Intake Air Temp = Ambient Temp???

[jspaeth]

I have a PowerFC D-Jetro, and I have my IAT sensor mounted into the cold pipe, just in front of the throttle body.


Now, the sensor nearly ALWAYS reads the same temperature.

That is, I start the car, and it essentially reads the same as the initial water temperature, which is the same as the outdoor air temperature.


However, even when I am under full load, I DO NOT see the temperature change, or if I do, it is barely at all.


Is this strange, or is my intercooler just supremely badass and cooling the charged air ALL THE WAY down to ambient temperature.

FYI I am running the beef-dog Greddy intercooler....I forget which one it is, but whatever the most expensive one you could get like 3 years ago for an S14...I think it is RSPL or something.


Is my intercooler amazing or is the sensor not registering air that may be heated up due to the turbo?

Post up and let me know if what you guys see in your cars as well.

[Monooxide]

I had the same issue with my Electromotive ECU at first. I unplugged it and fiddled with the wiring, it seemed like the wire wasnt seated in the plug.

IAT sensors will default to a standard air temp rather than super cold or hot when they receive a bad/no signal from the thermister. Check your wiring.

[jspaeth]

I had the same issue with my Electromotive ECU at first. I unplugged it and fiddled with the wiring, it seemed like the wire wasnt seated in the plug.

IAT sensors will default to a standard air temp rather than super cold or hot when they receive a bad/no signal from the thermister. Check your wiring.


No....it does respond, just not quickly enough. If I let the car sit there and idle, then eventually, heat builds up under the hood and the charge air temperature goes up by a few degrees.

I was reading this on another (BMW) forum where people were seeing the same thing....

Basically they took a blow dryer to the sensor, and it took almost 5-10 seconds for the sensor to register a large change.

I am wondering how much this effects the tune....

I think for any full throttle pull, if the temperature is consistently going up in the same manner, then this essentially is "hidden" in the tune....i.e. even though you aren't "registering" the increase in temeperature correctly, maybe you are taking into account indirectly by dialing in the right timing and fuel.


Perhaps with a unit like the PFC, the IAT sensor is NOT intended to be used as an "instantaneous" temperature detection tool to affect timing and fuel, but rather as a more "global" tool to detect the outside air temperature as a way to globally trim the fuel/timing maps due to changes in the air's initial (ambient) temperature....


Just some thoughts....maybe Steve or JohnGriff will chime in on this.


EDIT:

Also, in response to your post, yes this does happen.....I recently had a loose ground wire, and it was reading a default value of -33*C hahahaha

[steve shadows]

I have a PowerFC D-Jetro, and I have my IAT sensor mounted into the cold pipe, just in front of the throttle body.


Now, the sensor nearly ALWAYS reads the same temperature.

That is, I start the car, and it essentially reads the same as the initial water temperature, which is the same as the outdoor air temperature.


However, even when I am under full load, I DO NOT see the temperature change, or if I do, it is barely at all.


Is this strange, or is my intercooler just supremely badass and cooling the charged air ALL THE WAY down to ambient temperature.

FYI I am running the beef-dog Greddy intercooler....I forget which one it is, but whatever the most expensive one you could get like 3 years ago for an S14...I think it is RSPL or something.


Is my intercooler amazing or is the sensor not registering air that may be heated up due to the turbo?

Post up and let me know if what you guys see in your cars as well.


The ideal placement for the IAT is directly infront of the throttle body on the cold pipe.

Now you need to make sure that the Sensor is threaded deeply into the pipe so that it is directly in the flow path of the air coming into the inlet of the throttle body.

You will also want to double check the wiring as other have mentioned.

