Inlet Air Temp Sensor.

[foxspy]

Hey guys,

I've had my F.A.S.T ECU in for about 2 years now, and I've never hooked up the inlet air temp sensor. Now I'm finally getting into the fine tuning, and I have it running perfect one day, then it seems when the outside air temp is cooler or hotter, it doesn't run the same. So, how important is the inlet air temp sensor, would it make a difference if it were plugged in. I have the enrichment vs. air temp table at zero all the way across. Does anyone have a ballpark figure on what I need to look for when adjusting this table. When I had the fuel map perfect, and I plugged in the air temp sensor, it went lean, so I unplugged it. But now, if it's going to make a difference, I'll redo the map.

Thanks in advance.

 

[foxspy]

I plugged the inlet air temp sensor in tonight to see what happens and it went WAY lean. The inlet air temp was 115*, and when I started it, it barely ran for about 20 seconds, then died cause it was so lean. I adjusted the VE table and my idle numbers were around 65, and that's what I had set at WOT w/o the sensor plugged in.

Any tips or suggestions?

 

[HighPSI]

You need to tune it with the inlet temp in the correct location. With it unplugged you will run waay fat. Even if you zero out the air temp correction table the FAST still uses the sensor in it's fuelling calculations. It's my unerstanding the air temp correction is more like a "trim" table to tweak to your specific application.

 

[foxspy]

Yesterday I plugged it in and it went way lean, so I had to add a ton of fuel. At idle, I had my VE numbers at 32-35, then with the inlet air temp plugged in, I had to bump the numbers up to 62. Do you think that the sensor could be bad?

 

[HighPSI]

No, it is probably working correctly. When it is unplugged the FAST thinks the air is very cold. This would cause the engine to run richer (so you used smaller VE numbers). When you plugged it in, the FAST thought the air was warmer and it leaned the motor out.

 

[V6 Beast]

Wouldn't cold air make the engine run leaner rather than richer? I thought cold air was denser and had more O2 in it. Cal, do you think it is ok to run the MAT sensor after the turbo?

Steve

 

[HighPSI]

When the sensor is umplugged the ecu thinks the air is very cold and richens it up. When you plug in the sensor it sees the air as warmer and leans it out. Cold air is denser, that is why the ecu corrects for it in it's fuel calculation. In your situation the air temp isn't really changing, just the sensor being plugged in.

Yes, definitly run the air temp sensor after the turbo. I install them in the intake manifold on my customers cars. I have seen people put them in the up pipe, also.

 

[fast4d]

I have an question regarding this topic

currently my air temp sensor is located in the lower intake which samples 1 port.

should I relocated the sensor before the throttle body? I suspect the heat of the lower intake (alum) might cause it to read hotter due to heat transfer?

 

[Otto J]

I put an extended wire on mine and tapped it into the intercooler on the cold side. This way i also can see how cold the actual air stays on a run without adding engine temp to it

 

[bruce]

Re: I have an question regarding this topic

Originally posted by fast4d
currently my air temp sensor is located in the lower intake which samples 1 port.

should I relocated the sensor before the throttle body? I suspect the heat of the lower intake (alum) might cause it to read hotter due to heat transfer?

The plenum is a mini Tornado. The air circulates extremely well in there. The GM MAT sensors pick up about 0 heat from the manifold. I've tired better insulating and they read the same.

IMO, you want to sample the air as close to the intake valve as possible. That way the ecm knows what's actually going into the engine. And on a hot soak you'd be amazed at idle how hot the air actually is. Depending on how much work you put into the table you can see the table move a little at 120-140dF as you start hitting the evaporation point of the lower end aromatics in the fuel.

 

[bruce]

Originally posted by HighPSI
I install them in the intake manifold on my customers cars.

Sounds like the best place to me.

I'm bettin it also helps correct for fuel temps being there. This hot soak stuff, IMO, matters. Hot soak, IMB also includes times when the engine's running and the cars not moving, ie like when staging.

 

[topfuel]

Yes, definitly run the air temp sensor after the turbo. I install them in the intake manifold on my customers cars. I have seen people put them in the up pipe, also. [/B][/QUOTE]

Excuse me for buttin in, but does this relocation of the sensor benefit a stock ecm car?
I need to find a new home for my MAT sensor, maybe in the
up pipe after the alky nozzle would be a good spot.

 

[bruce]

Originally posted by topfuel
Yes, definitly run the air temp sensor after the turbo. I install them in the intake manifold on my customers cars. I have seen people put them in the up pipe, also.

Excuse me for buttin in, but does this relocation of the sensor benefit a stock ecm car?
I need to find a new home for my MAT sensor, maybe in the
up pipe after the alky nozzle would be a good spot. [/B][/QUOTE]

If you change the calibration to take advantage of it. The MAT timing correction table in the stock code is all 0'd out. And it would throw off the MAF fueling correction. BUT, with the right changes, it would help.

 

[topfuel]

Thanks Bruce.
Changing correction tables is way out of my league, so I'll
have to put it back to a pre-turbo location for now.

Man I wish I had the knowledge of you smart guys, I'm always amazed at how much you really know about these cars.

 

[Superskwrl]

There's alot of conflicting opinions on the subject, so i did my own "testing". With the car 100% stock with a FAST i had the temp sensor in the stock location(#5 cyl lower manifold, 3" away from head), then i went and got another sensor and put it in the plastic tube before the T/B. I opened' the FAST's "dashboard" where i could see the IAT which with the car 100% warmed up. The temp was about 150, ambient was in the mid 50's. I then pulled over and plugged in the other sensor and it read within 20* or ambient, i then started driving along and the hottest it got was mid 70's I'd attribute that to it being located above the pass side header and maybe a lil heatsoak.
I did not notice and difference in performance fwiw

Again this is a 100% stock 5.0 mustang

I have since added a turbo and the sensor is in the stock location (lower intake) i plan to move it to the tubin prior to entering the engine compartment in the intercooler tube AFTER the intercooler

 

[bruce]

Originally posted by Superskwrl
There's alot of conflicting opinions on the subject, so i did my own "testing". With the car 100% stock with a FAST i had the temp sensor in the stock location(#5 cyl lower manifold, 3" away from head), then i went and got another sensor and put it in the plastic tube before the T/B. I opened' the FAST's "dashboard" where i could see the IAT which with the car 100% warmed up. The temp was about 150, ambient was in the mid 50's. I then pulled over and plugged in the other sensor and it read within 20* or ambient, i then started driving along and the hottest it got was mid 70's I'd attribute that to it being located above the pass side header and maybe a lil heatsoak.

Repeat the above with a TR. And after running in boost for a while, with the stock intercooler the temps can climb to 200dF, and being able to correct the timing as the I/C heat saturates can make a noticeable difference in how the car runs.

Not to mention the scenario, of staging and being in boost, with NO airflow across the I/C.

Not to mention the effects of MAT on the fueling and timing are also dependent on the sampling rate of the ecm, the sampling rate sets how often the ecm actually corrects for sensor change. Just as a gross exaggeration, if the ecm only sampled the MAT once every 20 secs, you'd never see any changes in the time it takes to stage and make a pass.