"IAT = Intake Air Temp sensor" on the Focus?

Penguini66 · Oct 7, 2003

\"IAT = Intake Air Temp sensor\" on the Focus?

After running across the below quote on the FordChip website, I did some searching here and didn't come up with much. Most search results came up with: "immediately". Forgive my ignorance, I'm still somewhat of a noob when it comes to all the details. It seems that the more I research, the more I find out how little I know.

Blown cars and IAT/ACTs

IAT = Intake Air Temp sensor.
ACT = Air Charge Temp sensor.

These are two different names for the same sensor. The EEC uses these sensors to help determine ambient air temps. These sensors are always mounted after the MAF and before the cylinder heads. On most newer Fords they are mounted in the inlet tubing before the throttle body. Beginning in the late 90s Ford started using an integrated MAF/IAT design. This design now has a 6-wire MAF vs. the old 4-wire style.

FordChip highly recommends that any blown car remount the IAT/ACT to a position between the blower/turbo and the throttle body. By doing this the EEC will be able to see the temp of the "boosted" air and can be calibrated to remove spark only as necessary under boost. This is a great benefit and safety measure for blown cars. In hot weather the EEC will be able to "see" the air temps and can pull the necessary timing. On those cool days the EEC will allow you to run as much timing as possible safely. This prevents a car that was calibrated on a cool day from "knocking" when the weather gets warm. It also allows max power on those cool days.

FordChip is one of very few tuners that can max tune a blown car using the IAT/ACT. The "other" off-the shelf companies can't. We have datalogged 100s of cars can get you close even by mail-order if we know your engine combo, blower and max boost.

Anyway, have we [FJ] looked onto relocating the IAT sensor on the Focus? Is it even really a big deal? What specific effects does the IAT have on the Focus ECU?

The Focus has a 6 wire MAF right? So that would mean that the IAT is integrated into the MAF sensor right? What would it take to relocate the sensor? I'm thinking that you would have to get an IAT sensor from another (older) car and mount it somewhere after the turbo. Then re-route the appropriate wires from the MAF to the new IAT sensor. I guess finding an IAT sensor that provides the same signal as the integrated MAF/IAT could be a problem.

Any thoughts?

lourenco · Sep 6, 2004

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

I found information on the pectel 039 sensor or NTC M12-L. http://www.bosch-motorsport.com/deutsch/product_overview/Sensoren/Temperature/T-table.pdf . It has a response time of < 10 s ,which seems very slow for me. There are other sensor bosch makes that will response faster, but nothing else shows it holds up to boost. I will probably try a ford ait to see how it compares to what I have now.

Welding Rod · Sep 6, 2004

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

Bumping for Blox.

once again · Mar 7, 2004

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

Thanks Rod.

Welding Rod · Mar 7, 2004

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

I am bumping this in reply to a PM sent by "Once Again".

Here you go - the info you asked about is on page 6.

P-51 · Dec 8, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

I guess you missed the discussion about what the Pectel is doing.

First of all, it reads the sensor much more frequently than that. Like 1/10th or 100th of a second. Second, the "fast response" has nothing to do with reading, and everything to do with thermal inertia.

As I've been saying, the standard Bosch IAT sensor heats up like a mofo, and really measures engine temp more than air temp.

sct · Dec 6, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

The transfer functions are the same, so the electrical response will also be the same. The sensor is only "read" every 1/3 of a second or so so a "fast response" isn't necessary. Unless you have an issue with the plastic sensor getting blown out of the discharge it's just fine. I've seen the plastic sensor used many times, and even had one on my Mustang for a while. The range maxes at 250 degrees but you need to run cooler than that anyway!!! My Vortech S-Trim non-intercooled blew 220 degree air!!! Some of the non-intercooled roots style blowers are even worse (v8 again, m90 based).

CharlesWA · Dec 6, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

I posted this earlier in the thread, it came out of the Ford 2000 Model Year factory service manual CD. The IAT stuff seemed to be a general catch-all section, so I suspect it's consistent across all applications, but I'd like to see somebody verify that from another source just to be safe.

