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emperature Differences
The temperature data I took is very basic, but yields very obvious results. The data was collected with a Tektronix thermocouple meter, with one thermocouple as an ambient reference (outside temperature), and the other located in the manifold itself. It was placed in the manifold via a slit in one of the vacuum lines located next to the factory intake air temperature (IAT) sensor. I felt this would give not only the most accurate readings, but also the most repeatable ones (compared to an OBD2 diagnostic tool). It also gave me a reliable ambient reference.

The data is in the table below. Measurements were taken with an ambient of 68°F to 70°F, for both data sets, throughout the testing. The same path was driven, with the same speeds and even same gears used. The driving was kept as consistent as possible. The times for events were also approximately the same. Essentially, the testing "variables" were kept as consistent as possible.

Test Description Factory Temp. (°F) "Insulated" Temp. (°F)
Ambient 70 69
2 Bars on Gauge 80 73
3 Bars on Gauge 83 73
3 Min. (30mph, part throttle) 85 74
0-70mph 0:95 70:105 0:82 70:100
15 Sec. Idle Start:108 Stop:115 Start:89 Stop:89
2 Min. (40mph, part throttle) Start:105 Stop:115 Start:89 Stop:91
15 Sec. Lift Throttle (in gear) Start:110 Stop:120 Start:108 Stop:110
Head/Manifold delta (see notes) Start:9 Stop:5 Start:50 Stop:50

The numbers point to an obvious trend: reduced temperature in the manifold. The only numbers that don't make sense at this point is the 0-70mph run. I'm not sure why there was an 18°F rise with the insulator compared to the stock numbers. Honestly, I'm not sure why the temperature rises at all, I would think that the airflow through the manifold would reduce the temperature quickly. It might be that the slowing down and idling I did (less than 10 seconds) before the 0-70mph run was enough to heat soak the manifold such that the air temps rise, but that still doesn't explain the higher differential with the insulator.

The most startling number is the head/manifold "delta" temperature, the difference in temperature between the head/manifold junction. While this does not entirely determine the IAT or even the temperature of the manifold, it is a large factor- it tells you how much insulation or resistance the manifold has from the heating effects of the head itself. Since the surface area where the head contacts the manifold (the flange) is the largest area for heat exchange, this is an important bit of information. For this test, it was measured here:

There is a "dimple" in the head and a crease in the manifold that are no more than 1" apart. Since they are the closest areas to the gasket while still having some "meat" between them (and were easy to get to!), I decided to measure there. The results as you can see are astonishing. The "start" condition was after a 20 minute test drive (seperate from the others) with mixed 70mph freeway and 30-40 start/stop driving. The route was the same and the ambient temp was within the range for the other tests (i.e. the variables were as similar as possible). The "stop" condition was when the fans kicked on. In both cases, this was exactly 185°F, and start-to-stop took between 1 and 2 minutes. I considered this a good test as it mimicked "average" driving and insured that the fans did kick on, which would happen in moderate traffic or at a stoplight. The highest differential is obviously preferred, since it means the greatest resistance to heating through the head.

Stock, there was an 8°F temperature differential at the start, and a 5°F one when the fans kicked on. There was a 50°F difference with the insulator, and it was consistent for almost 2 minutes. The difference in temperature did not rise, meaning that while it did get warmer, the insulator kept the differential- something that you simply cannot do when stock.

For the remainder of the "tests," and for both average driving and average overall temperature, the numbers are clear: at least a 10°F drop, closer to 25°F in "hot" conditions such as idling. With the spacer the intake took noticeably longer to heat when both warming up and idling, and seemed to have a higher resistance to "heat soak." At the end of the testing, when stock, the IAT didn't seem to want to go above 130°F (that was the most I saw after 20 minutes of testing and mixed driving). With the spacer, it seemed to still want to creep, though I never saw above 110°F. On top of that, the manifold cooled more quickly with the spacer, and came back down to the high 80's with part throttle driving. Stock, the temperatures never went below 115°F after seeing 130°F. In all, I would say that a 25°F+ drop in IAT, or a potential 12+ HP gain, is well worth the effort!
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