Landtank MAF surprising scangauge results

[Lugboot]

I should also mention that they don't do the dyno test with the sniffer; they simply rev the engine to some set RPM and sniff the tailpipe. That means no real load and it might mean skewed NOX readings compare to real load tests.

That's a Two Speed Idle test. NOx is not a criteria for Pass or Fail for that type of emissions inspection. Measures HC, CO, CO2.

They typically take a sample at idle and then rev the engine to 2500 RPM and take another sample.

We have a 2-wheel Clayton dyno in the back of my office. I could try to get the software to run the dyne off a laptop because we also have 5-gas analyzers, too. I think Rick's MAF is great thing but I like data, too, and it would fun to get one of these on a dyne and see what happens.

Based on what everyone has seen when using these MAFs (no MILs, no emissions failures), if they do cause a lean condition, it must not be high enough to trigger anything in the system to say it's a problem.

 

[landtank]

in my opinion any fluctuations in rail pressure such as you mentioned in a higher altitude would show up as a difference in LTFT%. As you started the climb the ECU would see a change in the AFR from the O2 sensor and begin by adjusting the STFT%. Because thsi isn't a short term condition those changes would slowly be migrated over to the LTFT% value. Coming back down the hill it would be reversed.

Now if this accent was of a nature that you were not in closed loop but open loop then there would be no adjustment and you would be relying on the fuel cut safety circuit to ensure you don't damage your engine.

This is one reason that boosted trucks run a EGT sensor or wideband sensor when commonly making these climbs. It's one way to be sure that you aren't damaging your engine as boosted engines at 8psi are far more sensitive than a NA engine.

Don't worry about the thread, it's part of life here in the 80 section.

 

[TrickyT]

The following is only peripherally relevant to the discussion here about permanently changing the way fuel rail pressure is controlled by removing the vacuum line to the FPR, but I thought I'd point out that there's a control circuit for doing something similar that's already built in. It's not mentioned in the Fuel Systems Overview document that Christo posted, but the fuel pressure regulator is connected to the intake manifold by way of a vacuum switching value that is controlled by the ECU. According to the FSM (pg EG-299), if engine coolant temperature is "too high" during engine starting, the ECU turns on this VSV for a couple minutes to vent the FPR diaphragm to atmospheric pressure in order to raise fuel rail pressure and help prevent vapor lock when the engine is warm. Of course by-passing vacuum modulation of the FPR for two minutes is a whole lot different from permanently by-passing it.

Rick, my reading of your comments in this and the MAF development thread is that you disabled FPR modulation in order to create a richer AFR at idle. Do you recall if you noticed any difference in LTFT or wideband O2 measurements when FPR modulation was disabled at throttle positions other than idle? Of course in closed loop mode you'd just expect the ECU to compensate for the different fuel rail pressure based on O2 sensor readings. But I'm wondering if you saw differences in any of your measurements.

 

[sleeoffroad]

Originally Posted by fjfar80

1. If the stock MAF becomes saturated at 25lbs of air, how is Toyota compensating or correcting this with the stock MAF on a truck with an SC
installed?

As far as I know they aren't doing anything about it. The truck runs insanely rich and that is just the way it is.

How do you know it is saturated. Did you actually plot the voltages of the MAF at the high airflow? How do you know the ECU knows what to do with more aiflow numbers?

2. If you are running a stock MAF and the above happens, how would it happen, and what would happen.

From testing we have run the MAF to a point of reading 36lbs and it still did not saturate. At that point the O2 sensors were still on line and we were seeing a good improvement in AFR according to a wideband sensor

Did you actually plot the voltages of your MAF at 25lbs and more to compare if you are even at the same voltage as the stock one? You do not need a flow bench to do this. This assumption is based on people seeing a value higher than 25 lbs of air on a OBD2 reader. This is a calculated value from the ECU. Calculated based on a voltage reading from the MAF and assumed size and response from the stock MAF. Without calibrating the sensor you don't know if this 33lbs is even right, or does than mean 25lbs in reality. If your MAF was reading 33lbs of air don't you think the ECU would even be putting more fuel into the system? You assume the maps go beyond 25 lbs of air.

