WIRING TO BOOST SENSOR (AKA INTAKE TEMPERATURE SENSOR)
10-18-2007, 06:08 PM
#1
WIRING TO BOOST SENSOR (AKA INTAKE TEMPERATURE SENSOR)
Am I correct that this is the intake air temperature sensor (it says "Boost sensor" on the top)?
Is this the connector that people stick a resistor in to fool it into thinking the air is cooler than it really is?
And, is the red wire hot; i.e., a 12v source?
Is this the connector that people stick a resistor in to fool it into thinking the air is cooler than it really is?
And, is the red wire hot; i.e., a 12v source?
10-18-2007, 06:17 PM
#3
Don't put a resistor in place of the IAT, that's just stupid. You'll run richer than the A32 already does, and (even though the FSM says IAT is used for nothing bit diagnostics) does the ECU even read the IAT in open loop?
In any case, instead of a resistor, just buy one of those high performance chips on eBay, add +20whp.
10-18-2007, 06:55 PM
#4
Don't put a resistor in place of the IAT, that's just stupid. You'll run richer than the A32 already does, and (even though the FSM says IAT is used for nothing bit diagnostics) does the ECU even read the IAT in open loop?
In any case, instead of a resistor, just buy one of those high performance chips on eBay, add +20whp.
10-18-2007, 06:56 PM
#5
Yes, of course it reads the IAT in open loop, or in any mode for that matter. open loop has nothing to do with the IAT sensor, it means that ecm is not taking into account 02 sensor voltages to adjust the air fuel mixture. intake air temperature is always being used and is NOT just for diagnostics. your timing tables (high and low) as well as many other factors are calculated (in part) from IAT readings.
10-18-2007, 07:03 PM
#6
10-18-2007, 07:04 PM
#7
Yes, there are IAT correction tables to add or subtract timing based on the intake air temperature. This is done at any given cylinder airmass (g/cyl) and at any given intake air temperature. For example, at lets say .52 g/cyl and the air intake temp is say 70*F, i can add 5degrees of timing to just that one spot if i wanted to.
10-18-2007, 07:06 PM
#9
Yes, there are IAT correction tables to add or subtract timing based on the intake air temperature. This is done at any given cylinder airmass (g/cyl) and at any given intake air temperature. For example, at lets say .52 g/cyl and the air intake temp is say 70*F, i can add 5degrees of timing to just that one spot if i wanted to.
10-18-2007, 07:13 PM
#10
Don't put a resistor in place of the IAT, that's just stupid. You'll run richer than the A32 already does, and (even though the FSM says IAT is used for nothing bit diagnostics) does the ECU even read the IAT in open loop?
In any case, instead of a resistor, just buy one of those high performance chips on eBay, add +20whp.
With all due respect, please read the following:
http://www.nissanforums.com/a32-1995...e-chip-bs.html
Why is it that every time I ask a question, someone assumes that I am going to do what it is I am asking???
10-18-2007, 07:17 PM
#11
Well, there is nothing attached to the snorkel in my car. Could it be part of the resinator box?
Also, now that you mentioned "drop resistor," what exactly is the mod that people do to boost tranny line pressure?
I'm just curious...
10-18-2007, 07:24 PM
#12
Oh...I forgot to ask you if the red wire coming out of it is 12v, and, if it is, then whether it is hot all the time or only when "ON."
As you may surmise, I'm trying to find a connector with a 12v wire that is only hot when the ignition is on, and that I can "back probe" as a 12v source. If I did not need a line to be off when the car is off, I'd go directly to the battery.
BTW, I'm looking for a connection in the vicinity of the air box and battery.
Thanks for your help.
10-18-2007, 07:25 PM
#13
Seems like you asked me a trick question there.
You asked it in a way that would lead one to believe that you were intending to do so.
As far as the DR mod, usually one would just hook up a NC microswitch to be activated by the throttle cable...thing, with that switch wired inline with one of the wires of the DR harness. When WOT, switch disconnects, TCM sees this lack of (proper) resistance and reverts to full line pressure shifts.
