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  1. #1
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    Intake Air Temp Tests III: Street Heat *Results*

    NOTE THIS THREAD WAS REORGANIZED, but I left the original first two posts largely as-is since people had made posts discussing them. If you are coming to this thread now note the following: *PROPERLY ORGANIZED* RESULTS FOR ALL TEST LEGS ARE FOUND IN POST #3. OVERALL RESULTS ARE IN POST #4.
    =========================


    Don't know what this is all about? Read about it here. And refer to that thread for the explanation of the protocol.

    OK so today was the day that the 'fender pull' intakes were tested.I have five logs per intake, and while I got back late today, I thought I would do what I can to at least get up one comparative graph. Since I can't overlay Predator logs directly, what I did was sample the data at rough one second intervals (every 10 entries in the Predator log) and make up my own graph using Microsoft Graph. If someone knows how to do this in Excel and wants to help out, give me a shout.

    I started the graph at the moment I launched and stopped them as soon as the temp reached its minimum for the run. And yes, these are 18-second graphs. If you launch softly on the side of the road from a dirt shoulder, thats what you get. This wasn't a speed contest.

    If you want to see all of the PIDs I was capturing (like RPM, MPH, ambient temp etc.) you can download the complete Predator datalogs here and load them into your Predator dataviewer. Look for the fifth log in each series. That means 0105.log, 0205.log, 0305.log and 0405.log. #1 is alloy, #2 is steel, #3 Nomex/silicone and #4 RT stock.

    At the bottom of the graph are the actual temperature samples, entry by entry.

    So displayed first is the "1/4 Mile Drive". What this is in fact is two tests. The first component was a 6-minute cook ... I sat and idled the engine for six minutes to deliberately soak it. This more or less simulates those last few minutes in a staging lane when you have to close your hood and line up.

    Unquestionably, the materials tested did not finish in the order I expected them to. I'm going to run the cook portion on the steel again tomorrow to make sure I didn't do something stupid like shut the motor off, but don't expect any change. (edit: ran it again and results shown in cook test graph below. Something is off as the steel came out equal to two other intakes and not way below them)

    The corrected ambient air temperatures for each test is as follows:

    • Alloy: 83 degrees
    • Steel: 82 degrees
    • Nomex/Silicone: 85 degrees
    • RT Stock: 86 degrees

    Here's how they shake out when you equalize every curve for 83 degrees ambient.



    One BIG thing thats worth noting: Over the years, a lot of people have quoted airflow statistics and made calculations that prove to us that the air doesn't stay in the tube long enough to heat up. I've believed it myself. Well, looking at those curves. Bottom line is the instant-cooling argument is out the window if IAT readings are your measure for intake air temperature. In other words, maybe the air DOES change instantly, but if it does the IAT sensor doesn't see it that way. And since the IAT governs HAL its the IAT reading that matters.

    Also note how close the units ended up. Only 9 degrees separate them, even if its only at the end of the 1/4 mile drive. And thats before I have corrected the chart for the few degrees of temp variation.

    There's lots more, and more graphs need to be made up to illustrate what was tested. Don't draw any conclusions about a given production material over this one test.
    Last edited by MattRobertson; 07-30-2015 at 03:42 PM. Reason: Revised the datalog link.
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  2. #2
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    OK here is the first round on the short rams. I didn't get the plastic unit tested today but I'll add it. It won't be difficult finding a hot day in this temperature range.

    Speaking of which, all tests were conducted at 82 degrees so no correction is necessary.



    And here are all of the intakes together, temperature corrected to 83 degrees.




    ================================================== ================================================== ===========

    SO... the test above was a 1/4 mile drive, which was datalogged as you can see. What I didn't do on that day was datalog the 6-minute cook portion of the test. Looking at the results of the steel test, I smelled a rat. If I had datalogged the cook segment, we would have had a complete picure of how we got to the starting points on the above graph.

    So lets do that. I re-ran the 6-minute cook segment in my driveway and, since it wasn't in the middle of nowhere 105 miles away from home and 50 miles from the nearest toilet or power plug, this was a much easier test to both run and control. Exterior temperature was either 52 or 54 degrees since this wasn't run in the middle of a desert, and the lower temperature gives us some extra room to observe temp increases that are due to IAT warmup rather than it just being a hot day.