<font class="small">Code:</font><hr /><pre> TEMPERATURE SENSOR VOLTAGE AND RESISTANCE SPECIFICATIONS
.-------------------------------------+----------------------------------------.
| Temperature | Temperature Sensor Values |
+------------------+-----------------+------------------------+---------------+
| øC | øF | Voltage | Resistance |
| | | (volts) | (K ohms) |
+------------------+------------------+------------------+------------------+
| 120 | 248 | 0.27 | 1.18 |
| 110 | 230 | 0.35 | 1.55 |
| 100 | 212 | 0.46 | 2.07 |
| 90 | 194 | 0.60 | 2.80 |
| 80 | 176 | 0.78 | 3.84 |
| 70 | 158 | 1.02 | 5.37 |
| 60 | 140 | 1.33 | 7.70 |
| 50 | 122 | 1.70 | 10.97 |
| 40 | 104 | 2.13 | 16.15 |
| 30 | 86 | 2.60 | 24.27 |
| 20 | 68 | 3.07 | 37.30 |
| 10 | 50 | 3.51 | 58.75 |
+------------------+------------------+------------------+------------------+</pre><hr />

P-51 · Dec 6, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

The plug on the Pectel wiring harness for the IAT looks basically like a fuel injector plug. Same design.

Do either of the Ford sensors have a connector that looks like that?

Pectel wants $100 for the fast response sensor, which is nuts. If the plug fits, I'd like to try Ford ones.

And do we have any temp vs. voltage graphs?

Penguini66 · Dec 6, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

David, I think most of us understand the importance of re-locating the sensor and I don't believe there are any wars being started here.

Does anyone know if there is a way to tell if the threaded Lightning sensor is different electrically than the all plastic sensor I used? If the Lightning sensor is better, than I will switch.

sct · Dec 6, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

I won't get into a war here, but we have data to support what we say. If necessary I'll dig up some datalogs that show the temp increase when the intercooler is removed, and the resulting timing changes that were necessary to prevent detonation. With the IAT sensor correctly located and tuned for you can run the exact same tune with or without an intercooler. We've done this many many times. I wouldn't even bother responding to this post except we really feel this is important when tuning an FI car. EPA testing never goes into boost anyway, so that is not why OEM's move the sensor. The PCM is a feedback control system and needs accurate feedback.

Once again we really feel this is important so I'm trying to stress that point!!!

David

doogie78 · Dec 6, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

The part number Eric listed (F6SZ-12A697-A) is correct for the Lightning sensor. The pigtail is Ford part number 3U2Z-14S411-JUA ("kit, wire assembly"). It consist of the proper connector with maybe a foot of the two preconnected wires and some heat shrink tubing.

Rock on!

Welding Rod · Dec 6, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

The part number Eric listed (F6SZ-12A697-A) is correct for the Lightning sensor. The pigtail is Ford part number 3U2Z-14S411-JUA ("kit, wire assembly"). It consist of the proper connector with maybe a foot of the two preconnected wires and some heat shrink tubing.

Penguini66 · Dec 5, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

I don't have a Ford part number for the all plastic sensor that I used. Just the Napa number that I mentioned above. The Ford part number for the threaded sensor is F6SZ-12A697-A. Hopefully Rod will have an update for us shortly since I think its the route he went.

One thing to note. With either sensor, you want to make sure that the actual thermistor is far enough in that it will not receive radiated heat from any heat soaked metal parts.

FFIW If I was to do it over again, I would probably use the threaded Lightning sensor. From what SCT guy metioned, it appears that the Lightning sensor might be a better sensor that is designed for a blown application. And if installed correctly, it should not have a heat soak problem. But we really don't have any proof now if its actually different electrically than the sensor I used. I'm just not sure how to get my hands on the pigtail connector. Perhaps Rod can shed some light on it.

doogie78 · Dec 5, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

Penguin? Anybody? Plastic or brass?

doogie78 · Dec 3, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

Any updates guys? Part numbers? Are we sticking with the plastic? Can we get a short how-to for less intelligent boosted foci?

Welding Rod · Dec 1, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

I have not got my SCT tuning yet, but I did relocate my ACT a few days ago. I used a new Lightning sensor and OEM replacement connector. The pigtailed connector cost almost as much as the sensor - about $70 total for both.

