[Lugboot]

Originally Posted by Brian894X4

My 1995 is OBD II, but because of the year is usually sniffer tested, not plugged in. Since I have this mod, if I could get it sniffer tested, what would I be looking for? What readings? And what would it prove?

Originally Posted by aclos3

On my old truck and sniff testing in Washington State they'd give you a print out that showed carbon monoxide/dioxide, hydrocarbons, oxygen and NOx. If your state sniff tests NOx (I would think most would, since NOx contributes to smog), you're in luck. I would think if we were running lean enough to cause any kind of damage, we'd fail the NOx sniff test. I don't know this for sure though!

Originally Posted by aclos3

I wonder if our emissions test facility would allow me to test even though I just got new tabs through Jan. 10. I also wonder if they'd humor me and give me a sniff test if I asked. I know I've seen a print out of NOx emissions on a Washington sniff test performed on my old truck. They're pretty by the books at these state run facilities and probably wouldn't allow this kind of exploratory testing though.

To have access to just a couple tests! I'd run it with the stock MAF and the modified one a few times and see if we're getting high NOx with the new MAF. I need to make a friend at the emission test facility.... hmm.

Originally Posted by landtank

well, there is over a 150 trucks out there running this MAF and I have only heard of one issue and that was a visual in CA. (trickyT)

Does everyone just scan the ECU now? I have to believe some have had the sniff test.

Something to clarify on emissions testing here--it really depends on what program your state runs. Yes, 1995 and older vehicles get tailpipe tests and mostly 2-wheel dyno ASM (Acceleration Simulation Mode) tests at that (which measure NOx because that is produced under load).

HOWEVER, unless your state's program has 4-wheel dynos, most non-disengageable 4-wheel drive vehicles (Cruisers) DO NOT receive a loaded ASM dyno test. They receive a simpler TSI (Two-Speed Idle) test, which DOES NOT measure NOx because there is no real load put on the engine.

You'd have to do one of two things to get tailpipe readings for NOx--

1. Find a 4-wheel dyno and 5-gas analyzer.
2. Remove your front driveshaft and find a 2-wheel dyno and 5-gas analyzer.

And, the majority of states now only test the OBDII system in 1996 and newer vehicles. Some DO have fallback tailpipe testing in conjunction with the OBDII test, but again, the type of tailpipe test dictates whether you get a NOx reading or not.

And most OBDII tests only scan the system for codes and report pass or fail. They DO NOT churn out readings for the monitors.

[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..

[jamisobe]

I would hope that the Toyota engineers, who designed the programing for detecting lean operation, would be insightful enough to set the parameters of NOx detection in such a way that the engine would be protected from longer term damage.

The idea that they would fail to be appropriately conservative in designing this critical error detection feature seems like a far fetched "what if".

I still have the stock MAF set-up. If someone would like to purchase it send me a pm.

[Riad]

I am gonna keep Landtank's MAF on with the new sensor and FPR caps; it's been flawless thus far; I also have the OEM MAF for backup and I ain't selling it, yet. I wish there was a 4WD dyno nearby so I could get some real data to clear up my own (and hopefully others') confusion. Pinged a semi local dyno test shop (about 60 miles away) and haven't heard back from'em yet. I am guessing I'd have to travel pretty far to find one.

If I may suggest this, I am sure this has come up numerous times before; nevertheless, Rick, may be you can do a dyno before and after your MAF install. I think this gives your product a more concrete value. You should raise the price for the product after the dyno results are public. Just my $0.02.

[sleeoffroad]

Originally Posted by landtank

Christo has made up his mind that I'm wrong about how this MAF works and how the fueling system on our truck works. There is nothing more to be said to him about this. Repeating myself another 100 times is not going to change anything and only lead to more disagreement.

I've stated numerous times that if you plug in the vacuum line from the FPR that the LTFT% will shift about 18% and not to do it. I've even stated it here earlier on.

So what does he do, he plugs in the FPR and has an issue with the fact that the LTFT% is way out of whack at idle.

He now what's answers to his questions as in his mind this is evidence that there is a problem with the MAF sensor. He knows full well what my answer is but refuses to accept it.

The basic problem here is that he refuses to accept the idea that he may be wrong about how the 80 fueling system works. He is not ready to question his own understanding and ready to consider another opinion.

