$24 4.0l ccv breather “upgrade”

[maxbraketorque]

Having the IAT sensor off the manifold should make it read cooler and cause the engine to run richer, so at least its in a safe direction away from factory mapping. If your XJ is OBD-II capable, it might be worthwhile to do some OBD-II logging to see where the fuel trims are going.

 

[Woodswanderer]

Having the IAT sensor off the manifold should make it read cooler and cause the engine to run richer, so at least its in a safe direction away from factory mapping. If your XJ is OBD-II capable, it might be worthwhile to do some OBD-II logging to see where the fuel trims are going.

99 sport, obdII for sure

Thats kind of where i was going with the mod. In theory it will cause richer, yes. PCM should adjust over time though to compensate for it. Like it did with my 4 hole injectors after about 500 miles (was nice to see 23.5mpg highway at 70mph at first lol)

Without a proper remap/tuning of the PCM, im really not taking advantage of any gains from the things i’ve done. Havent dug that far in yet to see if its possible to remap or chip the 99


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[RCP Phx]

9 In theory it will cause richer, yes. PCM should adjust over time though to compensate for it.

The PCM can not compensate for what "it thinks" is correct but in reality is being tricked!

 

[maxbraketorque]

It can be remapped, but I'm not sure I see the point. This does remind me thought that besides running richer, the ECU will add more timing when it sees a cooler IAT. Take your pick on whether you think that's good or bad.

 

[Woodswanderer]

The PCM can not compensate for what "it thinks" is correct but in reality is being tricked!

Point taken. But by moving it back into the intake tube, closer to the cold air its giving the pcm a more accurate reading rather than tricking it. The pcm is always going to adjust to maintain stoichmetric regardless what parameters come in

Im curious now and want to hook up a data logger between the two sensors. Tbh i dont expect to see much difference in intake air temp unless under WOT conditions where the engine is sucking in as much air as possible (and arguably the most efficient use of a cone filter setup but thats for another discussion )

If i wanted to, i could set up a relay and switch between both sensors so i can toggle between them.

Realistically? If theres no difference between the two sensors when i data log, i’ll likely remove the new sensor from the intake tube and replace the old one in the manifold with it...cap off the hole in the tube.


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[maxbraketorque]

The bigger difference will likely be at low throttle position where the air flow rate is lower. This gives the intake manifold more time to heat up the air.

 

[Woodswanderer]

The bigger difference will likely be at low throttle position where the air flow rate is lower. This gives the intake manifold more time to heat up the air.

I got ya.

More or less moving the sensor to what i see as a more traditional location i suppose. Theres tons of articles online about this “mod”. Most agree its snake oil, the pcm will compensate. I cant find any dyno info before/after for empirical evidence and im too cheap to pay for an hour on a dyno


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[Woodswanderer]

Side trail too, im pretty sure this isnt the only reference sensor used to calculate fuel trims. If its set up as i suspect, the pcm also takes the coolant temp sensor data to adjust too


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[maxbraketorque]

Side trail too, im pretty sure this isnt the only reference sensor used to calculate fuel trims. If its set up as i suspect, the pcm also takes the coolant temp sensor data to adjust too


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Yeah, coolant temp as well.

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[Woodswanderer]

Now i really need to datalog between them excuses to spend money on a scan tool


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[RCP Phx]

The original mapping was based on their design so that's what calibrated for.

 

[RCP Phx]

Btw the way, if you read my thread you see that I dropped my intake temps for real so that the PCM sees them as correct!

 

[Woodswanderer]

Btw the way, if you read my thread you see that I dropped my intake temps for real so that the PCM sees them as correct!

I’ll have to spend time reading thru from the beginning. I kinda skimmed quick, havent had the chance to get back to it.

This wasnt really so much about lowering intake temps. Its more a just because im curious thing. Im certainly not the first person to do this (pretty sure i saw it on cherokee forums first ). Datalog will show if its really worthwhile. Mpg hasnt changed around town but its still too early to tell


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[Woodswanderer]

38*f this morning. WOT from a stop light produced a stumble/power cut.

Swapped sensor back to factory location, will update with results


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[Woodswanderer]

38*f this morning. WOT from a stop light produced a stumble/power cut.

Swapped sensor back to factory location, will update with results


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Unrelated to the sensor. My fuel pump decided this morning to start death throws. Gauge has always been weird since i bought it, so no surprise. Already had a new pump on hand waiting to go in


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