temp sensor relocation

[jons999]

I have heard that if you move the intake air temp sensor from it's normal spot (usually on the intake manifold) to a cooler location like the air cleaner, it will give you more power and better throttle response. Apparently because the air in the air cleaner is 40-50 degrees cooler than in the intake the engine will think it is running cold all the time and inject more fuel and advance the timing. Does this really work? Are there any bad effects from it? Gas milage is no concern.

-Jon

 

[GregLocock]

Does this really work?

Probably not in the way described, since your EEC uses engine coolant temperature to decide if the engine is hot, not air intake temp. Given that your source has got even this elementary fact wrong, how much would you trust them?


Are there any bad effects from it?

Well you are right, it will mess up the mass air flow rate calculation, so when you run open loop it will chuck more fuel in. This might burn your cat out eventually, depending on the duty cycle.

I'm not too sure whether it will increase or reduce the power, I think most people here who have tested engines on dynos would claim you need to be slightly on the lean side of stoichometric for maximum power.

Have a think about it. When we calibrate an engine we want to maximise the power output within the other constraints of the engine. If just chucking a bit more fuel in at WOT helped with no downside, don't you think we'd do it? To my shame we actually chuck extra fuel in anyway just to keep the exhaust valve and the cat cool - adding more really won't burn any more oxygen, so it won't create any more power. Cheers

Greg Locock

 

[Chumley]

jons999: The intake air temperature sensor isn't the only sensor input to the ECU. As Greg says about open loop, you may run slightly richer, but in closed loop the O2 sensor will see the extra fuel and tell the ECU to lean out the mixture essentially canceling what you are trying to do. It
does that to prevent the premature failure of the catalytic converter.

It may then turn on the MIL (malfunction indicator light) if the sensors appear to be reading out of the normal range for the air/fuel/ignition map that the ECU is currently using. Or, depending on the sophistication of the ECU, it may punish you for listening to your uninformed friend by putting you in limp home mode since it is unable to administer dope slaps. Some vehicles require a trip to the dealer to reset the mil codes which they may charge you for especially if they see your relocated sensor. On the other hand, some technicians might refuse to work on your vehicle as soon as they see that you have modified your emission control system. Altering emission control systems is taken very seriously by the EPA in areas considered to be environmentally sensitive.

See this link for some emission control theory:

http://www.smogsite.com/5gastheory.html

Chumley

 

[jons999]

I'm not worried about the MIL/emmissions stuff since i am a tech. at a dealership so i have access to a scanner. It seems though that the general consensus here is that it doesn't work.