems counter-intuitive to me.

 

[sleeoffroad]

Semlin, thanks for sticking with me on this and also helping to summarize this. Also for having an open mind on this.

i am not sure if you are saying the fpr accurately matches fuel pressure to manifold pressure when under boost, but i get that it will produce enough fuel pressure to match up to the manifold pressure from 20lbs of boost. i agree that this is useful and desirable even if the fpr is not precise under boost.

20PSI of boost was a arbitrary number, but yes, in general that is what it does and that is how it is designed to work. Both to the positive and negative side.

so, just returning to the discussion as a whole for minute, i think you are saying that landtank's maf install procedure clashes with a bonus feature in the FPR that you have found useful for increasing fuel pressure in boosted trucks.

Yes,

i think you are also saying that you have a hard time believing that landtank's maf can keep up with the fuel requirements for a boosted truck when the truck is seeing lower fuel pressure than in your boosted installations. that skepticism extends over to regular unboosted operation.

No, I am saying that they are seeing reduces AF ratio's (which will make the truck run better) but the reason for this is attributed to a more accurate sensor, when indeed it might be due to drop in fuel pressure differential.

I am also saying that they are putting value to a reported 33lbs vs 25lbs of airflow, when they have no way of knowing that it is actually 33lbs of air being flown.

I am also saying the airflow is THE major parameter in load calculations that is used in open vs closed loop decisions. And if those are not right, then decisions is made by the ECU based on incorrect information. Those are really important since Toyota might have determined that under a specific set of parameters that truck should run under open loop for safety, it could now be running under closed loop in the exact same situation due to incorrect load calculations.

If this happens, you are relaying on a O2 sensor that is inherently not accurate to determine if everything is OK. From experience I can tell you that you will blow a motor way before you know something is wrong.

I am not saying this is going to happen, but I simply asked questions and pointed out wrong assumptions. People can do with it what they want.

however, for regular unboosted operation, disconnecting the FPR is increasing fuel pressure to the maximum unboosted pressure specced by toyota. so there is no increased danger of the engine running lean from this modification in a non-boosted truck. at worst, you are just wasting fuel.

See the above about incorrect load calculations. That is applicable for any situation.

so really your concerns boil down to three issues:

1. you can't understand how the ecu is compensating for the increased air volume from landtank's maf in boosted and unboosted trucks, especially with lower fuel pressure in boosted trucks.

I do understand that. I just pointed out incorrect assumptions they made and conclusions based on incorrect and false data.

2. you don't understand why the FPR is causing a trim problem only at idle for the landtank maf, and suspect it must be causing the same problem at higher rpms.

I do know, the reason is more air is entering the system than what is reported to the ECU. The truck sees it is lean, and adjusts the fuel trim. However the LTFT is to high. It should be around 0. So they disconnected the FPR, which ups the fuel pressure. So now for the same injector duration, more fuel is entering the system and the truck adjusts the LTFT down again. This ia a band aid fix for a incorrectly sizes housing or a the specific sensor.

3. you do not like landtank's fix of disconnecting the FPR because you think it might be masking a problem with the maf, and because you do not like the idea of losing the bonus fuel pressure bump for boosted trucks that the FPR can give.

Am i missing anything?

Yup, that is the long and the short of it.

 

[96r50]

I think this got lost on the bottom of the last page so I'll repost it here, as I am still interested in the potential for some real numbers to go along with all the chatter (It has been very educational chatter)

"Taking a few steps back here, how can we compare Rick's MAF housing to the OEM one? What would be the ideal test to see if they are both working with the same values? I would guess that measuring voltage output on one of the pins (which one?) while blowing a specific volume of air through each would tell us if each MAF is producing the same output for the same airflow. Correct or not? How would we test the two MAFs?"

 

[sleeoffroad]

Adam, yes it can be done, and that is what am suggestion. I even posted a link about a company that does this. Scroll back a page or so.

 

[semlin]

First, thanks for your explanation on the FPR. I obviously had it backwards.


