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reading lower intake temps

Discussion in '80-Series Tech' started by landtank, Aug 20, 2006.

  1. landtank

    landtank SILVER Star

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    I've been wrestling with Sumotoy's results with the hood louvers lowering intake air temps and providing an improvement to the engine's running. If that proves out then everyone would get a nice benefit from installing them.

    Because my house is in the middle of a renovation I can't seem to find my LC manual.

    My proposed method would be like this.


    Swap the egr temp sensor with the brake boost line at the intake plenum. This would put the sensor directly in the air stream.

    Now run the truck to a full heat soak with the hood closed and take a reading of the sensor.

    Then simply lift the hood to simulate the vents being installed and look for a temp change in the air.

    I realize I might get CEL but it shouldn't hamper my readings.


    The question I have is if a scanning tool such as Autoenginuity (which I have) detects the egr temp through the ECU?

    If not I should be able to read a resistance change across the sensor and get an idea of how much the air temp had changed.

    I'm running out of hot weather fast around here so this needs to get done soon because cooler weather might not be as a dramatic result.


    Any thoughts?
     
  2. landtank

    landtank SILVER Star

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    Seems I've over thought this.

    I moved things around and hooked up my scanner. I'm now monitirong water temp and air intake temp (not egr).

    Anyone know where the air intake temp is coming from?
     
  3. landtank

    landtank SILVER Star

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    Ok, so here are my results:

    Ambient temp outside read by my digital thermometer 76*F
    air temp read by ECU at start up 77*F

    Readings after heat soak (idling for 1/2 hour or so)

    Under hood temp 127*F (read at brake booster)
    water temp 187*F
    air temp 109*F

    Readings after lifting hood (idling for more than 1/2 an hour until stable)

    Under hood temp 100*F
    water temp 185*F
    air temp 95*F

    And at this point the air temp coming out of the cooling fan was 109*F

    At this point I'd like to build a temporary hood out of plywood and experiment with location and size to see how close I can come to a no hood environment.

    However I'm in the process of residing my house and can't take time for this anytime soon but at least I got this far.

    I did use the new 4.1 version software from Autioenginuity and simply pulled down the items I wanted to monitor, pretty slick.
    The water temp dropped almost immediately but it took some time for the heat within the compartment to dissipate.
     
  4. Tools R Us

    Tools R Us

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    Those numbers are close to mine and I don't see any big problems with them?

    By opening the hood you got a temp drop of, underhood 27F, coolant 3F and intake air 14F. The hood is what about what 16 sq. ft of vent area and can flow virtually all of the air that the underhood environment can produce. By putting a couple of vents that have what 20-30 sq. inches of effective vent area and flow what maybe 40 cfm when the truck is stopped, what percentage of that drop is going to be seen, probably very little.

    By driving with sensors on the truck for a month I have observed that the underhood temp is dominated by fan output temp, as expected, it's by far the largest contributor of airflow. One sensor is at fan output and have been moving the others around. As they are moved closer to the motor the readings are higher than fan output, as expected, the air picks up heat cooling accessories and from the motor. When moved closer to the fenders the readings are lower than fan output, there appears to be good cool flow introduced on both sides closer to the fenders.

    All temps dropped significantly when the fan clutch fluid was upgraded, this is a good first step for stock truck cooling performance, probably the best bang for the effort and $$$. The airflow's are well defined, with hotter air flowing close to the motor and cooler near the fenders. Probes placed just a few inches apart show big reading differences with the truck at speed, it looks like the designers were aware of this and mounted most of the electronics and other heat sensitive devices in the cooler areas.

    Some of this was an effort to find the "trapped air" spots that have been talked about. I define trapped, dead, stagnate air as air that is not flowing, flows circularly in one area getting constantly heated and is not getting flushed out. This should be easy to find with a temp probe, it will be a reading that continuously rises or is greatly higher than the surrounding area with no good reason. From my finding so far there is good airflow, if it were blocked or stagnate air, all of the air under the hood would heat soak and be much closer in temp, the well defined zones signify strong airflow.

