Well, after almost 10 years, I found my tailpipe dangling by the mounting point that anchors it to the frame last night.  Not gonna complain, since I've only spent $40 on the exhaust in 10 years (one of the only perks of living in Florida, and not having snow/salt).  Anyway, the whole system looks pretty rusty from my first few years up north, so I'm thinking about having a good muffler shop down here give me a new exhaust.  Maybe I can get a few extra horsepower out of the deal as well. 

Anyway, I'm hoping a few of you might chime in on this:  I'm planning on having the 2.7L (probably from a 2003 XL-7 w/183 hp) dropped in sometime in the next couple of years, when my 2.5L dies.  So, I'm trying to keep that in mind as I  have this exhaust done.  I'd like something that will work with the 2.5 and be futureproof for the XL-7 H27 engine as well.  Any ideas?  Thanks in advance.  It's been a while since I've posted.....life's a little crazy right now.

the main exhaust isn't the real bad part for restriction, its the crossover pipe between manifolds,

change that while your at it, and i bet you will see a change in hp.

ive been meaning to do it to mine as well, just dont have the time

Here is what i noticed modding my gv.

The 2002 has a bigger exhaust i think it was .25" bigger

I did a intake tube and noticed some pick up there.

The main exahust i did notice a good jump in power. Now after the exhaust and intake. I did a cross over pipe assembly out of 2.5" manderal bends. I used the stock flanges and welded them up together to a merge collector and a flex joint to a 2.5" resonator and flow master 40 series muffler. If you watch some of my vids you can hear it. Everyone thought i swapped in a V8 in it lol. The power difference was big time noticeable.

Ill find some pics for you

Ill find more pics but you get the idea. I have long tube headers on the truck now and with the 2.7L im in the low 15's with the 30" tires.

That exact Y-pipe is on my GV.  I'm happy with the power difference.  I wouldn't go back to OE exhaust nowat all, especially with all that extra weight (skid plates, RockRails) hung under the truck now.  It sounds nice at idle, and sounds really cool at 4000+rpms WOT, but on the highway it drones and I hate it.  No one wants to come with me in my GV.  I saw my mother covering her ears when she was in the back seat while I was trying to drive up a hill.  I put up with it up to now, but 3 weekends ago I went off-roading on an "easy" trail  and landed on a rock which bent the exhaust and cracked a weld on the Flowmaster 60.  So now I figure enough is enough and I'm going to try doubling-up on the mufflers.  I kept my Edelbrock RPM muffler from my old Plymouth Voyager turbo minivan after it was totalled.  Edelbrock doesn't make this particular muffler anymore, but it's more, but not totally "straight-thru"-ish compared to a flowmaster which is more twisty-turny.  So hopefully the Edelbrock shouldn't affect flow very much at all.  If I can't fix the crack on the Flowmaster 60 then I'm gonna change brands.  I love everything about the exhaust except for that drone.  The power, the idle burble, and high-rpms WOT especially, but...

James

Yes, you have the famous K-series drone.  The V6 engines are basically a Mazda design, and the engineers had to work very hard to design the exhaust systems in the Mazdas to eliminate the drone.  When people put aftermarket exhausts on the cars, they ALWAYS got the drone, and extra mufflers did not eliminate it.

When my GV V6 exhaust started leaking, I had a stainless steel replacement (including downpipes and cross pipe) "crafted" to fit.  It drones, but somewhat less then a Mazda, and it is reducing as the system soots up - my theory is that the soot acts as a resonance damper.

When I used to care about my GV...

Yankee Bob and I were going to install a dual exhaust with 1.75" tube, maybe as small as stock Sammy 1.3 (1.3 + 1.3 = 2.5ish).  This would keep the tone quite, but open up the breathing.

And be just damn cool.

Ill find more pics but you get the idea. I have long tube headers on the truck now and with the 2.7L im in the low 15's with the 30" tires.

You need some heat wrap from the manifold down to the flex pipe, but nice job.

Heat wrapping it would just make it rust in 2 years.

The drone on a V6 is normal sucks. My long tubes have a magnaflow with a ultra quiet resonator and a bullet resonator.

If you guys want quiet use the dynomax super turbo

Hmmmm....I'd rather not have the drone.  My truck still sees a lot of highway driving.  There's a pretty good muffler shop here that's been around since 1958.  They do custom stuff, and they're very reasonable.  I wonder what the dual setup would run........(salivating   )

Well after a couple weeks of intense evening Google researching and sleeping on it, I've ordered a Dynomax SuperTurbo muffler to replace the Flowmaster on my GV.  I hope to have it done within the next two weeks, I'll let you know how it sounds.  I've looked at a lot of different performance mufflers (eg.  Hooker AeroChamber, etc) but I figured with the size of the engine and how they rev on the highway, a chambered / sound reflecting muffler just won't work well with smaller engines, especially on the highway.  Just not tuned for it.  The clincher for me was a discussion on a Cavalier forum, someone wanted to put a flowmaster on his j-body and immediately everyone said NO go SuperTurbo.  Flows better and is quieter.  One guy said flowmaster gave him a headache after driving to the beach.   Good for larger v6s and 8s but bad for smaller higher revving engines like ours.

James

My truck inside.

Grand Vitara with H27

Gv At the track

Well it's been about a week or so since I got the Dynomax SuperTurbo installed.    This particular muffler is 2.5" dia in/out, and center/side.  There's a long-body and a short-body.  I got the longer one.  I left the glasspack "resonator" in place and just replaced the busted Flowmaster.  On first startup my reaction was "OMG what did I do?"  It was very quiet, like practically stock quiet.  However it doesn't feel any slower.  In fact a couple times I shot past my target speed because it was quiet.    So there was zero effect on performance compared to the flowmaster.  Also since it has been a week the batting in the muffler is getting "broken in" the muffler is starting to get slightly louder.    On the highway it's a LOT better, my brother says there's still a very slight drone but much MUCH easier on the ears.   Overall I'm very happy with it and I recommend this muffler to anyone looking for decent performance but without the "cool noise".  ...Yeah it doesn't sound like a racing inline-6 BMW at 4000+rpms WOT anymore, and doesn't sound like a v8 at idle,  but I can live with that.  The biggest thing was that highway drone.  I can hear the reduction gears in 4LOW again.  Anyways I'm gonna leave that glasspack "resonator" in place for now but I intend to toss it if/when it rusts and just go with a straight pipe to the muffler.  Internally that glasspack's actually less that 2.5", more like 2" or maybe even 1 7/8", then I'll see how it sounds again.

James

Very interesting thread!

Did somebody take picturees of an entire custom 2,5" exhaust system?

Is it easy, with some pre-bended tubes to pass over the rear axle ?

And some ideas to have a better looking tail pipe?

Just to clarify, I re-read my post, the new muffler IS just as fast as the old flowmaster...

JDMCRX did my whole exhaust with the flowmaster.  The tailpipe over the rear axle, and the Y-pipe at the front are the hardest parts.  If they rust out I'll have to either take them to a guy and say "copy this" or order up stainless (maybe) mandrel stuff myself and roughly mig it all together myself (not recommended).  If I run into a problem though, I'll be stuck without a vehicle.

Every time I have the car up in the air I never have my camera.  Oh well maybe next time.... 

James