Moving the ACT and the Impact on the ECU

vristang

15 Year Member
Mar 31, 2005
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Seattle
I posted this last night in another thread...
http://forums.stangnet.com/showthread.php?t=688872

I was hoping some of you guys who have relocated the ACT could offer some feedback.
Who knows, maybe something listed below will shed some light on a chronic problem you are having?

Since this has come up before, I decided to do a little research using the tweecer to check how the computer might react to lower than expected ACT temps/readings.

Here is my new writeup...

Hope it helps,
jason


How will the Fox computer react to the ACT being moved from the lower intake to the Intake Airbox?
Thumbing through the TwEECer (CalEdit) this is what can be seen...

In the X3Z Calibration
FN 825B - ACT will increase the engine idle rpm after about 192F, maxing out at 64rpm by 208F
FN 220 - EGR Multiplier is 0 until 58F, maxes out at 1 by 60F
FN 126 - Spark advance starts to retard at 160F maxing out at -2* by 190F
FN 135 - WOT spark advance is retarded starting at 150F, maxing out at -6* by 240F
FN 300 - Open Loop Fuel Multiplier is unaffected by ACT (always 1)
SCALAR - ACT MUST be between 100F and 200F for the Adaptive Strategy to start learning

In the A9L Calibration
FN 825B - ACT will increase the engine rpm by 48rpm at 200F, and a max of 72rpm at 226F
EGR Multiplier is .8 until 0F, then rises to a max of 1 by 56F
FN 126 - Spark advance starts to retard at 160F maxing out at -2* at 190F
FN 135 - WOT spark advance is retarded starting at 150F, maxing out at -6* by 240F
FN 300 - Open Loop Fuel Multiplier is .64 until -40F, .81 by 0F, and maxes out at 1 by 76F
SCALAR - ACT MUST be between 100F and 200F for the Adaptive Strategy to start learning

So what does this mean?
Idle speed – Obviously for both calibrations the affect is going to be minimal, assuming all other idle contributors are working properly. Moving the ACT to a cooler location should not have a major impact on idle speed.

EGR – Moving the ACT to a cooler location will affect the function of the EGR. It would not be recommended to try and pass an emissions test with the ACT in the airbox on a cold day (below 60F).

Spark – The Spark Advance is RETARDED with higher temps. Moving the ACT to the airbox can help to keep ignition timing higher. However, keep in mind that Ford used the ACT as a ‘Safety Factor’ for preventing high temp detonation. False information to the EEC-IV will make detonation more likely when the engine is warm/hot.

Fuel Multiplier – The Fuel Multiplier increases with higher ACT temps. Due to the low temps at which the ACT will impact the Fuel Multiplier this is not likely to cause an issue.

Adaptive Strategy – This may be the most critical one for most daily driver Mustangs. Not allowing the Adaptive Control to function (because the ACT never sees 100F in the airbox), could hurt fuel economy and could cause drivability issues.
 
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It works good for me... But I live in Central Florida - the lowest winter temp so far is 32 degrees F. The overall under hood temps are probably 100 degrees after a nice drive to get the water temp up to 180 degrees.
 
SCALAR - ACT MUST be between 100F and 200F for the Adaptive Strategy to start learning

I have a small question about the ACT as it pertains to a supercharged car. The adaptive strategy works between 100F and 200F, what and what affect does a 200F+ intake charge affect driveability?? I ask because when I datalog using an innovate wb I have seen intake temps in excess of 200F. I am only using the ACT to datalog this and seem concerned about the temps. This is on my 88gt that is in my sig below. I have a gt40 intake and the ACT sensor is in the lower intake. I have tested the sensor and have found it to be in working condition. The outside air on the day I datalogged was only around 70F. Thanks. By the way I am using an A9L computer with a plug in chip with tune.
 
