Forcing Air into the Engine Compartment, Engine Cooling ??? Options

[Highland]

I'm guessing it's been tried, but is there a downside to forcing fresh oncoming air into the engine compartment? I've read that removing the rain tray does not help cooling which tells me the 2 engine compartment side vents are more than adequate to feed the centrifugal cooling fan; so perhaps increasing engine compartment air pressure and reducing relative air temperature would help.

So don't laugh too hard at the pictures (IMG:style_emoticons/default/av-943.gif) It's a first pass attempt.

I did a couple of runs on my normal joy ride and am qualitatively seeing about a 5 to 10 degree head temp reduction and quicker cooling to normal temps after an uphill grade. Also cruising at 65mph in 5th I'm seeing about a 10 degree reduction in steady state temperature. I have a big hole in the back due to a 3D print problem and my duct tape keeps on flying loose so not getting full duct air. I just have a VDO head temp gauge on #3 plug. As many of you know the VDO has 50 degree hash marks; so not real accurate reads.

So is it correct that head temps are not affected by outside air temp, that's an oil temp thing?

Has anyone tried this? The stock grating is still in place. Can I be doing any harm?

[SO.O.C914er]

I’ve been trying to think of ways to bring more air to the motor but was looking at coming from the underside….Paul (IMG:style_emoticons/default/driving.gif)

[Craigers17]

Kinda reminds me of the old swamp coolers.....only for your engine.

[arbitrary]

Years ago I played around with a data logger and a fairly sensitive air pressure sensor - would be interesting to see if the air pressure in the engine compartment is affected by removing the lid completely.

[Mikey914]

I think he’s on to something here. The area is a lower pressure, so simply removing the lid would change airflow, but forced air from the edges would really add movement in areas that should benefit from it.

[Chris914n6]

The rain tray is not a tight fit so plenty of air flows thru that section too.

The MR2 aftermarket has a nice looking air duct.

It is a general consensus of opinion that the area over the engine lid has slightly lower pressure.

[Highland]

I think Jake R said removing the rain tray made no difference to engine temps, so I doubt removing the lid would improve fresh airflow through the fan.

I'm just guessing here but my assumption is the airflow over the engine fresh air intake area does not provide an efficient supply for the engine compartment. By forcing air into one intake port, I'm hoping to provide a flow of fresh air to constantly evacuate the engine compartment (through the opposite port and seam leaks) and provide positive pressure to the fan intake.

I do need to redesign the intake for better fit, mounting and printability. Still learning the capabilities and limits of the 3D printer.

Didn't want to reinvent the wheel if someone has already tried this and has results. Also wanted to get opinions if I could cause harm to my car of which are not obvious to me (IMG:style_emoticons/default/confused24.gif)

[Montreal914]

I would use a temperature compensated thermocouple setup on your #3 spark plug instead of your VDO gauge.

The VDO gauge, although good looking, has the connections between the K-Type TC and the voltage leads in the engine bay which will basically give you the temperature delta between your engine bay temperature and your head temperature, which is not accurate.

Using a new ring type TC with longer thermocouple wires would allow you to make that connection in the cabin which would be cooler and closer to room temperature (temperature at which the gauge is factory calibrated) but still hotter in the summer time than room temperature.

Having a temperature compensated gauge will ensure your head temperature measurement is accurate no matter what your surrounding temperature is.

In your current setup, changing the ambient air temperature in the engine bay may affect your reading independently of the head temperature.

The results of your investigations are only as good as the quality of your measuring setup. (IMG:style_emoticons/default/smile.gif) Good luck with your project! (IMG:style_emoticons/default/smash.gif)

[Olympic 914]

I think Jake R said removing the rain tray made no difference to engine temps, so I doubt removing the lid would improve fresh airflow through the fan.

Although I have no scientific evidence, My personal experience differs.

One day my engine was overheating sitting in stop and go, to mostly stopped traffic on a local interstate highway. I had pulled over to let the engine cool, and opened the engine lid to facilitate that.

When pulling back into traffic I neglected to close the engine lid and being on the highway I just continued driving with the lid up. I was surprised how much cooler the engine ran with the lid up. ( I did have a rain tray installed)

Since then I installed one of Sergio's GT lids and have noticed that my head temps stay much cooler in the hot summer weather.

In the winter, I reinstall the regular lid with rain tray.

[914werke]

Perhaps Im dense. (IMG:style_emoticons/default/rolleyes.gif) What are you trying to accomplish? Reducing head temps by adding/forcing cool air to the top of the engine (presumably to feed the impeller fan)?

[barefoot]

I would use a temperature compensated thermocouple setup on your #3 spark plug instead of your VDO gauge.

The VDO gauge, although good looking, has the connections between the K-Type TC and the voltage leads in the engine bay which will basically give you the temperature delta between your engine bay temperature and your head temperature, which is not accurate.