I didn't read some tech manual or discuss this with some trained technicians I reversed engineered it. To understand what that means, I did a series of tests and evaluations on the system to determined there effect on how the ECU managed them.

The first and biggest assumption he has made is that the vacuum line is there to maintain a constant pressure differential. I don't know where he got this idea but I can tell you with great certainty that this is not the case.

I am sorry, but it is not an assumption. Here is the relevant pages from the Toyota training manuals. Please tell me where I assumed wrong?




If you leave the FPR hooked up and the fuel trims go up, it means the truck is running lean with the new setup. This can only mean that there is a calibration issue with the sensor and housing as to what the ECU is expecting, ie, more air is entering the motor than what is being reported. Your unplugging the FPR is masking this by increasing the fuel pressure.

If there is a calibration error at idle, then there is an issue with the response curve of the sensor and/or the bore of the housing. Without doing a calibration on a flow bench and comparing the response curve with given flow between the stock and your MAF there is no way to know if you are correct.

Yes, you can monitor fuel trim and yes people are reporting better improvements, mostly because the truck is running leaner.

The bottom line is Toyota did not bandaid a inaccurate MAF sensor by connecting vacuum to the fuel pressure regulator.

I could go into detail how me and Cattledog determined this but it's more clear to just say that on a boosted truck with a stock MAF sensor at WOT the engine is running crazy rich. He already knows this and posted it up way back years ago and showed this to everyone on a dyno chart he has.

So if Toyota designed the system to need a constant pressure differential why is it running so rich? If anything you want less fuel and a drop in fuel rail pressure is needed.

I do not know why Toyota made the truck run that rich. Adding forced induction to a truck that was normally aspirated has it issues, and the overly rich condition is one of them. You started this development for your turbo build, and that was a good thing. However stating things about why mods are done that is incorrect is not.

What Christo needs to do is accept the idea that I might be right, install the unit as instructed and then get out of his chair and actually eval the piece for himself. This way at least he can ask some pertinent questions. And if he is sincere about wanting to sell these then he needs to do this anyway to validate the product.

We will do that when we get the time, however as the vendor of the product, you also have a responsibility to post the correct info, or at least obtain it.

But I'm sure I'll come back here with a line edited reply from him telling me why I'm wrong and how he knows better.

And that is why I've not been engaging with him on this thread and a few others. There is no point to it and only leads to the demise of a thread.

Yes, and I am sorry it has come to this. But facts are facts.

[-Spike-]

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..

Pot, meet kettle.

'Worry about some of your own products'. Nice.

'Vendor to vendor'. How about using a PM then?

Talk about rude.

I will add, that perhaps Christo could have PM'ed or phoned Landtank. However, this is another case of some people wanting to bury their heads in the sand and hope there isn't a problem. If I had done something to my truck on someone else's advice I'd be very interested to know why, especially if a person knowledgeable about the system had questions about its safety. If I were that knowledgeable person in a business and had to deal with possible future ramifications of a mod, I'd want an explanation as well. I'm not in any way taking sides on the actual issue, since I know nothing about the mod or the system, nor have I purchased the MAF in question. However, this situation is exactly why we have a forum- to discuss things.

-Spike

[bpassmore]

I do not have this mod, heck, after Sunday I wont even own an 80 anymore, but Slee does not seem to be thread crapping to me. He is bringing up important information and it needs to be discussed.

I do find it odd that Frankie is now advocating PMs as a vendor to vendor information exchange after seeing what happened in the spring thread.

I for one appreciate the vendors hashing the issues out with their customers in an open forum.

[Riad]

I say some one do a dyno so we can put an end to this. I would hope a dyno for a stock truck with or without forced induction is already available. All we need is a complete 4wd dyno for a truck with the modded MAF and sensor.

Ain't no one out there ???

[SeanAndHis80]

Originally Posted by Riad

I say some one do a dyno so we can put an end to this. I would hope a dyno for a stock truck with or without forced induction is already available. All we need is a complete 4wd dyno for a truck with the modded MAF and sensor.

Ain't no one out there ???

It would still be apples and oranges. Same truck, same day, same temp, same gas, same as much as possible or it will solve nothing.

I have an email out to a local dyno about me dropping my front driveshaft to use their 2WD setup - maybe I'll give it a shot.

