[Waggoner5]

Originally Posted by frankies off road

This has created allot of confusion for most of the readers of this post.
The answer you seek christo are from another vendor and you should have worked this out in private.
You should worry more about some of your products that need attention over this thread.

Vendor to vendor this was just rude..

Yep, just like yours and Darrens wonderful conversation when HE asked some legit questions. Your remarks toward me were very non professional in that thread as well.

The reason that I am confused in this thread is that I still have unanswered questions on the MAF mod and will lurk until they are answered. Colorado has and does 4 wheel dyno testing and if my truck fails as Christos did because of an aftermarket part, I would like to know why. My friends truck is at Slee getting an S/C installed and has one of Ricks MAFs. I completely understand Christos hesitation on leaving the FPR unhooked as both Toyota and TRD want it hooked up. Who is going to pay if something happens to an engine because of an aftermarket part? Yep, you guessed it...the customer, not the installer. TRD warrantees their S/C if installed by the directions and by a accredited shop. So if my engine melts down who pays? I hope its the guy who has product liability insurance.

[frankies off road]

[quote=Waggoner5;4109417]Yep, just like yours and Darrens wonderful conversation when HE asked some legit questions. Your remarks toward me were very non professional in that thread as well.



now I know who all the slee cheerleaders are thanks for responding to my post with the others.

[landtank]

Well Gary it would be up to your friend to decide how he wanted to proceed. I'm not sure how my MAF sensor would damage a SC but I guess anything is possible.

One thing to note is that with my MAF the O2 sensors stay active thoughout the operating range of a SC'd truck. The stock MAF will become saturated at around 25lbs of air and then the O2 sensors are taken off line. I believe that the ECU sees the MAF condition as a failure and goes into limp mode or something similar.

It's my opinion that since the O2 sensors are still active with my MAF that all the built in fuel cut off safe guards that Toyota programmed in are still functional. I have no way of knowing this for sure but I believe it's a reasonable assumption.

[Waggoner5]

I wasn't assuming that it would damage an SC, just asking questions. More interested in passing emissions right now.

Cheerleader? Wow this thread has degraded also. I respond when the BS gets thick.

Rick, I appreciate you being polite and professional through this. No one is looking for winners and losers, only some answers. This is what tech info is all about. There are no other vendors building a MAF like yours, and I for one do not doubt your ability or design.

[landtank]

Originally Posted by frankies off road

now I know who all the slee cheerleaders are thanks for responding to my post with the others.

I'd appreciate it Frankie if you could refrain from this sort of thing. I want the people who are running my MAF to get the info on how it was developed and reserched as clearly as possible.

[Kernal]

(Just a newb; my head hurts after reading everything, and do not want to get in-between the major players).

Do any Toyota dealerships have the required testing equipment? Anyone here work at a dealership?

Will the MAF sensor and housing from the newer version of the 1FZFE (or the 2007 Venezuelan model 80) fit and work any better? (assuming they may be different/newer?) .

I'll sit back and watch.

[frankies off road]

OK i need to go work in the shop anyway,I think i take this stuff to personal at times,I hope no one is to hurt over my actions if so please take my humble apology ..

[Waggoner5]

Originally Posted by Kernal

(Just a newb; my head hurts after reading everything, and do not want to get in-between the major players).

Do any Toyota dealerships have the required testing equipment? Anyone here work at a dealership?

Will the MAF sensor and housing from the newer version of the 1FZFE (or the 2007 Venezuelan model 80) fit and work any better? (assuming they may be different/newer?) .

I'll sit back and watch.

This is part of my reasoning for questions. Christo has 2 techs with combined many years of Toyota experience working at dealerships as well as high performance back grounds with Toyota products. This is why I take my Toyota stuff to them for service and evaluation. I was there when a 100 series failed inspection for high NOX which meant a lean condition. I like Ricks MAF and want one for my truck, but emissions is pretty strict around here.

