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Engine Bay Temps

Old 09-07-2015, 08:20 AM
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Engine Bay Temps

So I was doing a lot of research on the aftermarket intake setups people are running. From what I'm gathering is that the big restriction from running you're basic aftermarket intake is that you'd be drawing in hot air from the engine bay, thus reducing HP (from the little that we have).

So I agree, yes if you want to run an aftermarket intake, make sure it's routed out of the engine bay, normally through the front.

But what go me thinking is, what have people been doing to lower engine bay temperatures? I mean if it's that in the engine bay, could the intake be getting heated up and reducing HP as well? Possibly wrapping the intake manifold or routing ducts into the engine bay somehow to alleviate this.

Just something I thought of while researching.

- Chris
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Old 09-07-2015, 08:36 AM
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The air that our airbox gets comes from the "outside":
https://encrypted-tbn3.gstatic.com/i...imSir5jdCLH7TK

After reading the last bit of your post I think I understand what you are getting at... Have to find out how much heat is being transferred to the air as its coming into the engine, my guess would be not too much while the vehicle is in motion.

Last edited by Love_Hounds; 09-07-2015 at 08:38 AM.
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Old 09-07-2015, 11:10 AM
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From what I've seen it's not really right in front of the car. I bet this can better formed to provide cooler air.....
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Old 09-07-2015, 02:28 PM
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When the car is moving, the intake air temperature is within 2 degrees F of the ambient air temp when running the stock intake. Data logging has proven this many times over. Aftermarket intakes, including CAIs, provide almost no gain over the stock unit, and most degrade performance.
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Old 09-07-2015, 03:38 PM
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Originally Posted by yapakanichi View Post
From what I've seen it's not really right in front of the car. I bet this can better formed to provide cooler air.....
REVi Ram Air Duct for 04-08 RX-8 - Racing Beat
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Old 09-08-2015, 01:21 AM
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I like the idea of the ram airbox, but at $150 + shipping I don't know. I'm thinking about getting dry hose and routing it to the front bumper. The rex needs something I don't know I"ll figure it out though.
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Old 09-08-2015, 09:41 AM
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You could cut a hole right in front of the VFAD and put a fancy piece of carbon fiber trim around it like you see on alot of 350Z's and S2000's. I have thought about that, and would if it were class legal. Maybe after I get a second bumper?
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Old 09-08-2015, 10:05 AM
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Or you could just leave it alone because intakes for RX-8's are nothing more than expensive noise makers and do more harm than good. The stock intake system brings in cool air from outside of the engine bay and uses a filter that actually filters debri from getting into your engine. The high flow filters do not filter well.

As for intake temps, at low speeds/idle any intake system will heat soak. and as Steve said, at speed intake temps should be close to ambient with the stock system.
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Old 09-08-2015, 10:58 AM
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I don't see how doing what DAT2RTR said harming the airflow of the intake. I get it, the research is there and I read it. I'm just thinking outside the box. Stock intake box with a different attachment on the front. I'm sure you've been around long enough to have seen how the stock tubing is routed.

I've also read that deleting the VFAD does absolutely zero harm to the intake and HP. Maybe I don't want heatsoak at idle. Maybe thats the case. But I'm not talking about doing some short ram intake like you see with K&N.

I was also thinking of ways to possibly lower engine bay temperatures (besides removing the hood). Maybe routing lines into the engine bay to blow cool air in. I don't know. Just spitting ideas.
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Old 09-08-2015, 11:25 AM
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You are not thinking outside of the box, anything you can think of that is intake related on the RX-8 has been thought of and tried already.

As for ways of dropping engine bay temps, well that too has been thought of and worked on in different ways many times over the years and there are many threads on the subject.

I have a Flir, I have taken measurements of just about everything in the engine bay and everything aside from the exhaust manifold and the area near the exhaust ports sits at about the same temperature which is around 200-220F. Vents in the hood are the only real way to evacuate heat from the engine compartment.

Last edited by 9krpmrx8; 09-08-2015 at 02:29 PM.
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Old 09-08-2015, 02:22 PM
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My hood dropped my temps pretty significantly. Hopefully helps the longevity of my engine. Probably not though
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Old 09-08-2015, 02:32 PM
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Dropped what temps and and what was your method of determining that?
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Old 09-08-2015, 02:43 PM
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Curiosity, a thermal gun, and a pen and paper. After installing my under tray and hood and taking a couple short drives temps dropped a few degrees. Enough for me to be happy. Was it a "scientific experiment", no.
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Old 09-08-2015, 02:48 PM
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Sounds legit.
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Old 09-08-2015, 02:55 PM
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Hater.
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Old 09-09-2015, 04:15 PM
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Actually the intake IS right in the front of the car.
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Old 09-09-2015, 04:31 PM
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And the air in that area is about as "cold" as it is going to get.
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Old 09-09-2015, 09:09 PM
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He's going to make me post this again, isn't he?



Green is ambient temperature. Red is intake temperature. They are substantially the same when the car is moving. These data were captured at the track, where my average RPMs were 7200, which means I was generating a ton of heat. At cruising speed on the street, the two temps line up nearly perfectly.

A person could expect maybe 2HP more from a more perfect intake at 7500RPM, but how much of your drive time is spent up there if you are not a track rat?

All cars heat soak their respective intakes while sitting still. There isn't much of anything that can be done about it. Hell, even the ambient temp sensor heat soaks when the car is sitting still.

.

Last edited by Steve Dallas; 09-10-2015 at 07:18 AM.
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Old 09-10-2015, 05:19 AM
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Ok that is what I wanted to see.

@Steve Dallas: I assume that you are running stock intake with stock filter or a K&N drop-in?

Edit: whats the blue?
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Old 09-10-2015, 06:32 AM
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Originally Posted by yapakanichi View Post
Ok that is what I wanted to see.

@Steve Dallas: I assume that you are running stock intake with stock filter or a K&N drop-in?

Edit: whats the blue?
coolant.
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Old 09-10-2015, 07:17 AM
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Blue is coolant. The graph shows several minutes of sitting in grid followed by 20 minutes on the track and a cool-down lap. The ambient temperature that day at that time was ~88F.

I am running the stock intake with an OEM filter that I change yearly. K&N filters do more harm than good in these cars.
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