[turbocruiser]

Originally Posted by sleeoffroad

I am sorry, but it is not an assumption. Here is the relevant pages from the Toyota training manuals. Please tell me where I assumed wrong?




If you leave the FPR hooked up and the fuel trims go up, it means the truck is running lean with the new setup. This can only mean that there is a calibration issue with the sensor and housing as to what the ECU is expecting, ie, more air is entering the motor than what is being reported. Your unplugging the FPR is masking this by increasing the fuel pressure.

If there is a calibration at idle, then there is an issue with the response curve of the sensor and/or the bore of the housing. Without doing a calibration on a flow bench and comparing the response curve with given flow between the stock and your MAF there is no way to know if you are correct.

Yes, you can monitor fuel trim and yes people are reporting better improvements, mostly because the truck is running leaner.

The bottom line is Toyota did not bandaid a inaccurate MAF sensor by connecting vacuum to the fuel pressure regulator.




I do not know why Toyota made the truck run that rich. Adding forced induction to a truck that was normally aspirated has it issues, and the overly rich condition is one of them. You started this development for your turbo build, and that was a good thing. However stating things about why mods are done that is incorrect is not.



We will do that when we get the time, however as the vendor of the product, you also have a responsibility to post the correct info, or at least obtain it.



Yes, and I am sorry it has come to this. But facts are facts.

Christo, again another inquisitive and insightful post, and, for whatever its worth, I still don't see you attacking this mod (although I do see why people who don't know you or Rick personally would think that but you're both very brilliant people and you both have questioned one another's products in past so no harm no foul at least as I see it). However, I'd still like to twist this with you the way that I twisted this with Sumo who was making a major effort at attacking the mod if you ask me ... IF as my and others' widebands have proven over and over the AFR's are safe and steady at all ranges of operation including WOT, how much off can this calibration aspect you are worrying about be? IOW, the way that I see your statements is an incredibly stretched "What If" and you're asking Rick to answer that with formal flow bench tests, all sorts of gas analysees (sp?) and other expensive efforts. His answer is that through reverse engineering and normal band/wide band measurements, OBD-II measurements and all sorts of observations from users, everything is exactly within normal operating parameters except the AFR's are better, the economy is better and performance is better. You are deliberately doing something not suggested which is attaching the FPR and I understand why but to twist this the other way have you considered that the AFR's are 20% too rich in stock setup and this mod corrects that?

The equivalent analogy would be someone running your super sweet front bumper upside down and declaring that their approach angle sucks and that the stock bumper was 20% better than your bumper upside down. All along the truth was that the stock bumper was 20% worse than your bumper installed correctly. So, again, with all our observations thus far, how much off can this MAF mod really be. Respectfully, TC.

[Lugboot]

Originally Posted by SeanAndHis80

It would still be apples and oranges. Same truck, same day, same temp, same gas, same as much as possible or it will solve nothing.

I have an email out to a local dyno about me dropping my front driveshaft to use their 2WD setup - maybe I'll give it a shot.

I'm assuming you have the Center Diff Lock switch installed? You'll need it to do this. Do they have a 5-gas bench and diagnostics? It'd be sweet to get the exhaust readings as well as the dyne readings. And throw in the OBDII stuff, too.

[sleeoffroad]

Originally Posted by turbocruiser

IF as my and others' widebands have proven over and over the AFR's are safe and steady at all ranges of operation including WOT, how much off can this calibration aspect you are worrying about be?

What is your long term fuel trims while driving your truck?

IOW, the way that I see your statements is an incredibly stretched "What If" and you're asking Rick to answer that with formal flow bench tests, all sorts of gas analysees (sp?) and other expensive efforts.

I am questioning the disconnect of the FPR and why the sensor is not working with it connected and leave the truck as Toyota designed it with the FPR setup.

Also, on a NA truck, if you cap the FPR you have no altitude compensation on fuel pressure as well. If you vented it to the airbox and left it open, at least you will have that.

His answer is that through reverse engineering and normal band/wide band measurements, OBD-II measurements and all sorts of observations from users, everything is exactly within normal operating parameters except the AFR's are better, the economy is better and performance is better.

Yes, I never doubted that people are seeing improvements. The truck is running leaner. Normally if you do that you get improvements in performance up to the point where you damage the system.