Will set a CEL (or, at the least did in mine and a few other A32's), but with the DR mod I'll spin on the 1-2 shift in the dry.
10-18-2007, 07:31 PM
#14
Oh...I forgot to ask you if the red wire coming out of it is 12v, and, if it is, then whether it is hot all the time or only when "ON."
As you may surmise, I'm trying to find a connector with a 12v wire that is only hot when the ignition is on, and that I can "back probe" as a 12v source. If I did not need a line to be off when the car is off, I'd go directly to the battery.
BTW, I'm looking for a connection in the vicinity of the air box and battery.
Thanks for your help.
As you may surmise, I'm trying to find a connector with a 12v wire that is only hot when the ignition is on, and that I can "back probe" as a 12v source. If I did not need a line to be off when the car is off, I'd go directly to the battery.
BTW, I'm looking for a connection in the vicinity of the air box and battery.
Thanks for your help.
FSM only states ignition On, so I'd assume from that that it's a switched feed.
Of course, easiest way to know is by taking a multimeter out there and checking. I would, but no boost sensor here...
EDIT: Oops, didn't notice it's only a 5V lead. What about the MAF wiring harness, isn't that a B+ switched?
EDIT2: You could always unmount the fusebox, undoubtedly there are several B+ switched leads in there...
Last edited by pmohr; 04-15-2008 at 04:36 PM.
10-18-2007, 08:09 PM
#15
According to the '97 FSM:
FSM only states ignition On, so I'd assume from that that it's a switched feed.
Of course, easiest way to know is by taking a multimeter out there and checking. I would, but no boost sensor here...
EDIT: Oops, didn't notice it's only a 5V lead. What about the MAF wiring harness, isn't that a B+ switched?
EDIT2: You could always unmount the fusebox, undoubtedly there are several B+ switched leads in there...
FSM only states ignition On, so I'd assume from that that it's a switched feed.
Of course, easiest way to know is by taking a multimeter out there and checking. I would, but no boost sensor here...
EDIT: Oops, didn't notice it's only a 5V lead. What about the MAF wiring harness, isn't that a B+ switched?
EDIT2: You could always unmount the fusebox, undoubtedly there are several B+ switched leads in there...
Thanks.
10-18-2007, 08:30 PM
#16
Yes, of course it reads the IAT in open loop, or in any mode for that matter. open loop has nothing to do with the IAT sensor, it means that ecm is not taking into account 02 sensor voltages to adjust the air fuel mixture. intake air temperature is always being used and is NOT just for diagnostics. your timing tables (high and low) as well as many other factors are calculated (in part) from IAT readings.
The IAT sensor is used only for diagnostic purposes as per the Nissan Factory Service Manual. Many ECUs do have different maps that take IAT into account, the 4th gen maxima does not.
10-18-2007, 08:39 PM
#17
http://forums.maxima.org/showpost.ph...5&postcount=10
http://forums.maxima.org/showpost.ph...8&postcount=11
Although, granted, neither of these two have unequivocal data, such as dynos, etc.
10-18-2007, 08:47 PM
#18
I am going have to disagree. Even though i dont have any definitive proof, but me and a few other people have noticed, that with the IAT sensor not in place, either just hanging there or not connected the car feels sluggish and throttle response doesnt seem the same as it use to. I believe mazzivart and NmexMax were the other 2 who seemed to have the same opinion.
Although i have no definitive proof, i may be able to try when i go dyno the car.
Although i have no definitive proof, i may be able to try when i go dyno the car.
10-18-2007, 09:07 PM
#19
I am going have to disagree. Even though i dont have any definitive proof, but me and a few other people have noticed, that with the IAT sensor not in place, either just hanging there or not connected the car feels sluggish and throttle response doesnt seem the same as it use to. I believe mazzivart and NmexMax were the other 2 who seemed to have the same opinion.
Although i have no definitive proof, i may be able to try when i go dyno the car.
