Cooling coils
 

Has anyone measured the temperature that the coils reach in normal use?

I bought the Versatuner and started to change parameters and adjust some maps. When it was the turn of the coil permanence map (DWell), before touching anything, I decided to look at the temperature reached by the coils and thus control possible overloads when the loading time began to increase.

I have taken an unpleasant surprise: in normal conditions the coils were always above 80 ° C, exceeding even at times the 100 ° C soon after you squeeze the engine or catch a jam.

I have also observed that these temperatures go hand in hand with the temperature of the oil, which has a certain logic to be located very low, which receives the heat that rises from the Carter, which adds to the internally generated by the coils.

That is why I decided that before modifying the permanence I had to do something that would allow the coils to "cool" something.

First, I modified the support so that the coils are separated and so that some air can circulate below them.

https://cimg0.ibsrv.net/gimg/www.rx8...df317b7e2d.jpg


I have also put a fiberboard under the support, to reduce somewhat the heat it receives by radiation from below.

https://cimg4.ibsrv.net/gimg/www.rx8...1fe1cb6bcc.jpg

Finally, I have put a flexible tube from the front to bring fresh air to the coils.

https://cimg7.ibsrv.net/gimg/www.rx8...532ed56c92.jpg


https://cimg4.ibsrv.net/gimg/www.rx8...97470bbb57.jpg

With these modifications I have achieved that the temperature in the coils drops between 20 and 30ºC with respect to that of the oil.

It only approaches that of oil when I'm in traffic jams or very slow traffic, but as soon as you get some speed the temperature drops.
Circulating above 90 km/h the temperature is always maintained between 50 and 60ºC

Dope engineering. Sucks you didn’t test each step to see the differences they made along the way. I suspect the fresh air duct probably does the most good.

This raises the question if that one RX-8 performance bracket does any good all on its own.

To be able to control the effect of each modification, from the beginning I had attached a temperature sensor on the back of the 2nd coil (to be used as a reference) with which I can see the temperature of that central coil, continuously, in a indicator in the cabin.

The first attempt was to insert a piece of ceramic blanket between the coils and the support, but I barely noticed any improvement, so I went to separate the coils (1 cm approx.) Keeping the insulating blanket, but still did not obtain significant improvements.

That led me to think that the heat accumulated in the engine compartment was responsible for the temperature increase, which added to the internal heat of the coils. In addition, the heating was almost the same circulating at a slow or fast pace, which indicated that there was hardly any air circulation in the area of ​​the coils.

Therefore, choose to provide a fresh air flow from the nose. The stepped design that I show in the photos seeks to facilitate the cooling of the most delayed coils. To avoid problems due to thermal shock between the cold air and the hot coils, I did not direct the air jet towards the coils, rather I have directed it towards the gap between the support and coils, so that it flows under them and as the channel narrows it is also forced to circulate among them.

As in the end I have greatly increased the separation of the coils from the support, I replaced the ceramic blanket with a fiberglass plate (recovered from an old electronic project).

The difference between having or not having the fresh air jet is appreciated very well when you are standing in a traffic jam, since the heat in the engine compartment causes the coils to rise rapidly to the temperature of the oil. However, once you start driving and air starts to come in, the temperature drops little by little until you are between 20 and 30ºC below the oil, maintaining that difference throughout the journey.

I have seen someone who placed some insulating padding under their OEM coils a long time ago.

You mean the one with big holes below the coils?

If nothing else, it does prevent the corona effect from occurring(which causes those white spots), so more electricity can go to your spark plug.

Yep, the one with the holes for cooling and avoiding that lighting discharge white spot. That’s what I have on mine. Wish there were actual data available but for now, I guess I have no choice but to believe the guys who made it that it works.

I think a 68F - 86F reduction in temperature is an amazing achievement. You’ve intrigued my interest to lower my temps as well. Replacing coils every 20-30k miles in fear of them failing is something I’d rather not do. Running at a much reduced temp should theoretically increase longevity and performance of the coils.