Husemoller

I broke one of the little pins on my air intake temp sender on the elbow on the tb.

Can i still use the car without that hooked up? Also is the n/a and t2 senders the same? I have one on my n/a car at my dads shop i can go take off.

calio64

yes its the same, and without that hooked up the car will run but rich, get that hooked up asap

Icemark

That sensor is only for warm/hot start anyway... the real air temp sensor is in the AFM.

The throttle body/dynamic chamber air temp sensor won't really affect anything except for telling the ECU to limit the fuel when starting warm. Once the car is running though it does nothing.

HAILERS

The ECU will default to a set value if that sensor is disconnected. See the fsm for the value. It's in the Fuel Section.

NZConvertible

That might be the case on NA's (although I doubt it), but it's certainly not on turbos. It's a very important sensor, as the intake air temp can vary so much depending on boost pressure, intercooler core temp,, ambient air temp through th intercooler etc. Both fuelling and ignition timing are adjusted according to intake temp. The AFM air temp sensor is only used to convert the AFM's air volume reading into a mass flow reading.

WAYNE88N/A

Logically, since it's not just a simple switch that actuates at 176*F, but a thermister (with a hell of a temp range at that), one would think that the ECU is constantly using the input...

SureShot

Cool - Is that true for turbo's also?

Icemark

I think you are confusing the operation for this thermosistor.. This is the dynamic chamber temp sender that is a simple thermosistor that at around 180*F closes. The whole sensor.

Its only operation is on hot start, (when the thermosistor has between .35 and 3k ohms resistance).

If you don't belive me, drop a 2.5k ohm resistor in there, and see if there is any difference between that and 20K ohm resistor.

The only difference you will see is that when starting with the 2.5k ohm resistor, the idle will stay at about 800 RPM for the first minute and a half, and drop to 750 after that.

This is considerabbly different than the AFM, and its operation. The ECU directly uses the temp in the AFM as the temp intake reference (despite the posts suggesting otherwise).

Again simple resistors inline prove this

WAYNE88N/A

I just watched this sucker the other day going to work during my "semi-annual" ECU input checkout, Mark, and the voltage inputs varied the entire trip. For instance, 3.7v engine "warm" (sitting a couple hours after shutdown), 2.4v not long after shutdown (on a 95*F day, dang close to the FSM's spec of 1-2v at 176*F, which tells me that sucker has got to be hotter than hell to kick in the hot start system), and 3.2v during highway cruise of 75mph. So, this guy is feeding continuous temp info to the ECU, it's not acting like an on/off switch...The reason the FSM has you check out the system with resistors is so you can simulate the voltages present that requires the ECU to enable the hot start system, without having to toast the engine trying to attain the temps with the sensor connected...

NZConvertible

Mark, sorry man but your info goes against all EFI wisdom, and really makes no sense. It's vital the ECU knows exactly what temp the air is as it enters the engine. Measuring it only at the AFM only gives the ambient temp, but the air temp will change drastically as it is heated by the turbo and (hopefully) cooled by the intercooler. If the intercooler is hot for example, the air will not be cooled as much and the ignition timing must be retarded to stop detonation from occuring. The AFM thermosensor would be of no use in this situation. For a constant ambient temp, the actual intake temp can and does vary considerably, so it makes no sense that the AFM temp sensor is used for anything other than the volume-mass conversion.

Icemark

Okay, I hear what you are saying Jason, but in Mazda's case (as well as many Toyota products) the air temp in the AFM (or air filter housing) is what is read by the ECU.

I could be wrong, but based on personal testing with resistors swaps as well as the factory operation flow charts in the factory shop manuals, It pretty much backs up what I am saying by 100%.

HAILERS

I doubt. On a turbo the intercooler inlet temps WILL be above 200 degrees at times and the stock intercooler will only lower that down to the 120's. I doubt Mazda overlooked the results of that in fuel managment.

It ain't a switch. If they wanted a switch device they would have installed a switching device.....similar to the water temp switch in the lower part of the radiator... as used on the series four.

Icemark

Then why is the test for it reading resistance above 170 and below 170???

Unlike the AFM which uses a half dozen different resistances in testing?

And why is the flow charts only showing the ECU using the input on idle/start (BAC control) and hot start assist???

All that sensor is doing is sensing the dynamic chamber temp to prevent hot start flooding... not air temp.

Husemoller

Oh man! Never thought I would start something like this between you 3 :P

I have driven it a little bit and i dont really notice any difference, but I probably wouldnt unless I had something to test how rich and such I am i guess.

So tomorrow I am just going to get that other sender that is in the n/a and toss it in there then.

HAILERS

A thermistor can have more than one function in life........like the engine air intake temp sensor.

HUSEMOLLER........Stop spreading hate and discontent! Trouble maker. Gonna have you banned from this site. humor, please.

Husemoller

Thats what I do. I like to see everyone fight over topics on who is right and wrong :P

Makes me feel like I actually started a good thread for once

Icemark

No hate, or fighting... just casual discussion.

This will only be proven one way or the other, by someone that has broken down the programming to actually see.

NZConvertible

That might be the case on non-turbo engines, but as Hailers and I have pointed out, the actual air temp at the engine is going to be much higher than the reading at the AFM, and not by a consistant amount. The AFM reading is totally useless once the air has passed through the turbo and intercooler.
The S4 FSM lists three temp vs. resistance values for the air temp sensor, at 20, 50 and 85degC (pages 4A-81 and 4B-84). If this was only to be used for the hot-start assist then Mazda would've just used a 60degC temp switch, not a thermistor.
S5 FSM pages F1-76 and F2-74 lists both fuel injection amount and ignition timing as being affected by the engine air intake temp sensor.