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 Post subject: Re: 06 CRD REPLACEMENT MAP SENSOR -CHEAP-
PostPosted: Wed Apr 18, 2018 1:23 pm 
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mrhemi wrote:
I contacted Keith regarding the pressure discrepancy I initially was concerned about, asking for an explanation of the control philosophy. Didn't get into the temperature question at the time. Regarding the pressure discrepancy he told me if it is not out enough to through a code the ECM is happy. I did not actually get into an explanation of the control philosophy.

It would be very nice to know how the temperature deviations between the two sensors in real numbers (data) impacts actual fuel curves and / or boost curves for the many users that are running the 845 sensors... :banghead:
If there is enough difference in efficiency and performance, even in warm climates, between the two to offset the huge cost difference, I am sure many of us would go back to the 437 sensor. :roll:

Found this:
Quote:
“T-MAP” sensor sensors allow the engine management system to accurately detect both manifold pressure and inlet air temperature within one sensor in order to make an accurate assessment of the weight or mass of air being inducted by the engine.

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 Post subject: Re: 06 CRD REPLACEMENT MAP SENSOR -CHEAP-
PostPosted: Wed Apr 18, 2018 6:30 pm 
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I've used both sensors and never noticed and change in MPG.
But of course, I live in Florida.

Personally, I don't think the difference in IAT calibration is much of a factor. Now matter how cold your climate is.
Here's why:
Once the engine is warmed up, the intake manifold gets warmed up too.
And the IAT sensor is on top of the intake manifold getting warmed up.
Turbo boost, even with the intercooler, will also naturally be warmer than ambient.
Therefore, IAT will always be higher than ambient.
Approximately 20-50F higher depending on operating conditions.

Years ago I wired in a variable resistor inline with the output of the IAT.
This allowed me to fool the ECM into thinking IAT was cooler than it actually was.
On hot summer day with the AC on my IAT would get up into the 140-150F range and I noticed that the engine felt a bit sluggish.
Adjusting the output so that the ECU only saw 90F seemed to bring back some power.
Also, if I adjusted the output to below 70F, I noticed a slight drop in rail pressure (as seen on my fuel rail pressure gauge).
This slight drop in pressure could mean that more fuel is being injected or it could mean nothing. Either way, I didn't notice much change in performance in that instance.

All the above of is subjective to my local climate, my driving style, the calibration of my right foot, and the calibration of my butt.

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 Post subject: Re: 06 CRD REPLACEMENT MAP SENSOR -CHEAP-
PostPosted: Wed Apr 18, 2018 8:43 pm 
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flash7210 wrote:
I've used both sensors and never noticed and change in MPG.
But of course, I live in Florida.

Personally, I don't think the difference in IAT calibration is much of a factor. Now matter how cold your climate is.
Here's why:
Once the engine is warmed up, the intake manifold gets warmed up too.
And the IAT sensor is on top of the intake manifold getting warmed up.
Turbo boost, even with the intercooler, will also naturally be warmer than ambient.
Therefore, IAT will always be higher than ambient.
Approximately 20-50F higher depending on operating conditions.

Years ago I wired in a variable resistor inline with the output of the IAT.
This allowed me to fool the ECM into thinking IAT was cooler than it actually was.
On hot summer day with the AC on my IAT would get up into the 140-150F range and I noticed that the engine felt a bit sluggish.
Adjusting the output so that the ECU only saw 90F seemed to bring back some power.
Also, if I adjusted the output to below 70F, I noticed a slight drop in rail pressure (as seen on my fuel rail pressure gauge).
This slight drop in pressure could mean that more fuel is being injected or it could mean nothing. Either way, I didn't notice much change in performance in that instance.

All the above of is subjective to my local climate, my driving style, the calibration of my right foot, and the calibration of my butt.

I agree, I am not sure we in the south are affected very much by difference.
But I am curious to see the actual data curves between the two for comparison!

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 Post subject: 06 CRD REPLACEMENT MAP SENSOR -CHEAP-
PostPosted: Thu Apr 19, 2018 12:59 am 
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So I did some checking and shortly after i purchased our used 05, in August of 08, we had a boost problem. Dealership replaced the MAP as part of the fix on warranty. I have cleaned it twice since then but never paid much attention to the part number. See photo for what the Jeep dealer installed in 2008. Image


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 Post subject: Re: 06 CRD REPLACEMENT MAP SENSOR -CHEAP-
PostPosted: Thu Apr 19, 2018 1:13 am 
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I found and ordered two MAP sensors at IDParts.com. $21.49ea plus $1.10ea for the o-ring. Plus priority mail shipping. They are Bosch units 55206797.


