Landtank MAF surprising scangauge results

[semlin]

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

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

i agree that introducing the MAF causes the result, but that does not mean there is a fault in the MAF. it could be another component in the system that cannot adjust to the differences between the two MAFs.

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

or the possibility that the landtank MAF is still sending a signal and staying in closed loop when the stock MAF would have dropped out, but that either the FPR pressure or the injectors are not able to deal with the resulting fuel trim.

 

[sleeoffroad]

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

I am worried, it will not go into open loop when it should.

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

Yes, but only under closed loop.

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

Yes, I am not disputing this. What I am saying is there is no way to know if this is due to benefits of MAF (as claimed) or the fuel pressure differential that drops off (due to boost in manifold) and thus less fuel is injected per injector firing. The net result if the truck is running leaner.

there is no way that could be happening unless the ECU fuel trim map for turbocruiser has adjusted itself to take into account the extra air volume from the maf.

Yes it can, the pressure drops, less fuel goes in. Truck runs leaner. Now there is also more air flowing, but we do not know how that is reported (ie, response curve of the sensor) So we have no idea what is fed to the computer. Bottom line is, it is correcting, and by luck and testing different sensors they got it close. It is just the wrong way to go around choosing a sensor.

if it didn't do that, then under boost, the truck should be running very lean and showing major ltft issues both because it has a bigger air opening than stock and because the FPR pressure is limited to atmospheric pressure.

Yes that is what I would expect. I have yet to see a log showing LTFT values for normal drive cycles. Rick posted it was around +2 for him and -6 for trucks up here. I would like to see those or when time permits I will gather some with the truck we have here.

since it is not doing that, the ecu's definition of "normal fuel trim" must vary from truck to truck within certain parameters.

Not sure what you mean here.

therefore that means the 18% fuel trim discrepancy at idle with the FPR connected is a variation from the tweaked fuel map that takes into account the extra air flow.

Yes, 18% more fuel is added to get the mixture right with the new MAF. Rick proposed that the stock MAF reads wrong (or not very accurate) at idle and the FPR was used to lean it out. All I did was ask for proof of this incorrect reading.

so it is not the extra air volume showing up but something that causes the engine to run leaner than the ecu expects based on a fuel map that incorporates that extra air volume.

So what is making it run lean so that the truck needs to add fuel?

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

Again, I would like to see the LTFT logs to confirm this.

 

[turbocruiser]

Again, I would like to see the LTFT logs to confirm this.

For the third time, do you want me to send them again or do you still have the ones that were sent so long ago?

 

[sleeoffroad]

or the possibility that the landtank MAF is still sending a signal and staying in closed loop when the stock MAF would have dropped out, but that either the FPR pressure or the injectors are not able to deal with the resulting fuel trim.

The MAF does not know anything about closed or open loop. That decision is made by the ECU based on MAF output, which is assumed to accurately reflect the amount of air entering the engine. There is no evidence (measured response) that that stock MAF saturates (ie measured on a flow bench). That is my point re: their comment on 33lbs of air. That number is not calibrated and can not be used to decide anything until it is confirmed. That is what was used to conclude the stock MAF is saturated.

Could it be that the housing flows more, but the new sensor's response curve is such that it actually reports there is more air in some points and less in others. Thus the injectors duty cycle is adapter accordingly? It is all speculation. You could have a situation like below, although exaggerated, where at some points it is reporting above the factory MAF and some points below. We simply do not know.

All I am saying is, it would be better to know vs just relying on interpretation of the the vehicles feedback systems responses.

 

[sleeoffroad]

For the third time, do you want me to send them again or do you still have the ones that were sent so long ago?

Sure. I don't believe I can dig them up that far ago.