    So here's the chart:

    Some observations: The steel fender-pull still did well. I continue to think that something skewed the 1/4 mile drive starting temp for that intake - and this test bears that out since it started at almost the same spot and ended at exactly the same spot as two other intakes. If the original 1/4 mile test had been accurate, we should have seen its ending temperature be way lower than it was here.

    Some surprises:

    • The short ram alloy intake had the lowest temp during the 1/4 mile and clearly heated up the slowest of the bunch in this test, even though its ending temp was exactly the same as the steel and stock intakes.
    • The short carbon fiber intake was the worst of the lot. Anecdotally, I burned my fingers taking the thing out of the engine bay afterwards. This is a Gen 1 AirHammer and is made MUCH more thinly than the very solid Gen2. Perhaps thicker cabon fiber would make a difference?

    Some not-so-surprises

    • The RT stock intake did really well. It essentially matched the curve of the steel fender-pull, and shares the lowest ending temperature reading with two others.
    • The steel AirHammer was the second-wost of the bunch.
    Last edited by MattRobertson; 06-25-2009 at 02:11 AM.

  3. #3
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    OK lets try and get organized. I started writing up this thread as-it-happened but that wasn't working. Especially since its August 1 2009 as I write this and much time has passed. Sorry I was busy. I'm going to leave the first posts alone as much of the dialogue that follows is predicated upon their original content.

    The test was set up in legs, and lets display the data with all intakes included, leg for leg. Also since the graphs can be hard to read, I am including a 'score' chart for each test, and overall. These are essentially easy-to-read report cards on who did well and who sucked. The score card is arived at simply by averaging the temperatures you see in the data chart. And remember, if you want to dice up the data even more finely, the link to the data logs - which provide data every 1/10th of a second - are provided in Post #1. Knock yourself out.

    If you want an explanation of what the legs are, generally those can be had - including satellite maps - in the thread linked in Post #1.

    Leg #1
    To equalize the starting environment, at the moment of engine start the Predator datalogger was told to reset its connection. This results in roughly a 45-second heat soak.


    NOTES:
    Clearly, the short steel and short carbon fiber intakes (a Gen 2 steel AirHammer and a Gen 1 Carbon Fiber AirHammer, presently sold by Airflow Innovations Corp. as Arias) have the two highest starting temperatures - they soaked in heat the most quickly prior to the stat of the run. From the looks of it, not a whole lot separates the field once the car gets moving. However, the short alloy (a Frankentake IV) spiked very high (up to 110 degrees, not seen due to the time scale on the graph) as soon as the motor was put into gear, but prior to getting up to speed. This points to the unit being very sensitive to external conditions.

    SCORE:

    ================================================

    Leg #2
    After the 40 mph cruise, the protocol called for stopping on the side of the road, raising the hood and sitting with the engine off for five minutes. Following this, the hood was dropped, the motor restarted (using Mopar remote start for uniformity) and the next leg was run while holding 60 mph on cruise control.


    NOTES:
    While there are differences, and once again the graphs are not the easiest to read when overlaid over one another, one thing is clear: Some intakes heat up a LOT after engine shutdown even if you raise the hood. And some don't. This time all of the short rams fared the worst, with short steel once again turning in a worst-of-group performance in terms of initial temperature.

    SCORE:

    ================================================

    Leg #3
    I'll warn you right now... this test is going to look like a mess. Just learn to love the messy graph because if anything, this one test did what I set out to do in the first place: See how an intake performs in start and stop conditions.

    To recap, while I wanted to test start and stop conditions, I knew that such a test was by its nature an invitation to imprecision. Urban traffic is not even and rhythmic, but to get decent results I had to try and come up with such a thing. I got the idea on how to do it by accident when driving through the small, middle-of-nowhere town of Chowchilla, California on my commute to work. This realization wound up causing me to completely relocate the entire test to take advantage of this urban environment. As stated elsewhere in the protocol thread, Chowchilla is a VERY small town. Its downtown area consists of a grid of small, 25 mph streets and most intersections have no stop sign controls. Some do but most do not. I went thru the town and developed a route that allowed me to slowly drive through at a slow, IAT-unfriendly speed, with occasional VERY brief stops, where thanks to the lack of traffic (automobile, bicycle or horse-drawn) I could just tap the brakes to a stop and continue right onward.