    If I saw the need to add vents in the hood, they would be close to centered. This is where the highest temp flow is and if your going to vent, it makes sense to vent the hottest air? Also the vented hot air and fumes would be more likely to go over the roof of the truck and be less likely to effect the passengers. But I doubt that it will have much effect on intake temps or any of the cooling systems on a stock configuration truck. For intake temp reductions maybe looking at the right marker light area, like opening the trim under it may lower it a few degrees when moving. Possibly sealing the area where the air tube goes into the fender cavity with foam any have an effect? But would feel any power increase, would it make an improvement, or would it be more of a good sig line trivia like, I lowered my intake temp 8F?
     
  5. landtank

    landtank SILVER Star

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    If I have time I'm planning to see exactly how much venting it would take to keep the temps down at idle. This seems to be where the truck gets hot. Another thought was to heat soak the engine as I did and then go for a drive and see what happens to the air intake temps while moving.

    I figure it will either prove or disprove the need for vents and if needed, what size they need to be to be effective.
     
  6. Tools R Us

    Tools R Us

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    Put the sensors on and drive and you will see how it works. When you stop it heat soaks, all of the air temps rise, the fan output some, but mostly the cooler areas heat to closer to fan output. As soon as it starts moving the temps drop and the cool air areas are better defined. The cooler air is brought in by ram air, so when stopped it is greatly reduced, unless cool air fans are added or the hood is removed, it will always act this way. I don't see it as a problem, every vehicle that I have measured has worked this way and I am sure that the designers know and design for it. As long as the system temps stay stable, coolant, A/C, etc., why worry about it?

    The stock system with the upgraded clutch works well and recovers from idle heat soak very quickly up to about 105-110F. After that it struggles, recovery times are much longer, it's probably normal as most systems are probably running close to Max capacity at that temp.

    My air temps dropped about 15-30F with the clutch fluid change and system temps are now very stable, pleased with it's performance. The only thing that I may play with is sealing the air cleaner neck to the fender opening and maybe venting that area from the front to see if it drops the intake enough to be worth it. Next test is making a couple of trips with the right corner light out and see what effect that has on intake temp. Photoman's idea of making that light a grill may work or opening up the slot under it maybe good for a few degrees?
     
  7. Waggoner5

    Waggoner5 SILVER Star

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    Rick, I did this on an LT1 conversion that lives in Florida. This did make a huge improvement in underhood temps and in this case helped the IAT temp because of the open filament aircleaner. Granted its major work, but it made a 10 degree diff in water temp and a 50 degree diff in IAT. With the GM though, I could go in and change the IAT parameters. GM was looking for a hotter temp relationship between the IAT and the coolant temp just like Toyota.
    i.JPG
     
  8. SUMOTOY

    SUMOTOY

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    Rick:
    Good data. I repost the below here, since it is most relevent to what you are doing. And in fact, he got a 34F rise in intake at idle at 104F ambient, you have a 32 degree rise in intake at 77F ambient. Interesting?! You have to identify which goal you are after IMO. If it's only low speed IAT temps, then center of hood is probably best vent location. If it's high speed IAT temps and/or ram air convective heat release at speed, then outside the hood rise is probably best vent location.

    This is exactly the principle behind "cold air intakes". Which may support a more effective mod at addressing *only* IAT.

    Edit: Glad you were able to find the IAT output value

    ST

    ---------------------------------------------------
    From: Added Airflow to the 1FEFZ thread, the hi:banana: version...
    Tools R Us
    Ambient temp = 104F
    In filter (IAT) = 138F



    ... Now, let's take those numbers and work with them a bit, in an effort to show how density affects performance, then maybe the need for vents. This is a preamble to Part IV of my ABC thread, but the data is quite convenient. Thanks for nabbing it *in* the airfilter. A good other measure would be airfilter to box as a relation for those not so probe equipped.

