FAQ: The Exhaust Thread

Here's a shot of the Riviera from below:

so since a aftermarkt down pipe must be welded, (like ZZP 3" shorty DP) is there a need to buy the 2 exhaust gaskets?

No need. Sometimes they come with the pipe. My headers came with gaskets, a flange, and hangers.

ok just making sure before i order mine from ZZP the shorty pipe is what i need right?

As you can plainly see, we have a 2 1/4" exhaust that splits into 2 dinky 1 7/8" sections with a more or less "T" shaped split.

Aaron's pic done up a different way

ok in this above pic can u see the U bend???

Rivs don't have a U-bend.

HUH r u serious !!!!!!!!!!!!!!!! wow is that only GTP then?????? well then for me would i be able to install a 3 inch down pipe would that help me since i dont have headers??

W-bodies have them (GTP/GS). A 3" downpipe would certainly be an improvement!

Hey everyone. There is a shop near me that is having a special with no cost for labor on all exhuast systems. They said they can put in any kind of muffler or whatnot. What has everyone here had success with in terms of exhaust? I will be heading out there tomorrow to hopefully get this thing done. Any advice is welcome. Later guys.

If you're just talking about replacing mufflers, Borla and Magnaflow are solid choices. If you want a true exhaust performance mod, look into a 3" downpipe. Imo this is where the most restriction lies. I'm still sportin' the OEM exhaust from cat back. I like the sound, and performance is more than adequate.

I want to do 3" all the way through and branch it off to dual 2.5" at the mufflers but I see that being very difficult where we have that hump in the pipe towards the rear. I think I could manage to plumb 2.5" pieces through that section but I don't even know where to get 3" bends and stuff let alone know if I can fit that stuff into the space. I wonder how much money it would be to have a shop run that 3" pipe through there nicely..

Has anyone done this already on a riv?

Have you already done a 3" DP?

1998 Riv wrote:

Have you already done a 3" DP?

not yet but I can get that later. My down pipe isn't my current annoyance so it can wait. I may just wait for headers too.

I am really put off by the fact that our stock down pipe is solid and has no braided joints to worry about so why do all the cheap or expensive headers+DP and individual DP's have this braided flex joint that seems to inevitably leak?

turtleman wrote:

1998 Riv wrote:

Have you already done a 3" DP?

not yet but I can get that later. My down pipe isn't my current annoyance so it can wait. I may just wait for headers too.

I am really put off by the fact that our stock down pipe is solid and has no braided joints to worry about so why do all the cheap or expensive headers+DP and individual DP's have this braided flex joint that seems to inevitably leak?

my Favorite is RANDOM Technology, they have very sweet 3" downpipes with or without the cat. They are a little more expensive, but you get what you pay for. Not to mention that it bolts right up, no flex, and it looks very good. as for the rest of the exhaust, im sure an exhaust shop can at least madrel bend something for you if you were gonna do it yourself or they could do the whole thing.

I'm not gonna lie. "random technology" is the most RETARDED name for an auto part manufacturer lol. It just makes me think of a group of gorilla hacks beatin on a pipe with a huge sledge hammer and calling it a high quality part. I know that's not the case at all but I just hate the name.

So are you suggesting that they don't leak like others or what. I just think it's stupid that you have to pay close to a grand for an SLP header/dp and then you have to put a bunch of tape on it every year to keep it from making noise that the stock exhaust never made.

There are different types of braids. Some use multiple layers that don't leak as much. SLP uses a single braid. It's quality made, but it's just noisy by design. That's fine with them because it's off-road equipment. I wrap mine because I want it to be quiet for street use.

The thing about the DP is, I believe it is the #1 limiting factor in our exhaust system. If you do mods to any other part, you're not going to see true benefits if you keep the stock DP in.

If you're concerned about the noise a flex pipe makes, I would think twice about getting headers. They are a bit noisier than cast iron manifolds, even if you seal them up real good.

turtleman wrote:

[...........so why do all the cheap or expensive headers+DP and individual DP's have this braided flex joint that seems to inevitably leak?

I haven't read anywhere about these leaks in the flex joint??? Anyways... Hogan's DP flex joint is optional, according to their website. You should be able to order it w/o.

Alex, most run of the mill exhaust shops won't have the expensive equip to do mandrel bends. Maybe a larger performance specialty place? Dunno...

My Hogan DP doesn't look to me like it will be leak-prone. On the inside of the joint, I can see steelflex pipe, and what appears to be a double wrapping of the braided stuff on the outside.

AA wrote:

.....................The thing about the DP is, I believe it is the #1 limiting factor in our exhaust system. If you do mods to any other part, you're not going to see true benefits if you keep the stock DP in..

I can see the stock DP being a problem, but what about the decreasing size of tubing as you go back? 2.25 after the resonator, then 1 7/8 pipes to the mufflers? I wish someone would offer a mandrel bent replacement system that didn't run so small.

corsa has one, but be prepared to pay the big bucks ($1000 US +). It's for the STS and has the same bends. 304 SS. They don't advertise the diameter though.

From what I understand about exhaust from reading and talking to the JEGs guys is, you need bigger diameter pipes up close to the engine because the hotter exhaust gases are moving faster and benefit more from less restriction. As the gases cool down (they do so very quickly), they also slow down. To maintain proper velocity for the scavenging effect, you want the pipe to gradually get smaller as it goes back. You want to do so with very gradual tapers, not sudden changes in diameter. This ensures that exhaust gas moves with enough velocity so that it can get out of it's own way, helping to "pull itself" out of the engine.

Exhaust systems that are too large in diameter are not tuned for the scavenging effect. They do not maintain the velocity needed to aid the engine in flowing exhaust, so you lose torque. To be fair, turbo and blown engines don't suffer as much from an exhaust that's too large, but you must keep boost levels high enough to push everything through. But it doesn't matter what type of engine you have, if you don't allow the hot exhaust to move upstream, you'll not see as much benefit from widening pipes cat-back, mufflers, resonators, etc.

Yeah, I figured the cooling, with the resulting volume reduction, is why smaller tubes can be used further back. Funny though, you don't see that on old cars. Aftermarket systems for old iron are always pretty much same diameter front to back.

Jason, that Corsa system is way too much... yikes. Cat back? Or DP back? I emailed Wbody Store last night about their DP's for H-body, and theirs is in fact a Hogan DP, same price listed. EXCEPT, Hogan adds $10 if you want the flex joint, while WBS pictures it with the joint, but no upcharge. Shoulda bought WBS I guess. I'm thinking about ordering a bolt-in Magnaflow cat from Hogan, $125, to go with their DP I have on the bench, includes O2 bung installed. For $75 more they offer a "True OBDII" cat, with more substrate and an additional precious metal, supposedly prevents P0420(?) codes. Don't know if it would be worth the 75.

BTW, WBS says they're working on cat-back systems, on a long list of to-do items.