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2005 Liberty CRD Limited 94k
Stock
Intercooler hoses (64k)
Brake Calipers, Pads, Rotors&Flush(64k)
F/R Differential service(64k/93k)
Water Pump(75k)
Timing Belt(75k)
Cooling System Flush(75k)
Crank Shaft Sensor(80k)
Diesel Fuel Induction Service(93k)
Alignment(93k)
2006 Durango 74k
2008 Ram 2500 Laramie 6.7 Cummins 112k


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 Post subject: Re: 06 CRD REPLACEMENT MAP SENSOR -CHEAP-
PostPosted: Thu Apr 19, 2018 10:47 am 
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WWDiesel wrote:
flash7210 wrote:
I've used both sensors and never noticed and change in MPG.
But of course, I live in Florida.

Personally, I don't think the difference in IAT calibration is much of a factor. Now matter how cold your climate is.
Here's why:
Once the engine is warmed up, the intake manifold gets warmed up too.
And the IAT sensor is on top of the intake manifold getting warmed up.
Turbo boost, even with the intercooler, will also naturally be warmer than ambient.
Therefore, IAT will always be higher than ambient.
Approximately 20-50F higher depending on operating conditions.

Years ago I wired in a variable resistor inline with the output of the IAT.
This allowed me to fool the ECM into thinking IAT was cooler than it actually was.
On hot summer day with the AC on my IAT would get up into the 140-150F range and I noticed that the engine felt a bit sluggish.
Adjusting the output so that the ECU only saw 90F seemed to bring back some power.
Also, if I adjusted the output to below 70F, I noticed a slight drop in rail pressure (as seen on my fuel rail pressure gauge).
This slight drop in pressure could mean that more fuel is being injected or it could mean nothing. Either way, I didn't notice much change in performance in that instance.

All the above of is subjective to my local climate, my driving style, the calibration of my right foot, and the calibration of my butt.

I agree, I am not sure we in the south are affected very much by difference.
But I am curious to see the actual data curves between the two for comparison!



Well, when you are driving at 75 mph blowing -25F air through the CAC, yes the IAT is hotter than ambient, but still in the temperature range that could be impacted by the difference in the temperature curves. The observed results from fooling the ECU into seeing a lower temperature would appear to confirm that the ECU is over fueling when a false low temperature is experienced.

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 Post subject: Re: 06 CRD REPLACEMENT MAP SENSOR -CHEAP-
PostPosted: Thu Apr 19, 2018 2:05 pm 
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mrhemi wrote:
The observed results from fooling the ECU into seeing a lower temperature would appear to confirm that the ECU is over fueling when a false low temperature is experienced.


True. Any false IAT reading can mess up things and produce either poor or better performance and economy depending on the circumstances. Charge air density varies based on temperature, high is not good and that's the reason for having an intercooler. ECU may be lowering boost to allow intake air to cool down, or balance fuel delivery and injection timing in response to lower/higher intake air temps that affect cylinder pressure and combustion temps.

I switched back to the old 437 sensor for a couple of weeks and did not see any change in economy, but engine runs smoother when ambient temp is around 30C. Looking at IAT, it now ranges between 45-60C, previously it was reading between 55-80 in similar conditions with the 845 sensor.

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 Post subject: Re: 06 CRD REPLACEMENT MAP SENSOR -CHEAP-
PostPosted: Thu Apr 19, 2018 2:25 pm 
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mrhemi wrote:
Well, when you are driving at 75 mph blowing -25F air through the CAC, yes the IAT is hotter than ambient, but still in the temperature range that could be impacted by the difference in the temperature curves. The observed results from fooling the ECU into seeing a lower temperature would appear to confirm that the ECU is over fueling when a false low temperature is experienced.

So that begs the question: what are the temperature data curves for each sensor and how much is the differential between the two?
I was able to find the Bosch data sheet on the 437, but not one for the 845. IF anyone knows where a data sheet is located for the Bosch 3.0 Bar T-Map Sensor / 0 281 002 845, please share.

for the 437,
Image

Did find this for the temperature verses resistance curve on a 3 Bar Tmap sensor, not sure if it fits perfectly or not.
But this is what we need for a true comparison between the two sensors!

Image

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 Post subject: Re: 06 CRD REPLACEMENT MAP SENSOR -CHEAP-
PostPosted: Fri Apr 20, 2018 10:56 am 
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wetherellak wrote:
I found and ordered two MAP sensors at IDParts.com. $21.49ea plus $1.10ea for the o-ring. Plus priority mail shipping. They are Bosch units 55206797.


