Landtank MAF surprising scangauge results

[jamisobe]

I will agree, that piggyback is not always the ideal solutions, but without calibrating this MAF, it is a much more accurate system and predictable.

Proof?

 

[sleeoffroad]

Irrelevant maybe. But nobody has shown anything that proves any risk in disconnecting the FPR on this application. Only unfounded precaution. With the vacuum disconnected, the pressure in the fuel rail is much higher than normal at idle which means the engine would run richer if anything. Then it would contiune to be richer as RPMs build.

The disconnecting of the FPR clued me in that there was a calibration error. Sorry, but I can simply not accept that calibration error when a part of the fuel system is disabled. You say tight pants, you can say whatever you want, it is simply not right.

The FPR has nothing to do with anything at higher RPM ranges since it saturates at about 80% flow.

Except for boosted trucks, or altitude changes. Do you know what percentage of a average drive cycle the fuel pressure is actually modulated?

The only risk of running lean would be at higher RPMs when there would be a potential of increased airflow from a better MAF outpacing static fuel settings. But the fuel settings are not static, have nothing to do with the FPR at WOT, and are adjusted by the ECU throughout the RPM range.

Except in OPEN loop.

Lean schplean.

I am sure you would not say that if you pop a motor.

 

[sleeoffroad]

christo, do you have a 93-94 FSM? I cannot find "volume 2" of mine right now anywhere (it tore in half), but I think that if you look at the FSM discussions on the VAF and the FPR or in the introduction to the EFI section you will find a comment about the FPR compensating for the fact the VAF does not work at low rpms.

I do, and a brief reading of the fuel system did not show anything about that. Might have missed it.

if it's not there then i guess i hallucinated it, but i recall reading it and being concerned about it when i was looking at doing a vaf-maf conversion. if it is there, then i do think it is relevant. it offers a possible explanation here since we seem to be talking about the same parts on the same motor.

and the obd1 and obd2 toyota ecu's are very similar (obd1 and obd2 ecus on karman vortex supras are plug and play interchangeable, and on the vaf supras the stock obd1 ecu will accept a maf or map conversion easily with a maf translator to reverse the voltage signal).

The flapper valve is a different animal. It is also one of the reasons why that 93/94's don't like forced induction.

 

[sleeoffroad]

Proof?

OK, I should have added, if tuned properly on a DYNO for a specific vehicle and setup. A piggyback is not something I would ever just sell to the general public.

It is more accurate since we know exactly when we need to add fuel to the injectors. We have never used a piggy back to modify the MAF system, even though they can be.

 

[sleeoffroad]

Uhhhh, proof? Sounds like a double edged sword to me.

How about 3 years of trouble free (exceptional) operation on boosted and non-boosted trucks.

Why is it a double edged sword? Just because it works does not proof anything regarding sensor output.

Then there is that common sense thing...

If the concern is disconnecting the FPR the risk would be too rich, not too lean. The FPR being disconnected will not be the cause of lean operation.

On boosted trucks it will be. If you don't see this, then you do not understand how it works.

If the concern is more airflow then the ECU can compensate for then an O2 sensor would send a lean signal at WOT at least once on the hundred or so trucks running this upgrade. Anyone???

Sometimes it helps to be a simpleton when you really want to understand things.

It probably also helps to stick your head in the sand. In all this I have explained how it works and also asked for proof about certain statements that can be made. The only thing that I got back is that "Hey look it works, the statements must be right"

 

[semlin]

The flapper valve is a different animal. It is also one of the reasons why that 93/94's don't like forced induction.

agreed. that is one reason i and some others were looking very hard at doing a vaf to maf conversion for the earlier trucks a while ago. if i had a heated garage it might have gone somewhere, but i spend my winters indoors these days.

 

[semlin]

On boosted trucks it will be. If you don't see this, then you do not understand how it works.

ok, i don't understand your point here. are you worried that on a boosted truck, the truck will run lean if you disconnect the FPR because it will not maintain the fuel pressure higher than manifold pressure?

i thought that disconnecting the FPR vacuum caused the FPR valve to restrict flow to the return pipe at the maximum setting and so increase fuel pressure to the maximum. so by disconnecting the vacuum you are making a lean condition in a boosted truck less likely?