    We know from Ideal Gas Law Theory that D=P/R*T, so air density drops as a function of temperature increase (pressure constant), or as a function of pressure decrease (temperature constant). They are directly related. Let's assume Kevin to be at sea level (1000 mbar = 1 atmosphere = 14.7psi). Convert the 138F to 59C and the 104F ambient temp (rounded) to 40C. First, let's see the reduction in pressure due to temp. This chart is handy to compare percent loss of air density due to temperature.

    http://www.ce.utexas.edu/prof/kinnas...S/densgif.html

    So, if we follow 59C on the density curve we get a value of 1.05 and at 40C we get a value of 1.15 a difference of 9% in air density going from 40C temps to 59C temps.

    We also know that if temperature is a constant, but pressure decreases, we also lose density. The rule of thumb for altitude is a decrease of 3% air density for every 1000ft in altitude (temperature constant). So, to compare Kevin's measured air temps vs air density to altitude, an airbox temp measure of 138 (vs 104 ambient) 9% decrease in air density would be equivelent to running his truck at 3000ft.

    An airbox measured temp of 155 (vs 104 ambient) is 12% decrease in density or equivelent to 4000ft.
    And an airbox measured temp of 176 (vs 104 ambient) is a 15% decrease in density or equvelent to 5000ft.

    What does all this mean? Well, if those airfilter temps get high enough, you might as well drive your truck in Denver! I compared altitude because those that have brought trucks into denver know they get doggy. This is also a good way to understand how cold air makes your truck feel peppier, because you have increased the intake density. This is also the logic and reasoning behind 'cold air intake' mods.

    The bottom line. If we can reduce airbox temps by vents, shielding, ducting, or airflow improvements, we can increasse the performance of our trucks. The closer we get to ambient temps in the airbox, the closer we are to 'actual' altitude vs effective altitude.The closer we get to ambient temps in the airbox, the closer we are to 'actual' altitude vs effective altitude.
     
    Last edited: Aug 21, 2006
  9. SUMOTOY

    SUMOTOY

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    A couple of thoughts...
    From what I read of your experiment, your null hypothesis is that hood venting has no effect on IAT. Your data and experiments will either support or not support that null. It appears to already support that from your data (an open hood is a hood vent by definition). Defining all the advantages of less than an open hood will be the bigger question and implications for further research...

    The data could either support or not support the addition of hood vents to address IAT part of the equation under the hood. It's not accepted testing methodology to claim you "prove or disprove" anything. "To be effective" and it's definition could and might be different between a stock truck and an SC truck. In a stock truck, IAT variations may have some ecu offset as Gary seems to propose. In a force inducted truck, intake air density (pressure and temp) affect compressor efficiency and charge air temps. Our best hope is that the benefits between stock and forced induction are measurable and comparable as we define only extreme environment.

    I also don't believe it will prove or disprove the 'need for vents' if you have not somehow addressed the lowered backpressure of airflow under the hood. Remember radiator fan efficiency 'as installed' includes factoring vacuum in front or thru a core, and pressure on the back side of the blades. It might result in a measureable temperature variation, but that needs to be correlated and supported.

    I say just get as much data as you can for now. IME, this forum will take on the debate of it's worth.

    :cheers:


    ST
     
    Last edited: Aug 21, 2006
  10. landtank

    landtank SILVER Star

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    Scott, slow down buddy, I'm only in the exploritory stage here.

    Remember, I take baby steps not leaps and bounds like yourself.

    My next test which should happen this weekend will be to determine the possible effectiveness of venting at driving speeds.

    I'll do this by setting up the laptop to record the IAT, start the truck and immediately drive the truck.

    I'll drive the same route that I did for the clutch testing which is some secondary roads, a highway run and then back to secondary roads to the house. Once I arrive at the house I'll open the hood and then compare the IAT during the drive and that with idling for 15 or so minutes or until the IAT stablizes.

