Removing Restrictive Air Flaps

[amartz]

I'm having a hard time following the logic of this whole discussion. At speed, the dual air-scoops just under the hood are going to be pulling in pressurized air, as in a ram-air system. I would think you would want the flapper closed in that condition, so as to preserve the pressurized air feed into the motor.

 

[NSXNEXT]

I'm having a hard time following the logic of this whole discussion. At speed, the dual air-scoops just under the hood are going to be pulling in pressurized air, as in a ram-air system. I would think you would want the flapper closed in that condition, so as to preserve the pressurized air feed into the motor.

That's what is happening. The flap will only open under wide open throttle conditions (or near WOT).
You need a big enough vacuum from the intake system to overcome the hold of the magnet.

 

[zielritter]

I wonder is the flap is there to help preserve low end torque at the expense of some top end power due to the extra restriction and hot air?

Think about it in terms similar to exhaust velocity theory. A smaller pipe (which is what we have here before the flap opens) is going to flow less air but the velocity is going to be high ensuring optimum power until a point (being the RPM at which the pipe diameter becomes a restriction to the amount of air the engine needs).

At that point, the flap pops open and feeds the engine more air. Unfortunately, that extra air comes unshielded from the engine bay and goes through some crazy near-180 degree bend before getting to the filter. IANA engineer, just thinking about it logically with my limited knowledge of flow velocity and power.

This probably explains why I see some V6 coupe dynos lose some peak torque while picking up a large chunk of top end power when testing with an intake. A tune seems to be the best way to bring the torque back up - unfortunately us sedan guys are up the creek on that front.

 

[amartz]

I wonder is the flap is there to help preserve low end torque at the expense of some top end power due to the extra restriction and hot air?

You're discussion makes sense when the car is sitting on a dyno. On the open road, at speed, the pressure from the front scoops changes the dynamics, I would think.

 

[TheMikeJones]

Just did this modification after an oil change today and I noticed zero change in sound or my butt dyno.

For any folks going about this and might have trouble removing the flap, like mine which was incredibly stubborn, I simply opened the flap and put as much of my hand in there to get a grip and pulled up to get it out.

Not sure about fuel economy or anything but as far as sound is concerned, seems like no change to me.

 

[Jabald]

I have a 2011 4.6 130k miles, well maintained by a truck fleet mechanic and I... runs like a dream, will run up a bill if you don’t know how to work on it.

My best performance mods were getting a new fuel pump, cleaning the injectors and valves the correct way, and cleaning the pcv and egr valves. These aren’t mods at all, but are far more imporant to your car’s performance than any of these $&@$ing flapper mods...

I did this mod when changing my air filter. after reading all the threads and tutorials on this forum, I decided to check it out. this magnet doesn’t do anything for my driving style.

I think the only thing this magnet is good for is choking the engine at idle to boost mpg.

The biggest negative I’ve noticed while using the stock flapper is lurching from a halt. You press the gas and the car hesitates, then launches and burns rubber.

I did not remove the flapper unit, completely. I do think the hyundai engineers knew what they were doing when they designed the stock airbox. Instead of removing the flapper completely, I took the magnet out of the door part of the flapper. Easily comes out just push in the clip to access the magnet.

DANG THAT MAGNET’S STRONG!
I could pick up every tool I had with that rare earth magnet! I had a screwdrivers, wrenches, and sockets stuck to the bare magnet.

After removing the magnet and setting aside, I found a small piece of metal that I pounded into a box shape that fit tight where the magnet sat. Now the weird magnetic door is about 10-15% magnetic power from what it was (no I didn’t dyno it or put some led light in the airbox) I wanted to retain the flapper to keep the air flowing As hyundai intended. Kind of like lowering a dam instead of removing it completely. Probably makes unnoticeable changes, but has worked great for me.

The car no longer Lurches forward into intersections from red lights. The throttle is now smooth as butter. No more lurching, and you can hear the engine purring so much smoother from low to high rpms. This mod really made the genesis more of a pleasure to drive. I recommend it.