I had a set of K3’s installed on my charger today. They are facing down behind the front bumper but there is a plastic aero tray about 1/4" thick right below the longest trumpet. They cut a fist sized hole under that one and another hole around the size of the top of a coke can below the middle bell. It seems like the sound waves are not fully escaping to hit the ground and spread out. How much volume do you guys think I am I missing outside the car? Also it seems so much louder inside the charger than the k3 set on my e55 AMG did years ago (those were facing down, unimpaired under the trunk).
Hi and welcome to the forum. It makes a BIG difference. I had same situation as you (see here) ; after installing my K3. The hole they cut into your aero tray obviously isn’t big enough or not positioned correctly. Get rid of the tray if you can.
Okay, thanks for the feedback. I’m asking on the Charger forums if the fellas see any harm in removing a 19"X7+" section of that underbelly aero tray. If they say it’s kosher, I’ll go back to the shop to have them basically dremel the opening in it on my lunch break.
Welcome to the forum. K3s should be fairly loud. What pressure and size of air line are you using?
It is ungodly loud but it seems to be getting too much back into the cabin of the car. I had this same set up (tank size, K3’s and 150psi) on a benz before and though the horns were in the trunk of the benz, and the benz was likely more insulated with sound deadening materials, the difference is pronounced. I’m thinking that the tray is deflecting the sounds waves around and possibly sending them rearward through the dash.
Outside of the car, the horn rocks but I’m thinking it could be better with a clear path for the sound waves exiting the trumpets.
Here is what I need that front belly pan to look like…
Welcome to the forum.
If you don’t mind a little cutting, let 'em breathe!
Wow - fancy tipping your whole car on its side just to show the holes!
HarHar … Hmmmm tough crowd.
Seriously though, in my opinion you may as well get rid of the plastic/plate all together because by the time you start cutting massive holes in it, any aerodynamic benefit it would have had will be long gone.
If his Charger SRT8 is as low to the ground as my 06 300C SRT8 was (I sold it two years ago … and miss it), cutting holes may not make much difference. The SRT8’s tend to sit so low to the ground for aerodynamic reasons that the front spoiler/air dam tends to scrape on even modest concrete parking stops, curbs, and the like … and I seriously doubt the plate in question is much lower (if any lower) than the front air dam.
Then again, a lot could have changed between the 05-06 Charger & 300C SRT8’s and the later models … and I’m speculating based only on what I know of the 05-06’s.
If I had to hazard a guess, I’d say it’s a combination of:
[ul]
[li]Craptastic sound deadening in the Charger SRT8 (this is one reason I bought a 300C SRT8 years ago!)[/li][li]Holes being too small, currently[/li][li]Proximity of pavement to horns[/li][li]Proximity of driver to horns – compared to when they were in the Benz’s trunk[/li][li]Proximity of Charger SRT8 to pavement (i.e. ride height) compared to Benz’s – the Charger SRT8 may well sit lower than the Benz did[/li][/ul]Even if the holes are enlarged, the pavement’s probably only 6" from where the plastic plate currently is. It might make some difference to open it up, but I can’t see it being human noticeable. Certainly it’d show on a dB meter … but I just don’t think a human would be able to tell.
As for the occupant feeling that it’s louder now than it was before, in the Benz, the sound is basically emanating from a bit in front of the driver’s feet and radiating from there under the car, now … instead of emanating from the trunk area and radiating from that space. The Benz was most assuredly better insulated than the Charger … and both cars have more dampening material (seats, jute under the carpet, actual carpet, etc.) in the aft section of the car than near the engine compartment. The dash cavity is also a nice hollow space that’s going to amplify certain sounds – not to mention the open spaces in the engine compartment.
Replacement of the OEM hoodliner with a light but high density aircraft firewall material would help, some. Fatmat/Dynamat on the floorpan and cabside of the firewall would also help. Filling the dash cavity with insulation might also help. But we’re talking maybe 5-6dB reduction between all three approaches … and at K3 dB levels, I just wouldn’t spend the money/time if that’s the only reason you’re doing sound deadening.
I can’t see that plastic being the sole cause of funneling more sound into the cab; I truly think it’s a combination of things. As for removing more of it … he shouldn’t notice any issues with normal driving if he removes it or cuts it way open – but there will be a small (likely not human-noticeable) MPG hit … which if he’s driving a SRT8, he clearly doesn’t care about. However, what may be relevant is that he’ll have less down force at high speeds (i.e. track speeds) if he cuts it open or removes it, as one of its purpose is to help funnel air under the car (instead of it rising up into the engine compartment and generating extra lift, there). It also helps keep dirt, debris, etc. out of the engine compartment – which is relevant for a car this low to the ground on snow-covered roads, gravel roads, etc.
The reduced down force is likely a non-issue, too … unless this guy happens to be The Stig or something, at which point every ounce of performance becomes relevant. (But he drives a SRT8, so we know he’s not The Stig!)
Lots of good points here. I was thinking along the same lines. I’ll open up that plastic a bit and see if it helps at all. I don’t know that there is much more to be done that is practical to keep the sound out of the cabin of the car. The Benz (E55 AMG) was pretty low so I think the horns likely were roughly the same distance from the street’s surface. They may be about 1 foot closer to my head in the Charger than they were in the Benz. The horns were much closer to the tank, compressor, etc. in the Benz which, in theory should make them louder than the 20+ long distance the air is routed in the Charger. Then again, the install on the Charger was actually done by a more professional outfit so maybe things aren’t leaking as much over the distance. Lots to think about here.