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ShelGame
04-23-2008, 08:58 AM
Anyone ever run a straight open downpipe? I'm thinking about removing the muffler from my race car to save weight (if nothing else). The muffler on it now is a Dynomax 3" in - dual 2-1/2" out. It's pretty much just straight thru, I doubt it does much 'muffling'. But, I bet it weighs 15+ lbs.

t3rse
04-23-2008, 09:04 AM
yes. it's kind of loud, but not unbearable.

ShelGame
04-23-2008, 09:21 AM
Loud is good! I can never hear my engine over the V8 in the next lane anyway...

How far back should the downpipe go? I was thinking of just buying a 3" inlet shorty megaphone and letting it hang right under the floor. Nice and light...

t3rse
04-23-2008, 09:23 AM
I'd get it past the shifter so you don't get high in the staging lanes, depending on how well your car is sealed.

ShelGame
04-23-2008, 09:32 AM
Auto shifter, so just a grommet for the single cable...

mcsvt
04-23-2008, 11:07 AM
I drove a couple hundred miles with a 3" open DP...

It's a bit loud but like mentioned not unbearable. Plus with your helmet on I bet it wouldn't be to bad. It will definitely help connect you to the car since you'll be able to hear it so much better. Plus listening to the spool down is fun :)

Turbo3Iroc
04-23-2008, 11:17 AM
I ran my car at the track with an open down pipe and it does get pretty loud. I think the main reason for the car becomming an echo chamber was the sound waves would bounce off the ground and then right into the car. You might want to angle it out under the pass door.

Pat
04-23-2008, 12:02 PM
I've run with an open downpipe at the track also. With a helmet on, it's tolerable. No helmet, it rang my ears pretty good.

overlordsshadow
04-23-2008, 12:03 PM
I run all my turbo cars dp only all the time. I just put a tip on the end to get the noise to the ground, makes it just as loud outside but quieter inside.

mcsvt
04-23-2008, 12:16 PM
I ran my car at the track with an open down pipe and it does get pretty loud. I think the main reason for the car becoming an echo chamber was the sound waves would bounce off the ground and then right into the car. You might want to angle it out under the pass door.

That's a good idea. When I went over open bridges it was like a completely different exhaust.

tryingbe
04-23-2008, 12:25 PM
Does this count?

http://www.thelostartof.net/tryingbe/dodge/exhaust.jpg

vntodd
04-23-2008, 12:54 PM
My first GLH had a flange in the exhaust so I could "uncork" the exhaust at the dragstrip. All stock except for an MP computer I gained an average of 4/10ths in the quarter mile. Went from 15.20's to 14.80's with no other changes. Turbo lag pretty much disappeared also. Wish they had FWD slicks back then ( '86-88)...car would've been a blast.
I still had the stock exhaust on the car, so I experienced more of a gain than would be seen in your case, of course

glht_omni
04-23-2008, 10:23 PM
yup, i cut the cat out of a 89 turbo van with the 2.5" dp and ran it like that for a day till i got the test pipe for it.
but man did it spool way faster and sound like a giant pissed off bumble bee, lol. i actually hung with a 01' ws6 fender to fender from 0-65mph running a mitsu on 15psi the same night i cut the pipe.

Birddog
04-23-2008, 10:30 PM
I've heard some cars on an open DP and it was or seemed liveable.. I ran Omni on an open 3" and hey homey it sucked!

GLHNSLHT2
04-23-2008, 10:55 PM
I had a 2.5" downpipe that was only about 12" long, exited just behind the kframe and didn't bend to go under the car. Was very tolerable. No droning at all. I then put on a 3" Rick setup that exited right under the shifter. OMFG!!! You couldn't hear yourself think 10 minutes AFTER getting out of the car. I put a downturn on it and it was loud but at least your head didn't hurt. So just run a foot long secition getting it behind the kmember but still pointing at the ground and you should be fine.

unluckyty
04-24-2008, 12:46 PM
Her is mine at the track, the band clamp broke right past the K-member.
Definitly loud, especially at Norwalk with stands on both sides.

http://media.putfile.com/Norwalk-2007--29/e

Greg

3Bar_Mopar
04-24-2008, 01:02 PM
I've pretty much ran an open downpipe on all my TDs and I don't think it's half as bad as some Hondas with fart mufflers. Radios are useless and i can hardly talk on the phone at highway speeds (3500rpm at 80mph with the 413 auto).
I have a gutted interior on my Sundance, so it's probably a bit worse.

Captain Chaos
04-24-2008, 01:14 PM
Both of my last two TD's were conversion cars where the stock exhaust wouldn't bolt up. The Horizon I drove about three months with the exhaust coming straight out of the swingvalve. I've been test driving the Shadow the same way. Neither car is as loud as my SRT-4 was with the straight 3" no cat no muffler exhaust.

BadAssPerformance
04-24-2008, 01:16 PM
Open DP is bearable, especially with a helmet on.

On the Shadow, 2.25" SV, stock '87 DP open downpipe vs. full 3" after the DP same mph... So if you go open DP, make sure it is 3" with at least a 2.5" SV :thumb:

ShelGame
04-24-2008, 01:30 PM
Well, I currently have a 2.5" SV (Mitsu) with a 3" DP. But, it's welded up to the muffler setup. I was going to keep that as-is in case I ever wanted to put it back on for some reason.

Here's what I'm thinking: I have a spare (new) 2-1/2" DP that I was going to weld a 18" megaphone to just past the bend over the k-frame. So, it'll be about 8-10" of 2-1/2" DP going into the long taper mega, exiting just behind the k-frame. I'll probably slash-cut the mega, too, so that it's outlet is parallel to the ground.

