Progress Thread My Kenne Bell Twin Screw'd Foxbody thread, (new addition to the family)

[Bullitt347]

I Possibility of a heat soaked ACT sensor which will get moved this winter.

ACT sensors do not heat soak. They measure actual air temp, to a point. Anything beyond 255* or so the sensor stays pegged as it is out of range of the sensor to measure. As soon as ACT lowers to 254* it makes note of the change. I doubt that the air in your intake manifold goes beyond 255*, though it is possible under non intercooled boost conditions. If 255*+ was reached while under boost, as soon as you came off boost the air temp would drop back down.

 

[FoxMustangLvr]

ACT sensors do not heat soak. They measure actual air temp, to a point. Anything beyond 255* or so the sensor stays pegged as it is out of range of the sensor to measure. As soon as ACT lowers to 254* it makes note of the change. I doubt that the air in your intake manifold goes beyond 255*, though it is possible under non intercooled boost conditions. If 255*+ was reached while under boost, as soon as you came off boost the air temp would drop back down.

There is much debate to this I guess. On an 85-90* day I'll have cruising temps between 145-160*. In boost for short periods of time on the street it'll jump up to 175'ish which is where my ECU starts to pull a little timing. When the car was on the dyno we made several pulls and then beat on it out on the street pretty hard and my data log showed max ACT temp reached was 225*. That's the highest I've seen it. I guess I'm not too worried about it since meth injection is underway. Thank you for you input Vernon, I do appreciate it.

 

[Bullitt347]

I think to many people do not understand what heat soak is and assign that name to whatever concern they have. At what temp is "heat soak" attained? If everything is 160* in, on or around the engine, can it be said that it is heat soaked? One would think that the Ford engineers would have seen this phenomenon while under pre-production testing at the Arizona proving grounds and addressed the issue. Anyway, always lurking around on builds like this and occasionally chime in. Looking forward to the end result.

 

[a91what]

"Heat soak" is the reason why the act sensor was moved into the maf housing. In some ecu the act is referenced in restart conditions, this high temp is false data and causes hard starts. Fast moving air is barely affected by the heat of the manifold. I have found that the sensor in runner #5 can and will show a false high reading at idle and low rpm cruise, this was confirmed using datalog. The air temp would drop when going into wot, this is what prompted me to move the sensor out of the #5 runner.

A point to mention, if the car is boosted the act sensor must be in the pressurized portion of the intake or piping. This cannot be overlooked.

 

[Bullitt347]

"Heat soak" is the reason why the act sensor was moved into the maf housing. In some ecu the act is referenced in restart conditions, this high temp is false data and causes hard starts. Fast moving air is barely affected by the heat of the manifold. I have found that the sensor in runner #5 can and will show a false high reading at idle and low rpm cruise, this was confirmed using datalog. The air temp would drop when going into wot, this is what prompted me to move the sensor out of the #5 runner.

A point to mention, if the car is boosted the act sensor must be in the pressurized portion of the intake or piping. This cannot be overlooked.

At what temp is "heat soak" an issue? At what temp is it not called "heat soak"? All of my datalogs show a very responsive sensor. Throttle moves, temp changes. KOEO temp is one thing, the instant the engine fires (or for that matter cranks) the temp changes lower. There is no delay. The sensor tip is so small in mass that it can not retain any latent temp. That is why there is no difference in temp reading between a plastic sensor and the stock brass one. I have tried to "heat soak" my ACT sensor. The only thing I can do is get the temp reading so high it does not register the changes, which is right at 255* as anything above that is out of the range of measurement. And having temps higher than a sensor can measure is not "heat soak".

 

[a91what]

Exactly what I stated, when the air becomes heated by the manifold temp. The difference between runner #5 and the tubing before the tb is almost 60*F.

I have only noticed this issue at idle and low rpm cruise. It matters a lot when tuning a megasquirt, the fuel algorithm uses the ideal gas law to calculate air density based on the act reading. This causes a lean condition on a correct tune once the engine is fully warmed up. Moving the sensor solves this issue.

The lean condition is only a real problem at idle, I ignore o2 feedback to reduce a hunting idle.

 

[Noobz347]

For an ACT sensor, "Heat Soak" is when the sensor is getting more of its input from the temperature of the surrounding components than it is from ambient air.

 

[Bullitt347]

Except ambient air is not sitting in a hot intake runner. The sensor is reading the hot air, not the components that got the air hot. Also, we notice that as stated the ACT sensor is now part of the MAF sensor and no longer in the intake runner. This was the result of two changes that coinsided. One was the use of plastic intake manifolds which stay much cooler and thus placement of the ACT sensor is not as critical, and two, having the technology to have one sensor record MAF and ACT saves cost and simplifies packaging. It had nothing to do with "heat soak". Otherwise millions of 5.0's and other engines with the ACT in the aluminum intake runner would have had everyone having hot restart problems, which never happened. This "heat soak" of the ACT sensor is pretty much limited to those who use some sort of MS tuning system. It is not an issue with stock electronics or pretty much any other after market tuning system. So blame the "heat soak" phenominon on MS as they seem to have invented it.