    Driving over and over at slow speed through a small rural farming town in a lowered, rumbling hearse with purple flames running down the side is probably not the brightest idea if I wanted to get in and out in one piece, so I took the precaution of discussing my plans and explaining what I was up to with the duty officer of the day at the Chowchilla Police Department. This would keep me from getting pulled over, and if anyone dialed 911 and told them Satan's skinhead minion was casing the joint, emergency response would let them know not to worry.

    When you look at this thing, try and focus on the starting and ending points and only the general trend of the curves. Make use of the data set displayed under the graph when things get dicey, visually.

    and remember... This leg begins after a 5-minute engine stop on the side of the road with the hood DOWN.

    OK out with it.., here's the performance graph:



    NOTES:
    Good God in heaven what a mess. First of all, lets see why we have the temperature variations. This is a screen shot from the datalogger. This one comes from the Alloy test and after you look at it I will explain why the alloy test is longer than the rest, and why they all more or less have different time durations.



    What you are seeing is a lot of quick starts and stops, with some intersections that are uncontrolled so I can just roll thru them slowly. Note the two relatively long intervals of stoppage just prior to two minutes and just after 8 minutes. Thats the stoplight at the edge of town. This run was a loop that entered town, ran thru it in a grid pattern and then exited again. The alloy test had the bad luck of being the only one that caught both lights. Some of the others caught just one and the shortest you see made them both. c'est la vie.

    I *could* spend the time to trim the test to be roughly between the two occurrences of the lights for a more pure subset of data, and someday I may do this, but honestly I don't see this as being particularly critical - and besides if you, gentle reader want to help out and do this, feel free to download the logs from post #1 and get to it.

    SCORE:



    The graph above is with all temperatures equalized to 83 degrees. Here is the actual temperature of each test, where I used a separate thermometer than the that gives the datalog PID in the logs you can download.


    ================================================

    Leg #5
    Described in the first two posts above, one thing worth noting is the short steel intake was given 20 rather than 18 data points because, unlike the other units that all reached their minimum by 18, the short steel didn't stop falling until 20. Only the first 18 data points will be used to calculate its score to give it equal footing with the other units.

    NOTES:
    See Posts #1 and #2

    SCORE:

    ================================================

    Leg #6
    Described in the second post of this thread.

    NOTES:
    See Post #2 above

    SCORE:
    Last edited by MattRobertson; 08-11-2009 at 11:50 PM.

  4. #4
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    So whats the overall score? Here it is so far:



    A green-shaded box means that intake scored best on that particular test, and a red-shaded box means the opposite. The Overall score is an average of each leg's results.

    Right now the short ram alloy intake is walking away with the low-temperature prize and I have to say that *is* a big surprise that I would have never called.

    But it ain't over yet. There are is four three two one more test legs, and even I don't know what the datalogs say until I run the graphs (if you want to know before everyone else does, download the datalogs and see for yourself).
    Last edited by MattRobertson; 08-12-2009 at 12:12 AM.

  5. #5
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    Did you end up getting a Carbon Fiber, or use a plastic aftermarket intake?

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  6. #6
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    Interesting


    Like you said, not what someone would expect. I notice from datalogging during my quarter mile that the IATs are very important and they don't instantly drop when you begin to roll (even with a RDP fed at the front bumper brake duct).

    I also wondered whether my black powdercoated intake and black silicone tune absorb alot of heat from the sun from sitting with the hood open. I think they do and in some cases throwing a white (reflective) damp (for evaporative cooling) towel over the intake tube might help more than a bag of ice over the intake manifold.
    8's N/A? Been there done that





  7. #7
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    Quote Originally Posted by Leadfootluke View Post
    Did you end up getting a Carbon Fiber, or use a plastic aftermarket intake?
    yup he got mine

  8. #8
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    Regardless of what the mfg engineers say, it takes time for the IAT sensor to cool down once it's heat soaked. The only way an IAT sensor will cool more quickly is if it is sprayed upstream from the sensor since a mist will draw off the heat more quickly than high speed airflow alone. No one has yet come up with a way to fool physics.