[landtank]

Originally Posted by Waggoner5

I wasn't assuming that it would damage an SC, just asking questions. More interested in passing emissions right now.

Cheerleader? Wow this thread has degraded also. I respond when the BS gets thick.

Rick, I appreciate you being polite and professional through this. No one is looking for winners and losers, only some answers. This is what tech info is all about. There are no other vendors building a MAF like yours, and I for one do not doubt your ability or design.

I'm not sure what CO wants for emissions but LXtreme had a CA sniff test and passed just fine. As I stated above, I'm unaware of anyone having issues with the exception of a visual in 1 case.

[Waggoner5]

Cool, I will give it a shot then. Thanks.

[landtank]

Originally Posted by Waggoner5

I was there when a 100 series failed inspection for high NOX which meant a lean condition. I like Ricks MAF and want one for my truck, but emissions is pretty strict around here.

I can't understand how a lean condition could be anything other than a O2 sensor or injector. Do you know what was wrong with this truck?

[Waggoner5]

Not exactly..I think it was several issues. I just was wondering about the trucks running lean and thought about that particular truck not passing thats all.

[turbocruiser]

I easily passed CO emissions with the LT MAF attached and the Safari Turbo System attached and the twin catch cans and the alternate style vacuum modulator and an aftermarket High-Metal/High-Performance catalytic converter and a 3" custom ceramic coated exhaust and all sorts of things that would alter the "visual" as well as the "emissions" of the system.

Of course this was at a Grease Monkey that runs tests for the State, but, I passed.

Ohh, I should mention I passed with flying colors both pre and post LT MAF.

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.

[fjfar80]

Originally Posted by landtank

Well Gary it would be up to your friend to decide how he wanted to proceed. I'm not sure how my MAF sensor would damage a SC but I guess anything is possible.

One thing to note is that with my MAF the O2 sensors stay active thoughout the operating range of a SC'd truck. The stock MAF will become saturated at around 25lbs of air and then the O2 sensors are taken off line. I believe that the ECU sees the MAF condition as a failure and goes into limp mode or something similar.

It's my opinion that since the O2 sensors are still active with my MAF that all the built in fuel cut off safe guards that Toyota programmed in are still functional. I have no way of knowing this for sure but I believe it's a reasonable assumption.

Rick, I have a question for you in regards to a SC install and your MAF. As you know I purchased your MAF and I have a SC both waiting in Memphis...I want to make sure I do this right so, here goes:

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?

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

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

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?

5. From a product development stand point, how many miles were put on your MAF and the new sensor combination, prior to selling them? Can you describe the engine testing - as in the miles, conditions, what procedures you used to see if any damage was done, etc?

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.

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

Thanks.

- Mark

[landtank]

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.

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

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

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.

5. From a product development stand point, how many miles were put on your MAF and the new sensor combination, prior to selling them? Can you describe the engine testing - as in the miles, conditions, what procedures you used to see if any damage was done, etc?

that was over two years ago and I used several configurations from around the country to get a varied sample. I was concentrated on getting repeatable results as far as fuel trim and AFR readings.

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.

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.

Thanks.

- Mark

answers in red

[Brian894X4]

Rick, thank you very much for staying on board and in the line of fire and answering some of these questions. I really appreciate it. And I think others do as well.

[jamisobe]

Rick / Slee,
I understand that the ECU should throw codes if the engine is running too lean. What I don't understand is how some would anticipate that disconnecting the vacuum control on the FPR could potentially cause a lean condition?

The post by Slee that shows that the FPR diagram and a description of its operation explains that the vacuum is strongest at idle which opens the return to the tank which also causes pressure in the fuel rail to be at its lowest. As throttle increases vacuum is reduced and the pressure builds in the fuel rail until WOT when the FPR is at its fullest restriciton creating the highest pressure in the fuel rail.

