Thread: How to completely get rid of MAF on de-EGR'd TD5

Unglaublich. I suppose all good topics must come to an end eventually.

Thanks for starting this topic Mr. sierrafery on what really was an alternative to disconnecting a faulty MAF by simulating expected reading based on throttle position (for manuals and all other caveats noted). As you reminded people it was not meant to be a tuning or performance mod as such but as has pointed out by many all mods come with some downside.

Good luck with your EGT testing and full marks for taking this advice on board. Somehow I suspect all it will confirm is throttle flat to floor and EGT goes up, and throttle backed off to normal cruising speed and temps comes back down. Even a stock motor with no mods can see high EGT under continuous full load conditions and when you think about it, it was quite an oversight by the LR engineers to not fit an EGT probe and use this as an input into the ECU as well to trigger a limp mode (which would then lead to more electronic-trickery boxes to clamp the EGT output, like the boost box does to allow people to push the turbo output beyond its original specs).

yes it seems so...what i could do and i'm sure it would work is to figure out a pure electronic circuit as to induce a limp mode based on EGT output spliced with a blocking diode into the ECT sensor's output as when the EGT is critical to trick the ECM on the ECT circuit to go to overheat protection


after this harsh experience here i think i'll limit myself to pure electronics

This is the end of this

the fact is that i feel lucky that i started this thread even if i was a bit humiliated but tha'ts life

i posted the quoted part in the forums where i made public this mod so i think there's nothing more to say:

Warning about the MAF bypass mod

Guys, it seems that my electronist mind failed in this particular case...i better swallow the shame than cause trouble to somebody who makes the mod then he'll have some serious problems... i didnt make it public especially for this reason untill i've tested it for long time on my own car without any trouble for around 30000Km but from all the info i've got lately on the aulro site it becomes more clear to me that this mod might be risky so disregard it and i apologise for making it public ... no harm done though cos it cant hurt on a short run but better be affraid than get scared IMO ...so that's it

i'll fit an EGT gauge on mine and keep testing it just for my own curiosity though cos it sems my car can bear it without probs but i felt i must launch this warning :sorry:

even though i think i'll never be able to understand from electronic point of view how it's possible that a signal with a certain waveform to create different reactions of it's target ... might be just a proffesional malformation of mine


dont blame just me, blame those who wrote RAVE too

Originally Posted by sierrafery

1. ok, can you give me a link with what to download please?

This sort of learning needs to be self-directed. I've given you the name of the software and you already have engines of interest to search for binary files from.
Joining a tuning forum like ECUconnections would help immensely.

Originally Posted by sierrafery

3. i'll learn as much as possible cos it's a kind of hobby to me but what i cant understand is that limiters or not on inputs as long as the output to injectors is the same where is the gist of it? ... so those limiters will do what to keep the injector output steady but modify the EGR output more on MAF input variations? ... in the end the ECM is an electronic microprocessor/controller like a kind of the engine's ''brain'' isn't it? ....so those limiters within the ECU how can they ''impose'' e.g rpm limitation? ... not through the output to injectors? ... and if they do i presume this woukd show on that output signal's waveform or amplitude... as it happens very visible on the EGR output... as i said in a previous thread i made these measurements on the running car too with the same result(only the waveform was a bit different due to the solenoid's load)


in a nutshell: is the engine behaviour (rpm, torque, smoke, etc) managed through the output from ECM to injectors or not? that's what i keep asking simple as for a limited electronist brain

When you understand the operation of ECU's and the structure of the command and output signals it will all make perfect sense. But that will take a long time.

The mass airflow input is one of the most important to an EFI engine. Replacing that with any other signal removes the ability to match fuel to air.

Originally Posted by sierrafery

the fact is that i feel lucky that i started this thread even if i was a bit humiliated but tha'ts life

We should all feel lucky that you did start this thread as there is a lot we can all learn from each other's experiences. Providing we can stop attempts to point score and humiliate people for sharing their opinions then I think this topic deserves some experiments.

Okay - so I did my first MAF bypass test today. No not the "sierrafery MAF mod", but let's call it the "please explain MAF mod".

First test, confirm MAF is behaving as expected.

At idle 52kg/hr. When driving below 1500 rpm it goes to around 130. At 100kph reads 300. Throttle off at 100kph drops below 200. At 2000 rpm in 3rd gear and floor throttle, jumps immediately to 450 and then as engine revs out to max revs, peaks at 660 kg/hr.