 

[semlin]

Not sure what you mean here.

i am saying that the base "neutral" fuel trim map from which the truck measures and reports +/- fuel trim is learned and specific to each truck.

in other words, the base fuel trim map on a truck with landtank's maf will look different than the base fuel trim map on the same truck with a stock maf once it has "learned" it.

there is obviously extra air getting into landtank maf trucks at a given air flow rate as measured by the maf. the opening is bigger and the sensor takes up less space. the ecu does not know this when you turn it on, so it must be learning a new fuel trip map for these trucks or else it would show constant significant fuel trim to offset the added air.

so the 18% fuel trim issue at idle is not necessarily 18% relative to a stock maf (it could be normal fuel trim for a stock truck). it is 18% relative to a learned fuel trim map that has already taken into account the larger air flow in the chamber using o2 sensor feedback.

so when you are looking for an explanation why the fuel trim is off 18% at idle from what it should be remember is is 18% of what the landtank maf should require based on a curve learned by the ecu at every other rpm. it is not necessarily a problem with the maf: it could be something else in the system that is not adjusting to the maf.

 

[sleeoffroad]

i am saying that the base "neutral" fuel trim map from which the truck measures and reports +/- fuel trim is learned and specific to each truck.

Yes,

in other words, the base fuel trim map on a truck with landtank's maf will look different than the base fuel trim map on the same truck with a stock maf once it has "learned" it.

Yes,

there is obviously extra air getting into landtank maf trucks at a given air flow rate as measured by the maf. the opening is bigger and the sensor takes up less space.

Yes

the ecu does not know this when you turn it on, so it must be learning a new fuel trip map for these trucks or else it would show constant significant fuel trim to offset the added air.

Yes,

so the 18% fuel trim issue at idle is not necessarily 18% relative to a stock maf (it could be normal fuel trim for a stock truck). it is 18% relative to a learned fuel trim map that has already taken into account the larger air flow in the chamber using o2 sensor feedback.

This is where I get lost as to what you are trying to say.
No, it means there is enough extra oxygen in the exhaust stream that the truck is adding 18% extra fuel (by changing injector cycle) to get the O2 sensors maintain equal swinging around the .5v (expected to be a 14.7 A/F ratio as by design of the 02 sensor)

so when you are looking for an explanation why the fuel trim is off 18% at idle from what it should be with the landtank maf based on a curve learned by the ecu at every other rpm. it is not a problem with the maf: it is something else in the system that is not adjusting to the maf.

There is more air entering the truck that what has been reported to the ECU. There is nothing else that needs to adapt to the MAF. Plain and simple. Unplug a large vacuum hose past the MAF and the same thing will happen.

http://www.autoshop101.com/forms/h58.pdf is a good read on that. Also note the area where they talk about the 14.7 ratio and why it is there. As well as the diagnositic info on page 7 and the comments on page 8

 

[sleeoffroad]

Here is another part that might be of interest to some people.

This is one of the concerns that we have when people say that the truck runs in closed loop longer. You can see from the above that you do not always want closed loop and being in closed loop longer is not necessarily a good thing.

 

[landtank]

WOW you guys have been busy.

First off my assembly won't match the stock unit so I really don't see the point of testing it and when you see the difference what will that tell you, really only that there is a difference.

First I'd like to point out that the ECU could care less if the FPR is attached or not. It is of no concern. All tgh eECU does is take the information that it's receives from the MAF sensor, calculate a base injector timing and feeds that to the injector. As long as the O2 sensor likes the out come it won't adjust the fuel trim

Theoreticaly lets aay the stock configuration is a constant pressure differential system. The the signal from the MAF has to be tuned so that base calculation matches that condition.

I can say with 100% certainty that with the vacuum line removed the system is now a inversely proportional pressure differential system. And I tuned my MAF so the base calculation would work in harmony with that type of system.

So Christo, if all this is to feel good about selling these, that ship has sailed. So continued hammering at the fact that you have questions would only be as a buyer and I can honestly say you aren't going to get the answers you want so there is no reason to keep pushing for them unless it's to discredit my work and part.