On this though....didn't LT disconnect the FPR to reduce fuel usage at idle? If disconnecting the FPR increases the fuel rail pressure to maximum (or perhaps more accurately maximum in a non-boosted scenario), then why would the fuel usage go down at idle?

Maybe that was explained, but it seems counter-intuitive to me.

i thought he did it to reduce the fuel trim at idle. my understanding is that he was getting a steady 18% long term fuel trim, meaning that based on o2 feedback the ecu was having to send 18% more fuel than indicated by the MAF sensor reading in order to avoid a lean condition at the o2 sensor.

i believe the ecu will accept a discrepency of +/- 20% between the fuel that would be called for by maf readings and the trim called for by o2 sensor feedback, before it throws a code. so 18% is just within spec.

christo's theory is that this reflects the fact that there is more air volume flowing through the landtank maf at a given airflow rate because the passage is larger. he believes that the ecu is missing this extra air because it is applying a fixed constant multiplier to the reported airflow rate from the sensor based on the stock maf passage size. i agree that it will have started out doing that after the ecu is reset, but my understanding is that the ecu has to be flexible to address variances in individual vehicles as to air flow meter, injector and o2 sensor performance, and so it learns by doing and will very quickly adjust to a new reality and map a new neutral fuel trim map using o2 feedback so long as the new map is not too far at variance from the starting fuel map (so if the landtank maf signal versus o2 results was too far out, a truck would throw a code immediately).

my view is that the fact this only shows as an anomoly at idle means it is not a MAF air volume problem. the idle fuel trim discrepancy is relative to the learned neutral fuel trim map at all other rpms that would take into account the extra air volume that worries christo.

so i am looking at what is going on at idle, and why disconnecting the fpr addresses the fuel trim issue. logically, there are three variables at play: air volume, fuel volume and fuel pressure (or, more precisely, the differential between fuel pressure and manifold pressure). i think that one or more of those variables has been mechanically or electronically locked in by toyota, perhaps because they did not trust the MAF to report air flow accurately.

 

[96r50]

Hey Christo, I read Abaco site and I am still a little confused. My understanding is that we are would like to plot the airflow vs voltage curve for each MAF sensor. Is that all?

 

[sleeoffroad]

i thought he did it to reduce the fuel trim at idle. my understanding is that he was getting a steady 18% long term fuel trim, meaning that based on o2 feedback the ecu was having to send 18% more fuel than indicated by the MAF sensor reading in order to avoid a lean condition at the o2 sensor.

i believe the ecu will accept a discrepency of +/- 20% between the fuel that would be called for by maf readings and the trim called for by o2 sensor feedback, before it throws a code. so 18% is just within spec.

Correct, but you want it to be close to 0% since 18% eliminates one of the sides of correction since anything more than 18% will throw a code.

christo's theory is that this reflects the fact that there is more air volume flowing through the landtank maf at a given airflow rate because the passage is larger. he believes that the ecu is missing this extra air because it is applying a fixed constant multiplier to the reported airflow rate from the sensor based on the stock maf passage size. i agree that it will have started out doing that after the ecu is reset, but my understanding is that the ecu has to be flexible to address variances in individual vehicles as to air flow meter, injector and o2 sensor performance, and so it learns by doing and will very quickly adjust to a new reality and map a new neutral fuel trim map using o2 feedback so long as the new map is not too far at variance from the starting fuel map (so if the landtank maf signal versus o2 results was too far out, a truck would throw a code immediately).

Any code is based on a certain drive cycles. If the truck goes to 18% LTFT at idle something is wrong. Period.

my view is that the fact this only shows as an anomoly at idle means it is not a MAF air volume problem.

If the only thing you change is the stock MAF to LT MAF and the fuel trim jumps, then the issue is the MAF, nothing else. I would like to see what idle ltft is when you disconnect the battery, install stock MAF and then do the same with LT MAF.

the idle fuel trim discrepancy is relative to the learned neutral fuel trim map at all other rpms that would take into account the extra air volume that worries christo.

so i am looking at what is going on at idle, and why disconnecting the fpr addresses the fuel trim issue. logically, there are three variables at play: air volume, fuel volume and fuel pressure (or, more precisely, the differential between fuel pressure and manifold pressure). i think that one or more of those variables has been mechanically or electronically locked in by toyota, perhaps because they did not trust the MAF to report air flow accurately.