02 sensors do not go off-line. I remember seeing this in turboscruisers logs, but it could merely be a point where his software recorded 0 when it went in open loop. O2 sensors always produce readings, they are just not used sometimes.

Also, how do you know the leaner condition is not from a effective drop in fuel pressure due to the boost in the plenum? And not from your MAF at all?

3. With your MAF and the new sensor installed what would happen at the 25lbs of air level?

Nothing, it just continues to read air flow

Again, an assumption based on feedback and not verified by a simple voltage meter.

4. At the bad end of the spectrum what would happen to an engine with a SC installed, your MAF, and new sensor if the engine was indeed running lean (under the radar) for an extended period of time?

I have no experience with this phenomenon and can't imagine that prolonged exposure would be good. Toyota has built in safe guards for running lean and I rely on those safe guards just as Toyota does to protect the engine.

Toyota does not measure exhaust gas. The 02 sensor is the best attempt at it. Prolonged lean condition will eventually damage the motor. A truck can run lean without engine codes.

6. Do you recommend your MAF and the new sensor combination mainly for boosted trucks or for stock trucks - and why or why not? I read the develpment thread and it looks like you were gearing this for boosted trucks, but I just wanted to make sure that I read everything correctly.

Originally this started out as investigating fuel management issues with boosting a 95+ 80. At that point no one was able to dial it the AFR. There were many attempts but nothing solid to work with. My first goal was to get the MAF to work properly on a stock truck. Once I felt comfortable with how it worked on mine and Cattledog's I enlisted a few boosted trucks for further review. It turned out to improve the driveability on on both NA and boosted trucks.

Yes that was the initial idea and I still think very viablle if some more testing is done.

7. Lastly, are there any negatives to running the SC on a stock MAF, on a stock sensor, in a stock configuration?

the negatives are as staed above. The MAF saturates and the ECU dumps fuel at a very high AFR and the O2 sensors go off line which I believe with also eliminate the fuel cut safe guards.

02's does not go off-line. Truck goes into open loop and yes it might run rich, but also safe.

 

[sleeoffroad]

this a weird thread. i have obviously been out of 80s tech for a while. when exactly did rick become considered a "vendor" instead of a longtime valued contributor here?

When he sells a 150 units on this board. Supplied caster plates to another vendor that sells it on the open market. 150 units at $200 a pop is $30k in gross sales from MAF's alone.

this is a mod worked out by a couple of board members here in their spare time.

Yes, but actively marketed on this site by Rick.

it was a pretty brilliant and interesting project. the history of the development is written here in threads. now, because it worked and a lot of people bought them of him, people are discussing it as if rick is going to be liable if an engine fries on a 12 year old truck with over 100000 miles on it simply because Rick's obviously and admittedly limited testing data indicates it seems to work better when you disconnect a vacuum hose and he might be wrong to have gone with that? that is ridiculous.

Selling a product for profit has consequences. Product liability is a whole different thread. Sold to a unsuspecting user, and installed as per Ricks instructions, and the guy pops a motor because of this )or whatever other reason. Who do you think is going to win the case if the user brings in a Toyota engineer? I hate that part of the business but that is reality and that is why insurance companies makes tons of money from us.

christo, i totally understand your technical point here, and your business concern about doing a build with rick's mod not fully understood, and i think you did try to raise it in a fair fashion, and that the technical discussion should continue, but this thread has sort of broken loose from a bunch of posts by different people and acquired a tone of its own where rick is now on trial and being required to account for himself.

Rick is not on trail, but he made statements in both the development thread and his advertising thread that was wrong and based on assumptions of the vehicles operation that is also incorrect. Should we just let that go?

That is just wrong. i don't think anybody here has the right to expect more from rick than what he has already provided, which is a complete description of his product development and reasoning.

Even based on assumptions that were never proven?

i realize rick has sold a bunch of them, but i have a hard time with the idea that this was ever anything more than a mudder's project. he is not selling it at pep boys. read the data threads about this mod yourself and takes your chances people, and ask rick nicely if you have a question. and if by some amazing twist of fate it turns out rick made a mistake and it does blow your motor, put on your big girl panties and deal.