I pointed out that he states a reason why the idle LTFT is higher and why he disconnects the FPR that is incorrect. I posted the data that shows this. Rick has not posted anything in terms of sensor response, other than conclusions made from measurements. Statements are made about more accuracy in the lower air flow situation as well as statements about airflow and turbulence with no data to back it up, other than conclusions from checking 02 sensors or a wideband.

You are deliberately doing something not suggested which is attaching the FPR and I understand why but to twist this the other way have you considered that the AFR's are 20% too rich in stock setup and this mod corrects that?

Because the underlying reason for doing the FPR disconnect is wrong. If I left this FPR disconnected on this customers truck and the motor pops, will Rick accept the liability? If the AFR was 20% to rich on a normally aspirated truck, then the LTFT would be negative and backing it out.

The equivalent analogy would be someone running your super sweet front bumper upside down and declaring that their approach angle sucks and that the stock bumper was 20% better than your bumper upside down. All along the truth was that the stock bumper was 20% worse than your bumper installed correctly. So, again, with all our observations thus far, how much off can this MAF mod really be. Respectfully, TC.

Rick stated that he sold 150 of these units. With that quantity sold, there should be money to do proper testing on the sensor and not rely on the feedback circuits to hope everything is right. And when things are not, disconnect a major part of the engine fuel managment to get the fuel trims correct.

Have you searched on High NOX and no check engine light?

Also, Rick has already done the work on the housing. Would it not make sense to investigate the sensors that might actually match the factory one in terms of response curve?

[SeanAndHis80]

Originally Posted by Lugboot

I'm assuming you have the Center Diff Lock switch installed? You'll need it to do this. Do they have a 5-gas bench and diagnostics? It'd be sweet to get the exhaust readings as well as the dyne readings. And throw in the OBDII stuff, too.

Yes, I do. If they are willing to work with the Bruiser with CDL locked and driveshaft out - I will ask what their gas analysis abilities are next.

[Lugboot]

Originally Posted by SeanAndHis80

Yes, I do. If they are willing to work with the Bruiser with CDL locked and driveshaft out - I will ask what their gas analysis abilities are next.

Duh, I should have read your sig line.

[Brian894X4]

I went back through the EPC and found something interesting. On the 4Runner 3.4 V-6 we have an engine that Toyota originally put our old MAF sensor in and then starting in 1998, they upgraded to the new sensor that we use for this modification.

And guess what? Toyota used the same fuel pressure regulator for both sensors.

So, you can see the confusion here.

Now, that said, I looked up a few other engines that use this same sensor and the Camry 2.4 liter where my used sensor came from, does not appear to have a FPR...only a damper. But the fuel rail also does not appear to have a return line. Looking at a few other cars, this seems to be a common theme among newer vehicles.

No fuel return line, no FPR. But if there is a fuel return line, there appears to always be a FPR.

So, my concern is why did Toyota choose to continue with the FPR if it was no longer needed with the new sensor? Does a serve another purpose not really qualifiable through any computer program? Is it harder on the injectors to have the higher pressure all the time? It is harder on the fuel as a whole?
I'm just guessing.

And I don't quite understand why the computer and new sensor wouldn't be able to compensate for the lower fuel pressure at idle, if other vehicles can. It is a limitation of the computer system?

Personally, I think Christo brings up some very valuable and crediable concerns. There are things that cannot be reversed engineered through sensor and emissions testing alone. It's very clear that Toyota chose to continue to use the FPR on rigs like ours that converted over to the new sensor, and so far no explaination.

To be honest, I like the power increase, but overall vehicle reliablity is absolutely number 1 to me. I find myself out in situations where I could be hundreds of miles from the nearest help and considering Christo's altitude compenation and lean concerns, we could be several miles high and in extremely hot conditons.

If the new sensor was able to truly compensate for all measurements at all conditions, it would probably be fine, but what worries me about "tricking" the system to think one thing to achieve a result, if that's what's happening, is that the system might not be able to compensate correctly for all conditions, such as the extreme conditions of altitude and or heat.

I'm heaviliy leaning towards putting the old sensor back in, unless some of these concerns and questions can be answered. I'm not saying there is a problem or even that the percentage chance of a problem is that high or that I wouldn't recommend this product to anyone else. I'm just a little extra anal about reliability than most, so that would be the only reason I'm having second thoughts.

