jag xj40 air flow meter

hi if i bore out my air flow meter by few milimeters lets say 3. made by hitachi on my 1990 4.0l jag will it need to be recalibrated or will it recognice the modification and readjust it self? just an idea red about this hot wire and dont know how it works any help welcome;)
 
Not quite sure what you are trying to achieve here my friend, I would be interested to learn more about what it is that you are trying to do?
 
The hot wire system should automatically recalibrate itself. The hot wire system is a very shrewd engineering solution to the issue of measuring accurately the mass air flow;-

There are actually two identical wires. One is mounted in the air stream, the other is enclosed away from the air stream. With no airflow both wires exhibit the same electrical resistance. When air flows over the 'free' wire its temperature decreases. As a result it's resistance also decreases compared to the enclosed hot wire. The change in temperature (thus also the change in resistance) is truly representative of air mass rather than air volume.

It's a brilliant piece of engineering because it accounts for changes in external air temperature and atmospheric pressure completely automatically by virtue of its nature of operation.

However, I doubt that increasing the MAF diameter by 3mm is going to have any material effect upon performance.

It might even be detrimental to mid range torque because it will have the effect of slowing down the airflow, which will impinge upon the quality of mixing of air and fuel. The injectors are mounted to spray fuel onto the back of the open inlet valves and to assure optimal air and fuel mixing you want the airflow velocity as high as possible.

Nice car by the way. I was very fond of the '40. Which model do you have?
 
Cool - they're a fast disappearing classic. My dad has a 3.6 XJ40 Daimler, lovely car but lots of minor electrical gremlins. The engine itself is sweet as though, silky straight six that just feels as if it could go on forever.
 
hi well thanks for your interest in my fidle all im trying to do is to get the engine to breath beter if pos,got rid of middle boxes mount it biger down pirpe have got k&n induction kit and have got handy machinist so im trying to bore out valve trotle body and air flow meter any ideas regards boyan
 
i have been all over EU with it irland to greese and back lots of fun the germans give me a bit of hard time and a fine of 100 euros i also lost my black windos there and then but thats them what coloure is your old mans one?
 
I can kind of see why. Straight six is the archetypal 'British' engine but Jaguar's V8 engines are just as smooth as the straight six and V12 models and equally as sparkly to drive.
 
well guys i got it done. little while ago i feted a kit on a xjs suplied by AJ enginering for a friend i allso droped 4.0 in it as it was 3.6 the air flow meter was biger in internal diametre on the one that aj suplied so my machinist copid it what i got is a bit wierd high acseleration but no much torque on this xjs i feted a aj enginering full exhaust,air filter inlet manifold and uprated fuell presure regulator and it sounds and goes fantastic even that my mate scott spend over 40k in total on his xjs my xjr is not as fast as his xjs the aj guy told me when i spoke with him that i got problem with inlet manifold on mine is to short coud this be true?
 
well guys i got it done. little while ago i feted a kit on a xjs suplied by AJ enginering for a friend i allso droped 4.0 in it as it was 3.6 the air flow meter was biger in internal diametre on the one that aj suplied so my machinist copid it what i got is a bit wierd high acseleration but no much torque on this xjs i feted a aj enginering full exhaust,air filter inlet manifold and uprated fuell presure regulator and it sounds and goes fantastic even that my mate scott spend over 40k in total on his xjs my xjr is not as fast as his xjs the aj guy told me when i spoke with him that i got problem with inlet manifold on mine is to short coud this be true?


?? struggling to follow this
 
ok i did bore out the air flow meter as i had intesion to do so on my jag xj40 twr and the achivment was waist of time first of all the fuel consumtion was 3 times as much, acseleration was not there no torque and engine was pinking over 4000 rpm regardles of the timing adjustment .hdi fun was right with his tred thanks again. not worth it
 
hi no i didnt twr fabricated the inlet manifold on my xjr made by twr ,but on the xjs aj6 enginering fabricated their own manifolds with the kit exe,bit of a james bond........stuf regards boyan
 
ok i did bore out the air flow meter as i had intesion to do so on my jag xj40 twr and the achivment was waist of time first of all the fuel consumtion was 3 times as much, acseleration was not there no torque and engine was pinking over 4000 rpm regardles of the timing adjustment .hdi fun was right with his tred thanks again. not worth it

Well thanks for the feedback anyway boyan, it's good to know the end result.
I wonder whether it would be simpler to replace the air flow meter now and go back to stock OEM or would the whole thing benefit by a remap to take into account the enlarged hole in the AFM to try and achieve the result you were originally looking for :blink:

One for HDi I think! ;)
 
from my experience of a 20 year old ecu on my astra. It couldn't be mapped. But there where plenty of chips available for the necessary adjustments. With an exhaust, airfilter and chip it made 17bhp and similar torque over the standard figure
 
hi i think that the ecu has allready been remaped by twr 20 years ago at list thats what they claim ? but could it be remaped again .?
any way i went to the factory today and asked my mate chris to rebore the (valve throttle body this time by 5mm and make a new flap, buter fly) so we will see next week also i have intension of making my own 6 branch down pipe and geting rid of this cast iron manifolds...... found lockaly rolling road to folow what im spending my money on and awoiding being pulled ower by old bill on over 100mph like last time.....
 
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well all done 1 new valve throtle body rebored from 71mm to 75mm few photos posted, fantastic feels better all the way trough and polls beeter to,, sounds lovley i dont Know about fuel consumtion yet, but i think i shoul keep that to my self :)
HAPPY NEW YEAR TO YOU ALL FROM TORQUECARS
 
Does not matter about the fuel consumption as long as you are happy with YOUR car! Glad it is all sorted now ;)
 
since i,ve visited last time I've done some more work on my jag, as boring out air flow meter turned up to be bad idea, i increased the flow on throttle body by 5 mm made my own down pipes and u prated the fuel pressure regulator to 3 bar next think will be matching inlet manifold
i also posted some new photos of my achivment:)
 
removing all screens as noted on an old auto speed article is said to remove the most intake restriction, did this on my 01 turbo jetta-bora and most recently purchased 01 audi TT 225Q close to 300 now with chip exhaust and intake improvments
 

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