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Here is the link to the Denso MAF sensor. It doesn't use a screen but a probe instead.
The operating principal is the same between the X300 and X308 sensors, but the important thing is the transfer function. That's the relationship between the voltage reported by the meter and the mass of air flowing past the meter. This relationship is hardcoded into the car's ECU, so you would have to match it to the MAF in the airstream to have the car run right.
There is a very important distinction between a mass flow element and a mass flow meter. The picture of the X308 is the element, the X300 is the meter. The element is only half the equation, the tube it fits into is a vital part to the relationship between voltage and air mass (the transfer function). The element and tube are integrated into one part in the X300.
As an example 2005 and later Fords use a slot type meter. The element itself is the same for just about everything from the smallest Focus to the biggest Super Duty truck engine. What changes is the diameter of the tube that the element is put into, and that in turn changes the transfer function that is reported to the ECU. The actual sensing element is the same part though.
The element only senses the small amount of air that passes it. They are quite small sensing areas, about 1/8"x 3/16" and it reads a voltage. However the total amount of air flowing will be very different if the element is in a 50mm dia. tube vs a 90mm diameter tube; it's 3.24X as much air in the bigger tube.
So we would need mass element + calibrated tube + transfer function = mass air meter.
In the X300 the meter is one piece (non interchangeable element), in the X308 the element is replaceable. In the X300 the screen isn't a sensor, it's an airflow straightener; it reduces turbulence and makes the meter more accurate.
Last edited by Jagboi64; Feb 20, 2016 at 01:11 AM.
The operating principal is the same between the X300 and X308 sensors, but the important thing is the transfer function. That's the relationship between the voltage reported by the meter and the mass of air flowing past the meter. This relationship is hardcoded into the car's ECU, so you would have to match it to the MAF in the airstream to have the car run right.
There is a very important distinction between a mass flow element and a mass flow meter. The picture of the X308 is the element, the X300 is the meter. The element is only half the equation, the tube it fits into is a vital part to the relationship between voltage and air mass (the transfer function). The element and tube are integrated into one part in the X300.
As an example 2005 and later Fords use a slot type meter. The element itself is the same for just about everything from the smallest Focus to the biggest Super Duty truck engine. What changes is the diameter of the tube that the element is put into, and that in turn changes the transfer function that is reported to the ECU. The actual sensing element is the same part though.
The element only senses the small amount of air that passes it. They are quite small sensing areas, about 1/8"x 3/16" and it reads a voltage. However the total amount of air flowing will be very different if the element is in a 50mm dia. tube vs a 90mm diameter tube; it's 3.24X as much air in the bigger tube.
So we would need mass element + calibrated tube + transfer function = mass air meter.
In the X300 the meter is one piece (non interchangeable element), in the X308 the element is replaceable. In the X300 the screen isn't a sensor, it's an airflow straightener; it reduces turbulence and makes the meter more accurate.
Thanks for the good info. That helps. I have seen somewhere where you can get calibrated tube and sensor that will work on the X300. I'll try and find that again and post it.
Sorry for the thread revival, but since this thread is solely about MAF's, I thought it would get more exposure posted here. Ive just replaced my MAF after cleaning had no effect on the hesitation I was experiencing.
I decided to go for a new aftermarket unit from worldcarparts, like another poster on this thread, and am happy to report that the hesitation is gone, and the unit is almost identical to the original, build quality is excellent.
Good find . What is the part # of the Denso insert , not the whole LNA-1620AA unit ?
K & N air filters did a study on the modes of failure of the MAF sensors to dispel the belief that the oil on the filter contaminates the thermistor which is the probe device in the air stream . What they found over hundreds of examples is the silicon used as a manufactures seal off gasses during curing or migrates contaminating the thermistor and on the other side of the seal the electronics signal resolving package . Off the top of my head before looking up the document , most of the sensors failures were because of this . If there was a way to clean the silicone off the thermistor and the electronic package by chemical or mechanical means may negate the need to buy a new MAF sensor . I've been looking for a source of just the thermistor only without the electronics package .
Good find . What is the part # of the Denso insert , not the whole LNA-1620AA unit ?
K & N air filters did a study on the modes of failure of the MAF sensors to dispel the belief that the oil on the filter contaminates the thermistor which is the probe device in the air stream . What they found over hundreds of examples is the silicon used as a manufactures seal off gasses during curing or migrates contaminating the thermistor and on the other side of the seal the electronics signal resolving package . Off the top of my head before looking up the document , most of the sensors failures were because of this . If there was a way to clean the silicone off the thermistor and the electronic package by chemical or mechanical means may negate the need to buy a new MAF sensor . I've been looking for a source of just the thermistor only without the electronics package .
I have just bought a aftermarket one that I tried for diagnostics, but my problem turned out to be ecm so anyone in uk need one I'll sell to them..let me know..its a full unit used for 5 mins...
Last edited by Stevieb76; Oct 8, 2017 at 03:55 PM.
LHA1620AA for supercharger / LHE1620AA ( Lucas 20 AM or 70390B as marked ) for normal aspirated 4.0 and 3.2. They most likely have 2 different map or maps in the 2 different ECU's and don't pair up . Something to do with the volume related velocity ( higher in SC ) hitting the area of the saturation point in the thermister response curve so there is a difference in the 2 MAF meters .
Still looking for a source for the thermistors if anyone can help break the code and get to possibly a very cheap resolution as the whole meter units disappear .
Last edited by Lady Penelope; Oct 8, 2017 at 05:43 PM.