[sleeoffroad]

Originally Posted by Brian894X4

I went back through the EPC and found something interesting. On the 4Runner 3.4 V-6 we have an engine that Toyota originally put our old MAF sensor in and then starting in 1998, they upgraded to the new sensor that we use for this modification.

And guess what? Toyota used the same fuel pressure regulator for both sensors.

So, you can see the confusion here.

Now, that said, I looked up a few other engines that use this same sensor and the Camry 2.4 liter where my used sensor came from, does not appear to have a FPR...only a damper. But the fuel rail also does not appear to have a return line. Looking at a few other cars, this seems to be a common theme among newer vehicles.

No fuel return line, no FPR. But if there is a fuel return line, there appears to always be a FPR.

Non return line systems as you mention is a different setup.

So, my concern is why did Toyota choose to continue with the FPR if it was no longer needed with the new sensor? Does a serve another purpose not really qualifiable through any computer program? Is it harder on the injectors to have the higher pressure all the time? It is harder on the fuel as a whole?
I'm just guessing.

The fuel injection system sprays fuel via the injector. Fuel demand is obviously different at different time. The only thing the ECU ca do to cary fuel delivery is to open the injector for a different durations.

Now consider the injector spraying into a chamber. If that chamber is at atmosphere, vs under vacuum or under positive pressure, the amount of fuel delivered will be different if the rail pressure on the other side of the injector is constant. That is why the fuel rail pressure is varied (by the regulator) to produce a constant differential, so that the same amount of fuel is delivery for a specific duration, even if the chamber pressure differs. .

The truck does not measure fuel pressure. The ECU programming is set up for a specific pressure differential. That is how the system is designed to work. So you can see that disconnecting the FPR is not a good thing.

And I don't quite understand why the computer and new sensor wouldn't be able to compensate for the lower fuel pressure at idle, if other vehicles can. It is a limitation of the computer system?

The truck does, and that is what fuel trim is all about. However with Ricks MAF long term fuel trim at idle (with FPR connected) is at about 18%. That means that the truck is trying to put more fuel into the system because the O2 sensors are telling it the truck is running lean. The reason for this is that "unmetered air" is entering the system. That means the sensor is not reading correctly.

You can achieve the same thing by creating a vacuum leak post the MAF sensor. The ECU does not know this air has entered the system, so the fuel calculations is done based on the MAF reading. The truck will run lean and the Air fuel ratio will go up. The feedback from the O2's tell the truck that it needs to put more fuel in, and it will do it to a point.

There really is two issues.

1. Is it a good thing to disconnect the FPR from it's reference signal. We believe not neither does Toyota.

2. If you do leave it connected, what is the LTFT during idle and normal drive cycles. If they are high with no check engine light, what is the NOX readings and is the truck still running optimal AF ratios.

[sleeoffroad]

Originally Posted by Brian894X4

If the new sensor was able to truly compensate for all measurements at all conditions

it is important to know the sensor can not compensate. All it does, it produces a voltage when placed in a air stream. This voltage varies as the airflow varies. The calibration of that sensor is hardwired into the ECU, ie, the ECU says, hey I read 3 volts, that means in this truck, that translates to 20lbs of air per minute (or whatever unit it uses). The voltage value is a function of the sensor's response curve, the amount of air is calculated from that and the diameter and specs on the housing.

Now you have a new sensor that produces 3 volts, but no-one knows if that 3 volts means the same thing since no-one knows the response curve of the sensor. The housing is also changed. So the ECU still thinks it is getting 20 lbs of air since it saw 3 volts, but in fact it is not. That is the real issue here.

Both turbocruiser and Romer commented on what they were seeing as airflow in terms of pounds of air and how that number was increased from the stock MAF (both on boosted trucks). This is a calculated value from the the voltage produced by the sensor. The sensor's response curve could be such that for a given airflow, the voltage reading is higher or lower. So you can not really interpret those numbers to mean anything as well. So this also shows that it is important to know what the response curve is.

Rick is relaying on the trucks feedback systems and some experimenting with different sensors to keep things in line. That is simply not the way to make a sensor choice if you are selling these units.

, it would probably be fine, but what worries me about "tricking" the system to think one thing to achieve a result, if that's what's happening, is that the system might not be able to compensate correctly for all conditions, such as the extreme conditions of altitude and or heat.