You shouldnt see a huge movement around in air temps. If you have a good intercooler and piping then you should see between 70 degrees or so at idle and low loads and about 85-95 degrees at the most when you are really flying and have heated up the motor after several hard runs or some road racing. This is slighlty dependent on your local's weather and ambient temps but this is general change in temps is only going to be 20 degrees or so here and there. It shouldnt be too dramatic

[jspaeth]

Steve the wiring is correct, because the temperature DOES correctly read the ambient air temperature.....and yes, I have it so the sensor literally protrudes almost to the middle of the cold pipe, when looked at from the end of the pipe.

But like others have seen (on BMW forums), this style sensor (PFC calls for a RX-7 sensor I believe) do NOT seem to respond to changes in temperature unless they are exposed to it for like 5-10 seconds.

So, unless you are holding the pedal down for like 20 seconds and under boost the whole time, it seems that the IAT sensor will not really record any change....

Fortunately, I have a really good intercooler, so I am not too worried about my charge air being too hot, but I was just interested about this from a tuning standpoint, that's all

[djcobra]

I always thought the ideal placement for the IAT sensor was directly in the Intake Manifold as per HKS; that's where I have mine plugged in for my the HKS V-Pro.

Steve.

[jspaeth]

I always thought the ideal placement for the IAT sensor was directly in the Intake Manifold as per HKS; that's where I have mine plugged in for my the HKS V-Pro.

Steve.


Not saying this is a bad idea, but cold pipe seems really good....bc the cold pipe itself doesn't get as warm as the intake manifold, less likely for that heat to be transferred through to the sensor.

[Monooxide]

I have mine installed in the intake manifold itself, however upstream of the throttle body can be slightly better in the fact that you're not getting heat soak from the conducted heat in the manifold itself.

My sensor albeit different changes very quickly to IAT changes.

[jspaeth]

I have mine installed in the intake manifold itself, however upstream of the throttle body can be slightly better in the fact that you're not getting heat soak from the conducted heat in the manifold itself.

My sensor albeit different changes very quickly to IAT changes.


Which sensor are you using? I am using the Mazda sensor used in RX-7s....this is what is recommended in the PFC manual.


I just wanted to see what was going on. Like I said before, if the turbo warms up the air "roughly" the same way depending on RPM and boost, then this is something that is just "hidden" in the tune....i.e. it's been taken care of by properly tuning timing and fuel, without explicitly knowing upfront how much hotter the air has gotten.

[juggernaut1]

The sensor needs to react quickly to changes in intake temps - for this reason open element sensors are used - for example Bosch part number
0 280 130 085 or 0 280 130 039.

Having the sensor mounted in the intake pipe just before the throttle is generally recommended by most aftermarket ECU manufacturers as it negates the effect of heatsoak in the intake manifold which is not necessarily representative of the air entering the combustion chamber.

[Monooxide]

Which sensor are you using? I am using the Mazda sensor used in RX-7s....this is what is recommended in the PFC manual.

I am using the "305-71220" which is a GM Style MAT sensor.

[jspaeth]

I am using the "305-71220" which is a GM Style MAT sensor.


Yep, that's what I read on that BMW forum, a lot of people ar running those GM sensors....

But do you guys get my point....?

I feel like if the turbo spools nearly the same way under full load pulls, then the temperature of the intake air should increase above ambient in a similar fashion each time....

Thus, this is being "indirectly" taken into account when you adjust AFRs and timing appropriately.

Perhaps I am wrong though.....

I just feel like for the PowerFC, with the way that Air Temperature Correction works (it applies a fuel correction to the WHOLE map), the IAT sensor (in the context of a system like PFC) is meant to be used to trim fuel based upon changes in ambient conditions...

bc you cannot change fuel due to changes in IAT on a cell by cell basis.

I'd like to hear more discussion on this, as I am sure that my opinion/thoughts are not necessarily correct.

[reactor]

The stock RX7 IAT sensor is useless, which is the reason why a lot of RX7 guys (including me) have changed out those worthless sensors with a fast reacting sensor instead. Go over to the 3rd gen section on rx7club and there is a whole thread on it.

[jspaeth]

Okay thaks for the help....just wondering if that "faster reacting sensor" would just wok the same....like if I could use it with Power FC..

