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I noticed this weekend that the front of the engine cover it starting to lift up at speed. Is this because the airflow over the car is sucking it up, or is the air coming through the nose pushing it up? I am running in my first track day on the 3rd at Autobahn Country Club and would like to improve the situation before then. If it's sucking up I guess I can tape it down, or maybe just leave it alone.

Graham

I would guess high pressure air in the engine compartment.

I did not bother covering the frame where the front suspension attaches and it seems to act as a pretty good "vent". Can you remove the sheet metal in that area and see if it helps?

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-Andrew
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Perhaps add some "vents" in the front end of the hood... A louver panel or a rectangular cutout with mesh wire to keep debris out. A lot of Seven-ish clones have similar openings, likely for the same reason.

JD

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That is what I was thinking, as long as it's behind the radiator it should be good, I was just trying to get some confirmation it's internal pressure that's lifting the hood.

This is the best picture I could find

http://ts4.mm.bing.net/th?id=H.49683547 ... 6&c=7&rs=1

Graham

Graham, at highway speed, I sometimes get the rear edge of the cover sucked up, then popped back down. I think my problem has to do with the direction of the headwinds. I have no "special" venting either in the nose, the cover, or on the side panels. I am afraid to make changes as my rotary has no overheating problems with my Civic radiator. It would be interesting to hear about how any changes your implementing work out. Keep us informed.

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It's not pressure under the hood, it's the pressure differential between the top and bottom of the hood. If you don't have much slope to the hood, the faster you go, the less pressure above the hood. It's probably not practical to slope the hood more, and you're never going to get the air under the hood to move as fast as the air over it, so you probably need to look at a better way to attach the front of the hood.

How about taping some same-length tufts of yarn at regular intervals (2D matrix) across the top of hood and video taping while trying to induce the problem (assuming you know how to reproduce it). It won't tell you what's happening underneath, but if you see erratic behavior in the area in question just before or during the lift, that may indicate the slope issue Nick talked about, which should induce separation and turbulent behavior.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Mine's been doing that, ever-so-slightly, since 2006. I stop looking at it.

I think it may also have something to do with the air flowing over the curve of the nose, then hitting the flat(-ish) hood, creating lift.

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The Lethal Locost
The Lethal Locost 2 - Even More Lethalerer

Technically both could be valid ways to describe what is occurring, depending on your frame of reference. Either way, if you give the higher pressure air under the hood a lower pressure place to go, the issue should improve and may even go away entirely. Out the sides or out the top both have been used successfully before. Even out the bottom works, but has its own drawbacks that make it a less than desirable option for high performance use.

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-Justin

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As I expected I did not get a definitive answer. So I will do the track day on Monday and see what happens. I guess I will monitor to see if the problem increases or decreases with speed. I will let you know

Graham

for the track day you might want to run a strip of duct tape across the front...would hate to have it pop off at speed.

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JPS, I was think about that. I will monitor it during the first session and see what is happening, if it looks like an issue I will run a stripe of duct tape over the joint.

Graham

try riveting a lip to the front of the hood that goes under the nose cone about half an inch, just remember to hook it in first as you put the hood on.

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Next time make the hood out of thicker aluminum.

Al

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Super Seven 3.4

It turn out it was not a big deal. It lifted but did not increase with speed. so after the first session I ignored it. But I like John's idea of putting a little tang on the front of the hood so it engages under the nose cone.

Graham