Although i have no definitive proof, i may be able to try when i go dyno the car.
I had access to a Nissan Consult II. Hooked it up and watched ign timing along with a/f ratio while sensor was in a cup of ice (not touching the ice, just surrounded by cold air) and then placed in the engine bay near the intake manifold.
In the ice cup, temp got down to about 42F, IIRC it got above 140F in the engine bay. Like I said, I watched those two factors, at various RPMs. I saw no difference in a/f or ign timing between the two temps. I did not test this at WOT, but (correct me if I'm wrong) WOT is closed loop, and in this case the ECU wouldn't care about what it sees from monitoring this anyway.
IMHO, IAT sensor has 0 affect on performance.
10-18-2007, 10:49 PM
#21
Though the FSM does indeed say that, NmexMax and (I believe) nismology both have noticed differences depending on location of the IAT (in intake tract or dangling in the engine bay), leading one to believe that the ECU does react on the value in some way.
http://forums.maxima.org/showpost.ph...5&postcount=10
http://forums.maxima.org/showpost.ph...8&postcount=11
Although, granted, neither of these two have unequivocal data, such as dynos, etc.
http://forums.maxima.org/showpost.ph...5&postcount=10
http://forums.maxima.org/showpost.ph...8&postcount=11
Although, granted, neither of these two have unequivocal data, such as dynos, etc.
i'd be a bit more inclined to believe at least some sort of quantitative analysis such as mowgli seems to have done. if someone else has quantitative analysis indicating otherwise though, I'd like to see it.
wish this thread had come up prior to me going to the track last, I'd have done some testing such as IAT dangling in the engine bay itself, installed in it's proper location, and inside maybe a little bag of ice water or something, and seen if there was any difference in my trap speeds or something of that nature.
10-19-2007, 12:23 AM
#23
Back on this day.
http://forums.maxima.org/showthread.php?t=356346
I was running the stock resonator so i either had the temp sensor just hanging there or not installed at all.
I would say the temp sensor has no effect on performance.
http://forums.maxima.org/showthread.php?t=356346
I was running the stock resonator so i either had the temp sensor just hanging there or not installed at all.
I would say the temp sensor has no effect on performance.
10-19-2007, 08:33 AM
#24
I do have SOME proof. I don't think the IAT sensor matters....
I had access to a Nissan Consult II. Hooked it up and watched ign timing along with a/f ratio while sensor was in a cup of ice (not touching the ice, just surrounded by cold air) and then placed in the engine bay near the intake manifold.
In the ice cup, temp got down to about 42F, IIRC it got above 140F in the engine bay. Like I said, I watched those two factors, at various RPMs. I saw no difference in a/f or ign timing between the two temps. I did not test this at WOT, but (correct me if I'm wrong) WOT is closed loop, and in this case the ECU wouldn't care about what it sees from monitoring this anyway.
IMHO, IAT sensor has 0 affect on performance.
I had access to a Nissan Consult II. Hooked it up and watched ign timing along with a/f ratio while sensor was in a cup of ice (not touching the ice, just surrounded by cold air) and then placed in the engine bay near the intake manifold.
In the ice cup, temp got down to about 42F, IIRC it got above 140F in the engine bay. Like I said, I watched those two factors, at various RPMs. I saw no difference in a/f or ign timing between the two temps. I did not test this at WOT, but (correct me if I'm wrong) WOT is closed loop, and in this case the ECU wouldn't care about what it sees from monitoring this anyway.
IMHO, IAT sensor has 0 affect on performance.
10-19-2007, 08:42 AM
#25
So far, I've found nothing but hot lines running to the fuse box -- which makes sense since that is where you would expect a fuse to be; i.e, preventing a power overload from reaching a switch or relay.
I am still looking for a safe, 12v line, near the battery, that is only on when the engine is on, to which I can make a connection. By "safe," I mean a line that does not go to a sensor.
