Dead pedal / “Engine falls flat” potential fix..

[daviderle]

Indeed, the 4.6 also has the same setup, just in case anyone is wondering...

The small open intake is fed from these scoops, while the air door is fed air from inside the engine bay, like so:

I agree, the air door may be only relevant for WOT or low speed operation, but once highway speeds are reached, there should be sufficient pressure build up in the air box, adding to the magnet forces which may prevent the door from opening at higher speed.

i.e., if the flapper/air door is removed, it actually may have a negative impact at highway speeds, which may impact cabin noise as well as air intake pressure which may affect performance, MPG among other things that we do not know about (yet!)...

As a summery, at this point we may have several potential solutions to try 'fixing' this issue:

1 - Reversing the magnets, to weaken the door force.
2 - If that is too difficult, one could try 'felt' / tape to weaken the door force.
3 - Remove the door all together.
4 - Implement a custom CAI / Cold air intake solution.

Again, if you do not have dead pedal issue, it may not be worth trying any of these things (i.e. "if ain't broke do not fix it" )...

Just my two cents...

 

[amartz]

4 - Implement a custom CIA / Cold air intake solution.

On this note, I agree with another poster here that has insisted that the aftermarket intake solutions presented here are *not* Cold Air Intake solutions. The stock setup we are discussing here *is* a true Cold Air Intake solution, at least when the flapper door is closed.

 

[sluggo]

Thanks for posting the diagram of the air ducting. It clears up some of the confusion I've felt while reading some of the other postings here. Just a few thoughts:

- So if the "flapper" is in the housing marked "3750V", then when you accelerate from any partial throttle condition and pull a higher vacuum in the plenum ("28112"), the flapper opens to permit more air into the plenum. When you then decelerate, the pressure in the plenum rises and the flapper closes. Since the flapper is drawing from under the hood, any intake noise present during deceleration would, in the absence of the flapper, be directed to the engine compartment where it would resonate and become obtrusive. With the flapper in place (and closed) though, the noise that would escape to the engine compartment is greatly reduced. Most of the intake noise in the ducting is routed to the front-facing duct, where it exits to the outside air.

- There's no "ram-air" effect going on here, anywhere. First of all, the front-facing ducting is behind the grill. Second, the flapper won't even open unless there's a partial vacuum in the plenum. Third, the front-facing ducting forces the air to turn 90 degrees not once, but twice before it hits the filter. In addition, in between the two 90 degree turns the air from the "scoops" is mixed in the plenum with the air drawn from inside the engine compartment. There's no kinetic energy in the mass of air directed at the air filter and so no "ram-air" effect. And there can't be a net positive air pressure (pressure higher than atmospheric) in the plenum, because the plenum is vented directly to the engine compartment.

Does this analysis seem reasonable? That the "flapper" is merely a muffler for intake noise? That if they had room for more front-facing ducts they wouldn't need to pull in air from inside the engine compartment at all, and then no flapper?

 

[amartz]

There's no "ram-air" effect going on here, anywhere. First of all, the front-facing ducting is behind the grill. Second, the flapper won't even open unless there's a partial vacuum in the plenum. Third, the front-facing ducting forces the air to turn 90 degrees not once, but twice before it hits the filter. In addition, in between the two 90 degree turns the air from the "scoops" is mixed in the plenum with the air drawn from inside the engine compartment. Does this analysis seem reasonable?

I couldn't disagree more. I've included a picture from straight-on to try to illustrate the geometry of the scoops. As you can see, the ducts rest on top of the radiator, not behind. At speed, pressure will build up in front of the radiator, and the scoops would tap into this. I think the curves in the ducting are fairly smooth, to reduce restrictions to the air flow. But mainly, as speed and pressure builds, this will force the flapper to the other intake tube from the engine compartment to close. This turns the entire intake into a pressurized duct. Engine vacumn pulls that flapper open only in the absence of any pressure from the front scoops, i.e. at slower speeds.

 

[daviderle]

I couldn't disagree more. I've included a picture from straight-on to try to illustrate the geometry of the scoops. As you can see, the ducts rest on top of the radiator, not behind. At speed, pressure will build up in front of the radiator, and the scoops would tap into this. I think the curves in the ducting are fairly smooth, to reduce restrictions to the air flow. But mainly, as speed and pressure builds, this will force the flapper to the other intake tube from the engine compartment to close. This turns the entire intake into a pressurized duct. Engine vacumn pulls that flapper open only in the absence of any pressure from the front scoops, i.e. at slower speeds.

I am still in agreement with you on this one.

On a deeper dive, it appears that the current Custom Air Intake attempts, may actually be counter productive.

We may also have actual data to support these conclusions, thanks to the hard work done by TailWalker and GlassMan.

What has been baking my noddles for the last several weeks, is why TailWalker got 10hp less than GlassMan during their respective Dyno runs? both where using the OEM filter and the factory air box installation...