I understand that disconnecting the FPR isn't something that is normally adviseable, but apparently in this situation with this particular modification, the ECU, injectors, and O2 sensors don't mind full constant pressure in the fuel rail. So if I could get some answers to a few questions I will try to stop popping in on this thread...


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?

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?

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

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

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.

[semlin]

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

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. 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. 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.

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

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

[landtank]

there was a site around when I was working on this project but it has been taken down now. That particular site went into great detail how the Toyota ECU worked and gave some insight as to how it calculates and adjusts the injector duty cycle in relation to the MAF signal and injector size.

What it stated was that the signal from the MAF is used to calculate a base timing for the injectors. That timing is initially used to by the ECU when reset and then after warm up conditions have been met the ECU will go into closed loop. This action reads the AFR via the front O2 sensor and then "trims" the base calculation to meet design specs for AFR. This process starts out by adjusting the Short Term Fuel Trim (STFT) value and when that values has sustained a value other than 0 for a period of time it will then start to migrate that adjustment value to the Long Term Fuel Trim (LTFT) value. So as an example if the STFT% was constantly more than say 5% and fluctuated an additional .3% that would eventually appear as a LTFT% of 5% and the STFT% would remain as the fluctuating .3%.

Open loop operation happens a little different. In open loop there is no STFT%. That is because in open loop the O2 sensor readings are not used to finely adjust the metering of fuel. In this case the ECU uses a LTFT% calculated during the closed loop session and uses that plus the base calculation to meter the fuel.

The amount of fuel being delivered at any given pulse is determined by the pressure differential and injector size.

The pressure differential is calculated by measuring the fuel pressure with in the fuel rail and the atmospheric pressure within the intake manifold. The greater the difference the more fuel at any given duty cycle that will be delivered and the smaller the difference the less. As an example if the fuel rail pressure was 43.5psi and you actually had 43.5psi boost running on the engine then when the injectors opened up no fuel would come out as there would be no pressure differential.

One of the concerns of having a low pressure differential is that the metered fuel spray is not as consistent. So as you build boost some systems have the fuel rail pressure to fallow suit maintaining the differential throughout the operating range of the engine for a more consistent metering of fuel.

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

By removing the vacuum line on our trucks you are increasing the pressure differential with in the system. Now doing that alone you would produce a rich condition as the injectors would automatically meter more fuel for any given pulse. To counteract this you would need to either us a smaller injector or have the system calculate a shorter injector pulse when determining the base calculation.

Typically altering the base calculation is done through a piggy back system. This is some sort of programmable device where you can determine when and where during the engines operating range you want to influence the injector pulse to alter the amount for fuel metered.

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. 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.

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.

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.

[Brian894X4]

Frankly, I feel kind of bad about how this thread has turned out. I sincerely appreciate the technical info posted here from all points of view, but the whole reason this thread is here, is becaused I started it, by posting some h.p. figures a few days ago, so this is largely my fault. It wasn't more than a week ago that Rick was nice enough to take my order and ship this thing to me on the same day and I recieved it only a few days later. After all that, I end up repaying him with this headache of a thread.

Thanks rick for putting out that detailed explaination. That certainly helps my understanding.

One thing I do wonder is with the FPR capped off, are we sure that the regulator is allowing the maximum fuel pressure? If one was to drive at higher altitude, would the FPR normally add higher fuel pressure? If so, would it make sense to at least vent the FPR to outside air or the airfilter as mentioned earlier in the thread? I wasn't sure if the FPR was basically closed at zero vacuum or if maybe it can close even further with lower pressure and if the ECU would be expecting that.

When reading the STFT and LTFT and even the o2 sensors (valued at 0-99) what kinds of readings should I be looking for to indicate essentially normal operation, verses what could be a problem? This is more of a general question and not so much directly pertaining to this mod.

[Lugboot]

Originally Posted by turbocruiser

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]

Originally Posted by semlin

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]

Originally Posted by landtank

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]

Originally Posted by jamisobe

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]

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.