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The 1998 - 2000 LS400 Air Intake Tube is astride the 190 Fahrenheit thermostat housing with 1/4" spacing for several inches...enough exposure to increase air intake charge temperature.
The intake tube is quite warm to the touch and so determined to find a solution.
Design Engineering, Inc. Offers a line of thermal control products and selected their REFLECT-A-COOL self adhesive relective aluminum foil with a base layer of glass fiber.
Covering the bottom of the intake tube from the throttle body to the flex coupler required about a square foot of material.
It was unnecessary to cover the top half of the tube thus retaining stock appearance.
The bottom was thoroughly cleaned with CRC Air Intake Meter Cleaner(safe on plastic) to promote adhesion.
Air Intake Tube at thermostat housing before removal and application of Reflect-A-Cool.
Bottom of Air Intake before application of Reflecta-A-Cool
Moo
Slits were cut to allow material to better conform and sit flat on curved surfaces of Air Intake Tube surface without puckering or seperating.
Relect-A-Cool applied.
Air Intake Tube reinstalled with heat reflecting Relect-A-Cool tape. The tape is not visible from top of engine. (For those in the know..this is anthe more efficient S430 thermostat housing neck...)
The Air Intake Tube felt warmer to the touch near the area above the termostat housing...and that heat was acquired from someplace on the engine...The thermostat is in close proximity and has a set operating temperature, so perhaps the likely culprit.
Ideally someone with a thermal imaging device could capture this in color, or take point readings with an infrared thermometer device. My best guess is 3-5 degrees Fahrenheit to the intake charge.
The air cleaner inlet assembly (item 17751 on attached Lexus parts diagram) is also warm to the touch..possibly because it rests acoss the top of the radiator..and performs a secondary role as the top of radiator air inlet conduit...seems logical residual heat rising from the radiator would contribute to increased temperature there.
I suppose ambient temperature, relative humidity, elevation
and type of driving- city vs. Highway are all variables here
Am considering treating the bottom of the air cleaner inlet assembly with heat reflecting material as well.
It would be interesting to see if someone could capture a color thermal image of the top and bottom of the air cleaner inlet assembly during operating temperatures.
a thermal image would not actually be that helpful, the plastic intake tube doesn't conduct heat well so even if warmed up it would not pass much of it to the air passing through it. Especially when you consider it's in contact with the MUCH hotter throttle body and intake manifold.
The temperature of the air passing through it is what matters.
When touching the air cleaner inlet assembly(above radiator) and air inlet tube from air cleaner box to throttle body) at engine operating temperature, the surface temperature is greater than the ambient air.
It was 40F here yesterday, so the plastic intake components picked up heat elsewhere.
This suggests, while, arguably, being cooled by ambient temperature (40 F) airflow that it is still quite warm to touch...and being able to feel heat the plastic intake components are transferring heat be it to a hand or absorbed by intake tube air.
Since these components are absorbing heat, then the temperature differential between ambient and pre-throttle body intake plastic assembly is creating some level of airflow turbulence...not to the extent of our exhaust pipes which have heat shields to maintain velocity and reduce temperature differential induced turbulence...
The other factor is air density... the warmer pre throttle body air intake system experiences decreased air density as it warms. Perhaps you agree density does not increase when subjected to radiant heat from radiator, intake manifold and thermostat housing.
We know the throttle body temperature is coolant controlled, so am really looking at air density before that point.
Perhaps a ClubLexus member with a thermal imaging camera is willing to capture an image or take temperature measurements of the intake system.
Nice work in taking the initiative to try something out and share it, but ...
That product you used is aimed at reducing _radiant_ heat transfer, not convective. It prevents heat transfer by providing a reflecting barrier, not an insulating one (like conventional wall insulation glass fibers or neoprene).
So it would work well if you needed to protect a low-temperature part from a 400*F part or 1000*F cat converter. But the radiative heat transfer between a thermostat housing at coolant temp and the air intake will not be something to worry about. Radiative heat transfer varies by the absolute temperature to the 4th power (that's a high power, which means usually it's only high temperatures where radiation matters). At the temperatures you're dealing with here, the convective heat transfer would probably be more, and even that I would say is not something to worry about.
Regarding using a thermal imaging camera, those and IR pyrometers make assumptions that the emissivity (a property of the material) of all surfaces is a particular thing (like black or almost black). So a foil at x *F will read lower than a black body at x *F, even though they are really at the same temperature. The black item will just be emitting more, whereas the foil one will be emitting less and reflecting more, if there is more to reflect. So the IR measurements will be unreliable. A thermocouple with a voltmeter should measure those temps with no problem if you want hard data.
And after all that, even if you iced the whole intake, would it have any effect other than increased HP at WOT? I know that's a nice thing to have, but ...
Nice work in taking the initiative to try something out and share it, but ...
That product you used is aimed at reducing _radiant_ heat transfer, not convective. It prevents heat transfer by providing a reflecting barrier, not an insulating one (like conventional wall insulation glass fibers or neoprene).
So it would work well if you needed to protect a low-temperature part from a 400*F part or 1000*F cat converter. But the radiative heat transfer between a thermostat housing at coolant temp and the air intake will not be something to worry about. Radiative heat transfer varies by the absolute temperature to the 4th power (that's a high power, which means usually it's only high temperatures where radiation matters). At the temperatures you're dealing with here, the convective heat transfer would probably be more, and even that I would say is not something to worry about.
Regarding using a thermal imaging camera, those and IR pyrometers make assumptions that the emissivity (a property of the material) of all surfaces is a particular thing (like black or almost black). So a foil at x *F will read lower than a black body at x *F, even though they are really at the same temperature. The black item will just be emitting more, whereas the foil one will be emitting less and reflecting more, if there is more to reflect. So the IR measurements will be unreliable. A thermocouple with a voltmeter should measure those temps with no problem if you want hard data.
And after all that, even if you iced the whole intake, would it have any effect other than increased HP at WOT? I know that's a nice thing to have, but ...
Anyone with a thermocouple is free to try.
Meanwhile, does anyone dispute their plastic intake components are warmer than ambient or that cold air is denser than warm?
Meanwhile, does anyone dispute their plastic intake components are warmer than ambient or that cold air is denser than warm?
No, but the question is, is there any real benefit to doing the mod? Given that plastic and air are poor conductors and that air in that pipe is being constantly refreshed, is the temperature really going to much lower as a result of the mod? I really would have to say no.
No, but the question is, is there any real benefit to doing the mod? Given that plastic and air are poor conductors and that air in that pipe is being constantly refreshed, is the temperature really going to much lower as a result of the mod? I really would have to say no.
The plastic intake system components are warm..with ambient temperature air flowing through them.
My basic understanding of thermodynamics is heat dissipates to cooler surroundings...
The heat is coming from somewhere and dissipating to....
We all agree the warm intake components are not the result of ambient air.
What is debated is how much engine heat is sinking into the pre throttle body intake system, and It's effects.
Suggested the thermal imaging to demonstrate the heat is from cooling system components. Quite possibly these images will show cooler up top and much warmer below. My guess is if correct thermal management techniques and materials are employed, then the gain is 1-2HP...greater air density and reduced intake system turbulence.
If someone has Flir Thermal camera, PM me and I will arrange for sample product.
04-13-16, 03:03 PM
Reducing air intake charge temperature