 

[jamisobe]

The disconnecting of the FPR clued me in that there was a calibration error. Sorry, but I can simply not accept that calibration error when a part of the fuel system is disabled. You say tight pants, you can say whatever you want, it is simply not right.

Obviously your opinion is well known. It is also well known that the revised design (increase in fuel pressure at idle with improved airflow) works very well despite the tight pants.

Except for boosted trucks, or altitude changes. Do you know what percentage of a average drive cycle the fuel pressure is actually modulated?

Why? Your logic escapes me on this. If the fuel rail pressure is at maximum 100% of the time then how can the engine ever go lean due to the FPR's failure to reduce fuel pressure. That is ludicrious.

Except in OPEN loop.

I don't trust your opinion on the facts surrounding this matter. You are good and often helpful, but I have seen you mistaken on other less technical issues in the past. I feel that you are wrong on this as well. I trust LT on this.

I am sure you would not say that if you pop a motor.

I will be sure to report that LT's MAF caused my motor to pop if that were to happen, but I am not holding my breath on the possibility of that occuring. Good grief, its been out there for 3 years on over a hundred trucks with no issues. Maybe if you didn't have a dog in the hunt you would feel differently.

 

[sleeoffroad]

ok, i don't understand your point here. are you worried that on a boosted truck, the truck will run lean if you disconnect the FPR because it will not maintain the fuel pressure higher than manifold pressure?

Yes,

i thought that disconnecting the FPR vacuum caused the FPR valve to restrict flow to the return pipe at the maximum setting and so increase fuel pressure to the maximum. so by disconnecting the vacuum you are making a lean condition in a boosted truck less likely?

The FPR goes both ways. If you put boost to it, it will increase clamp down more than when just reverenced to atmospheric pressure. Since this truck was not designed at a boosted application, it is not documented, but that is the advantage of leaving the FPR connected on a boosted truck.

 

[sleeoffroad]

Except for boosted trucks, or altitude changes. Do you know what percentage of a average drive cycle the fuel pressure is actually modulated?

Why? Your logic escapes me on this. If the fuel rail pressure is at maximum 100% of the time then how can the engine ever go lean due to the FPR's failure to reduce fuel pressure. That is ludicrious.

See what I posted for Semlin. The fuel rail pressure is not at maximum it could be with the reference port vented to atmosphere. When you put boost to the pressure regulator it will up the pressure beyond what you think is maximum. If you completely close the return line, the pressure should go up to 57psi, which is higher than the normal operating pressure range.

So leaving the port connected ups the pressure and then it overcomes the boost pressure in the manifold, thus keeping the fuel pressure differential constant and not dropping it if the line is not connected.

 

[sleeoffroad]

JAMISOBE
The only risk of running lean would be at higher RPMs when there would be a potential of increased airflow from a better MAF outpacing static fuel settings. But the fuel settings are not static, have nothing to do with the FPR at WOT, and are adjusted by the ECU throughout the RPM range.

SLEEOFFROAD
Except in OPEN loop.

JAMISOBE
I don't trust your opinion on the facts surrounding this matter. You are good and often helpful, but I have seen you mistaken on other less technical issues in the past. I feel that you are wrong on this as well. I trust LT on this.

You don't have to believe me, but do you believe Toyota?

 

[semlin]

Yes,

The FPR goes both ways. If you put boost to it, it will increase clamp down more than when just reverenced to atmospheric pressure. Since this truck was not designed at a boosted application, it is not documented, but that is the advantage of leaving the FPR connected on a boosted truck.

are you saying the FPR goes to 11 if you apply boost now who is departing from the toyota manual procedures?

i thought the FPR had a spring that clamped down the fuel return valve to its most restricted setting and hence maximum fuel pressure, and a diaphragm that responded to vacuum by contracting and thus pulling against that spring to open the valve more and thereby lower fuel pressure.

in other words, the only thing that connecting the vacuum port can do is lower fuel pressure not raise it.

so are you saying the diaphragm also expands in response to boost and further contracts the spring? it seems highly unlikely to me that the diaphragm is intended to turn itself inside out when boost is applied to now expand and pressure the spring and even more unlikely that, while in this new expansion mode it would continue to exactly match fuel pressure to manifold pressure just as it does when contracting in response to vacuum. that would be an impressive design requiring a very precise spring tolerance and a very flexible and durable diaphragm.

have you actually measured the diaphragm expanding under boost to further compress the spring to see if it tracks manifold pressure?

also, assuming you are correct, the manual makes no mention of it. how do you know it is any safer than what landtank is doing?