I wish it worked like that in the real world. The problem is that one starts selling to just friends (mudders) that will never screw you, but soon it goes beyond that. So I urge Rick to look into product liability insurance if he has not done so.

this is the kind of thing that discourages people from doing a mod like this.

I would hope that it encourages him to do more and investigate it more. I am sure somewhere we have overlooked stuff as well. No-one is perfect, but if we do not discuss these things, then nothing will be developed. Ignoring issues does not make it go away.

by the way, my very insignificant moderator hat is off here for those who don't know me. this is simply my opinion.

Yup, understood and we call have them,

 

[sleeoffroad]

In our system however that isn't happening. Our FPR only reduces the rail pressure and does so the most at idle.

If the line is left on, the pressure from boost will actually up the pressure in the fuel rail since the pressure regulator will take the boost and clamp down.

In the case of my MAF, when idling it produces a signal that is lower than that of the stock MAF and the base calculation calls for a short injector pulse.

Rick, you should check the voltage of your sensor at idle compared to the stock one. Does it measure better or does it tell the computer the wrong value? This is the whole calibration issue I am talking about.

With the vacuum line attached and the pressure deferential at the stock amount this produces a lean condition. That is until the ECU sees that in closed loop and adjusts for it through manipulating the STFT and LTFT values.

By removing the vacuum line the fuel rail pressure is not reduced and this increases the pressure differential. This increase in differential means that at any given pulse the injectors will deliver more fuel. Since my MAF at idle already calculates a lower base injector timing this works to its favor. The lower calculated base timing is offset by the higher pressure differential. And if designed properly it will deliver the same amount of fuel as the stock setup will.

What you say is exactly what is happening. The issue is that it is a band aid fix. If the sensor was right and read the correct (ie calibrated) amount of air why would you need to disconnect the hose at all?

It is my opinion that it is this higher pressure differential that is responsible for eliminating the idle stumble that people are seeing. I believe that the higher pressure differential is producing a better and more consistent spray from the injectors which is eliminating the stumble.

That might be so, but that is at the cost of having control over the fuel pressure differential.

This post is just my understanding as to what is happening and in no way should be taken as absolute gospel on this subject and is only meant as an aid to understanding how I designed my MAF and intended on to work.

Understood.

 

[LC80Ducati996]

Honestly after all the turbo import cars I have tinkered with I recomend E-manage and a LC-1 wideband 02 sensor.

Greddy - Founded and Driven by Racers

Here is how to put one on a supra
2gz-gte e-manage install

 

[sleeoffroad]

FPR vacuum connected with the high flow MAF, is the ECU operating the injectors at idle expecting more fuel to squirt but stumbling when the fuel rail pressure is too low to provide the amount of fuel the ECU is trying to deliver through the injectors?

I do not believe so. It could be to do with pattern, it could be to do with a number of things. Personally we have never been asked to diagnose a stuble at idle, neither have I really noticed one on any of the truck that I have owned. Maybe never really concentrated to feel it.

Is the ECU blind to the amount of pressure present in the fuel rail at all times and is the fuel pressure in the fuel rail always at its highest when the FPR is disconnected?

ECU does not know anything about fuel pressure. On normally aspirated trucks yes and all other things staying the same, ie, temp etc etc.

Does any fuel still return to the tank even though the disconnected FPR is at its most restrictive state?

Yes

Is the fuel pump operation sensitive to pressure at all or is it on when the engine is running and off when its not?

Not sensitive to pressure per say. Yes, on and off, but there is control circuits sending different voltages to it depending on conditions. Also has overpressure devices built in.

I am trying to get my head around why some feel that there is a risk of running too lean (forgetting that the O2 sensors would detect lean burn), and what are potential pitfalls of constant full pressure in the fuel rail if running too lean doesn't make sense as a risk.

I think the case is that there are systems designed for constant fuel pressure in the rail with no return lines, however they are managed differnt.

 

[Jule]

Testing MAFs

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.

Another suggestion is to go to the local university and find a Mechancial Engineering student that would make a project out plotting both sensors voltage for given airflows points and their response time to various airflow changes.

