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.
yes. it's kind of loud, but not unbearable.
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...
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.
Auto shifter, so just a grommet for the single cable...
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
-Gary Mazzone-
1986 GLHS #168
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.
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.
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.
That's a good idea. When I went over open bridges it was like a completely different exhaust.Originally Posted by Turbo3Iroc
-Gary Mazzone-
1986 GLHS #168
Does this count?
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
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.
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!
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.
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
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.
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.
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
JT
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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.
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