For everyone else take a look at how the Supra guys used a MAF out of a LS400 to tune the stock ECU for larger injectors as well as how Touota handled the fuel injection on the 22reT. In both cases they simply lowered the output of the MAF and then compensated for the resulting lean condition with larger injectors.

It's not as Christo would like you to believe, it's quite simple and mathematically calculable.

 

[semlin]

This is where I get lost as to what you are trying to say.
No, it means there is enough extra oxygen in the exhaust stream that the truck is adding 18% extra fuel (by changing injector cycle) to get the O2 sensors maintain equal swinging around the .5v (expected to be a 14.7 A/F ratio as by design of the 02 sensor)

18% extra fuel compared to what?

my understanding is it is 18% more fuel compared to the base fuel map that the ecu has just learned for this truck with the landtank maf in place. e.g., the fuel map that has been adjusted to account for the extra air volume at all other rpms.

 

[sleeoffroad]

18% extra fuel compared to what?

my understanding is it is 18% more fuel compared to the base fuel map that the ecu has just learned for this truck with the landtank maf in place. e.g., the fuel map that has been adjusted to account for the extra air volume at all other rpms.

The LTFT is the adjustment of the fuel map. So it has to add 18% more fuel than the hardcoded map it has stored. The one that it defaults to when the battery is removed and the ECU is cleared.

The 18% IS the adjustment for the LT MAF.

 

[semlin]

The LTFT is the adjustment of the fuel map. So it has to add 18% more fuel than the hardcoded map it has stored. The one that it defaults to when the battery is removed and the ECU is cleared.

The 18% IS the adjustment for the LT MAF.

do you have a source for that? i have a hard time with that. it must be relative to the learned fuel map or the results make no sense.

if fuel trim were relative to the hard code base fuel map, then the fuel trim at every rpm and load should be off to the same extent because the landtank maf is allowing more air volume in every situation.

 

[sleeoffroad]

WOW you guys have been busy.

First off my assembly won't match the stock unit so I really don't see the point of testing it and when you see the difference what will that tell you, really only that there is a difference.

First I'd like to point out that the ECU could care less if the FPR is attached or not. It is of no concern. All tgh eECU does is take the information that it's receives from the MAF sensor, calculate a base injector timing and feeds that to the injector. As long as the O2 sensor likes the out come it won't adjust the fuel trim

Yes, but it also uses the AIR FLOW AMOUNT as your MAF is reporting it to decide between CLOSED and OPEN loop. If the AIR FLOW IS WRONG, this decision is also WRONG.

Theoreticaly lets aay the stock configuration is a constant pressure differential system. The the signal from the MAF has to be tuned so that base calculation matches that condition.

The initial (hard coded) fuel map is matched to the MAF output and all the other items in the truck, one being the assumption that fuel pressure if constant.

I can say with 100% certainty that with the vacuum line removed the system is now a inversely proportional pressure differential system.

What do you mean with this? Inverse to what? Does pressure drop based on something?

And I tuned my MAF so the base calculation would work in harmony with that type of system.

If you don't know the response curve, or the what the base fuel map is in the ECU, how did you tune it? Other than observe the FT's?

So Christo, if all this is to feel good about selling these, that ship has sailed. So continued hammering at the fact that you have questions would only be as a buyer and I can honestly say you aren't going to get the answers you want so there is no reason to keep pushing for them unless it's to discredit my work and part.

OK, I won't ask direct questions from your. However I don't see why we can not continue the discussion, but if you feel you don't want to, I would respect that. I tried to explain a couple of posts ago why I got into this.

For everyone else take a look at how the Supra guys used a MAF out of a LS400 to tune the stock ECU for larger injectors as well as how Touota handled the fuel injection on the 22reT. In both cases they simply lowered the output of the MAF and then compensated for the resulting lean condition with larger injectors.

I will do some searching to see what they come up with.

It's not as Christo would like you to believe, it's quite simple and mathematically calculable.

I am sorry, I can not see how you can calculate it, if you don't have the response curve and there are so many variables between the stock MAF and yours.