SCALAR - ACT MUST be between 100F and 200F for the Adaptive Strategy to start learning

I have a small question about the ACT as it pertains to a supercharged car. The adaptive strategy works between 100F and 200F, what and what affect does a 200F+ intake charge affect driveability?? I ask because when I datalog using an innovate wb I have seen intake temps in excess of 200F. I am only using the ACT to datalog this and seem concerned about the temps. This is on my 88gt that is in my sig below. I have a gt40 intake and the ACT sensor is in the lower intake. I have tested the sensor and have found it to be in working condition. The outside air on the day I datalogged was only around 70F. Thanks. By the way I am using an A9L computer with a plug in chip with tune.

If your ACT temps at cruising speed are consitently over 200F, then you aren't going to be seeing any adjustment to the fuel metering during that time.
Here is how the Adaptive Strategy works... (the short version)
During Closed Loop operation the computer calculates the required Fuel Injector PulseWidths, based on MAF, ECT, ACT, etc.
Since it is near impossible to create a set of equations that will provide exactly the right Fuel Injector PulseWidths for EVERY Mustang, Ford created a Multiplier in the tune which is based on feedback from the O2's.
When the O2's indicate that the exhaust is consistently rich, then the computer applies a multiplier of less than 1 to the already calculated pulsewidth.
For example if the the calculated pulsewidth were 20ms and a multiplier of .975 were applied, then the actual pulsewidth would be 20*.975=19.5ms.
If a lean condition is detected by the O2's, then a multiplier of greater than 1 is applied to the calculated pulsewidth.

In order to prevent the adaptive strategy from 'learning' when the engine is in a poor running condition, such as cold start or approaching overheating, restrictions have been applied to when the Adaptive Control can start to learn. For example, a minimum ACT and ECT temperature must be met. If the minimum temps are not seen, then the adaptive learning is not applied.

The same idea applies to over temps. If the ACT or ECT are registering too high, then adaptive learning will not be applied.


Now for your boosted application seeing over 200F...
When the temps are over 200F, adaptive learning is not applied. So the computer does not have the ability to compensate for being a little off from stoich. You may be slightly rich, or slightly lean during this time, and the computer would not be taking corrective action.
Is it something to worry about? Probably not.
When you should be most worried about the AFR is at WOT. There is no multiplier that is applied at WOT, so your fuel ratio should be the same as what your custom tune was setup to provide.

Hope that helps,
jason
 
Just for a reference what are N/A intake temps?? I am mainly concerned about the timing that will be reduced with high intake temps. I have a methanol injection setup for additional cooling at WOT which will richen the A/F. I originally wanted to tune for max power but have since decided to go with an overall power. I will leave the methanol on the lowest setting and tune for overall performance throughout the RPM range. This is a new motor and minor changes to the setup. I am only using the chip to break the motor in and will need to have it re-tuned. Thanks
 
Just for a reference what are N/A intake temps?? I am mainly concerned about the timing that will be reduced with high intake temps. I have a methanol injection setup for additional cooling at WOT which will richen the A/F. I originally wanted to tune for max power but have since decided to go with an overall power. I will leave the methanol on the lowest setting and tune for overall performance throughout the RPM range. This is a new motor and minor changes to the setup. I am only using the chip to break the motor in and will need to have it re-tuned. Thanks
My hard drive failed a month back, so I don't have any old datalogs for looking up ACT temp ranges.
Maybe someone else has a good idea?

As for the timing...
Since you have a custom tune, all bets are off. (my original post was focused on the affects of moving the ACT in a STOCK ecu)
If the tune was done properly, your timing will be appropriate even at high ACT temps. Your tuner would be the one to ask about that.

Actually, he may be able to increase the max ACT adaptive learning scalar as well?
Maybe increasing the max to 250F would restore the adaptive?
But keep in mind that the adaptive is applied based on a Load vs RPM table (there is no mention of ACT in this table); I can't say if that would be a good idea or not. :shrug:


jason
 
Something to keep in mind while reading intake temps via the stock probe in the stock location is.....heatsoak is unavoidable. You cannot accuratley get a measurement of the air temperature at that location. While it's fine for stock ecu, when I installed my megasquirt the fueling equation relies heavily on a accurate act reading. I was getting 180* temps just cruising at light loads on the freeway with the act in the stock location. Those temps dropped down to ambient after relocating the sending unit into the intake piping before the thottle body. If you are using the stock ecu still, you may want to hook up a second act sensor to monitor what the actual act temps are.
 
