Hi

does anybody know what is the actual difference between the XJR LNA1620AA and N/A 4.0 LNE1620AA in electrical and physical point of view?

in the EDM there is only one table for the voltage / air flow (attached)?


and yes mine (for XJR) probably did die... and all of the suppliers that I have checked are completely out of stock and being positive with replies like "completly obsolete... no stock anywhere"

 

Fuel injection Corporation in California can build you one if you send them your core. I read a article some where about Ford motor company uses the same air flow sensor for every model engine size they have, The only thing different is the size of the inlet tube leading to the sensor. Small tube size- small displacement. Large tube size- large displacement. Never had the two sensor bodies next to each other to confirm that was how Jaguar did it.
I did try a N/aspirated sensor in my AJ16 S/C motor once to find it drove the STFT and LTFT to -77 real fast.

Thank you.

Larry Louton

 

To check to see that your MAF is alive the middle wire ( Green / Yellow ) will read 1.2 volts DC at the correct idle speed

As a engineering rule of thump for every 1.0 liter of displacement the engine will consume 1.0 grams per second at 650 RPM

The idle speed on the AJ16 engine is higher so the consumption will be a bit higher without doing a crude calculation

You can see this reflected in the data chart in the PDF

In doing a crude calculation under isobaric conditions I came up with 165 grams per second at 5000 RPM for the non supercharged engine

The supercharged engine ECU has a different set of data " maps " or data arrays in it's own ECU to calculate the pulsewdith or time the injector is open charging the cylinder with fuel

Off the top of my head the supercharged engine is reported to be in the 225 range and that may be the smaller faster turning pulley modification

 

Just for grins on my spare LNA1620AA air flow sensor I hand fashioned a small plastic cap with a smaller diameter hole to restrict the air just a small bit and vehicle would not even start. Removed cap and vehicle did start and run.
This particular sensor has always had reliability issues so this test doesn't really mean anything. My good one that was refurbished by Fuel Injection Corporation has the mesh screen in it so I didn't want to screw up a good one just to test a Internet theory. Did you know that you cannot tell a lie on the internet?

Larry Louton

 

The flow rates vs voltage curves are different between the XJR and normally aspirated MAF meters. I think that table is actually for the XJR version, as I tried to use a N/A meter with the Megasquirt injection computer on my 1966 S Type and the table values were way off. I believe the XJR version is calibrated for a bit less than double the airlfow of the N/A version (650 vs 1018 kg/h)

Larry: The Ford MAF is very different, it has an insert that goes into a housing. To use it, you still need the transfer function for the meter/housing combination to make it work. The meters used in the X300 cars are made by Sagem. Land Rovers used similar meters, but I have not tried to find out what their transfer function is to see if they are interchangable ( but I doubt it). Physically, they would interchange, but not electrically I suspect.

 

@Jagboi64 yes seems like the table from EDM is indeed for SC as 0,284 kg/s translates to ~1022kg/h. I was kind of hoping that the sensor itself would have been the same and the MAF body would be different so one could extract the sensor from working n/a version and insert it to the SC MAF housing.

on side note I do have ms files from Jan from Sweden (who passed away some time ago) for XJR if you would like reference point

@Lady Penelope thanks


I found one place willing to repair the MAF (if needed) in netherlands but I will firstly measure and try to debug the bloody car more as I am not completely convinced that it is the map and not lambda that is the culprit for the running issues. I just need to locate my obd2 reader that I have loaned out...


additionally one could find physically suitable MAF with know transferfunction and try products like MAF translator or MAF manager https://movichip.com/product/movichi...engine-tuning/ I have not looked too much into this yet.

 

I don't know how this MAF could ever be repairable, you can easily remove the MAF from its housing and clean it up, which is by the way the only way to actually clean it up but past that its a properly sealed unit. You can remove the top cover, its holding up on 4 little torx screws in each of the corners, covered with some fairly soft glue but past that the internals are covered in a special jelly that protects the top side from damage due to engine bay shaking but the bottom side of it is glued up using super hard epoxy. No chance to remove it without destroying it all.
It's very clear that these suffer eventually from cold solder joints, I have two MAFs here that only work in a specific position or if I knock on them but like I said dont think its possible to resolder these fully due to all that epoxy inside.

 

Well I would guess that they change the sensor in the housing,which for the OE one needs to drill out the rivets. Seems like the aftermarket stuff is indeed fixed with tamper proof torx (https://www.jaguarforums.com/forum/x...3/#post1164409) And if we would know the type of the sensor unit it might not be that hard to do it yourself if one finds the sensor somewhere ?

 

The type of sensor penetrating into the airstream is called a thermistor

There is a catalog of different theristors and different characteristics , which one it is is a question and if they would sell to a non member of the MAF Mafia

Many class action lawsuits on the mater of a consumer being able to repair the MAF

The electronics package under the 4 fasteners resolves the signal

Without me seeing the electronics package the electronics may be in a potting compound which would make it harder to tinker with

 

Like I said, its in a black epoxy, unless you know of a chemical that could dissolve it without destroying rest of electronics I dont think it's possible to do anything with it.

 

try Worldcarparts. their ones work OK.
I may have a spare - do you need one?

 

I bought a worldcarparts one about a year ago for my xjr, sure it works but the fuel trims are way off, runs much too rich
There is no part number on the packing or on the maf itself....I suspect that worldcarparts supply the same maf for both the LNA & LHE part numbers

 

thanks Al, I managed to find used one from Norwegian used parts seller. I cleaned it with MAF cleaner and contactors with contact cleaners, and after plugging it in car works relatively ok.

 

Just a thought of the top of my head, could one fit a variable resistor in series with the output pin of a naturally aspirated MAF and adjust the voltage vs flow to match the hard to find XJR version? Would have to be done with care not to exceed 5 v and risk damage ECU or overly weaken the mixture.
I have an excessively rich mixture which I think is caused by a failing MAF, and also have a wide band O2 sensor that I could fit with some effort.
What do you think?

best regards,

John

 

I believe what you would see happen would be a lower voltage across the range which is not what you want.


Larry Louton

 

For some reason the Jaguar service manual only shows the air meter transfer function for the version for the supercharged engine (4.7volts = 0.284kg/s = 1022kg/hr). The MAFs for the supercharged and naturally aspirated engines are physically interchangeable by the different transfer functions mean that they are not electrically interchangeable. These items are so rare now that I keep loads of spares. I wouldn't attempt top repair one. I've compared the transfer function of LNA1620AA with a Bosch HFM5 MAF with curve 5 (part number 0 280 002 421). This is the highest flow rate version of Bosch HFM5 MAF. It will read up to 1000kg/hr, but unfortunately, at this flow rate the output is only 4.3312 volts. This correspond with about 800kg/hr with the Lucas part. Therefore if you used the Bosch then the fuelling would be about 20% leaner than standard at max power. This would be likely to cause engine damage. I could adjust all the fuelling maps in the ECU to compensate but it would be a lot of work. I would only produce a new ECU calibration , if there was a lot of demand for using the Bosch part. At least they are available and reasonably priced. I don't know if any other manufacturers of MAFs produce one with a closer matching voltage to airflow transfer function.