Trying to keep my single half bridgeport quiet
 

Living in California has been a real treat with a bridge ported single turbo FD. So far I've gotten one ref ticket already. Now I've been paranoid driving the thing around the block. I can't for the life of me get this baby quiet. I have a cat, a split flow muffler, a resonator, and a RB exhaust muffler. A total of 4 things that should quiet this bitch down, but it still is loud.

As I was adding things in the exhaust to make it quiet, I've noticed that the exhaust is more quiet but the car is still loud. There is a ton of noise coming from the engine bay and I have not found any exhaust leaks.. It has been a battle, but it seems to me that my large exhaust ports are just loud. Is it possible that I'm just hearing the exhaust through the turbo manifold itself? It seems to me that at least half of the noise output that the car is making is coming from the engine bay, is this normal for a bridgy? I'm almost really close to putting my stock engine back in with the single strapped to it just to make sure it stays quiet, but still have some fun when I want to. I blame the god damn street racers at this point for making it hard to drive a modified car in California.

That really doesn't answer my question because I'm asking about the noise that is coming from the engine bay itself, maybe you didn't read the second paragraph?

bridgeport are loud because of the loud exhaust ports, noise= power. you want it quieter then go with a small street or stock ports..


HOWEVER it could be that theres a loose/open pipe where the noise is coming out of the engine bay. Check your pipes

as I've said I've checked for leaks. Found none. I had it up on a lift. Although I'm thinking of doing a smoke check tomorrow. I'll pour some Seafoam in her and see if it smokes out near the engine. Its too bad I don't have anything to compare it to. My bridgeport is the only bridgeport that I've heard in person. I'm quite happy with how quiet it is out of the exhaust, its just all the racket that I hear coming out from under the engine bay bouncing off of the street. It doesn't even sound like an exhaust leak either.

I would try wrapping your downpipe and manifolds. If that still does not quiet it down make a buffer of some sort around the exhaust area and see if that helps. Is your manifold/ downpipe made of thin material?

i have a half bridge with a single turbo. I do get some noise from the engine bay but not nearly as much as the 4" exhaust. I ended up creating a dual path exhaust to shut things up at cruise. I have not done anything to shut up the intake side as i have not found it necessary. At idle when the exhaust is going through the quiet loop, the underhood noise is probably louder... but it really isnt that loud.

I've thought about that myself. I made my own downpipe, I used some really thick SS, cost me a pretty penny. The manifold is something I got off of eBay as a placeholder, but I never got around to replacing it since I've lost my job. All I know is that it is 304 SS and it appeared thick when I cut it up to fit my v-band wastegate.

Loud is subjective I suppose. California loud may be louder than St. Louis loud. I'll be sure to check for leaks a second time in the morrow.

I would talk to Wackaloo13^...

He made be an exhaust valve with holes in the butterfly that I installed in my 4" exhaust at the rear after the resonator but before the mufflers and when closed the car shuts up to like stock levels. It wont even boost 1 psi because of the restriction but it really quiets it down to almost stock levels.

Chris

man I know I said I was going to do the smoke test today, but I walked out to the garage and started breathing fire and called it quits. It is too hot right now.

Bridgeport has lots of overlap.

Time when exhaust port and intake port are open at same time.

You are hearing exhaust reversion through the intake.

You can quiet it down with a carefully designed air box.

With all you have done on the exhaust side to quiet the car down you are probably down power compared to where you would be with a streetport as engines with more overlap are very sensitive to exhaust backpressure.

I finally had some time to check things out. I did a Seafoam smoke test and there were no leaks. I took a real good listen and it just sounds like I'm hearing the exhaust combustion plinking against the turbo manifold. I suppose I'll be in the market for a cast manifold in the future. I've thought about wrapping the current manifold, but I have no idea how long the manifold will last. Has anyone had any success wrapping their manifold? I've wrapped headers on high performance sand rails before, but I doubt exhaust headers of an LSx engine see the heat that our turbo manifolds see.

heatwrap isn't going to make the car quieter. Clearly the exhaust port design has a lot to do with noise. Why else would Mazda put restrictive exhaust sleeves in the 6 port nonturbo engines (with no turbo to muffle the engine) and in the Cosmo (luxury car) motors?

when I enlarged my exhaust ports more I definitely noticed more noise under the hood.

I feel you man, I've been wanting to quiet her down. Right now I have no cat, so I'm hoping that will quite her up a bit. Of course, after mine warms up she goes from 1100-1200 idle to 1700! How are the idles on your HBP?

-charlie

a/c load i can get a 1200 or so that is steady with no brap. no a/c load i get around 1300 but that moves around and i get a nice brap. tuning idle on these takes a bit.

on my bridgeport there is more noise coming out the engine bay that out the exhaust,BRAP,BRAP BRAP(http://www.youtube.com/watch?v=ZHD_ly5d-mQi)have a 4 inch downpipe,magnaflow silencer and a racing beat muffler,single exhaust.I got pulled over to and i dont know how to quiet her down.

My idles at 900 cold BRAAAP,BRAAAP but when it gets warm goes to 1200RPMS BRA,BRA,BRA
http://www.youtube.com/watch?v=EOjEj96Jvsc

heat wrap
 

I did wrap my manifold,downpipe and it did work a little bit.You can tell the difference.

my friend has almost the same setup that i have but his manifold and downpipe are cast and is not that loud under the hood,mine in the other way with SS manifold and downpipe is loud really loud.

This is what i did to my exhaust. It is a half-bridge with a 4" exhaust.

Here is a view into the tailpipe, i designed/machined this vavle.
http://i182.photobucket.com/albums/x...3/IMG_1362.jpg

Here is the second hidden muffler. The next time i have the exhaust off i will recirculate the dump into the main tail pipe. I was lazy when i first designed everything. Valve closed =94-95 dB, valve open = 100-102dB.
http://i182.photobucket.com/albums/x...3/IMG_1363.jpg

Video of it at idle, car was just started, at the end it is idling at ~1500. Didnt want to rev it b.c it was not warmed up all the way and i dont have my radiator fan on the car at the moment.

http://www.youtube.com/watch?v=oFV3ZwCbpzk

Here is the valve in action, this is the one that was made for ChrisRX8PR. The plate has 10 1/4" holes in it. I do not have a sound clip of it but he said it was at near stock noise levels on a halfbridged rx8 w. 4" exhaust.

http://www.youtube.com/watch?v=cliHr85QO_4

a pic of the valve w. holes
http://i182.photobucket.com/albums/x...3/IMG_1351.jpg

On my car when the exhaust butterfly is closed and i have my hood open there is more noise coming from the front of the car than the rear. I have no problems driving past cops or anything. The car is wierdly quiet. When i get around to it i am going to hook up a boost switch to the control board shown in the second video. Basically when you apply power to one wire it triggers the valve one way, when you take away power it returns to the closed position.

I am planning on building an airbox to try and quiet down the noise off the intake but that is not particularly high on the never ending to do list for the car.

I hope some of this helps you with your noise issues. If you want i had a few extra valve bodies CNCd so i can make a few more.

Lee

Clearly you are wrong here. I just heatwrapped my manifold and there is significant noise reduction from the manifold. Now the next thing it seems is that the downpipe is making some noise and I'll be wrapping that next.