A thought on stock ECU programming and the idle stumble, remember Toyota and other OEMs will tune for emissions first and then power. Is full fuel pressure at idle a reliability issue or just the possibility of being a little rich on emissions?

Another thought consider when comparing the two sensors, just because they are both analog, does not mean that they both respond to changes at the same rate. I think LT is suggesting that his has a faster response time and more sensitive to changes.

Cheers,

Jule

 

[sleeoffroad]

Regarding the longer closed loop operation of boosted trucks.

One of the parameters for closed/open loop switching is the engine load. One of the parameters of engine load calculation is air flow. If the airflow is off, ie sensor is telling the truck it is 20lbs of air, when in fact it is 30lbs of air that is going into the motor, then obviously the load calculation is wrong. So the truck is really under 90% load, when it is calculated to be under 60% load. The ECU says, hey, things are still ok, so stay in closed loop.

Good thing or bad thing. Who knows. But you are also relaying on the feedback and failsafe systems to take care of things. So under the above condition, the truck might think, hey a LTFT of 20% or whatever is ok, so don't trip the check engine light, when indeed it is not because the truck is under 90% load and not 60%. (all values chosen arbitrary)

All these points to me just illustrate how important it is to make sure the correct sensor response curve is used. And when you start to mess with it, you have to know how all the sytems interact and not just some of them.

 

[sleeoffroad]

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.

Excellent idea, however I don't think a house fan is going to do this. The amount of air a motor sucks is incredible. You also have to bring the housing into play to determine the calibration between sensor reponse and actual air passed through the housing.

Another suggestion is to go to the local university and find a Mechancial Engineering student that would make a project out plotting both sensors voltage for given airflows points and their response time to various airflow changes.[/qutoe]

Yes, or find a company that does this and pay them.

A thought on stock ECU programming and the idle stumble, remember Toyota and other OEMs will tune for emissions first and then power. Is full fuel pressure at idle a reliability issue or just the possibility of being a little rich on emissions?

Who knows.

Another thought consider when comparing the two sensors, just because they are both analog, does not mean that they both respond to changes at the same rate. I think LT is suggesting that his has a faster response time and more sensitive to changes.

Could be, but when you look at the Toyota trucks where they used the old and new style sensors in the same 3.4 motor, they still used the same fuel system.

 

[Riad]

Regarding the longer closed loop operation of boosted trucks.

One of the parameters for closed/open loop switching is the engine load. One of the parameters of engine load calculation is air flow. If the airflow is off, ie sensor is telling the truck it is 20lbs of air, when in fact it is 30lbs of air that is going into the motor, then obviously the load calculation is wrong. So the truck is really under 90% load, when it is calculated to be under 60% load. The ECU says, hey, things are still ok, so stay in closed loop.

Good thing or bad thing. Who knows. But you are also relaying on the feedback and failsafe systems to take care of things. So under the above condition, the truck might think, hey a LTFT of 20% or whatever is ok, so don't trip the check engine light, when indeed it is not because the truck is under 90% load and not 60%. (all values chosen arbitrary)

Man, that sounds like some serious hacking to me. . It definitely sounds overwhelmingly important/dangerous to hack/tweak these parameters. Very interesting. The fuel system in our truck sure seems like a sophisticated thing to me now.

 

[semlin]

When he sells a 150 units on this board. Supplied caster plates to another vendor that sells it on the open market. 150 units at $200 a pop is $30k in gross sales from MAF's alone.

i do not think he set out to make money on this. it was just an interesting mod he shared with other mudders, that turned out to be very popular. even then, his "profit" would just about cover the cost of rebuilding one of the 150 used engines maintained by shade tree mechanics that he is apparently warranting will never melt down.

Yes, but actively marketed on this site by Rick.

if you call posting a thread in a technical web site marketing then yes. but he is marketing to people participating in 80s tech. not exactly pep boy customers.

