Bonnet Scoop - Air Vents for Cooling

[mx52nv]

Looking good Jeo - and great choice of ECU hehehehe

[Juffa]

For those of us that are following this thread with interest I thought the following link helps with explaining some of the terms/theories....

Part 1 - http://autospeed.com/A_2159/cms/article.html

Part 2 - http://autospeed.com/cms/A_2160/article.html

Part 3 - http://autospeed.com/cms/A_2162/article ... larArticle


J

[Jeo]

I got home from work today and started trying to get the laptop to talk to the ecu. Harder task than I initially thought, but after three different sets of usb to serial drivers and manually stuffing about with the com port addresses for a while, I was in business. Had a nice readout of exactly what the engine was doing and what the sensors were seeing.

Then the girlfriend came outside and said something along the lines of "What are you doing, did you forget we were going out for dinner?". Thus, inside it was and the project gets shelved for another day. Conveniently, January 26th to me means 'a day off to play with my car'

[wun911]

I like the side air vents on the BMW Z3

I'm wondering if anyone has done it to an MX5 just next to the indicator light would be neat.

[Hammer]

For those of us that are following this thread with interest I thought the following link helps with explaining some of the terms/theories....

Part 1 - http://autospeed.com/A_2159/cms/article.html

Part 2 - http://autospeed.com/cms/A_2160/article.html

Part 3 - http://autospeed.com/cms/A_2162/article ... larArticle


J

Great articles Juffa. It's always great to fully understand things like this. I also never even considered using boat vents for cars, but this article just open my eyes to other possibilities. It could be the ticket if I can't find an aesthetically pleasing and trully fuctional bonnet vents.

[Jeo]

Well today turned out less productive than I initially hoped. There were no real issues, the laptop showed the intake temperature fine, I managed to get consistent and repeatable results. The 'less productive part' was that the biggest difference I had between any of the tests was only two degrees C. Now I’m no expert on the subject, but I would have expected a larger range of results. There are a few factors that I think contributed to this, but I’ll talk about them where they are relevant.

My initial idea was to measure intake temperature at 40, 60 and 80kmh with each of the following…
Stock head light cover closed with an airbox
Stock head light cover open with an airbox
Vented head light cover closed with an airbox
Vented head light cover open with an airbox
Stock head light cover closed with an exposed air filter
Stock head light cover open with an exposed air filter
Vented head light cover closed with an exposed air filter
Vented head light cover open with an exposed air filter
Stock head light cover closed with an exposed air filter with a heat shield
Stock head light cover open with an exposed air filter with a heat shield
Vented head light cover closed with an exposed air filter with a heat shield
Vented head light cover open with an exposed air filter with a heat shield

All of the tests were done on the same piece of road, at the same revs. 40kmh = 2000rpm in 3rd, 60kmh = 2250rpm in 4th and 80kmh = 2500rpm in 5th. I started at the top of the list and worked my way down.

Now to show you exactly what the conditions were for each of the different tests, I even took photos for all of you nice people.

So this how my intake sits at the moment. I have a one piece cross pipe that is 75mm in diameter, which feeds from the stock airbox out of a VN V8 Commodore.




This is the vented headlight cover. No its not painted, yes it will be if this all works.




This is the exposed air filter. Note that the heat wrap on the cross pipe has been there for a fortnight or so, I just forgot to take a starting photo today.






And now we have a heat shield. 2mm sheet aluminium with 5mm heat shield foam either side. I hadn’t put it on for this photo, but there was also a foam strip the whole way around it, so that it made a seal against the bonnet/washer bottle/what ever that thing at the front is. Like I said in earlier posts in this thread, my idea here was to seal off the passenger side of the engine bay to basically make my own enclosed airbox.






First thing that popped up kinda surprised me actually. Regardless of which headlight cover I had on at the time, at all of these speeds, the headlight closed gave consistently cooler results. Because of this, I gave up on testing both open and closed after the airbox tests.

Next was the vented vs standard headlight cover. This was just as expected as the vented cover gave cooler results at any speed, with any filter arrangement.

While I’m sure this won’t come as a surprise to anyone, but the exposed air filter with no heat shielding gave the hottest results recorded. I even tried to give it the best chance possible, short of moving to the other side of the engine bay, by tucking it right up behind the headlight.

________________________________________________________40_______60_______80
Stock head light cover closed + airbox ________________________38.9_____38.7_____38.8
Stock head light cover open + airbox_________________________39.3_____39.5_____39.0
Vented head light cover closed + airbox_______________________38.9_____38.8_____38.9
Vented head light cover open + airbox________________________38.0_____38.2_____38.4
Stock head light cover closed + exposed air filter_______________39.6_____40.0_____39.9
Vented head light cover closed + exposed air filter______________39.3_____39.2_____39.5
Stock head light cover closed + exposed air filter + heat shield____39.2_____39.4_____39.7
Vented head light cover closed + exposed air filter + heat shield___38.8_____39.0_____39.3

As you can see, the heat shield didn’t seem to be doing all that much, so the obvious question, why? I started poking around under the bonnet straight after a run. It seemed to be doing its job as the cold side of the heat shield was significantly colder than the hot side. I got very annoyed here and dropped quite a few four letter words, because I leant my temperature probe to a friend a few weeks back and only realised just then that I didn’t have it. I will get it back and have another go at these last few tests to quantify the results, but for the moment you’ll just have to believe me that it was a remarkable difference. Even the filter itself felt cool to the touch.

So a little more swearing combined with a little more time and I’m now thinking it has to be to do with the cross pipe and/or the hot side of the silicone joiner. Went for another quick drive (vented headlight cover closed + exposed filter + heat shield) and same deal, hot side = really hot, cold side = significantly cooler. However this time I also had a feel around the other parts of the intake system. The outside part of the bend in the silicone joiner, the part that was closest to the exhaust; was really hot, far too hot to hold your hand on; and while the cross pipe was also quite warm, you could easily hold your hand on it.

This then lead me to believe that the silicone joiner was the next biggest problem. Like I said, I will get my probe back to quantify these results but for the time being, any thoughts on how to fix it? How can I stop the silicone joined getting so hot?

At the very least however, I am a fan of the vented headlight covers. They seem to work

[grump]

interesting results, not as bigger difference as I would have thought though. I guess that if the cross tube was made of an insulated material there could be more of a difference.