Figured since I started this thread I'd update my situation. Was running on the used MAF for a while with no problems. Gradually noticed the car feel more peppy and my long term indicated I was running rich at -10.5. Being too lazy to do any diagnosis I threw a Reman MAF from a1cardone I bought off rock auto. I told myself I would buy a new MAF if the used one fixed my problem and never got around to it. Drove for about 20 miles and the long term dropped to about -0.78. Drove another few miles and is currently at 0.00. Car doesn't feel as peppy but I guess it's running the way it was designed.
Last edited by Scarecrow; Oct 8, 2017 at 06:14 PM.
By way of an additional input on this topic, I recently misdiagnosed my MAF as faulty, and replaced it with a worldcarparts item. No difference from original MAF, and car now running faultlessly with it. Rich running turned out to be due to leak at manifold to downpipe flange.
XJR 6.
Rose's hesitating on acceleration has been getting worse in the past few days. Was suspecting that the clutch might be slipping (mine is converted manual) but mechanic test-drove it and said it is not the clutch but something like misfiring or a faulty airflow meter. Scanned Rose with IDS and she only threw one code P1137 - Lack of heated oxygen sensor switch, sensor indicates lean bank 1. Re-oriented the O2 sensors with IDS's programme and cleared the code which does not return any more. But car still hesitated when stepping on the accelerator and this happened at all speed and gears. I have a full set of Japan-made coils which I may try on, but I too suspected that it is more likely to be air flow meter. Checked the specs on mine and it is LHE1620AA, manufacture date S1/05, so presumably more than 13 years' old. So I recalled there is this thread about alternative source of the air flow meter. Unfortunately a quick web search showed that even generic airflow meter previously sold by WorldCarParts is all sold out. The only solution now is to buy one re-manufactured. Buying one used seems risky as even my own is 18 years old. Wonder if folks have any late discovery of other aftermarket product that would do the job without breaking the bank.
Last edited by Qvhk; Apr 22, 2018 at 12:15 PM.
Reason: I did the sum wrong, my airflow meter is 13 years' old; not 18.
Sounds like your O2 sensor is bad, not the MAF. Reorienting won't fix that; the purpose of reorienting was to correct the ECU if the O2 sensors were plugged in backwards, i.e. the upstream connector was plugged into the downstream socket. Reorienting flips the place the ECU looks for that particular O2 sensor.
I would start by replacing the O2 sensors and go from there. I'd use the NTK 25018, that's the OEM sensor. It's also smaller than most, and depending on which one it is, space can be at a premium.
Sounds like your O2 sensor is bad, not the MAF. Reorienting won't fix that; the purpose of reorienting was to correct the ECU if the O2 sensors were plugged in backwards, i.e. the upstream connector was plugged into the downstream socket. Reorienting flips the place the ECU looks for that particular O2 sensor.
I would start by replacing the O2 sensors and go from there. I'd use the NTK 25018, that's the OEM sensor. It's also smaller than most, and depending on which one it is, space can be at a premium.
The O2 sensors were replaced only a few months ago. It is the first time the code has arisen but it has not come back after clearing it. Anyhow, would still want to find an airflow meter just in case, particularly when it is now as rare as gold.
I have stainless steel exhaust manifolds installed, so no cracks; but there maybe exhaust leak down at the joining points where the exhaust manifolds meet the downpipes due to poor workmanship, but Rose has been running very well with a mild leak. Will take a look from the bottom to see if leak has worsen.
I have stainless steel exhaust manifolds installed, so no cracks; but there maybe exhaust leak down at the joining points where the exhaust manifolds meet the downpipes due to poor workmanship, but Rose has been running very well with a mild leak. Will take a look from the bottom to see if leak has worsen.
Hi Qvhk. I noticed your post and thought I'd mention the fact that I have the old AFM from my 3.2 donor car. I don't know how good or bad it is but it worked fine when the donor car was running. If you're interested, you're welcome to it if you're happy to cover postage, you know, the usual procedure. Let me know and I'll dig it out and get the part number off it.
Rose has been stranded pending a thorough check of exhaust leak. I can too replace the coils to see if that would cure the problem, but I still suspect that it is the airflow meter, and in any case would want to have a spare available if money can still buy me a new one. I sent a message to WorldCarParts through eBay and got a reply saying new stock will be available in 2-3 months time. Not sure if more enquiries will help speed up the stock replenishment. Have found a few refurished airflow meters online, for about the same or more money.
Hi Qvhk. I noticed your post and thought I'd mention the fact that I have the old AFM from my 3.2 donor car. I don't know how good or bad it is but it worked fine when the donor car was running. If you're interested, you're welcome to it if you're happy to cover postage, you know, the usual procedure. Let me know and I'll dig it out and get the part number off it.
All the best!
Many thanks. I just checked. According to JaguarClassicParts.com the XJR uses LNA1620AA, whereas the 4.0 NA and 3.2 uses LHE1620AA. So the 3.2's version would not fit my XJR. Just found that WorldCarParts has both offerings, i.e. LHE1620AA and LNA1620AA, but both are out of stock. Wonder how are they different. I found a shop online that claims to be able to remanufacture car ECUs, airflow meters, and practicaly any car electronics, so I wonder if it is worth a try.
Last edited by Qvhk; Apr 24, 2018 at 06:00 AM.
Reason: correction: WorldCarParts have both LHE1620AA and LNA1620AA; the latter is more expensive, but both are out of stock
Hi Marcus,
It is absolutely essential that you fit LNA1620AA not LHE1620AA to a supercharged engine. The relationship between airflow and voltage output is completely different for these to airflow meters. A supercharged engine will be massively over-fuelled if it is fitted with LHE1620AA.