Something to keep in mind while reading intake temps via the stock probe in the stock location is.....heatsoak is unavoidable. You cannot accuratley get a measurement of the air temperature at that location. While it's fine for stock ecu, when I installed my megasquirt the fueling equation relies heavily on a accurate act reading. I was getting 180* temps just cruising at light loads on the freeway with the act in the stock location. Those temps dropped down to ambient after relocating the sending unit into the intake piping before the thottle body. If you are using the stock ecu still, you may want to hook up a second act sensor to monitor what the actual act temps are.

What kind of sensor did you end up using?? I could then like you said run that sensor straight to the datalog for more accurate readings. With this also being said, the heatsoak has a built in safety feature for the stock in lower intake loaction. The higher the sensor reads ( heatsoak included) the computer will retard timing and increase rpm. The air in the intake tract may be cooler and cause the computer to advance timing and cause potential detanation. Seems like the consensus to me.
 
Jason, a very nice tech tidbit thread. :nice:

One more thing to add to the mix. If doing the ACT swap into the inlet air tract, if the sensor were incorporated into a chrome CAI, you might be able to more easily heat the sensor. This might more closely mimic the temperature gradient that the stock location sees.
 
What kind of sensor did you end up using?? I could then like you said run that sensor straight to the datalog for more accurate readings. With this also being said, the heatsoak has a built in safety feature for the stock in lower intake loaction. The higher the sensor reads ( heatsoak included) the computer will retard timing and increase rpm. The air in the intake tract may be cooler and cause the computer to advance timing and cause potential detanation. Seems like the consensus to me.

I took the stock sensor and swapped the location. As said before though, the megasquirt's fueling equation and timing trim is different than the stock ECU's. For that reason I would keep the ACT sensor in the stock location and buy another stock ACT sensor to place somewhere that heatsoak wont be an issue.
 
Jason, a very nice tech tidbit thread. :nice:

One more thing to add to the mix. If doing the ACT swap into the inlet air tract, if the sensor were incorporated into a chrome CAI, you might be able to more easily heat the sensor. This might more closely mimic the temperature gradient that the stock location sees.

It's a good thought, but a the damn heatsink....eh....I mean intake just get's to damn hot. I can firmly grab ahold of my steel intake tubing without any discomfort....and it's located directly above my turbo downpipe. The intake manifold gets far hotter...and hold's the heat in far longer.
 
Something to keep in mind while reading intake temps via the stock probe in the stock location is.....heatsoak is unavoidable. You cannot accuratley get a measurement of the air temperature at that location. While it's fine for stock ecu, when I installed my megasquirt the fueling equation relies heavily on a accurate act reading. I was getting 180* temps just cruising at light loads on the freeway with the act in the stock location. Those temps dropped down to ambient after relocating the sending unit into the intake piping before the thottle body. If you are using the stock ecu still, you may want to hook up a second act sensor to monitor what the actual act temps are.
First off,
Millhouse, thank you very much for jumping in :nice:
This is exactly the kind of discussion I was hoping for :nice: :nice:

While I currently don't have any datalogs to quote (damn computer viruses, killing my hard drive :nono: ),

I did hook a DVM to my ACT shortly before plunging into the tweecer. While it was tough to ascertain the true intake air temps from the DVM, I did notice that when I cracked the throttle, the intake temps would plummet (voltage jumped up).
To me this indicates that 'heat soak' of the ACT is not the issue, but rather the intake air temperature is really getting that high.
What I am saying is...
At higher throttle angles, the air does not spend much time in the intake, picking up less heat.
At lower throttle angles the air spends more time in the intake, picking up more heat.