Selling a product for profit has consequences. Product liability is a whole different thread. Sold to a unsuspecting user, and installed as per Ricks instructions, and the guy pops a motor because of this )or whatever other reason. Who do you think is going to win the case if the user brings in a Toyota engineer? I hate that part of the business but that is reality and that is why insurance companies makes tons of money from us.

"unsuspecting user" does not equate to his customer base. I'd say caveat emptor.

Rick is not on trail, but he made statements in both the development thread and his advertising thread that was wrong and based on assumptions of the vehicles operation that is also incorrect. Should we just let that go?

i agree it is fine to raise the technical issue. in fact you definitely should raise it. but take a look at the totality of this thread as it has evolved. i have a huge amount of respect for you christo, and i don't doubt you are telling it as you see it and shooting from the hip on this, but the whole time i was reading it i am wondering what on earth is up that people are pushing on rick so hard over this. if i were rick looking at this kind of thread i would seriously reconsider going through the hassle of any other innovations for this kind of response.

Even based on assumptions that were never proven?

everyone proceeds on assumptions. his work product is online for all to read and see for themselves. how many real vendors do that? he never pretended to have some secret nasa lab going here that had 100% reverse engineered toyota and then field tested the mod in the andes.

I wish it worked like that in the real world. The problem is that one starts selling to just friends (mudders) that will never screw you, but soon it goes beyond that. So I urge Rick to look into product liability insurance if he has not done so.

i agree that rick would be wise to get people to sign a waiver form when they buy it if he has gotten to 150 sales that would largely protect him from such a claim. I would be happy to draft it for rick if he is interested.

I would hope that it encourages him to do more and investigate it more. I am sure somewhere we have overlooked stuff as well. No-one is perfect, but if we do not discuss these things, then nothing will be developed. Ignoring issues does not make it go away.

i am sure the tech question and the fact that you know what you are doing and disagree with him does encourage him to do exactly that. the substance of this thread is fine. it is the tone of the thread, and the way he is being told he basically owes people an answer and has been delinquent in his research work that struck me as wrong. i am not singling you out for christo. i think it is a combination of different posts that got the thread to that point.

 

[Buckru]

I wanted to chime in for a moment and say thanks for all the good dialogue. I have never understood the fuel management system on our 80's, heck i still don't, but this thread is helping me to better understand how it works. So a big thanks to all those participating.

Buck

 

[sleeoffroad]

if you call posting a thread in a technical web site marketing then yes. but he is marketing to people participating in 80s tech. not exactly pep boy customers.

He has as thread in the merchanise sections as well. I do believe for some time they were available on ebay, but I might be wrong about that. Nothing wrong with it, but the line between a cruiserhead selling parts and now also supplying a vendor that sells to the open market pretty slim. Granted different product, but still selling to the open market. But all this is matter for a different thread.

"unsuspecting user" does not equate to his customer base. I'd say caveat emptor.

True, but you know people. They are only not unsuspecting until they want to be

i agree it is fine to raise the technical issue. in fact you definitely should raise it. but take a look at the totality of this thread as it has evolved. i have a huge amount of respect for you christo, and i don't doubt you are telling it as you see it and shooting from the hip on this, but the whole time i was reading it i am wondering what on earth is up that people are pushing on rick so hard over this.

He developed it and put it out for sale.

if i were rick looking at this kind of thread i would seriously reconsider going through the hassle of any other innovations for this kind of response.

I hope not, he has covered some areas where no-one else made parts for. That is a good thing, but as this grows, he needs to be aware of what come with it.

everyone proceeds on assumptions. his work product is online for all to read and see for themselves. how many real vendors do that? he never pretended to have some secret nasa lab going here that had 100% reverse engineered toyota and then field tested the mod in the andes.

True, but when assumptions are not correct, they are not correct.

i agree that rick would be wise to get people to sign a waiver form when they buy it if he has gotten to 150 sales that would largely protect him from such a claim. I would be happy to draft it for rick if he is interested.

Frankly waivers mean sh%*t when the sh#(&$t hits the fan. Talk to any product liability attorney or liability insurance company.

i am sure the tech question and the fact that you know what you are doing and disagree with him does encourage him to do exactly that. the substance of this thread is fine. it is the tone of the thread, and the way he is being told he basically owes people an answer and has been delinquent in his research work that struck me as wrong. i am not singling you out for christo. i think it is a combination of different posts that got the thread to that point.