 

[jamisobe]

Why is it a double edged sword? Just because it works does not proof anything regarding sensor output.

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).

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

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.

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.

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???

On boosted trucks it will be. If you don't see this, then you do not understand how it works.

Please explain how too much pressure in the fuel rail will cause a lean condition. I would like to be able to understand this if it is true.

In all this I have explained how it works and also asked for proof about certain statements that can be made.

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

The only thing that I got back is that "Hey look it works, the statements must be right"

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"

 

[semlin]

See what I posted for Semlin. The fuel rail pressure is not at maximum it could be with the reference port vented to atmosphere. When you put boost to the pressure regulator it will up the pressure beyond what you think is maximum. If you completely close the return line, the pressure should go up to 57psi, which is higher than the normal operating pressure range.

So leaving the port connected ups the pressure and then it overcomes the boost pressure in the manifold, thus keeping the fuel pressure differential constant and not dropping it if the line is not connected.

ok, i am assuming from this that you have seen 57 psi fuel pressure under boost. do you know for sure though that this increased fuel pressure above what the manual says is still tracked to be the correct increase of pressure above manifold pressure, or could it just be a random helpful additional pressure that is a side effect of there being some play in the compression of the spring?

 

[jamisobe]

You don't have to believe me, but do you believe Toyota?

Nice picture. What does a wideband O2 sensor do (like the ones used to capture much of LT's data)?

Do you have any data to support your assertion that an increase in fuel rail pressure will cause a lean condition?

 

[sleeoffroad]

are you saying the FPR goes to 11 if you apply boost now who is departing from the toyota manual procedures?

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.

i thought the FPR had a spring that clamped down the fuel return valve to its most restricted setting and hence maximum fuel pressure, and a diaphragm that responded to vacuum by contracting and thus pulling against that spring to open the valve more and thereby lower fuel pressure.

in other words, the only thing that connecting the vacuum port can do is lower fuel pressure not raise it.

It also responds to boost.

so are you saying the diaphragm also expands in response to boost and further contracts the spring? it seems highly unlikely to me that the diaphragm is intended to turn itself inside out when boost is applied to now expand and pressure the spring and even more unlikely that, while in this new expansion mode it would continue to exactly match fuel pressure to manifold pressure just as it does when contracting in response to vacuum. that would be an impressive design requiring a very precise spring tolerance and a very flexible and durable diaphragm.

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.

have you actually measured the diaphragm expanding under boost to further compress the spring to see if it tracks manifold pressure?

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.

also, assuming you are correct, the manual makes no mention of it. how do you know it is any safer than what landtank is doing?

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.

 

[sleeoffroad]

Nice picture. What does a wideband O2 sensor do (like the ones used to capture much of LT's data)?

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.

Do you have any data to support your assertion that an increase in fuel rail pressure will cause a lean condition?

When did I say this?

 

[jamisobe]

See what I posted for Semlin. The fuel rail pressure is not at maximum it could be with the reference port vented to atmosphere. When you put boost to the pressure regulator it will up the pressure beyond what you think is maximum. If you completely close the return line, the pressure should go up to 57psi, which is higher than the normal operating pressure range.

So leaving the port connected ups the pressure and then it overcomes the boost pressure in the manifold, thus keeping the fuel pressure differential constant and not dropping it if the line is not connected.

Yes, but...

LT and his crew experimented and gathered data with fuel pressure under high boost and found no issues. I think it was cattledog who said they theorized on methods of increasing fuel pressure and found it to not be necessary based on gathered data.

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.

 

[sleeoffroad]

ok, i am assuming from this that you have seen 57 psi fuel pressure under boost.

57psi is the spec to check if the fuel pump can produce enough pressure.

do you know for sure though that this increased fuel pressure above what the manual says is still tracked to be the correct increase of pressure above manifold pressure, or could it just be a random helpful additional pressure that is a side effect of there being some play in the compression of the spring?

Yes, that fuel pressure regulator goes both ways.

 

[96r50]

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?