That is exactly the issue. Again they are relaying that the truck will throw a check engine light when things get wacky. However from experience I can tell you that the feedback systems is not that precise. What if you have a faulty O2 sensor or a lazy O2 sensor. Now your sensor for your feedback system is also compromised.

[Brian894X4]

Very interesting.

At this point, unless someone can makea good case otherwise, I'm heavily convinced that disconnecting the FPR is a bad thing and I question using this sensor at all. And if there's no way to run this sensor without disconnecting the FPR, then, we'll...I guess it's an expensive experient and lesson to learn.

Before removing the new AFM, I will take some more scangauge readings and compare to the old AFM and post them for all to see for whatever it's worth. If anyone has any particular scan gauge reading requests under certain conditions, let me know.

I do want to say, that this is just my personal choice and I'm not making a recommendation to anyone else at all. Also, I don't think anyone would take away from ingenuity of this mod and especially the quality of the housing. Its top notch, so if someday we can put to rest some of these questions, I may go back to it.

[Riad]

Crap .

I'm gonna put the OEM back on to see if I notice any thing different.

[96r50]

Brian, if you have the later version of the Scangauge with the Add-a-gauge feature, can you not check the LTFT with it?

[landtank]

I'm really not sure why people are suddenly concerned with how this MAF sensor responds when not installed properly.

Guess what, when not installed properly it won't respond properly.

Anyone who has the ability to look at LTFT% and STFT% do so with the MAF installed and installed correctly. Take a drive and and what you are looking for is a relatively consistent total % throughout the operating range of the engine.

I've done this with my truck as well as others with boosted trucks and there is minimal variation. This indicates that the sensor is providing accurate information for calculating the base value for the injector timing throughout the operating range.

The fuel trim is there to compensate for variations in hardware and enviriment such as elivation and temperature.

For those who would like to see what disconnecting the vacuum line does follow this procedure.

When the engine is warm disconnect the hose. This is so the engine is already in closed loop and will quickly adjust for the change.

Now do the same drive. What you will see is that as soon as you depress the gas pedal the LTFT% will jump to a normal value and then continue on through out the drive as long as you are on the gas.

Now let off the gas pedal and instantly you will see that odd high value for idle. It doesn't matter what speed you are traveling fr the conditions of the road. As soon as the closed switch is triggered on the TPS that idle LTFT% value is used.

Disconnecting the vacuum hose is done only to influence the idle LTFT% value. So when a reset of the ECU takes place you don't want that idle value to be way out of the norm for the engine.

I'm posting this so people can confirm for themselves that their truck is safe to operate. According to the FSM an acceptable FT% is in a range of +/- 20%. I don't have my FSM handy so I can't give you the page number.


I've also had several people with wideband sensors do extensive data logs and there was nothing to indicate any issues. Christo himself indicated that this is the acid test for making sure that there was no fueling issues and is what the dyno shops use to tune ECUs with. I'm not sure what has changed since then?

[Brian894X4]

I do have the add-a-gauge scangauge, but I've never programmed fuel trim or o2 values in it. I will try to do that. But first I have some reading to understand what all this fuel trim stuff means. So, I will do that and then make some runs with both sensors and publish everything I find.

I think the concern, at least in my own mind and from what I'm reading is not so much that this mod doesn't work or that it's even potentially dangerous under normal driving, but how will it respond during an extreme circumstance. For example, has anyone test this thing at high altitude or in extreme hot weather, extreme cold weather and found any results to differ from the stock truck.

The other concern is are there factors that weren't taken into consideration that might affect some of the reading that were relied on during development. It may not be such a good idea to rely on the values of a new sensor introduced to an old computer system, because the system may not be reading what it thinks it is.

The answer to some of those concerns seems to be relying on the values of other sensors that were not changed or aftermarket sensors to determine that the engine appears to be operating correctly. I think this definately has some value, but the problem is, if we don't know for sure if the ecu is actually reading and interperting accurate data or if the ecu or other factors are simply compensating, then we don't know how the truck will perform in various adverse conditions. Such as the before mentioned different altitudes, extreme loads, extreme weather, if/when another sensor fails, or even different types of fuel.

To me, the mod seems like a good mod for someone looking largely for performance gains, who likes to experiement with their engine. For someone who runs an expedition type rig, especially out of country, but also in relatively remote areas that might undergo extreme conditions and where engine reliablity is absolutely number 1, that's where this mod becomes kind of questionable to me, without further testing. To be fair to this mod, under those circumstances, almost any major engine modification would be questionable under those circumstances, so it's not just limited to this mod.