Using a new ring type TC with longer thermocouple wires would allow you to make that connection in the cabin which would be cooler and closer to room temperature (temperature at which the gauge is factory calibrated) but still hotter in the summer time than room temperature.

Having a temperature compensated gauge will ensure your head temperature measurement is accurate no matter what your surrounding temperature is.

In your current setup, changing the ambient air temperature in the engine bay may affect your reading independently of the head temperature.

The results of your investigations are only as good as the quality of your measuring setup. (IMG:style_emoticons/default/smile.gif) Good luck with your project! (IMG:style_emoticons/default/smash.gif)

Here's a much more accurate thermocouple set-up.



Components: J type TC with 14mm spark plug ring & 10' extension, Cold junction compensated digital readout all very inexpensive, look on E-Bay

[Highland]

Although I have no scientific evidence, My personal experience differs.

One day my engine was overheating sitting in stop and go, to mostly stopped traffic on a local interstate highway. I had pulled over to let the engine cool, and opened the engine lid to facilitate that.

When pulling back into traffic I neglected to close the engine lid and being on the highway I just continued driving with the lid up. I was surprised how much cooler the engine ran with the lid up. ( I did have a rain tray installed)

Since then I installed one of Sergio's GT lids and have noticed that my head temps stay much cooler in the hot summer weather.

In the winter, I reinstall the regular lid with rain tray.

That's good to know. Thanks for the information.

I know the VDO gauge is not that accurate, but at least for the year + I've been using it it has been consistent. My understanding is that higher engine compartment temperatures would cause the VDO to read low. I can't imagine forcing fresh air in would lead to higher ambient, so at least my gauge will error "conservatively".

As to what I'm trying to accomplish: Just trying to find another way of improving our cars. I actually don't have an engine temperature problem, but lower head temps is always better. I guess the bottom line is I'm just playing and thought I'd share (IMG:style_emoticons/default/smile.gif)

[JamesM]

Are you running a pair of these?

https://914rubber.com/floor-pan-air-deflector-for-914

Rather than addressing the low pressure on the top of the engine, these are supposed to make the pressure lower under the engine to help pull the air through.

If I recall its been tested and having these in place does make a difference.

[moto914]

+1 on Sharing cooling ideas.
+1 on bringing air from below.
+1 on having the air deflectors.

[maf914]

Highland,

Interesting approach to forcing more air into the engine bay with your 3D printed scoops. I would think that well shaped scoops would help as it has been stated before that the area behind the 914 roof and targa bar is in a low pressure area. I am surprised the original 914 design did not include some form of ram air intakes for the engine compartment. The scoops you have made remind me of a more extreme idea, that Joe Sharp 914 Ranch has been developing in his build thread. Check out his scoop design beginning on page 16 of his build thread.

http://www.914world.com/bbs2/index.php?sho...5484&st=300

[wonkipop]

biggest problem a 14 has got is getting rid of the hot air out from underneath it when it is sitting running in stop start traffic in hot conditions? man it builds up under there in aus on a hot day. turns into a bubble of hot air under there all the way to the tops of the rear guards. engine tin seal rubber needs to be in very good condition to keep it under the car and out of upper engine bay where the fan can suck it straight back in - would be a bad feedback loop.

ok on the move with the air deflectors doing their job mentioned above.
almost like you need an extractor fan underneath some days in australia?

no getting around that the car was designed for european and north american climate.

standard vws with rear engines could start running notably hotter down here on extreme days - and they could discharge exhausted cooling air straight out the back and not trap it underneath. always used to back off in my old bug and squareback, drive it at 50 out on the highways in high summer super hot days. thats when they all blew up.

i avoid driving in high summer here. UV/southern hemisphere ozone depletion will get you anyway, so no fun. australia. if the spiders and the snakes don't get you the sunburn will.

-----

wondering if anyone in the USA has ever had that experience of sitting at the lights, on a warm day, and puff of wind blows and then a bubble of hot air dumps into the cabin if you have the roof off. just having been blown out from under the car. if you weren't sweating allready...........

[JeffBowlsby]

Read these 914 aerodynamics papers:

[Chris914n6]

I’ve been trying to think of ways to bring more air to the motor but was looking at coming from the underside….Paul (IMG:style_emoticons/default/driving.gif)

Not a good idea. The air on the street is 20F hotter.

(IMG:http://www.914world.com/bbs2/uploads_offsite/live.staticflickr.com-431-1628999618.1.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/live.staticflickr.com-431-1628999618.2.jpg)

[Krieger]

I've been thinking about this too for my track car. Maybe placing a deflector on the aft end of the roof. Something maybe 18 inches or so wide that sticks up about 4" above the roof line and spaced 3-4 inches behind. Not a scoop, but just brings air into the engine area

[Chris914n6]

Read these 914 aerodynamics papers:

There is a flaw in that paper. It is physically impossible for a significant amount of air to flow upward on a stock car.