SVX Engine cooling "Again & Again"

[SilverSpear]

Yeah... was thinking of tackling that area in my design:


Here is a rough side view of what to expect:

[neverLift]

It would need to extend right up to the windshield to be effective. Otherwise that gap/height difference will be generating high pressure still, stopping short like that will exacerbate the issue. Workable idea though!

This is perhaps a bit high on the windshield, but it illustrates what i'm after. Something like this with a 1/2" opening between the hood and windshield to allow air out could *potentially* work. It would still require experimenting and still may not lower the pressure enough, but without detailed analysis we're all just guessing at this point.


cheers
-Evan

[SilverSpear]

Originally Posted by neverLift

It would need to extend right up to the windshield to be effective. Otherwise that gap/height difference will be generating high pressure still, stopping short like that will exacerbate the issue. Workable idea though!

This is perhaps a bit high on the windshield, but it illustrates what i'm after. Something like this with a 1/2" opening between the hood and windshield to allow air out could *potentially* work. It would still require experimenting and still may not lower the pressure enough, but without detailed analysis we're all just guessing at this point.


cheers
-Evan

It would definitely work beautifully, but then you won't have a working hood anymore.

I am not sure I agree with your statement above. Since the SVX has a long nose, and with that modified smooth hump, I don't think air "will have time" to skew downwards before it reaches the windshield. But again this is all speculation, I am no aerodynamics expert

[BRZCory]

I was about to say, be careful how high you make that hump or it'll contact the hood!

[SilverSpear]

Originally Posted by BRZCory

I was about to say, be careful how high you make that hump or it'll contact the hood!

Sorry didn't get you, what you mean by "contact the hood"?
I will be developing a whole new hood/hump out of fiberglass.

Ok guys, have been doing some research on different wind tunnel cars. Here is the 2013 Viper:



As you can see, the hood bulges upwards in the front, then skews downwards between wheels/windshield. The air goes up first, then horizontal then up again which is not good in our case.

Here is what I am trying to say:





Making a hump right at the back of the hood will cause air to skew downwards a little bit right in the middle of the windshield and not at its bottom. Venting the hood from the back of the hump should work well, isn't it?

[Dessertrunner]

I have removed

[neverLift]

Haha yes, you wouldn't be able to open the hood how I sketched it, it was just to illustrate what I was attempting to say.

And I agree, the airflow does not turn down/dip quickly, this is part of the reason the high pressure region exists. You can't simple have an empty void below the laminar flow stream. So although the smooth laminar region does not dip down (i.e. the nice smooth smoke visualization you showed in the wind tunnel photos holds its course) but air will "peel off" in a sense. See below



In the 3rd flowline from the top, it is no longer attached to the body and starts to curl downwards, as it cannot dip down fast enough as you said and this happens where the air stream starts to slope upwards over the windshield.

Thats very cool with the hump. I can't say I've come across any research done on something like that, so I really am just guessing as much as anyone now. I think the hump would decrease cD, but increase the high pressure region since it is creating a larger void between the back of the hump, the hood and the base of the windshield. The yellow circle is the void I'm talking about and the difficult-to-see red lines are the flow "peeling off" the laminar region as I mentioned above.



I have no idea what kind of behaviour would happen with a vent located behind the pump, my gut feeling is it would still be in a high pressure region but I have no experience/evidence to back that up.

I'd say give it a shot and see what happens, instead of my wild speculation!

cheers
-Evan

[SilverSpear]

I would have to go with my gut feeling and sense of logic in this. Elevating the hump and the back of the hood at the same time making the vents on its back, at the same time doing an undercarriage that skews upwards across the firewall, air in this instance has no way but to move towards the only place it can vent from... the back the of the hump.

[neverLift]

Fair enough, I look forward to seeing how it turns out! I'm very curious as to how the air behaves in this SVX-specific case.

To confirm, you expect the flowline to look similar to the white line I've drawn below?


If so, I believe the vents at the back of the hump will still be subject to the high pressure region, highlighted in yellow, and thus not draw air out of the engine bay even if it is ducted as it will not be able to overcome the pressure gradient. But as I said, these are just (somewhat) educated guesses and only physical trials will tell us either way.

cheers
-Evan

[Tapani]

Why not think about the underside of the engine bay like Bazza did?

Do you guys still have all the plastics in place? Did you know the Euro style is different? The center portion continues further back under the engine. I wonder why....

I have never seen this - mine is also a USM vehicle.

Just a thought....

Tapani

[SilverSpear]

Evan, I expect the line above the hood to be straight instead and skews a bit down at 1/3 to 1/2 of the windshield.

Tapani, as for the underside, I never had a cover in my car and never thought the SVX had one.

[Tapani]

Originally Posted by SilverSpear

I never had a cover in my car and never thought the SVX had one.

Well - I trust this has an effect on the air pressures and exit flow from the engine bay. I will try to find a photo of the Euro style - the USM can be seen in the manual, for example.

- edit: here's the Euro style undertray for sale on ebay (de)

http://www.ebay.de/itm/Subaru-SVX-3-...item2573e91f4f

Also, the radiator (to body) seals play a big role - these tend to rot away. I made my own when I had the engine out for the HG job.

/T

[neverLift]

Originally Posted by SilverSpear

Evan, I expect the line above the hood to be straight instead and skews a bit down at 1/3 to 1/2 of the windshield.

Tapani, as for the underside, I never had a cover in my car and never thought the SVX had one.

Ah thats my lack of skill in paint, but we're on the same page which is good!

cheers
-Evan

[SilverSpear]

Originally Posted by Tapani

Well - I trust this has an effect on the air pressures and exit flow from the engine bay. I will try to find a photo of the Euro style - the USM can be seen in the manual, for example.

- edit: here's the Euro style undertray for sale on ebay (de)

http://www.ebay.de/itm/Subaru-SVX-3-...item2573e91f4f

Also, the radiator (to body) seals play a big role - these tend to rot away. I made my own when I had the engine out for the HG job.

/T

Interesting... never knew it even existed lol.

[Tireiron]

Well these should take care of my overheating issues.