What makes matters worse, although both have 4.6, technically GlassMan (2009=375hp) should be lower by 10hp, than TailWalker (2011=385hp)!!

It just dawned on me (just not sure why I did not think of it earlier..)...

GlassMan had fans pointed at his car during his Dyno run, while Tailwalker did not!!!

I just double checked to make sure:

http://genesisowners.com/hyundai-genesis-forum/showthread.php?t=14740

http://genesisowners.com/hyundai-genesis-forum/showthread.php?t=14227&page=2

The fact that Tailwalker got the 'extra 10hp' after the Custom filter / Air Intake installation, is neither here or there! because he may simply gone back to the factory stock HP readings (?2009?) while the hood is open!...

I.e, as soon as that bonnet is closed, all bets are off!

 

[Ram Air]

I'm going to have to side with sluggo on this one. In addition to what he describes (much better than I could), the whole air intake system should be totally reversed. When you have wide open throttle the flapper system should be drawing in cold air from outside of the engine compartment. The rest of the time, under the hood air would be fine. This is how it used to be done with carbureted engines in the 60's.
I wonder if Hyundai ever experimented with this?

 

[radiohack]

Thank you guys for posting this! Works great for me. I flipped the magnets like suggested before and the magnetism was reduced and took the delay from about 1.5 seconds to .5 seconds. It definitely responds better, but as mentioned before nothing is changed after it opens up, it just opens up sooner. Now to try the rigid collars next!

 

[daviderle]

Thank you guys for posting this! Works great for me. I flipped the magnets like suggested before and the magnetism was reduced and took the delay from about 1.5 seconds to .5 seconds. It definitely responds better, but as mentioned before nothing is changed after it opens up, it just opens up sooner. Now to try the rigid collars next!

This is wonderful news... the Rigit Collars 'should' provide a more stable ride (if installed correctly )

Tomorrow if it is not too cold, I will do the following:

1 - I will remove the current felt (permanently) from both my cars.
2 - Will reverse the magnates on my R-Spec to see if I can get the magnet force to match the 4.6.
3 - Will reverse the magnates on the 4.6 to see if they become stronger and try to create the issue on the 4.6.
4 - Restore the 4.6 magnet setup.

This may help to further validate, if this issue can be attributed to a manufacturing / assembly 'defect'!?

Will keep you posted...

 

[amartz]

GlassMan had fans pointed at his car during his Dyno run, while Tailwalker did not!!!

One question I've always wondered about dyno testing is how strong of a fan blowing in the air scoops would it take to duplicate the pressure the scoops are tapping into at, say, 100mph??

 

[amartz]

I'm going to have to side with sluggo on this one. In addition to what he describes (much better than I could), the whole air intake system should be totally reversed. When you have wide open throttle the flapper system should be drawing in cold air from outside of the engine compartment. The rest of the time, under the hood air would be fine. This is how it used to be done with carbureted engines in the 60's.
I wonder if Hyundai ever experimented with this?

I think you and Sluggo need to get your understandings reversed! Let me try to summarize. Keep in mind the flapper only controls whether the secondary air input is open or closed. It does not open or close on the primary air input feed. At WOT at 10mph, the airbox flapper is wide open, providing two air inputs into the filter box, doubling the available unpressurized air for the motor to draw, one input with a quite short low restriction scoop. At WOT at 100mph, with the short engine compartment scoop forced closed by pressure, the front scoops on top of the radiator are feeding pressurized air into the motor. This takes best advantage of the vehicle speed to boost engine performance. The system is designed by Hyundai to take best advantage of whichever speed and throttle position we are presented with.

The modification that started this whole thread was to get the secondary air input to open up much sooner, quickening the motor's response time. But, this should be done without loosing the ram-air pressure available at speed, which is why you need the flapper on the secondary air input to close when pressure from the front scoops builds enough to feed more air than with an unpressurized secondary input.

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[daviderle]

One question I've always wondered about dyno testing is how strong of a fan blowing in the air scoops would it take to duplicate the pressure the scoops are tapping into at, say, 100mph??

Something like this setup :

http://rspmotorsports.com/dyno-chassis_awd_300.html

It has been a while since I have done a Dyno run (TransAm), it was not fancy as the above setup, but they did a nice job...
---

Back to the subject at hand...

I would speculate that the door will completely close around 45-55 mph (depending on ZF vs 8), or somewhere around 4500 RPM in the second gear even with WOT...

Hmm, I wounder if I can build a remote sensor that would measure and record the door position?

 

[NJTom]

Quick question: does the 2009 v6 engine airtake have have the flap? I took apart mine and could not locate it.