 

[a91what]

Except ambient air is not sitting in a hot intake runner. The sensor is reading the hot air, not the components that got the air hot. Also, we notice that as stated the ACT sensor is now part of the MAF sensor and no longer in the intake runner. This was the result of two changes that coinsided. One was the use of plastic intake manifolds which stay much cooler and thus placement of the ACT sensor is not as critical, and two, having the technology to have one sensor record MAF and ACT saves cost and simplifies packaging. It had nothing to do with "heat soak". Otherwise millions of 5.0's and other engines with the ACT in the aluminum intake runner would have had everyone having hot restart problems, which never happened. This "heat soak" of the ACT sensor is pretty much limited to those who use some sort of MS tuning system. It is not an issue with stock electronics or pretty much any other after market tuning system. So blame the "heat soak" phenominon on MS as they seem to have invented it.

Almost, the stock ecu ignores the act sensor input data, it uses the ECT sensor for hot start. Conversely MS can be configured to ignore the act sensor as well on startup. This is how I setup the base tune for the OP, this is also why for him it's not a issue.

 

[CarMichael Angelo]

Huh,...and I was thinking I wanted to get in on this debate..

Way too many 3 letter abbreviations for me though.

Are we talking about intake air temps here? and why aren't we using that 3 letter designator instead of ACT?

My a2w keeps my non boosted iat at ambient, (90 degrees) as that is what the water is typically when I'm driving around...During several test pulls I'll watch the temps rise up to as much as 115-120, but just as soon as I lift and cruise around,..right back down they go,..guess there's something to be said for the cooling effect of water, as long as there's something cooling that water after it's cooled the hot air.
My sensor is the first thing post TB in the intake stream,..(I had the luxury to put the thing where I wanted it)

 

[a91what]

Mine is (was) right at the tb. Noticed the same. Act (air charge temp)

 

[FoxMustangLvr]

So "heat soak" occurs during low air speed (idle and cruising). The small amount of air flow or the sensor gets heated from the hot cast aluminum manifold but once the TB opens up more (acceleration) the air speed increases and the sensor begins to read the air temp more accurately.

So my question is, how quickly does the ACT sensor respond to these rapidly changing temps (from being heat soaked to reading faster moving air correctly when stabbing the pedal)?

 

[FoxMustangLvr]

Another thought, is the lower cast aluminum intake heat soaking the AIR or the ACT SENSOR?

 

[a91what]

So "heat soak" occurs during low air speed (idle and cruising). The small amount of air flow or the sensor gets heated from the hot cast aluminum manifold but once the TB opens up more (acceleration) the air speed increases and the sensor begins to read the air temp more accurately.

So my question is, how quickly does the ACT sensor respond to these rapidly changing temps (from being heat soaked to reading faster moving air correctly when stabbing the pedal)?

there should be an almost immediate response.

 

[Bullitt347]

Another thought, is the lower cast aluminum intake heat soaking the AIR or the ACT SENSOR?

The air, not the sensor.

 

[FoxMustangLvr]

The air, not the sensor.

If that's the case, the sensor is reading correctly since that heat soaked air is what's on it's way to the cylinders. So moving the ACT sensor elsewhere upstream is just tricking the ECU to make it think the air entering the combustion chamber is cooler than it really is. Right?

Not trying to argue with you Steve @a91what , I'm actually learning a bit right now. I've always thought that heat soak was in regards to the sensor actually reporting a false reading due to the sensor itself being heat soaked along with the air surrounding it. I've also read that other people that moved the ACT sensor to the discharge manifold did not get cooler IAT readings where as some others reporting cooler IAT's. So there's mixed results there too.

 

[a91what]

Your car do what you like, it will however skew the AFR at idle and cruise I have seen it in your log files. This has been accounted for with o2 correction at cruise and the idle should only be off by .2afr or so, you should be good.

I have datalog s before moving the sensor showing the air charge drop in temp from 160* at cruise to under 130* under boost....
After moving the sensor 90* at cruise and a small rise to 110* or so under boost, car is intercooled.
No more issue with the AFR being skewed due to air temp.

(If the intake is able to transfer that much heat to the air in the short trip from the throttle to the runner then a fully warmed up engine should show similar readings at the throttle blade with the hood closed at idle. The piping and blower sit directly above the driver exhaust manifold then move thru an intercooler then the rest of the piping and so on.)

Open the hood on a modern car after it's warmed up, I don't care what the manifold IS made out of. it is going to be at the same operating temp as the rest of the engine.

 

[Bullitt347]

Open the hood on a modern car after it's warmed up, I don't care what the manifold IS made out of. it is going to be at the same operating temp as the rest of the engine.

I will have a contest with you. We find identical vehicles, right down to the color, only difference is, yours has an aluminum intake manifold and mine has a plastic one. After driving around for a few hrs in stop and go traffic or what not, we stop the cars, pop the hoods and then you put your bare hand on the aluminum intake and I will do the same thing with the plastic one. Guess who is going to lift their hand off of the intake manifold first? Aluminum has the ability to store a lot more heat energy than plastic can. The air flow through the plastic intake is pretty much always be cooler, regardless of under hood temps.

 

[a91what]

You know what your right, all the hundred or more datalog s I have on my laptop are incorrect. The laws of air density are defunct. All the cars I've tuned must have similar problems even though the sensors and intake manifolds are all different.
I'm sorry for doubting you you win.

 

[Bullitt347]

You know what your right, all the hundred or more datalog s I have on my laptop are incorrect. The laws of air density are defunct. All the cars I've tuned must have similar problems even though the sensors and intake manifolds are all different.
I'm sorry for doubting you you win.

You are taking this personal...don't.. It is just facts and the laws of thermal dynamics at play, well and add in the F'd up way MS deals with this issue. It is a programming problem, nothing more. Like stated before, only MS has this issue.. If you run MS, then you have to deal with it the best way you can, but it does not change the laws of thermal dynamics.