I drilled a hole in my AC3 plenum pretty much even with the BOV hole, but rotated 90 degrees towards the front of the engine. The pigtail on the oem replacement connector was long enough to comfortably reach and connect to the (2 outside) MAF wires.

The sensor is pretty much a fairly thin walled threaded brass sleeve with everything else made of plastic. Threads are 3/8 NPT as was said in an earlier post. This tapered tap calls for a 37/64ths drill, but I used a 5/8ths (3/64ths over) to allow the sensor to sit deeper into the plenum, keeping the sensing head well away from the aluminum plenum wall.

I don't have any scanned data, but the car does seem to run better. I have noticed that when coming to a stop after cruising the RPM no longer hangs excessively or floats up and down before stabilizing. Not sure on this, but I have not noticed any more light load surging either.

Have to do more testing.

Welding Rod · Nov 25, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

Tom - "... only a 9 hp increase in the midrange.." ???

That is NOT a very desireable thing????

Penguini66 · Nov 25, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

Ummmm, we're here to learn. Not argue. Lets keep it on track. This was all somewhat new to the Focus community here so there's going to be some trial and error. And allot of us have not been doing this kind of work on cars for years. Also, most of the things I've done to my car are the first time I've ever done them on any car. You have to start somewhere right. And you can only do so much research before making a decision and moving forward.

Well, maybe there's something fundamentally different between the Lightning sensor and the Bosh sensor that P51 used. P51 saw heat soak in the Bosh sensor. Some of us made an assumption (a valid one at that) that the metal bodied sensors may have an issue with heat soak. Now it appears we know two things from peoples experience: (1)The Lightning sensor is different than the Pectal/Bosh sensor. (2)From individuals experience, the Lightning sensor does not have a heat soak issue if mounted properly.

The thermister in the sensor is a low load design that has fast time response and does not heat soak.

So, is there any reason for me to switch from my all plastic mustang style sensor to the threaded Lightning sensor. Does anyone know if the thermisters are the same. Or do only the blown factory cars have the low load/fast response thermister design.

And can anybody answer the question if a thermister has a polarity.

1turbofocus · Nov 25, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

SCT you are comparing QUOTE,,Why does the Ford Lightning, Cobra, Saleen Mustang, Roush Stage 3, SC GrandPrix, all have the sensor after the blower/cooler? It's not by coincidence

No its not coincidence its because to pass emmissions it needs the timing advanced as much as possible for a cleaner burn combustion, installing the AIT after the boost lowers the timing under extreem heating and makes the engine safer they cannot do what we can do to the tuning and get it to pass the emmission laws the OEM has to follow

You are here telling a bunch of guys most that dont even need to be tuning engines that this has to be done when in fact all that is needed is to pull a little timing from the start of where the boost realy starts to come on and let it go ,,Its not like we are talking about 20 to 30 HP gain for moving the AIT ,,I tryed this on my kits from the start because in theory i agree with you

With installing the AIT up stream testing it in 3 locations all i got was a 9HP gain in the mid range and the same power in the top because it ended up taking the timing to where we had it with the AIT in the mass air

Guys worry about the BIG stuff with the tuning the little stuff will take care of itself

Tom

sct · Nov 25, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

I have datalogs from 3 different positions that showed massive heat soak from conduction. First was in the metal elbow feeding the throttle body, second was the charge pipe near the coil, and third is the metal elbow attached to the FILTER, which is located in the fender well.

The air in that location is NOT 160 degrees, but that's how hot it reads when sitting for a minute.

First off the picture you posted is NOT The sensor in the Lightning,it's totally different. Actually the Lightning has two sensors, one in the air box and one after the cooler in the manifold.

The Lightning sensor has brass threads, that's it. The rest of the sensor is plastic. The thermister in the sensor is a low load design that has fast time response and does not heat soak. The few times I have seen a Lightning sensor act like this is when it's not threaded deep enough into the manifold and gets radiated heat off the manifold. This is not a sensor problem. The designer cannot design the sensor to protect for idiots. You need to have some understanding of how the system operates prior to taking the system on.