[sleeoffroad]

Originally Posted by landtank

I'm really not sure why people are suddenly concerned with how this MAF sensor responds when not installed properly.

Your "correct installation" disables and important part of the fuel management of the vehicle. I am sorry, I am probably coming off as an ashhole on this, but no-one questions these statements when they are simply not right.

This is what you said in the development thread regarding the reference for the FPR. You left of the part about manifold pressure. That is the 4th thing that needs to be considered.

I thought I'd explain the vacuum line a little more and how it benefits fuel delivery.

When metering fuel there is three basic components that need to be considered.

1. size of the injector
2. fuel pressure
3. duty cycle, the on time of the injector

Since the injectors remain the same lets talk about the other two.

The stock MAF has a minimum air flow that it can read accurately.
Air flow below this point is read the same as it's minimum. Because at idle the air flow is below this minimum it is read as a higher value or as if the truck was running at a higher RPM. To combat this Toyota uses a vacuum sensing line on the FPR and drops the rail pressure to compensate for an inaccurately high reading from the MAF

Where is your proof of the above? You stated it as fact, so I must assume you have it somewhere.

My MAF accurately reads low air flow at idle. Because of this it will signal the ECM to run the injectors at a lower duty cycle than that of the stock unit. Combining this lower duty cycle with the reduced fuel rail pressure gives a lean condition.

So by removing the vacuum line the fuel rail pressure goes up to 43.5 psi and is now matched to the lower duty cycle that my MAF is signaling for.

Where is your proof of this? Yes, the fuel rail pressure goes up and that is how more fuel gets into te system and fixes yor LTFT issue. How do you know it is changing the duty cycle of the injectors? How do you know it is not unmetered air getting to through the system.

At idle both setups are delivering the same amount of fuel, but with my MAF it's being done with less "on time" of the injectors.

Again, where is the proof?

The benefits are:

1. a smoother more consistent idle.

2. running at a lower duty cycle during non boosted times means there is more duty cycle "on time" left for when you are boosted and need more fuel.

As well as this. Yes smooth idle you can feel. Is it because it is running lean? Gets more fuel due to higher pressure? Yes, feedback will control that, but does it not also do so with the stock MAF?

Guess what, when not installed properly it won't respond properly.

Anyone who has the ability to look at LTFT% and STFT% do so with the MAF installed and installed correctly. Take a drive and and what you are looking for is a relatively consistent total % throughout the operating range of the engine.

Why does no-one want to post LTFT values or a log? Consistent and Consistant high is not the same thing. I never got an aswer to that.

I've done this with my truck as well as others with boosted trucks and there is minimal variation. This indicates that the sensor is providing accurate information for calculating the base value for the injector timing throughout the operating range.

Minimal variation or minimal variation from zero?

The fuel trim is there to compensate for variations in hardware and enviriment such as elivation and temperature.

To a point, but it is not the do all and end all.

For those who would like to see what disconnecting the vacuum line does follow this procedure.

When the engine is warm disconnect the hose. This is so the engine is already in closed loop and will quickly adjust for the change.

Now do the same drive. What you will see is that as soon as you depress the gas pedal the LTFT% will jump to a normal value and then continue on through out the drive as long as you are on the gas.

Now let off the gas pedal and instantly you will see that odd high value for idle. It doesn't matter what speed you are traveling fr the conditions of the road. As soon as the closed switch is triggered on the TPS that idle LTFT% value is used.

Disconnecting the vacuum hose is done only to influence the idle LTFT% value. So when a reset of the ECU takes place you don't want that idle value to be way out of the norm for the engine.

That is not the only thing that the vacuum line does. The truck is not just under vacuum at idle.

You have also disabled the high temperature fuel pressure control. This is what prevents the truck from not starting when it is hot. That vacuum line is connected to a VSV that uses engine coolant temp to determine if it should up the pressure at startup. The good news is that when the truck is hot, it wants more fuel pressure so when you disconnected it, you are doing this by default.

I'm posting this so people can confirm for themselves that their truck is safe to operate. According to the FSM an acceptable FT% is in a range of +/- 20%. I don't have my FSM handy so I can't give you the page number.