I am still looking for a safe, 12v line, near the battery, that is only on when the engine is on, to which I can make a connection. By "safe," I mean a line that does not go to a sensor.
10-19-2007, 09:41 AM
#26
But even if engine cold is different than engine hot, it still won't matter. Most people drive their cars at operating temp. right? and my tests were at operating temp. maybe I'm not thinking right...4 hrs of sleep FTL
10-19-2007, 11:40 AM
#27
Thats a good point and certainly a possibility. Next time I have a Consult I'll try to re-do the tests.
But even if engine cold is different than engine hot, it still won't matter. Most people drive their cars at operating temp. right? and my tests were at operating temp. maybe I'm not thinking right...4 hrs of sleep FTL
But even if engine cold is different than engine hot, it still won't matter. Most people drive their cars at operating temp. right? and my tests were at operating temp. maybe I'm not thinking right...4 hrs of sleep FTL
The manual says that the PCM uses the resistance values to "fine tune the fuel metering, " so that, in itself, would preclude any noticable change in performance.
My guess is that these two sensors do more to reduce emissions at colder temperatures than to increase performance.
10-19-2007, 12:33 PM
#30
Anyone willing to try it?
10-19-2007, 12:57 PM
#31
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Nope, catalyst efficiency codes are a completely different animal than the system readiness tests, they are for the most part based solely on the diference in switching frequency between the pre & post cat O2 sensors.
10-19-2007, 02:27 PM
#32
So, P0420 is actually a catalyst efficiency code and has nothing to do with either sensor?
10-19-2007, 03:58 PM
#33
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System Readiness Test: A term that applies to OBD-II compliant vehicles, It is a confirmation by the ECU that it has completed its self-diagnostics for certain sensors/emissions systems that aren't continuosly monitered. Several states (Crappachusetts being one of them) require all srt's to be ready in order to pass emissions testing. The following apply to fed/ca spec A32's (maybe not '99's though :shrug: ) Misfire Moniter, O2 Sensor Moniter (& heaters), Catalyst Function, Evap Emissisions, EGR system
The P0420 code isn't for one particular thing that's continuosly monitered by the ECU (take for example the MAF, if you disconect it, you will get an instant CEL) But the self test's that the ECU goes through uses the IAT reading to determine if the cat/s are working properly, disconnecting it won't cause the P0420 code, in fact it's possible it will cause the exact opposite, the ecu won't be able to complete its self-diagnostic's for a P0420 and all you will be left with is an IAT code even if you don't have a functioning cat. Confusing, I know. I'm still a little confused about how exactly the ecu uses the IAT to check the convertor function, my educated geuss is that the amount of oxygen is affected by the temperature of the incoming air and that it needs to know this information for more advance checking of the convertor functioning, by more advanced checking of the convertor I mean more than just switching frequency between the O2's, the Maxi is one of the more advanced cars that requires more advanced O2 sensor simulators, the kind that change the output after two minutes to simulate warm up and also change it randomly.
The P0420 code isn't for one particular thing that's continuosly monitered by the ECU (take for example the MAF, if you disconect it, you will get an instant CEL) But the self test's that the ECU goes through uses the IAT reading to determine if the cat/s are working properly, disconnecting it won't cause the P0420 code, in fact it's possible it will cause the exact opposite, the ecu won't be able to complete its self-diagnostic's for a P0420 and all you will be left with is an IAT code even if you don't have a functioning cat. Confusing, I know. I'm still a little confused about how exactly the ecu uses the IAT to check the convertor function, my educated geuss is that the amount of oxygen is affected by the temperature of the incoming air and that it needs to know this information for more advance checking of the convertor functioning, by more advanced checking of the convertor I mean more than just switching frequency between the O2's, the Maxi is one of the more advanced cars that requires more advanced O2 sensor simulators, the kind that change the output after two minutes to simulate warm up and also change it randomly.
Last edited by KRRZ350; 10-19-2007 at 04:02 PM. Reason: Gimme' a break, it's a long arse techincal post, I had some grandma errors!! Woohoo, off da drunk thread!