-Same voltage versus temperature, but just physically reacts faster? I don't think PFC would let you calibrate the IAT sensor if Voltage vs. T was different.

[steve shadows]

Yep, that's what I read on that BMW forum, a lot of people ar running those GM sensors....

But do you guys get my point....?

I feel like if the turbo spools nearly the same way under full load pulls, then the temperature of the intake air should increase above ambient in a similar fashion each time....

Thus, this is being "indirectly" taken into account when you adjust AFRs and timing appropriately.

Perhaps I am wrong though.....

I just feel like for the PowerFC, with the way that Air Temperature Correction works (it applies a fuel correction to the WHOLE map), the IAT sensor (in the context of a system like PFC) is meant to be used to trim fuel based upon changes in ambient conditions...

bc you cannot change fuel due to changes in IAT on a cell by cell basis.

I'd like to hear more discussion on this, as I am sure that my opinion/thoughts are not necessarily correct.

What is your point though?

Yes it is used to trim fuel based on ambient temps, like fuel should be different for a cold brisk winter night, vs. a warmer fall day etc.

You cannot change cell by cell Air temp, but why would you want to? It would be an infinite process. Unless this was a formula 1 car you really wouldnt see any gain from this. Now what many other EMS have is a map that you can interpolate and change correction based on RPM and Load, and temp which is in effect almost the same as cell by cell,but a range over range correction. It works great and I used to use this function all the time with Haltech EMS.

Also what is your point about the car pulling under load?

You arent going to see much of a power change, by using the BUTT dyno, it will be very hard to tell any difference. The fuel correction for air temp is typically used to insure security for your pistons and rods, especially wiht the crap nature of fuel at the pump these days. you want to have good solid and wet afrs under these circumstances

Also a common misconception is that Air Temps will rapidly change AFRs and effect power. This is not true, unless you are seeing EXTREME temp changes. If you are cruising at 80 degrees temp at your AIT and you hit the gas and start doing some pulls on the fwy and your temps crawl up to 95 degrees F, your AFRs are not going to change a whole lot, and your engines ability to make power is not going to be shocked. However if you have a fuel map that is really close to perfect and is on the edge of being the MBT and leanest mixture you can safely run with your particular fuel type then the correction map comes in handy for what it needs to be there for. Now you can tell the computer that at xyz temps you want xyz fuel input trim over the whole range of cells to counter for the temp change in order to keep the car safe and running cool (cylinder wise) with the right mixture.

[jspaeth]

What is your point though?


My point is how much would the "faster-reacting" (i.e. able to detect a change in IAT due to higher temps when you are under full boost for example) sensor help with a unit like the Power FC?


It seems like you can use the IAT fuel correction to correct for changes in the density of the ambient air, relative to the temperature at which you had the car on the dyno when you built the map.

So let's say you then put in some values, which basically trim fuel on the whole map.



Now, let's say you are back under the "initial" conditions you tuned the car at. You do a hard pull, and notice that the IAT go up 30 degrees over the ambient temeperature.

Now what? Even though you've detected that the compression of the air has increased it's temperature, you can't make a change to that part (high boost, or high load areas that you sweep through during a full throttle pull) of the map without changing all the other cells.


Basically, I am saying that the PFC doesn't allow you to SEPARATELY trim fuel based upon increased IAT due to ambient temperature or increases in IAT due to being under load.


In this case, I am saying I would imagine it's best to just use the IAT correction functionality as a means for trimming the whole map due to change's in ambient temperature (and thus density)

....and then, if the temps of the air go up during a strong pull under a lot of load, you take care of this directly by tuning those cells on the map, not by messing with the IAT correction.


I must be crazy, because I think I am not getting this across well (I'm not saying I'm right, I am just not sure I am conveying my reasoning well)



EDIT: Also, Steve, I am not saying this for gaining power reasons, more for efficiency/safeness of tune reasons.