 

[sleeoffroad]

do you have a source for that? i have a hard time with that. it must be relative to the learned fuel map or the results make no sense.

You can have a look at this document. It is probably the best explanation of how it works.

http://www.autoshop101.com/forms/h48.pdf

if fuel trim were relative to the hard code base fuel map, then the fuel trim at every rpm and load should be off to the same extent because the landtank maf is allowing more air volume in every situation.

LTFT Is not a single value, but it is calculated all the time. FUEL MAP is a term people use to explain a 2D matrix of fuel values. It is nor really a 2D matrix, but a injector duration that is calculated every time. With a battery disconnect (all FT values cleared) it resorts to a base injector duration calculation with FT=0

 

[turbocruiser]

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

Yes. Otherwise I wouldn't take the risk of running this with turbo without the wideband, per both Christo and Rick's advice at the time.

Sure. I don't believe I can dig them up that far ago.

Resent to the info.sleeoffroad.com address.

 

[semlin]

You can have a look at this document. It is probably the best explanation of how it works.

http://www.autoshop101.com/forms/h48.pdf

LTFT Is not a single value, but it is calculated all the time. FUEL MAP is a term people use to explain a 2D matrix of fuel values. It is nor really a 2D matrix, but a injector duration that is calculated every time. With a battery disconnect (all FT values cleared) it resorts to a base injector duration calculation with FT=0

ok well if long term fuel trim is measured from the base fuel map before "learning" then the fact the landtank MAF is generating such low fuel trim numbers with the FPR connected (outside of idle) must indicate that there is not a great deal of extra air volume entering the engine. It makes no sense to blame the 18% fuel trim at idle on the extra air volume if you can't replicate those results under load or at higher rpm.

 

[sleeoffroad]

ok well if long term fuel trim is measured from the base fuel map before "learning" then the fact the landtank MAF is generating such low fuel trim numbers with the FPR connected (outside of idle) must indicate that there is not a great deal of extra air volume entering the engine.

It makes no sense to blame the 18% fuel trim at idle on the extra air volume if you can't replicate those results under load or at higher rpm.

So if it is not extra air volume then what is it?

Did you see the part about checking the system by introducing an vacuum leak? What does that cause high LTFT values, but when we get that at idle with a different MAF it can't be attributed to additional air that is not "reported" by the MAF?

Did you see the diagam about the response curves? It could be that at higher air flow, it is actually backing fuel out due to the reported voltage to the ECU. We simply do not know unless the sensors are mapped.

I can not explain that and never did, but neither has anyone else, except they say it works. I reserve comment on this until I have checked fuel trim values myself.

 

[turbocruiser]

So if it is not extra air volume then what is it?

Did you see the part about checking the system by introducing an vacuum leak? What does that cause high LTFT values, but when we get that at idle with a different MAF it can't be attributed to additional air that is not "reported" by the MAF?

Did you see the diagam about the response curves? It could be that at higher air flow, it is actually backing fuel out due to the reported voltage to the ECU. We simply do not know unless the sensors are mapped.

I can not explain that and never did, but neither has anyone else, except they say it works. I reserve comment on this until I have checked fuel trim values myself.

You have the trim values again so unreserve your comments! Just fuel for fire here but what do you suppose would happen with 10psi put directly on the FPR?

 

[jamisobe]

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

Yes. Otherwise I wouldn't take the risk of running this with turbo without the wideband, per both Christo and Rick's advice at the time.

That was actually a rhetorical question after Slee posted this picture and said that LTs MAF does cause a lean condition. My response was to remind Slee that other trustworthy individuals have monitiored A/F under high boost without experiencing a lean condition.

 

[turbocruiser]

That was actually a rhetorical question after Slee posted this picture and said that LTs MAF does cause a lean condition. My response was to remind Slee that other trustworthy individuals have monitiored A/F under high boost without experiencing a lean condition.

[/I]

Ohh, sorry I'm super dense in determining rhetorical or sarcastic statements sometimes.