Do I need More Hood Venting?

[Scootsmcgreggor]

Sorry I don't have video to show what's happening so I need to describe it.

Current setup:
boxed radiator and oil cooler
trimmed fan shroud
RaceLouvers RT trim 15-17 center hood vent

Starting around 100mph the entire (visible parts from driver's seat) hood starts buffeting and gets worse as speed increases. Not sure what's happening on the leading edge as I cannot see it from the driver's seat. Its like my hood is a '22 F1 car porpoising down the track. Hard to tell the magnitude from the driver's seat, but I'd hazard a guess that its ~3/8". Seems like a lot form the driver's seat I know that much.

So question for you guys who know more about aero stuff. Is this buffeting created by pressure under the hood, pressure above the hood, or both? I know people put in more venting to increase cooling (but mine is fine now) and to reduce hood lift at the leading edge (but no idea if I have this since I can't see it happening) but not sure about what the fix is for buffeting in the aft half of the hood.

So will more vents reduce this buffeting or will cutting more out of the hood further weaken it and buffeting will remain?

 

[RES_22]

An equally important question could be....what design and tunnel-testing assumptions/conditions did the louvers vendor apply?

Stock rake, splitter configs, rad shroud completeness, etc......mass flow rates over and thru the hood vs road speed.

 

[Scootsmcgreggor]

Indeed. Ideally I'd rig up some barometers in the engine bay and on the top of the hood in various places to see what the pressure differential is but I don't have the equipment to do so.

 

[JDee]

You might get it fixed just by adding some side hood vents, can't tell from your car pic if you've got them or not. Worked for me and it was handy, Ford kindly having put those side holes in there and all. Those holes were just begging for some real vents to be installed.

 

[Bill Pemberton]

I have the Anderson Composites CF hood on my Mach 1 and I had a chicane23.com CF hood on the Boss 302S, and there was some buffeting at high speeds on both. Since both seem to be running reasonably cool on track I think the added downforce and cooling are meeting my needs , but like you the bit of lift did bother me at first. The one thing I did do that I do not notice in your pictures is to make sure both had solid hood pins and I would definitely suggest those for you your next minor mod. Whether the old style or the new aero ones, I do think that would give you some piece of mind and the hood lift is pretty common with many cars at higher speeds.

 

[Scootsmcgreggor]

Thank you Jdee and Bill.
Good call on the hood pins. Maybe I’ll do some side vents at the same time if I’m hacking at the hood anyways. There’s that slippery slope I was trying to avoid….

 

[SMGDHG]

Thank you Jdee and Bill.
Good call on the hood pins. Maybe I’ll do some side vents at the same time if I’m hacking at the hood anyways. There’s that slippery slope I was trying to avoid….

In theory if you had hood pins properly installed and adjusted, the hood wouldn't flutter, but that still wouldn't get rid of the forces of the air acting upon the hood. Since it is an OEM hood with nice OEM paint and durable construction you will probably be fine. But if it was a more flimsy aftermarket hood with marginal paint, you would maybe exhibit cracking near the areas with the most stress.

 

[Bill Pemberton]

In theory, yes, but it seems in practice the extra secured points do keep the hood down a bit. With CF the hoods seem to have more flex so it is a bit more noticeable, but you are correct that a good latch should keep things secure.

 

[VoodooStang]

Sorry I don't have video to show what's happening so I need to describe it.

Current setup:
boxed radiator and oil cooler
trimmed fan shroud
RaceLouvers RT trim 15-17 center hood vent

Starting around 100mph the entire (visible parts from driver's seat) hood starts buffeting and gets worse as speed increases. Not sure what's happening on the leading edge as I cannot see it from the driver's seat. Its like my hood is a '22 F1 car porpoising down the track. Hard to tell the magnitude from the driver's seat, but I'd hazard a guess that its ~3/8". Seems like a lot form the driver's seat I know that much.

So question for you guys who know more about aero stuff. Is this buffeting created by pressure under the hood, pressure above the hood, or both? I know people put in more venting to increase cooling (but mine is fine now) and to reduce hood lift at the leading edge (but no idea if I have this since I can't see it happening) but not sure about what the fix is for buffeting in the aft half of the hood.

So will more vents reduce this buffeting or will cutting more out of the hood further weaken it and buffeting will remain?

Thread 'AeroCatch install'
https://trackmustangsonline.com/threads/aerocatch-install.14412/

 

[VoodooStang]

Sorry I don't have video to show what's happening so I need to describe it.

Current setup:
boxed radiator and oil cooler
trimmed fan shroud
RaceLouvers RT trim 15-17 center hood vent

Starting around 100mph the entire (visible parts from driver's seat) hood starts buffeting and gets worse as speed increases. Not sure what's happening on the leading edge as I cannot see it from the driver's seat. Its like my hood is a '22 F1 car porpoising down the track. Hard to tell the magnitude from the driver's seat, but I'd hazard a guess that its ~3/8". Seems like a lot form the driver's seat I know that much.

So question for you guys who know more about aero stuff. Is this buffeting created by pressure under the hood, pressure above the hood, or both? I know people put in more venting to increase cooling (but mine is fine now) and to reduce hood lift at the leading edge (but no idea if I have this since I can't see it happening) but not sure about what the fix is for buffeting in the aft half of the hood.

So will more vents reduce this buffeting or will cutting more out of the hood further weaken it and buffeting will remain?

Post in thread 'Decrease hood lift'
https://trackmustangsonline.com/threads/decrease-hood-lift.13767/post-240354

 

[Scootsmcgreggor]

Thank you very much for both links!