That was not my intent, however I was also told that I did not know what I was talking about and did not understand the systems. It goes both ways.

Contrary what a lot of people might think right now, this was not a malicious attack on Rick or this mod. I think I pointed out a lot of things that can enable Rick to actually improve his product and sell way more than 150. It all depends on what he takes from it. I am not saying what I say is gold, but Toyota engineering and documentation is just that. Available to most anyone to further their knowledge and people to use when they develop products.

 

[semlin]

christo, i defer to you on 80s tech, but i am pretty sure i have been involved in more product liability litigation and insurance work than you

for someone like Rick, a carefully worded waiver could be viable. subject to local state consumer protection laws, it will at least partially protect him from being sued by the person who bought the product from him. it won't protect him from third parties, but third parties are unlikely to have a viable claim against him since, if the product fails, it is very unlikely to lead to any injury other than to the vehicle itself.

that said, my point was that it is a shame we are even talking about such matters.

 

[semlin]

dealing with the tech issue instead for a change

christo, my recollection from egr testing is that manifold vacuum pressure changes pretty fast when you turn the throttle on an 80. do you think the FPR could truly be accurately modulating fuel pressure through the full rpm range? I would think its impact likely tops out at pretty low rpms. that also makes intuitive sense: surely the design of the truck can't depend on a vacuum diaphragm to prevent the engine leaning out and cooking itself at high rpms?

 

[sleeoffroad]

dealing with the tech issue instead for a change

Yes, I hate the whole product liability etc etc deal as well, but hey, we live in that society and if we choose to make our living in it, we need to deal with it.

christo, my recollection from egr testing is that manifold vacuum pressure changes pretty fast when you turn the throttle on an 80. do you think the FPR could truly be accurately modulating fuel pressure through the full rpm range?

yes, otherwise why would they put it in, and keep using it. Biggest damage to motors get done under partial throttle and under some load. There will still be vacuum there and the pressure will be regulated.

I would think its impact likely tops out at pretty low rpms. that also makes intuitive sense: surely the design of the truck can't depend on a vacuum diaphragm to prevent the engine leaning out and cooking itself at high rpms?

No, but it is assumed to be constant and that is what all the programming in the ECU relies on. I am sure there is a margin of error built in there, but that is what is expected. Changing that changes a whole lot of other issues. My issue is with sensor selection that is not based on accurate testing of the sensor responses (or even an attempt) but purely on interpreting OBDII results. Some of those results were interpreted wrong and not verified, like the lbs of air flown for a given situation. Then when results that are out of spec are achieve, a system on the truck is disabled to compensate. Toyota has proved that the exact same system can be used with newer technology systems. So that means it is not impossible to achieve.

A $10 volt meter can be used to do some of this test, albeit in a very crude manner.

 

[sleeoffroad]

christo, i defer to you on 80s tech, but i am pretty sure i have been involved in more product liability litigation and insurance work than you

I better put your number in my cell phone

 

[semlin]

yes, otherwise why would they put it in, and keep using it. Biggest damage to motors get done under partial throttle and under some load. There will still be vacuum there and the pressure will be regulated.

No, but it is assumed to be constant and that is what all the programming in the ECU relies on. I am sure there is a margin of error built in there, but that is what is expected. Changing that changes a whole lot of other issues. My issue is with sensor selection that is not based on accurate testing of the sensor responses (or even an attempt) but purely on interpreting OBDII results. Some of those results were interpreted wrong and not verified, like the lbs of air flown for a given situation. Then when results that are out of spec are achieve, a system on the truck is disabled to compensate. Toyota has proved that the exact same system can be used with newer technology systems. So that means it is not impossible to achieve.

A $10 volt meter can be used to do some of this test, albeit in a very crude manner.

well, depending on the application, they might also put it in to increase fuel pressure at lower rpms where the early air flow sensors were not very good. I say that because I have an FSM that says that.

next question. is the FPR on a 95-98 the same as the FPR on a 93-94?