what does the IAT sensor affect exactly? I had a fault with mine recently and it felt like the car operated as normal, and after fixing the problem, it still felt the same
I wonder if maybe i have it set up wrong and thats why my idle is always kinda low?
IAT Sensor
Re: IAT Sensor
air temperature sensor in the intake manifold.
lower temperature, higher idle RPM.
high temperature, lower idle RPM.
lower temperature, higher idle RPM.
high temperature, lower idle RPM.
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Dodo Bizar
- Site Admin
- Posts: 2009
- Joined: Mon Jun 22, 2009 10:36 pm
Re: IAT Sensor
Air temperature is correct.
High and low rpm not, these are controlled by the coolant temperature (ECT).
The air temperature is a small correction for the amount of fuel that needs to go n the engine. On hot days the air is expanded more than on cold days. Meaning less molecules of oxygen enter the combustion chamber under the same ambient pressure conditions. Therefore a little less fuel needs to be injected.
The amount of fuel is approximately coupled to the reversed temperature as measured in Kelvin. Which means absolute zero point which is 273 below 0 deg Celcius. So roughly most people drive in conditions of 270 K to 310 K... giving only a relatively small band of differences in the amount of fuel injected due to the IAT sensor. With a broken sensor the ECU will assume a safe (cold) value and might enrich the engine a bit too much probably, or injection timing might be retarded to prevent detonation in most cases. Not sure which one is picked or a combi goes on while in CEL.
So yes, broken IAT can harm performance, but not really much. On top of that while driving in closed loop mode, the lambda sensor controls the amount of fuel as well, on a slightly slow pace, but it would correct for small temperature errors indirectly pretty easy.
Hope you can get your head around this info...
High and low rpm not, these are controlled by the coolant temperature (ECT).
The air temperature is a small correction for the amount of fuel that needs to go n the engine. On hot days the air is expanded more than on cold days. Meaning less molecules of oxygen enter the combustion chamber under the same ambient pressure conditions. Therefore a little less fuel needs to be injected.
The amount of fuel is approximately coupled to the reversed temperature as measured in Kelvin. Which means absolute zero point which is 273 below 0 deg Celcius. So roughly most people drive in conditions of 270 K to 310 K... giving only a relatively small band of differences in the amount of fuel injected due to the IAT sensor. With a broken sensor the ECU will assume a safe (cold) value and might enrich the engine a bit too much probably, or injection timing might be retarded to prevent detonation in most cases. Not sure which one is picked or a combi goes on while in CEL.
So yes, broken IAT can harm performance, but not really much. On top of that while driving in closed loop mode, the lambda sensor controls the amount of fuel as well, on a slightly slow pace, but it would correct for small temperature errors indirectly pretty easy.
Hope you can get your head around this info...
Re: IAT Sensor
Hmm, I had done the coolant by-pass thing, negating the hoses that go into the RACV and just having it loop back into itself, will this affect the ECT and therefore idle?
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Dodo Bizar
- Site Admin
- Posts: 2009
- Joined: Mon Jun 22, 2009 10:36 pm
Re: IAT Sensor
No, it will not affect ECT.
And it should not affect RACV, unless the back-up system is used. Back-up system uses the actual heat of the coolant temp. Normal system is the electronic control by the ECU. Should the ECU connection fail, the coolant temp should do its work. Bypassing the coolant may lead to failure of that back-up system, but I never have seen the need for the back-up system to actually work before.
And it should not affect RACV, unless the back-up system is used. Back-up system uses the actual heat of the coolant temp. Normal system is the electronic control by the ECU. Should the ECU connection fail, the coolant temp should do its work. Bypassing the coolant may lead to failure of that back-up system, but I never have seen the need for the back-up system to actually work before.