If the ACT sensor were saturating with heat, then it would take longer for the ACT to respond to throttle position changes.
This is not what I remember witnessing several months ago.
The Throttle Angle affect on the ACT was nearly instantaneous.

By design the ACT has a low mass. If an ACT is compared side by side to an ECT, the difference is obvious.
And ECT has more thermal mass to prevent small, sporadic changes in coolant temps from impacting the computer.
The ACT has a very low thermal mass to allow it to respond quickly to a changing environment.

Also, the actual sensor part of the ACT is separated from the main 'housing' of the sensor. The only part of the thermistor that will register the temperature change is the very tip of the 2 wires, which protrude from the sensor, into the intake runner. There is very little thermal mass at the tip of the sensor.

Hope this sparks some interesting debating :D
thanks again for the replies to this thread,


Jason, a very nice tech tidbit thread.

This is the fun stuff

Later JT,

jason
 
My comments about the heat soak were merely based upon my experience with a chrome CAI - during a stretch of 115* ambient temp days, I was shocked to see my IAT temps (this was on the '94, but basically it's the same ball of wax for the relativity of the discussion here IMHO).

The sensor was calibrated and measurement of ACT temps was done with an independent measuring device. The point was simply that a chrome CAI would likely hold more heat than a plastic air box, and thus relate more closely to the stock ACT sensor location [on a fox III] if someone is having drivability issues because of the relocation.
 
First off,
Millhouse, thank you very much for jumping in :nice:
This is exactly the kind of discussion I was hoping for :nice: :nice:

While I currently don't have any datalogs to quote (damn computer viruses, killing my hard drive :nono: ),

I did hook a DVM to my ACT shortly before plunging into the tweecer. While it was tough to ascertain the true intake air temps from the DVM, I did notice that when I cracked the throttle, the intake temps would plummet (voltage jumped up).
To me this indicates that 'heat soak' of the ACT is not the issue, but rather the intake air temperature is really getting that high.
What I am saying is...
At higher throttle angles, the air does not spend much time in the intake, picking up less heat.
At lower throttle angles the air spends more time in the intake, picking up more heat.

If the ACT sensor were saturating with heat, then it would take longer for the ACT to respond to throttle position changes.
This is not what I remember witnessing several months ago.
The Throttle Angle affect on the ACT was nearly instantaneous.

By design the ACT has a low mass. If an ACT is compared side by side to an ECT, the difference is obvious.
And ECT has more thermal mass to prevent small, sporadic changes in coolant temps from impacting the computer.
The ACT has a very low thermal mass to allow it to respond quickly to a changing environment.

Also, the actual sensor part of the ACT is separated from the main 'housing' of the sensor. The only part of the thermistor that will register the temperature change is the very tip of the 2 wires, which protrude from the sensor, into the intake runner. There is very little thermal mass at the tip of the sensor.

Hope this sparks some interesting debating :D
thanks again for the replies to this thread,




This is the fun stuff

Later JT,

jason

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.
 
My comments about the heat soak were merely based upon my experience with a chrome CAI - during a stretch of 115* ambient temp days, I was shocked to see my IAT temps (this was on the '94, but basically it's the same ball of wax for the relativity of the discussion here IMHO).

The sensor was calibrated and measurement of ACT temps was done with an independent measuring device. The point was simply that a chrome CAI would likely hold more heat than a plastic air box, and thus relate more closely to the stock ACT sensor location [on a fox III] if someone is having drivability issues because of the relocation.

Gotcha. :nice:
 
I love these types of discussions even though I own a 95 with the ACT in the air inlet tract. It's funny that some guys with 94 and 95's with superchargers move the ACT to the lower intake like fox cars because some kits like vortech move the ACT to the superchargers inlet not the discharge tube.
 
If I can say one thing about this thread, this is one of the most pure technical threads I have ever seen on this forum.
Isn't the ACT a test you have to take to get into college?

that what i was thinking. sometimes i sit back and think how in the heck do these guys know all of this:shrug: 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?