The only times I have ever seen a thread in Lightning sensor show 160 degrees is when it was really 160 degrees, normally at the end of the dyno pull or 1/4 pass. It then cools off very quickly.

Your problem is you are comparing your experience with a different sensor and drawing the conclusion that all sensors that look like that are bad.

Why does the Ford Lightning, Cobra, Saleen Mustang, Roush Stage 3, SC GrandPrix, all have the sensor after the blower/cooler? It's not by coincidence that when an OEM puts a blower on the sensor gets moved. Do you think that these companies would just allow the sensor to heat soaked and stay very high? That defeats the whole purpose of moving the sensor. Hell if that's the case, then just hardcode the air temp to 160 in the software and be done with it.

You had an experiece with a poorly designed sensor and/or location. You need to do something about that not just bash it. By your logic are all Middle Eastern people bad because a few dozen bombed the World Trade Center? No, don't let one bad experience close your mind.

Penguini66 · Nov 23, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

Rod, I can't really say exactly how the sensor is working since I have no way to datalog. All I can say is that the car seems to be runing the way its supposed to. I can tell that the car has slightly more power when cold (as it should). Once its got some temp in it, the sensor and the computer must be doing their job and pulling some timing.

Also, the dyno graph I posted in my "finally some decent numbers" thread was my third pull. And I didn't really give it any cool down time in-between(no more than 5 minutes). So to say that the engine was up to full temp is an understatement. But the one thing I have going for me is the fact that the high speed is fan coming on at a lower temp (well both fans actually...FYI - this is all part of the base tune). They come on soon enough that even with the stock thermostat, I can see that the engine coolant runs slightly cooler on the gauge. Some day when I'm boored, I'm going to set the fans back to their stock settings and use the 'dealer test mode' on the gauge cluster to see what the coolant is running at so I have an actual numerical comparison. And yes, the SCT programming also takes into account the ECT or Engine Coolant Temp in the spark tables.

The sensor I'm using is from a '96-'01 Mustang (I think). The Napa part number on the box is TS4039 and it shows up on the Napa website. Because its a plug-in style made to be pushed into a grommet on the vacume side of a N/A motor, I made up a gasket and used two button head cap screws to hold it down. I have a drawing for the mounting plate at work that I can email to you if you want to try this kind of setup. The only thing I did to the sensor is remove a little bit of material away on the flange with a round file so I could get more of the head of the screws over the flange. This also keeps the sensor from possibly spinning.

I couldn't find any information to determine if the sensor has a polarity or not. I asked a few of the EE's at work and they said that it shouldn't.

Welding Rod · Nov 22, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

Penguin

How is your IAT setup working?

Rod

P-51 · Nov 20, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

Maybe I'm a little wierd but my idea of fun is a high horsepower car that I can drive every day, pass emissions with, and still race on the weekends ...

I guess I have very little faith in most "tuners" out there. Very little. I've seen more absolutely clueless "tuners" than good ones, by far.

I have datalogs from 3 different positions that showed massive heat soak from conduction. First was in the metal elbow feeding the throttle body, second was the charge pipe near the coil, and third is the metal elbow attached to the FILTER, which is located in the fender well.

The air in that location is NOT 160 degrees, but that's how hot it reads when sitting for a minute.

Hypnotic · Nov 20, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

Ah....ok. What does a timeslip have to do with heat soak?

If they had a better sensor, maybe they'd be running 9's. The point is, you CAN'T tune for maximum power if your sensor isn't measuring the right air temp.

What I was trying to get acrossed was this, those 3 guys, along with many others, have logged countless hours of tuning on the dyno, and passes at the strip using these sensors. IF there was ANY way to squeeze MORE power/ e.t out of the vehicles they work on, they would use it. If the sensor was not a viable and solid working piece, THEY WOULDNT USE IT.

Hypnotic · Nov 20, 2003

Re: \"IAT = Intake Air Temp sensor\" on the Focus?

Having datalogged literally hundreds of blown cars with the threaded sensor we've never seen heat soak like you describe.

Thanks for the backup sct. Did you get the PM I sent you btw?

"IAT = Intake Air Temp sensor" on the Focus?

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