    If I can find a nice heavy quilted moving blanket I might do a second run before the open hood test with the filter canister wrapped in it for more comparison data.

    With this data we should be able to determine the greatest possible effect that venting could produce and then evaluate whether or not it is worth the effort to move forward.

    BTW, I'm at sea level or within 20 feet of it.
     
  11. SUMOTOY

    SUMOTOY

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    Rick:
    It would appear several are having some shakes over goals and targets, which IME on another thread, are better presented as nulls and hypothesis. They do have some value, and can identify differences and/or correlation problems.

    As one who was educated to squint/shake/tremor at the ability of a test to 'prove' anything, I wanted to take a pre-game time out, that's all.

    Data is absolutely fine with me!

    :cheers:
    SJ
     
  12. landtank

    landtank SILVER Star

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    my clutch thread was actually conceived after some thought provoking info was posted by Tools R Us about his observations with the new fan clutches.

    This thread was started because of your posts on lowering IATs.

    I don't mean to take any of the thunder from either of you for your contributions. But for me to completely understand some of this stuff I need base line values and what I see is a logical progression to a final conclusion.

    That's basically what I'm trying to do here. When I said prove, what I was thinking was if driving the truck yielded identical IATs as idling with the hood open than maybe the vents aren't going to yield any benefit at speed, proving no need for them. But maybe a poor choice of words.

    Somehow I think at some point I'll be driving the truck around my test course with the hood sitting in the garage just to satisfy to myself completely that I've considered all options and made all comparisons before deriving any conclusions.
     
  13. cruiserdan

    cruiserdan SupportingVendor Emeritus Moderator

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    Strap it to the roof, it will look more sporting.....:hillbilly:
     
  14. Cattledog

    Cattledog

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    Sumotoy

    I don't see where Landtank has made the the connection of the temp of the metal that makes up the air box to the IAT.

    I do observe that by opening a hole of 16 square feet above the engine provides better cooling in IAT, Coolant temp in a single test. I am interested in the IAT data vs atmospheric temp while running at 3000 rpm on the highway. And also what the IAT temp is before and after 1 minute leaving a stoplight (say 2 miutes stopped. Running at idle for 30 min is pretty extreme. It is a good test to look for heat soak though.

    You might want to consider the dew point will also have a notable effect on the air density. :popcorn:
     
  15. SUMOTOY

    SUMOTOY

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    Cattledog:
    I'm only intersted in whatever data one can come up with. We agree it's premature and inappropriate to prove anything. I've been advocating only that folks do things and take measures. My experiences here have been that a lot of folks want to be virtual assistants and professors. Taking any type of data isn't rocket science, it only needs to be identified and repeatable. From taking the hood off, to taking the shroud off, to just reading OBD outputs.

    I am very interested in taking action and taking measures, I've always done that with my automotive toys. Sharing my mods, my methods and my data with *my* conclusions. What makes that controversial? Only that some folks want to take no action, but tell me what I did wrong. Where's that data?

    Rick has taken that to heart here after a lot of prodding. I applaud him for it. I did take a time-out to put forth a gentle reminder that data doesn't prove or disprove anything, it supports or doesn't support other data, clearly identifying possible explanations for either scenario.

    What I have notice and consider all-good, is folks have moved from it feels better (that's not *my* origination) to picking up some sort of measuring device and quantifying that. I urge the pundits to encourage this behavior, eventually it might have significance. Right now, mine has none, because the 'n' sample is small, and the specific variables are many.

    That shouldn't stop anyone from data collection and reports.

    My .02

    Scott Justusson
     
  16. DaveyBoy

    DaveyBoy

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    And this is why this forum is not for the mentally challenged....myself included :D

    Seriously though, thanks for all the interesting research.
     