10-19-2007, 04:34 PM
#34
I am going have to disagree. Even though i dont have any definitive proof, but me and a few other people have noticed, that with the IAT sensor not in place, either just hanging there or not connected the car feels sluggish and throttle response doesnt seem the same as it use to. I believe mazzivart and NmexMax were the other 2 who seemed to have the same opinion.
Although i have no definitive proof, i may be able to try when i go dyno the car.
Although i have no definitive proof, i may be able to try when i go dyno the car.
On the camry the average IAT is in the mid 90s after warming to normal operating temp. With the max having a lower temp of high 80s to low 90s...that is just idling. After driving for about 30 mins in both cars the IAT rose to about 110 in the camry and was at about 95ish in the maxima. At that time the driving in both cars was crisp and throttle response was good. ignition adv was at normal areas with both....Not sure of the exact numbers of the top of my head...
After that I decided to take out the IAT sensor on both cars and let them sit in the engine bay. also both had been sitting for a couple hours. Both IATs were in the 80s again on startup. This time though both IAT temps rose to mid 110s after just idling to normal op temp.
After driving for 30 mins in both cars the camry's IAT was in the 150s and the maxima was in the mid 160s. Both cars felt very sluggish and seemed to lack power. timing was also multiple degrees lower then normal on both cars at average throttle all the way to WOT...on average the numbers were 3-5 degrees less on WOT runs.
Also testing was done on one day between 9am and 6pm....temps outside were about 77 at 9am and 82ish at 6pm. All this was done using my OBDII data logger....
In conclusion it seems that IAT does have some/slight effect on the ECU determining mapping and timing advancement.
If the IAT did not have any effect on performance then what would be the point of putting a CAI on the car....There would be no way the ECU would know that colder air was coming in thus the ECU would not chang fuel rates to get a proper A/F ratio. Unless I dont know if there are already set maps for WOT runs....
P.S. excuse any grammer mistakes...i wrote this at work in between calls.
10-19-2007, 04:38 PM
#35
Doesn't the MAF read air density, and adjust fuel injection accordingly?
10-19-2007, 04:59 PM
#36
After some searching it does....so well that doesnt matter...I totally forgot about that damn thing....
It still does seem that the IAT does have some sort of effect on ECU mapping.....
or it could be that if the IAT goes over some sort of range then the ECU may go into a limp mode...
It still does seem that the IAT does have some sort of effect on ECU mapping.....
or it could be that if the IAT goes over some sort of range then the ECU may go into a limp mode...
Last edited by bigpulve+; 10-19-2007 at 05:01 PM.
10-19-2007, 10:48 PM
#40
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I do have SOME proof. I don't think the IAT sensor matters....
I had access to a Nissan Consult II. Hooked it up and watched ign timing along with a/f ratio while sensor was in a cup of ice (not touching the ice, just surrounded by cold air) and then placed in the engine bay near the intake manifold.
In the ice cup, temp got down to about 42F, IIRC it got above 140F in the engine bay. Like I said, I watched those two factors, at various RPMs. I saw no difference in a/f or ign timing between the two temps. I did not test this at WOT, but (correct me if I'm wrong) WOT is closed loop, and in this case the ECU wouldn't care about what it sees from monitoring this anyway.
IMHO, IAT sensor has 0 affect on performance.
I had access to a Nissan Consult II. Hooked it up and watched ign timing along with a/f ratio while sensor was in a cup of ice (not touching the ice, just surrounded by cold air) and then placed in the engine bay near the intake manifold.
In the ice cup, temp got down to about 42F, IIRC it got above 140F in the engine bay. Like I said, I watched those two factors, at various RPMs. I saw no difference in a/f or ign timing between the two temps. I did not test this at WOT, but (correct me if I'm wrong) WOT is closed loop, and in this case the ECU wouldn't care about what it sees from monitoring this anyway.
IMHO, IAT sensor has 0 affect on performance.
