Member Since: 11 Mar 2009
Location: Somerset
Posts: 3551
After cleaning my map sensor 18 days ago the MPG have slowly gone up and response is much better now,my MPG has been poor lately but put it down to winter and the fbh running and short trips but as the weather warmed up was hoping to see an improvement but didn't and for a manual low 22s is so a couple of pics first one i took was a couple of days after cleaning the map sensor 2nd about 12 days and the last one today
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Click image to enlarge
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I'm thinking that just because the hole is not completely blocked this does not mean that there isn't any gunk inside the housing, the hole on my sensor wasn't completely blocked but I still got a lot of crap out of it by spraying in WD40 to soften it and rolloing the corners of kitchen towel and gently teaseing out the gunk. My MPG has seen a major benefit, as some have said, pretty much back to how it was new. I'm not as good as I once was........but I'm as good once as I ever was.
26th Apr 2011 10:41 am
jsamuelson
Member Since: 07 Feb 2011
Location: Cornwall
Posts: 214
I would be very surprised, from an engineering and technical point of view, if buildup like this around a differential pressure sensor opening tube did not affect the readouts.
Caveat: I am not an engineer.
But, if you look at, for example pitot tubes on an aircraft they are very precisely engineered tubes and if there is any obstruction or say, ice buildup, on the tubes - then the aircraft doesn't fly because there is a danger of spurious and incorrect readouts. Ask Air France about this...
I am sure that Hitachi (and Airbus for the example above) engineered the opening tube to be a certain length for a reason…and that it is calibrated based on the readings from a given length of tube using a lab-clean sensor.
If a tube wasn't required, just a hole, then no aircraft designer in the world would stick an unnecessary obstruction out into airflow. So I'm sure the tube length is quite critical.
If crud around the tube totally blocks it, then obviously the sensor is non-functional.
If crud around the tube effectively extends the length of the tube without actually blocking it, I would be reasonably confident of reduced accuracy in the readings.
I think that people who are seeing a decent improvement even though the sensor was not totally blocked were seeing bad readings from the sensor due to slightly restricted airflow to the actual sensor itself…which presumably was causing the engine management to adjust all sorts of things, such as fuel mixture and throttle response?
I am sure cleverer engineer-types will be along shortly…!
Last edited by jsamuelson on 26th Apr 2011 11:02 am. Edited 1 time in total
26th Apr 2011 10:52 am
C6REW
Member Since: 10 Mar 2007
Location: Devizes, Wiltshire
Posts: 576
jsamuelson wrote:
I would be very surprised, from an engineering and technical point of view, if buildup like this around a differential pressure sensor opening tube did not affect the readouts.
Caveat: I am not an engineer.
But, if you look at, for example pitot tubes on an aircraft they are very precisely engineered tubes and if there is any obstruction or say, ice buildup, on the tubes - then the aircraft doesn't fly because there is a danger of spurious and incorrect readouts. Ask Air France about this...
I am sure that Hitachi (and Airbus for the example above) engineered the opening tube to be a certain length for a reason…and that it is calibrated based on the readings from a given length of tube using a lab-clean sensor.
If a tube wasn't required, just a hole, then no aircraft designer in the world would stick an unnecessary obstruction out into airflow. So I'm sure the tube length is quite critical.
If crud around the tube totally blocks it, then obviously the sensor is non-functional.
If crud around the tube effectively extends the length of the tube without actually blocking it, I would be reasonably confident of reduced accuracy in the readings.
I think that people who are seeing a decent improvement even though the sensor was not totally blocked were seeing bad readings from the sensor due to slightly restricted airflow to the actual sensor itself…which presumably was causing the engine to adjust all sorts of things, such as fuel mixture and throttle response?
I am sure cleverer engineer-types will be along shortly…!
Whilst I am an electronics engineer my company is involved with pressure sensors.
As I understand it from reading this thread, this product measure pressure. If the hole is blocked or restricted then it goes without saying that the pressure reading is going to be incorrect with whatever results that will provide to the on board computing systems.
Best regards
Chris
26th Apr 2011 11:01 am
jsamuelson
Member Since: 07 Feb 2011
Location: Cornwall
Posts: 214
Thanks Chris! Do your (fluid) pressure sensors all have a tube or other opening?