  9. #9
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    Quote Originally Posted by MattRobertson View Post
    One BIG thing thats worth noting: Over the years, a lot of people have quoted airflow statistics and made calculations that prove to us that the air doesn't stay in the tube long enough to heat up. I've believed it myself. Well, looking at those curves. Bottom line is the instant-cooling argument is out the window if IAT readings are your measure for intake air temperature. In other words, maybe the air DOES change instantly, but if it does the IAT sensor doesn't see it that way. And since the IAT governs HAL its the IAT reading that matters.
    Maybe my "cool tube" idea (that we discussed over PM) wasn't so far off....and now shows even more merit for a test...

    Now as a test to see how valid the argument is for the IAT housing moving temp to the sensor.....
    Maybe you should try using a hair dryer on the IAT sensor plug while the engine is off and under idle and see how much temp is transferred to the IAT sensor.
    Actually a heat tape may give you a more consistent reading.
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  10. #10
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    You must keep in mind that the IAT element, the thermocouple bead itself that changes in resistance for a given temperature, is doing the measuring and is not subject to surrounding material temperature gradients.

    In other words, the element itself is responding "only" to the air temperature it is supposed to read, and not the plastic structure that supports it. If it were, then it would a very poor sensing design. BTW, the actual response rate (rate-of-change) of the sensor itself is "very" fast!

    Now "how" that raw signal is averaged and processed by the PCM to cause a change in A/F ratio needs to be considered.
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  11. #11
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    Quote Originally Posted by Hemissary View Post
    You must keep in mind that the IAT element, the thermocouple bead itself that changes in resistance for a given temperature, is doing the measuring and is not subject to surrounding material temperature gradients.

    In other words, the element itself is responding "only" to the air temperature it is supposed to read, and not the plastic structure that supports it. If it were, then it would a very poor sensing design. BTW, the actual response rate (rate-of-change) of the sensor itself is "very" fast!

    Now "how" that raw signal is averaged and processed by the PCM to cause a change in A/F ratio needs to be considered.
    Exactly,
    This is why I don't think the temperature of the "holder" for the IAT sensor has much effect.
    Last edited by netnathan; 06-25-2009 at 10:52 PM.

  12. #12
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    Quote Originally Posted by netnathan View Post
    Exactly,
    This why I don't think the temperature of the "holder" for the IAT sensor has much effect.
    ^^^Agreed, the plastic holder is not an issue. The key is the sampling rate of the ECU/PCM as it is reading and averaging the signal voltage.

    One of the other intake variables is the ECU/PCM sampling rate of the MAP (Manifold Absolute Pressure) sensor. Since both the IAT and MAP are leading indicators of the intake air charge, it would be also interesting to correlate the two readings along with the resulting injector cycle voltage (fuel charge). Has anyone isolated these sensor/injector values using a Dashhawk or StarScan? Don't know if it can be done, just thought it would make for interesting analysis.

  13. #13
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    Quote Originally Posted by Hemissary View Post
    You must keep in mind that the IAT element, the thermocouple bead itself that changes in resistance for a given temperature, is doing the measuring and is not subject to surrounding material temperature gradients.

    In other words, the element itself is responding "only" to the air temperature it is supposed to read, and not the plastic structure that supports it. If it were, then it would a very poor sensing design. BTW, the actual response rate (rate-of-change) of the sensor itself is "very" fast!

    Now "how" that raw signal is averaged and processed by the PCM to cause a change in A/F ratio needs to be considered.

    I would suggest the design of the harness and sensor holder could transfer radiant heat from the engine to the thermocouple, its not well insulated from the holder and a large portion of the holder is exposed to the radiant heat from the engine and radiator.

  14. #14
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    Quote Originally Posted by wheelife View Post
    I would suggest the design of the harness and sensor holder could transfer radiant heat from the engine to the thermocouple, its not well insulated from the holder and a large portion of the holder is exposed to the radiant heat from the engine and radiator.
    Could wrapping the external portion of the thermocoupler with a split loom heat shield help reduce the effect of radiant heat? Is it worth a try?

  15. #15
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    No, the mass (or lack thereof) of the bead and the manner in which it is suspended/isolated on the end of it's support housing makes it pointless. The actual temperature of the bead itself is the same as the air moving past it...

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