  17. SUMOTOY

    SUMOTOY

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    Humidity/dew point vs Density

    Cattledog:
    Dew point does indeed affect density. A variable we might be able to address at some point, but normally air density vs altitude use a 'correction factor' for the Dew point. Since Dew point and saturation changes with temperature and altitude, I'm not sure this can be as easily calculated as density vs altitude (proportional) or Density vs temperature (inverse proportional).

    What I would expect to see, if 'n' data gets high enough, is that those in hot dry climates (higher density) will see different results of heat management modifications than those in hot moist climes (lower density), or those in cold dry climes (higher density) vs cold moist climes (lower density). These differences might point out significance of changing a specific variable for maximum benefit *given* the ambient operating evironment.

    I look at ambient conditions as a variable I can't control. I *can* affect and control engine operating temperatures, I can affect and control lowering pre SC IAT's, I can affect and control underhood engine temps and pressures. I can't control ambient temp, pressure or it's dew point. Hence those are all givens outside the scope of relevence really. It may have some significance as to how much affect and control a given mod has, but that would require a lot more data collection.


    :cheers:

    Scott Justusson
    FZJ80 Supercharged
    Current med/low density ambient conditions
    78F - 61% humidity - 63F Dewpoint
     
  18. landtank

    landtank SILVER Star

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    It wasn't until I thought I had found a way to take some readings without any additional expense that got me to start to evaluate the system. I wasn't about to buy an IR gun based on what I had read in the ABC threads. Strange thing is that I already had the stuff laying around.

    Right now I'm just trying to base line some differences between idling and driving, hood no hood and maybe insulated filter can and not.

    With this data I'll first try and evaluate the worth of hood vents and if so, draw some kind of relationship between driving and idling because further testing will be idling only.

    If insulating the canister yields some benefits than that will have to be done prior to vent testing.

    If I enter that phase, I'll be systematically blocking off the hood opening in an attempt to evaluate where and how big the vents would have to be to have a good impact on engine performance. During this phase is where removing the fan shroud would come in as it would either decrease the need for venting or increase it.

    Thought I would just map out what I have in mind for some input.
     
  19. Romer

    Romer fatherofdaughterofromer Moderator

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    Sounds great Rick, I will be eagerly waiting your results.
     
  20. Tools R Us

    Tools R Us

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    Tried an experiment with surprising results. The goal was to get cooler air to the air intake at speed, maybe pickup some power for highway hill climbs. Fresh air for the intake is pulled from the cavity between the fender and fender well, supplied from air leaks around the lights and the grill area. I was thinking that opening up the trim under the corner marker light would provide additional cool air at speed.

    Put a temp probe in the air filter and went on my delivery, on the way, highway 60 mph 98F ambient, 139F fan output, 112F air filter. Stopped at Costco to feed the truck and I, while waiting on the fuel to pump, popped the right corner light out. Made a nice ~4" x 6" hole with the air intake box very visible, new ram air!:cool:

    [​IMG]

    Cruising the parking lot the temp was 12F higher than when I pulled in, WTF?:eek: Let it idle in the parking spot and checked the hole, hot air was coming out, not blowing out just a slight movement of warm air. Not better at low speed.

    Pigged on some pizza and hit the highway back to the shop, recorded at ~65 mph, 104F ambient, 148F fan output, 143F air filter, played with the speed on surface streets and the worst that I found was at ~30 mph between stop lights 158F fan output, 157F air filter, WTF!:eek:

    My guess is that the high pressure airflow at the front of the truck, becomes disconnected from the body as it flows around the edge of the fender, making a low pressure area sucking air out of the hole.

    [​IMG]

    The area along the fender well is normally one of the coolest spots under the hood on my truck, to get fan temp air over to the air intake that cool airflow must no longer be there? Anyway not a good place for a vent, if you were willing to make an air scoop it may work, but that is not what I had in mind. It wasn't a total loss, learned something and reinforced the need for careful testing when making airflow changes.:cheers:
     
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