26th Apr 2011 11:04 am
Dan_NL
Member Since: 19 Sep 2010
Location: world
Posts: 1213
jsamuelson, you might have a point. The length of the tube, turbulence and all may affect the measurement and so fuel consumption. But how accurate are the MAP-sensors to start with? In some pics of members who cleaned the sensor, loads of gunk were visible in the opening in the background. May be an idea to clean the whole air-intake out... So how about "tuning" the MAP-sensor ? A small tube fixed in the opening makes it longer, [take care it doesn't fall out while driving...]. Drilling a small transverse whole makes it shorter... But also modifying the signal opens up new horizons.
26th Apr 2011 11:12 am
jsamuelson
Member Since: 07 Feb 2011
Location: Cornwall
Posts: 214
In my Googling I have seen accuracies of +/- 1-2% for automotive MAP sensors - so pretty accurate. The next question is what are the thresholds for adjustments, what the error sensitivity is, and what adjustments does the ECU actually make based on this data?
Member Since: 10 Mar 2007
Location: Devizes, Wiltshire
Posts: 576
jsamuelson wrote:
Thanks Chris! Do your (fluid) pressure sensors all have a tube or other opening?
All do have an opening or 'orifice' and diaphragm. Because they are fluid the length of the tube is almost irrelevant for pressure. However, when you look at pressure of air, this will always be a different matter. Build up of, in this case oil/crud could effect the turbulence which in turn the relative pressure.
As Dan suggests it will be down to how accurate the measurement is for a normal sensor. If the tolerances are in the fractions of a percent then the build up will almost certainly be changing the readings dramatically.
Best regards
Chris
26th Apr 2011 11:30 am
jsamuelson
Member Since: 07 Feb 2011
Location: Cornwall
Posts: 214
So Chris…as an electronics engineer what do you reckon to the adjustable MAP in the link above?
26th Apr 2011 11:32 am
DSL Keeper of the wheelie bin
Member Since: 11 May 2006
Location: Off again! :-)
Posts: 72911
I'll let you lot play around with modifying the MAP sensor, I'm just happy that it's working.
26th Apr 2011 11:38 am
jsamuelson
Member Since: 07 Feb 2011
Location: Cornwall
Posts: 214
Don't you want to twiddle a knob and get moah powah from your Disco?
26th Apr 2011 11:40 am
DSL Keeper of the wheelie bin
Member Since: 11 May 2006
Location: Off again! :-)
Posts: 72911
Doing that on Thursday, it's getting it's remap back. 8)
26th Apr 2011 11:41 am
C6REW
Member Since: 10 Mar 2007
Location: Devizes, Wiltshire
Posts: 576
jsamuelson wrote:
So Chris…as an electronics engineer what do you reckon to the adjustable MAP in the link above?
Without looking at the way the car processes the information in depth I could not comment. However, if the Jeep boys have tested this and it works then I am sure it will do the job.
Of course it depends on how much gain you get as to whether it is worth the effort of course.
Best regards
Chris
26th Apr 2011 11:47 am
Dan_NL
Member Since: 19 Sep 2010
Location: world
Posts: 1213
OK, bottom line : clean it as often as checking tire-pressure, oil, etc... At least every month or so...
Just a thought : after cleaning spraying it with siliconoil... should keep it clean for a while ?!
26th Apr 2011 11:50 am
discoteca
Member Since: 08 Mar 2010
Location: Warwickshire
Posts: 1477
80k miles egrs blanked at 65k. Very gunked up, the hole was only just visible. Was so eager to clean it up forgot to take any pics.
Cleaned with brake cleaner spray and kitchen roll on the outside, repeatedly sprayed brake cleaner down the hole and tapped gently onto paper until the fluid exiting the hole was free from crud (about 5 cycles).
Seems to be a bit more perky than before when pulling at low revs and possibly a bit more eager to rev higher, although nothing overly significant. Too early to tell on the mpg, particularly as my mpg can be anything from 22 to 28 - very much dependent on what sort of driving I'm doing in a given week.
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and response is much better now,my MPG has been poor lately but put it down to winter and the fbh running and short trips but as the weather warmed up was hoping to see an improvement but didn't and for a manual low 22s is 
so a couple of pics first one i took was a couple of days after cleaning the map sensor 2nd about 12 days and the last one today 