BadAssPerformance
04-24-2008, 01:31 PM
That would probably flow quite well, but it's gonna be LOUD! ;)

bfarroo
04-24-2008, 07:24 PM
I'm assuming your not worried about boost creap, with the mitsu on my shadow with a 3in side exit an the wastegate hole on the turbo ported as big as I could I get 12-14 lbs with the WG hooked to manifold vacuum.

ShelGame
04-24-2008, 08:53 PM
I've been running the exhaust I mentioned (which is nearly wide open as-is) at 15-16psi for a while with no boost creep. Very steady boost. So, I don't expect that will get worse with just an open downpipe. But, I could be wrong...

ScottD
05-01-2008, 10:08 PM
Do you drive this car on the street? I'm not sure if your car is race only or not. I had an 87 Lebaron 2.2T1 sedan I raced for a season. I cut the downpipe past the k-frame and ran it open at the track, but used a band clamp too keep the exhaust together on the street. It was fine. It went from 15.23 to 14.97 just with the open downpipe. This was a 2.2T1 log car that wasn't intercooled.

TurboRon25
05-01-2008, 11:50 PM
9 years of open downpipe on my 87 2.5 tII Daytona Shelby. 2 1/4" garret, 2 1/4" DP. No problems, sounds great. Currently I have a small turndown on the end of a 2 1/2" downpipe. Sometimes you can't tell there is no exhaust. It's that quiet.

I spent a week with my wife's old TII 89 Shelby Daytona (2.2 TII 2.5" sv 2.5" dp) with an open downpipe.
I would give me a headache after 10 minutes of driving.

...go figure.

Ron

Ondonti
05-02-2008, 05:26 AM
If the exhaust exits under your butt, it will kill your ears.

One thing you have going for you is that you keep your motor near stock for that class you race in so I think that helps keep things quieter. Big cams and big turbos and open wastegate kill ears.

I would have to go with a sidepipe to be drivable in my car. Even then...

If you at least aim it at the ground, that will help. :thumb:

ShelGame
05-19-2008, 11:40 AM
OK, it's all done. Here's the finished product. Sorry for the pic kwality, my camera phone isn't great...

It's loud, BTW. But, it sounds like a racecar should now. :)

BadAssPerformance
05-19-2008, 01:06 PM
Looks good :thumb:

ScottD
05-19-2008, 01:36 PM
That's cool. I want to hear how it sounds.

ShelGame
05-19-2008, 01:58 PM
Going to the SDAC drag races next month? You'll hear it there...

ScottD
05-19-2008, 06:09 PM
Yep, I'm going. Looking forward to seeing it run ... and hearing it :-)

Turbo3Iroc
05-20-2008, 01:02 AM
Is it an echo chamber inside the car when you are on the throttle?

ShelGame
05-20-2008, 07:56 AM
Dunno yet. Hasn't left the garage since I installed it...

Captain Chaos
05-20-2008, 08:06 AM
I'm driving my Shadow on just a 2 1/2" downpipe. Acceleration is really loud inside, but cruising is only moderately louder than with a full exhaust no cat. And I don't have any exhaust fumes sitting still either, which is a plus. Rob that looks cool. When you go wheels up everyone will see your "bling" :thumb:

ShelGame
05-20-2008, 10:13 AM
:eyebrows:Wheels up, LOL....

glht_omni
06-07-2008, 11:15 AM
rob, i just took the r/t to the muffler shop. it had a full 3" with a 2.5" oval dynomax added to the end, it was pretty quiet. i had them cut it off so i could see if it wasnt too loud or if i wanted a muffler.
well it is loud as hell and i know the cops will hassle me for it and it will draw way too much attention on the street, i dont want either of those.
so i am going to do what i figured i would have to do...add a 3" dynomax round can where the catco is. i will get a sound/video clip and post the link here.
it does pull a little harder and sounds mean but its too loud for a residential driver.

overlordsshadow
06-08-2008, 12:36 PM
Ya, I guess you can say I'm an --- like that But I usually only Open it up on the freeways.

turbovanmanČ
06-08-2008, 02:14 PM
I just put a Walker cat on, its a tiny hi flow unit, Hooker MAX FLO muffler and its friggin loud under boost but sounds sweet. The side effect is drone at highway speeds, I put a resonator at the rear and it helped so now looking for a round muffler to put there but no one stocks anything locally and Ebay was no luck.
The boost hits INSTANTLY now whereas the old system it was laggy, much difference, :clap:

ShelGame
06-08-2008, 03:46 PM
Mine isn't too loaud really. It still has the Mitsu turbo - it's pretty restricive by itself. Though, I definitely can't start the car after the kids go to bed anymore. It'd wake them up for sure.

gasketmaster
06-08-2008, 04:07 PM
Our 90 Sundance has gone 13.36 and trapped 100mph with the stock 2.5" downpipe cut off at the cat ;)

It has the non-intercooled Mitsu like yours :)

Captain Chaos
06-08-2008, 08:39 PM
Our 90 Sundance has gone 13.36 and trapped 100mph with the stock 2.5" downpipe cut off at the cat ;)

It has the non-intercooled Mitsu like yours :)

Would it be a legal stocker? That things faster than the A/FS record.:thumb:

gasketmaster
06-09-2008, 02:49 AM
Would it be a legal stocker? That things faster than the A/FS record.:thumb:

Yes......I could take some weight out for A class I believe ;)