Next test, confirm EGT is behaving as expected. EGT at idle 150-160, at 110 kph 350-360. Normal acceleration sees peaks around 450-500. On engine run down (throttle off at 100kph), drops below 200 degC.

MAF and EGT readings appears to be functioning correctly. If anyone sees a suspect reading let me know.

Now the base line performance tests. Both test done in 4th gear, flat road, minimal wind, same direction, no gear changes. I also dropped my EGT high alarm from 650 to 600 degC.

4th gear 50kph to 110kph - 13.1 seconds. This starts at 1600 rpm so below the turbo boost kicking in.
4th gear 60kph to 100kph - 8.0 seconds.
Both tests did not hit the EGT alarm (highest I saw was around 550).

Now I disconnected the MAF. Readings drops instantly to 5kg/hr. The MAF is now not functioning.

Repeat EGT tests and no noticeable change in readings and again around 350 degC at 110kph and all other responses as above. Engine sounds the same, it revs the same, hits 4300rpm easily enough, and pulls as strong as when the working MAF was connected.

Repeat performance test and get the same 50-110 and 60-100kph times plus/minus about 0.1seconds. Again did not see any difference in the EGT readings (probably could have done with a co-pilot).

And to end the test I checked for any fault codes and none came up. Even though the MAF had been reading 5.0.

I realise this is one set of tests and yes I did reconnect the MAF at the end of the test because it works and I want to see the reading and also believe it must do something!

Now my car has done 460k, and the gearbox needs a rebuild, so I don't want to be the guinea pig here and repeat these tests to prove it is repeatable. But it would be interesting if others could repeat this test and publish their results and allow my Disco to have a rest.

My mods: EGR bypass, larger intercooler, DTUK electronic-trickery box wired up to only turn on at full "foot to the floor" throttle (via a toggle switch under the throttle). Rest of time the DTUK box is off and does nothing. Yes the box will be replaced with a remap in the near future.

As always, consider other road users and don't break any laws. Fortunately performance testing a Td5 can never be accused of being a hoon. All my tests done on an empty country road.

Well I believe no one has properly explained a MAF and what is meant by Mass of air. Dougal came close relating the air mass to temperature but that's not really the whole store. It's more related to the air density than temperature. It just so happens that cool air is usually more dense.

Happy Days.

Originally Posted by joel0407

Well I believe no one has properly explained a MAF and what is meant by Mass of air. Dougal came close relating the air mass to temperature but that's not really the whole store. It's more related to the air density than temperature. It just so happens that cool air is usually more dense.

Happy Days.

Face meet palm.

1. Hi again... i thought i rest my case on this but even if i didnt make more statements here i've been researching about that ... i must revert to a stage where were lots of various explanations about the MAF sensor , air MASS and DENSITY...but after many articles i've read it seems that the important thing in this MAF purpose is still the VOLUME of air, remember this? http://www.aulro.com/afvb/2187771-post103.html

from many the many files i saw it seems relevant for me the statements of the guys who are actually in the MAF testing/manufacturing business and the more i read the desciptions in theyr page and how/what is involved in the testings i find this statement too often to be neglected:
".... signal which is sent to the ECU, which inturn, adjusts injector duration in proportion to the volume of air flow"
this statement is as the end of each MAF (flap-vane, hot film, hot wire, Karmen-vortex) sensor type description
then when describe what theyr proffesional equipment does here it is:
"....the testing station the genetates and delivers pre-determined volumes of air through the unit being with the units output at each pre-determined air volume being displayed and compared against the output of the original unit stored in the software"

the whole story attached or can be verified here [ame]http://injectronics.com.au/assets/Catalogues/Air-Mass-Meterscatalogue201213.pdf[/ame]
now after so many more or less thermodynamical explanations, density, air-mass, etc about the MAF i'm wondering again if this sensor is not mainly an air flow sensor as i've once said but i was immediately corrected with complicated theories about MASS of air

2. didnt have the chance to drive my D2 much since the EGT sensor was fitted cos i'm in vacation and i'm mainly driving my boat than my car these days but in 150Km with boat attached and the wiring mod i've got the greatest reading of around 500, then undone the wire plugged a bran new MAF(which i've got prepared for the case the EGT readings will impose it) and drove 100km more untill my destination... now that's why i didnt put here these findings cos i've got greater(around 550) maximum reading with the MAF

i'll make a log with more and various tests soon cos now i just drove it normally and watched the gauge to see where it goes at max... wasnt very focused on detailes and that analogue gaige is not the most accurate neither