Yes, but if you are biased to the +20% side, then you don't have the range anymore and if something goes wrong, the truck is not going to like it.

I've also had several people with wideband sensors do extensive data logs and there was nothing to indicate any issues. Christo himself indicated that this is the acid test for making sure that there was no fueling issues and is what the dyno shops use to tune ECUs with. I'm not sure what has changed since then?

You disconnected the FPR line I never said it is the acid test, I just said it is better then a O2 sensor. Dyno with gas analyzer is the acid test.

Again, I am not saying this is a bad thing, I am just saying the selection of the sensor and it's calibration is in question. It's calibration and how it interacts with the ECU is important and can not be ignored. That is why I am hammering on seeing the response curves of the sensors. Both stock and the new one you recommend. However you don't have them. What is involved with getting them I am not sure, but I am sure someone out there does that kind of thing.

[landtank]

Christo take the truck out and eval it as I described. It's the best was for you to see the FT% and how they are.

No one to date has had a CEL for FT% error. On my truck at the time of testing I was at 3% total but I'm at sea level and that is to be expected. Others at elevation have reported -6% which again is expected since they are at elevation.

One thing to note is that during my testing of the sensor myself and Cattledog where going back and fourth and our trucks did exhibit some differences in FT% but I feel that this is do to the fact that they were different trucks,

As far as the logs go I don't have them anymore as they were on my PC but as I stated above you can take that truck out and get some fresh ones.

My comments above were based on my years of working with electronic devices for the last 27 years. As these devices are further developed the usual goal is for them to have larger operating windows and high resolution. It's my opinion that Toyota would also want the same for it's product. It is an assumption on my part and I could very well be wrong and the newer design might very well fall short of it's 11 year old predecessor.

As far as getting some high tech eval on the sensors you are on your own. I have no idea where to have that done and quite frankly don't have the cash to do it.

I'll ask that the development thread be deleted since it is full of my opinions.

[sleeoffroad]

Originally Posted by landtank

I'll ask that the development thread be deleted since it is full of my opinions.

There is no need to do that. It is good reading and there is a good history with the development in there. However I think it could do with an update.

[Brian894X4]

I was playing with the EPC again and some of this may be old info, but I found that sensor we use for the mod was used for most Toyota engines up to the 4.0 V-6 displacement.

However, for the 4.7 V-8, they chose a different sensor for some reason.

22204-75020 through about 2005 and 22204-75030 after that.

Anyone know why the different sensor? Would this one work any differently?

By the way, Toyota used this same sensor on all UZJ100 trucks sold throughout the world for whatever that's worth.

I was curious if Toyota only used the sensor we use for this mod in the North American market, but I see that it was used all other markets that I checked.

Also, in every return fuel system I looked up, they had FPR. I couldn't find a single model with out a return fuel system, no matter how modern, that didn't have a vacuum controlled FPR.

This isn't meant to prove anything. Just information only to add to the discussion. I hope the development thread stays in place, I really want to read through it in more detail as a learning experience. I know very little about the fuel managment system and all of this discussion has helped to educate me and I'm continuing to learn more and more and can hopefully come to a more indepedent verification of how this mod works and if I want to keep it.

My sincere apologies if I've caused any problems by starting this thread and continuing this discussion. That was never my intent.

[turbocruiser]

Christo, I sent you my data logs a long time ago (April, 2007), remember? IIRC there was 1% difference in LTFT. I think that I still have some of them and I'll try to send again if you indeed deleted them.

[Brian894X4]

Can someone help me with what I should be looking for when comparing the two sensors with the scangauge? I read a lot of about open loop/closed loop, FT and other readings, but I'm not really sure what I should be seeing? Other than I guess there should be minimal variations on all readings between the sensors correct?

Sorry, I know this is somewhat of a basic question. I'll be doing a lot of reading up on fuel injections between now and when do some more testing this weekend.

[sleeoffroad]

Brian, here is a good place to start if you need some reading material.
Automotive Training and Resource Site

[landtank]

seeing a difference between the two sensors doesn't mean much, in my opinion. Two identical sensors will not read the same so two entirely different ones are unlikely to be the same, in my opinion.

What I focused on was getting the FT% throughout the operating range as linear as possible and as close to the stock sensor as possible.

This was the best option that I had for evaluating comparability between the two and then followed up with Wideband AFR readings to ensure proper fueling.