If idle is closed loop (warmed up truck), then injector timing (amount of flow) is calculated (based among other things on air flow and 02 feedback). If FPR is left connected, it should be the same for both MAF's. So then the only other variable is actual air volume and the calculated air volume by the ECU.

 

[sleeoffroad]

Hey Christo, I read Abaco site and I am still a little confused. My understanding is that we are would like to plot the airflow vs voltage curve for each MAF sensor. Is that all?

You need to know voltage as reported by the MAF for a given airflow (known) through the whole range of expected airflow for the sensor.

Then compare that.

 

[semlin]

Semlin, thanks for sticking with me on this and also helping to summarize this. Also for having an open mind on this.

20PSI of boost was a arbitrary number, but yes, in general that is what it does and that is how it is designed to work. Both to the positive and negative side.

Yes,

No, I am saying that they are seeing reduces AF ratio's (which will make the truck run better) but the reason for this is attributed to a more accurate sensor, when indeed it might be due to drop in fuel pressure differential.

I am also saying that they are putting value to a reported 33lbs vs 25lbs of airflow, when they have no way of knowing that it is actually 33lbs of air being flown.

I am also saying the airflow is THE major parameter in load calculations that is used in open vs closed loop decisions. And if those are not right, then decisions is made by the ECU based on incorrect information. Those are really important since Toyota might have determined that under a specific set of parameters that truck should run under open loop for safety, it could now be running under closed loop in the exact same situation due to incorrect load calculations.

If this happens, you are relaying on a O2 sensor that is inherently not accurate to determine if everything is OK. From experience I can tell you that you will blow a motor way before you know something is wrong.

I am not saying this is going to happen, but I simply asked questions and pointed out wrong assumptions. People can do with it what they want.

See the above about incorrect load calculations. That is applicable for any situation.

I do understand that. I just pointed out incorrect assumptions they made and conclusions based on incorrect and false data.

I do know, the reason is more air is entering the system than what is reported to the ECU. The truck sees it is lean, and adjusts the fuel trim. However the LTFT is to high. It should be around 0. So they disconnected the FPR, which ups the fuel pressure. So now for the same injector duration, more fuel is entering the system and the truck adjusts the LTFT down again. This ia a band aid fix for a incorrectly sizes housing or a the specific sensor.

Yup, that is the long and the short of it.

ok, so add to my summary list the fact that you are worried that the truck may not go into closed loop mode when it should and dump a bunch of gas in there. i agree that is also a reasonable concern. but before i try to understand it i want to address something else.

Christo, something i finally articulated in my previous post is the fact that the neutral "correct" fuel trim map for a given truck is partially learned by the ECU.

for example, we know that turbocruiser's boosted truck is running the landtank maf with a wideband sensor and showing outstanding neutral fuel trim and AFR, even though it seeing higher than stock air volume at a given air flow or boost, and even though it is not getting the benefit of increased FPR fuel pressure when it is under boost.

there is no way that could be happening unless the ECU fuel trim map for turbocruiser has adjusted itself to take into account the extra air volume from the maf. if it didn't do that, then under boost, the truck should be running very lean and showing major ltft issues both because it has a bigger air opening than stock and because the FPR pressure is limited to atmospheric pressure. since it is not doing that, the ecu's definition of "normal fuel trim" must vary from truck to truck within certain parameters.

therefore that means the 18% fuel trim discrepancy at idle with the FPR connected is a variation from the tweaked fuel map that takes into account the extra air flow. so it is not the extra air volume showing up but something that causes the engine to run leaner than the ecu expects based on a fuel map that incorporates that extra air volume.

does this make sense? it is the only way i can see to reconcile how turbocruiser (and others) are not running with constant significant ltft issues.