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I don't have much confidence in any of the sensors that are being bought. If you go on ebay you can buy literally dozens of the "437" or "845" sensors between $10 & $100. Most have the Bosch label on them and some are unbranded. They have the Bosch tag saying manufactured in Germany and some state OEM while others say OEM replacement. Some list Bosch as the manufacturer and others state aftermarket manufacturers. I do believe some are knockoffs obviously. All these manufacturers may have multiple sources producing their products nowadays. I have no idea how anyone knows on this item which is which. I bought 2 that were supposedly Bosch produced and will try one. They were cheaper than the "845" that everyone was trying from GM. we will see what happens. I have the original "437" in at 145K miles.


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 Post subject: Re: 06 CRD REPLACEMENT MAP SENSOR -CHEAP-
PostPosted: Sat Apr 21, 2018 2:50 am 
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My Export 2002 2.5L CRD does not have the power output of the 2.8L variable vane turbo models obviously.

Years ago on the recommendation of one 2.5 CRD owner I purchased an Italian made "Performance" adaptor that connected in series with the MAP sensor and the harness to try and get some better performance.

This was obviously a simple resistor meant to change the resistance of the MAP sensor so as to fool the ECM into supplying more fuel.
Power improvement was very good but fuel consumption took a steep dive obviously so I was in two minds as to keep it fitted or to remove it.

My decision was made for me when on a long trip I heard a loud "bang" up front and the Jeep ground to a halt.
I removed this adaptor at the roadside and drove back home with the original MAP sensor doing all the work....power down and better fuel consumption once again.

I think I am due for a new MAP sensor now years later...the early Export CRDs use a different Bosch MAP sensor to the later 2.8 L models....my sensor has two small Allen screws holding it in place as apposed to the newer one-screw models. The Dealer price for a replacement is exhorbitant so I intend contacting the local Bosch Dealership to try obtain one with the same Bosch number as the original! :wink:

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 Post subject: Re: 06 CRD REPLACEMENT MAP SENSOR -CHEAP-
PostPosted: Sat Apr 21, 2018 3:00 am 
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Yes, I’m not even sure if this is my issue so just ruling it out hopefully. I had two codes, a fuel leak (large), and under-boost. The vehicle would go into limp mode after about 10 or 15 minutes of driving. This is Alaska so at the time the ambient temps were in the 20° to 30°f range. The fuel leak was at the fuel heater. I had not previously replaced that. The under-boost issue with limp mode is very intermittent now but is still occurring on occasion. My wife is the main driver so I have not driven it much since the fuel heater replacement. She has mentioned the limp mode a couple times over the past two weeks,on her commute, but not so much that she has complained. I will replace the MAP and then start looking at harder stuff.
Previously have replaced, in addition to previous MAP sensor and EGR valve, an intercooler hose, water pump, timing belt, crankshaft sensor.
Without a garage or carport up here there is usually about 8 months out of the year where i can’t tear into it and I take it to my mechanic. They do their best but it is probably the only one they ever see. Thanks to Lost Jeeps I am able to point them in the right direction most of the time.



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2005 Liberty CRD Limited 94k
Stock
Intercooler hoses (64k)
Brake Calipers, Pads, Rotors&Flush(64k)
F/R Differential service(64k/93k)
Water Pump(75k)
Timing Belt(75k)
Cooling System Flush(75k)
Crank Shaft Sensor(80k)
Diesel Fuel Induction Service(93k)
Alignment(93k)
2006 Durango 74k
2008 Ram 2500 Laramie 6.7 Cummins 112k


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 Post subject: Re: 06 CRD REPLACEMENT MAP SENSOR -CHEAP-
PostPosted: Sat Apr 21, 2018 8:56 am 
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You stated: "Previously have replaced, in addition to previous MAP sensor and EGR valve"
If your EGR system is still in service you really need to block it off with a simply block off plate or install a Weeks Elbow Kit from SasquatchParts.com
It can cause all kinds of problems and dumping all that burnt carbon into the intake is very bad on the engine.

For more information, see this thread:> viewtopic.php?p=804565#p804565

Image

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Ironman Springs/Bilstein/Shocks
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SunCoast/Transgo
Carter Intank-pmp
2mic.Sec.Fuel Filter
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 Post subject: Re: 06 CRD REPLACEMENT MAP SENSOR -CHEAP-
PostPosted: Mon Apr 23, 2018 11:47 am 
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Found answer.


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