Moving the ACT and the Impact on the ECU

[vristang]

that what i was thinking. sometimes i sit back and think how in the heck do these guys know all of this like with all the tweecer stuff. i have never used a tweecer(hell ive never seen one) so i dont know ho hard the difficulty level of understanding it but would like to know. would anyone recommened getting one and trying to learn how to use it? what are the advantages of it?

I would recommend the tweecer, IF you are willing to take the time to learn it.
However, instead of going into more details here, I will just ask that you start a thread in the 5.0Tuning section. There are a couple of tweecers here now, who would be happy to address your questions...

jason

 

[vristang]

While I too did notice a slight (close to 5 degree…and a bit slow to react) drop in temperature when stabbing the throttle, what bothered me was my datalogs barely noticed any difference in temperature while just cruising compared to full boost. I should have noticed a significant change in temperature while under full boost for any significant duration. That alone pushed me into moving the sensor to a location that would be less prone to heatsoak. This has been noticed by many over on the megasquirt forums with all types of vehicles that use similar ACT sensors. Now, I would assume that you would notice a small temperature rise with the short dwell time the air has in the intake….but certainly not the 100F+ degree temperature difference that I have noticed.

OK, I have been focusing my thoughts on N/A applications, while you have been focusing on Boost applications.

I have not played with boost yet (and I did say YET), but my understanding is that the higher the boost level the higher the air temp will be.
Considering this, I don't find it hard to believe that your ACT temps are not changing significantly.

I guess I am still not convinced that heat soak is what is causing your high ACT readings. I would guess it to be due to the process of compressing the intake charge. I am sure heat soak does play a factor, I just don't see it contributing ALL of the heat retention you are seeing.

Again, thanks for posting. Your comments have made this a great discussion, as most of this stuff never would have crossed my mind otherwise.



jason

EDIT: WOW, already on the second page...

 

[sweet88gt]

Lets ask another question about inlet air temp sensors. I have a PMS mass air with 6 pins. Two of which I do not use. I am told these two pins are for ACT sensor wires. I assume the 6 pin mass air is similar to the Lighting mass air. Why then would Ford chose to use the ACT senor in the inlet air tract rather than in the lower manifold?? My guess is that the newer computers can change and process this information better than the Fox computer. Any thoughts.

 

[HISSIN50]

Lets ask another question about inlet air temp sensors. I have a PMS mass air with 6 pins. Two of which I do not use. I am told these two pins are for ACT sensor wires. I assume the 6 pin mass air is similar to the Lighting mass air. Why then would Ford chose to use the ACT senor in the inlet air tract rather than in the lower manifold?? My guess is that the newer computers can change and process this information better than the Fox computer. Any thoughts.

MHO is that the inlet tract is more sensitive in regard to measuring *actual* inlet air temps. The caveat is that if something is going on and the air is getting heatsoaked by the time it reaches the chambers, the IAT cannot possibly know this. The lower intake location gives a reading closer to where it matters but I fear it's slower to react to real time air-temp changes (the magnitude of air temp changes isnt generally great anyhow, so maybe that's a moot point).

Glad I could muddy the waters there.

If not already touched upon, the ACT is the Air Charge temperature sensor, aka, IAT (Intake air temperature sensor). I segregate the nomenclature as follows: if the sensor is in the lower intake, it's an ACT. If it's in the inlet tube, it's an IAT.

It really doesnt matter (like other similar acronyms: IAB, IAC or as the RT guys say, ISC).

 

[millhouse]

OK, I have been focusing my thoughts on N/A applications, while you have been focusing on Boost applications.

I have not played with boost yet (and I did say YET), but my understanding is that the higher the boost level the higher the air temp will be.
Considering this, I don't find it hard to believe that your ACT temps are not changing significantly.

I guess I am still not convinced that heat soak is what is causing your high ACT readings. I would guess it to be due to the process of compressing the intake charge. I am sure heat soak does play a factor, I just don't see it contributing ALL of the heat retention you are seeing.

Again, thanks for posting. Your comments have made this a great discussion, as most of this stuff never would have crossed my mind otherwise.



jason

EDIT: WOW, already on the second page...

Just a bit more information on what I have noticed with my setup.

I previously mentioned that once the engine was heatsoaked, the ACT read a fairly constant 180* during cruise, idle and showed a slight temp decrease during WOT.

With the relocated ACT sensor, early fall temps were in the mid 70's while WOT temps increased into the mid-high 80's. This is what I would expect to see in boosted applications with an intercooler.

The heatsoaking that was occurring was making it extremely difficult to tune with the megasquirt. With the extreme ACT temperature differences between pre-heatsoak and heatsoaked my fueling was getting thrown way off. You can see the megasquirt fueling equation here… http://www.megamanual.com/v22manual/mfuel.htm#equation

Correct me if I'm wrong, but I believe the stock ECU only retards timing based on the ACT readings. It's my understanding that the air density differences between hot and cold is differentiated via the MAF sensor in which the computer then adjusts. I don’t believe that with the stock ECU heatsoak is an issue….as it does not serve quite the same function.

I also don't believe the air dwell time in the lower intake is sufficient to increase temperatures and significant amount…especially the 100*F that I noticed. The only time the air will subject to heat transfer of that magnitude is when the car is shut off for any significant amount of time. I myself have to adjust my startup enrichments based off of engine temp in which I can compensate for this.

Anyways, just some argument and food for thought.