 

[Ram Air]

I've been debating whether I should reply to post # 50 & 51 or let the thread die. Replying won out because I don't want us to continue with the dead pedal CAI issue with misconceptions about what is going on. So, I'll try to do it with math. Here goes.......
Question: What amount of air does the 5.0 require? (you can plug in different values for 3.8 and 4.6) Answer: @ 6000 rpm * 305 cubic inches=1830000/3456=529.5 CFM (cubic feet /minute) Assuming 90% efficiency ( that's high) that works out to 477 CFM. Let's say 525 CFM at it's highest rpm.That's 907200 cubic inches per minute. Remember that number.
Question: How much air can our little scoops deliver? (Yes, I remember! I didn't know they were there a week ago. Thanks amartz.) Each scoop measures about 8.5 inches * .75 inches high= 6.375 sq. inches *2= 12.75 sq. inches.
Now the tricky part. At 60mph/60 *5280 (feet in a mile)*12 (inches in a foot)=63360 inches per mile per minute. 63360 *scoop face (12.75 sq.in)= scoop intake volume per minute ... which is 807840 cubic inches. It will deliver a lot less than this because of it shape and path. Maybe 50% efficiency.
Observation: What the engine requires is more than what the scoops can deliver in volume.
Conclusion: This is why the flapper valve has to open otherwise it wouldn't get enough air.The flapper door will not close at 45mph! It can't. Not enough pressure!
Note: These are the numbers in a perfect world where tube length should be as short as possible with a minimum amount of bends, wall angles of the scoop should be less than 30 degrees, depth of scoop should be more than the width of the scoop......... and so on, and so on. I won't bore you further.
Ideally you want a scoop that can deliver 10 times the amount of air the engine needs at a given rpm and speed. Think 6 PACK ROADRUNNER hood and you're not far off.
Oh, by the way. The scoop must be the sole source of air for the intake so it can build pressure. Remember, when the flapper opens pressure is lost.
You guys can play around with the numbers and see what theoretical speed you would need to have an actual ram air system that delivers the amount of air the engine requires. My guess is that it is faster than the car can go. So we have an under hood induction system (UHIS) or grill induction system (GIS).
Im done!

 

[daviderle]

RamAir, good analysis, which merits additional study...

In general, I tend to focus on measured data, repeatable observations and avoid being drawn into speculations (apologies, not sure what happened here )...

To your point, we need to refocus this thread back to helping people who are suffering from this issue and continue to collect additional data that:

1- Measure how prevalent this issue among the different models / owners?
2 - Do any of these solutions (/variations), corrects or minimize these issues?

Unfortunately I did not have the chance to test the 4.6 due to a severe case of the Flu...

 

[daviderle]

Quick question: does the 2009 v6 engine airtake have have the flap? I took apart mine and could not locate it.

NJTom, It will help a great deal, if you can post a picture of the inside of your air box (after you remove the air filter).

 

[amartz]

So, I'll try to do it with math. Here goes.......
Question: What amount of air does the 5.0 require? (you can plug in different values for 3.8 and 4.6) Answer: @ 6000 rpm * 305 cubic inches=1830000/3456=529.5 CFM (cubic feet /minute) Assuming 90% efficiency ( that's high) that works out to 477 CFM. Let's say 525 CFM at it's highest rpm.That's 907200 cubic inches per minute.

I hope you are not done, I enjoyed the analysis! But, I think you are forgetting something. Your flow analysis might be accurate for a motor with nothing on the intake manifold, just pulling in as much air as it can. But, the real bottleneck is going to be the throttle and mass air sensor, or whatever the genny uses to measure air flow and calculate how much gas to inject for as much air is flowing. I think you'll find that the diameter of the throttle-body is smaller than the intake tube feeding it. So, you'd have to do the math for what that can flow, vs. what is available from the front scoops. Might change the results just a bit, I think.

 

[amartz]

Oh, by the way. The scoop must be the sole source of air for the intake so it can build pressure. Remember, when the flapper opens pressure is lost.

This is where I disagree. (Sorry daviderle, I'm enjoying this too much for the moment!) The flapper does not require positive pressure to close. Open the air-box, remove the filter, pull the flapper open, and let go. Guess what, it closes! No positive air pressure required to force it closed. The weight of the flapper door, and a couple of pesky little magnets take care of the the closure. So, in practice, it takes a certain amount of vacumn to hold the flapper door open. Anything less, and the door falls shut. As airflow from the front scoops builds, it's going to dilute the vacumn holding the door up, closing the door, and at that point positive pressure can build in the intake system.

 

[amartz]

http://rspmotorsports.com/dyno-chassis_awd_300.html

I would speculate that the door will completely close around 45-55 mph (depending on ZF vs 8), or somewhere around 4500 RPM in the second gear even with WOT...

Hmm, I wounder if I can build a remote sensor that would measure and record the door position?

Nice setup! Not cheap, I'll bet!! I like your thinking about watching the door openings and closings. Hmmm., anybody got a go-pro that will fit inside the air box?? ;-)

 

[BkBlue]

So what is the translation for non gear heads? Is the original fix proposed no longer recommended? If not, is there an equally simple alternative?

For the record the "dead" pedal effect routinely rears its head on my '14 R-spec.

 

[Rob]

Been silent on this for a week. Took apart my 2009 3.8 and found no flapper. So much for a quick fix on this car with this problem.