custom Camaro exhaust idea, comments please!

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Brangeta
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custom Camaro exhaust idea, comments please!

Post by Brangeta » Fri Aug 07, 2009 5:52 pm

Q: Why am I designing this in the first place?
A: When I get a Camaro Z28, I want to smooth the burble out of the LT1's natural tendency at idle into a very unique sound for a Camaro. I might as well do the research now rather than when it is sitting somewhere waiting for work to be done.

Anyway... on with the show...

This is the way a stock Camaro Z28 looks underneath. For '96 and '97 there was an additional catalytic converter directly on the driver's side manifold. From '93 to '95, the cars only had the single cat mounted under the legs of the front seat passenger, I believe the cat used from '93 to '95 was more restrictive than the ones used '96 and '97 because the dual cats bumped hp up by 10 hp.

After the catalytic converter under the passenger, the exhaust goes to a Y-pipe and from then on travels to the muffler as one single 3" pipe instead of two 2.5" pipes. Once it gets to the muffler, it splits off into dual exits and you have your dual exhaust.

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Some people want true dual exhaust, and don't like the Y-pipe and instead go with an X-pipe or H-pipe. They usually remove the cats altogether.

Most people who use an X pipe on Camaros are typically drag racers who run the plumbing down the center of the car--Camaros aren't made for that. 90% of them have the mufflers mounted mid-ship and have them dump before the axle to avoid the major clearance issues dual 3" pipes run into when going over the axle. Some manage to find ways to run the pipes out the back by relocating suspension/driveshaft/etc. parts. Either way, they sacrifice a lot of ground clearance, but drag racers don't care, because they don't have lowered cars usually.
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This guy has more ground clearance overall, but still has the pipes running through the center of the car (can't see them too well in this pic unless you look for them in the darker area of the photo), but he was smart and mounted some extremely thin mufflers along the outside of the underside of the trunk (or as I call it... the pit... because it is very, very deep for a trunk). So he only has about 3 inches less ground clearance instead of 4 or 5 inches like the guy above.
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An idea that works even better (in my opinion) is to go alongside the passenger side of the car (like the stock exhaust plumbing), go over the axle with both pipes where the stock plumbing does, put a dual inlet/dual outlet muffler (same size as stock or likely smaller to accommodate the extra pipe that will take up space there) where the stock muffler normally goes, and then run two exits on the driver's side, or do what this guy below did. This way you don't sacrifice but maybe an inch or two of ground clearance in certain areas if any at all!
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All three of the above applications have 1 thing in common: they are all illegal modifications. They won't pass inspection, because they took off the catalytic converters, they don't have O2 sensor(s), and besides that, it's illegal to change the location of the cats, which is why most aftermarket exhausts are cat-backs. I want my car to pass emissions without a single issue, so there's no way I would do exactly what these guys did.

My idea is to keep the stock Z28 exhaust manifolds and stock cats. Everything after that will be changed. Now here's the interesting part...

The Maserati Gran Turismo S has an extremely beautiful exhaust note. It is a nice humming sound at idle, and when revved, it releases a bark. Ex: http://www.youtube.com/watch?v=XuiH4zPCONU The way it apparently does this is through the use of a resonator mounted just after the cats and well before the mufflers. The mufflers are a very interesting shape and likely have something major to do with the sound as well, however, what is important here is that the resonator is what blends the combustion cycle into a nice even hum, and when revved, the gasses are moving too fast to be subdued by it. Camaros do not have a resonator. Mine will.

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Gran Turismo (not S version) cats, resonator AKA central muffler according to Maserati, and plumbing:
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Gran Turismo S mufflers AKA silencers according to Maserati:
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I looked into it, and I can get the 'central muffler' which is actually a resonator combined with an x-pipe for about $538 online. Pricey. I can probably get it locally much cheaper (or even free?) from the Maserati dealership when they install aftermarket exhaust on a Gran Turismo or Gran Turismo S (which is sadly common, because then it no longer has the smooth idle, as the aftermarket does NOT use a resonator at all, just an X-pipe). It's #5 in the illustration, and about the length of a loaf of bread I would guess. Probably weighs around 15 pounds.
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Re: custom Camaro exhaust idea, comments please!

Post by Brangeta » Fri Aug 07, 2009 5:53 pm

From that part, two 2.5" pipes will lead over the passenger side axle into one of those dual inlet/dual outlet mufflers similar to the Speedster centerline exhaust, and out the tips.

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Flowmaster, Magnaflow, and Dynomax all make a muffler like this, but the Flowmaster looks like cheap crap, and although Flowmaster makes several different types of mufflers... at least the 40 series sounds almost like... :-lookleft ... diarrhea... :-stare... so I'm not sure what to look at on their site. I'm already biased against Flowmaster.
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the Dynomax looks slightly less cheap, but I haven't found size specs for it yet, and haven't bothered to research the sound of one of their mufflers.
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and while the Magnaflow looks just fine, I absolutely hate the way Magnaflow sounds on a Camaro with their standard single inlet/dual outlet muffler, so I assume this one will sound just as bad. Ex: http://www.youtube.com/watch?v=Odga7s4bQo8 I hate the way when you get off the throttle it pops. Hate it...
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You Corvette and Callaway guys always know the better quality stuff, so it's worth seeing what you guys know of. :thumb1

What do you think? Do you know of any other mufflers with dual inlets/dual outlets I could research? Some brand that tends to sounds less like a wet fart on an LT1 and more like the Gran Turismo S?
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Re: custom Camaro exhaust idea, comments please!

Post by SurfnSun » Sun Aug 09, 2009 6:05 pm

Brangeta,

I think most guys would like to be able to turn their cars into something that sounds like an italian V8 :-thumb Its just not gonna happen tho. :-Irked Firing order is one of the single biggest factors in an exhaust note. Unfortunately that is something you really can't change.

I think you've got some good designs here to borrow from. The muffler you choose will make the single biggest change in your sound vs having an Xpipe or Hpipe. The piping configuration will have a greater impact on performance and less on sound. It will just get louder or softer. Ive had multiple different after market exhausts on my C4's, so Im loved, some not so much.

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Re: custom Camaro exhaust idea, comments please!

Post by Brangeta » Sun Aug 09, 2009 6:51 pm

Thanks for the reply Surf! :jsmile

The biggest goal of all, by far, by the entire operation, is to change the LT1's burble at idle into a smoother hum. It'd be great to have it sound like the Gran Turismo! But it's impossible just as you say.

I know you are probably VERY familiar with what an LT1 sounds like, but this video shows a comparison of how my mom's LS1 sounds compared to my sister's 100% stock LT1. My mom's car has SLP exhaust, but an LS1 that came with GM's regular factory exhaust sounds similarly smooth, just quieter. LS1s don't have that muscle car burble to them like LT1s have--they are much smoother. I'm no engineer--I have no idea why it sounds smoother, I just know it does. :wtf
http://www.youtube.com/watch?v=hyyQGa2efTY
For additional support, here is a '95 Z28 with 14k miles on it that I visited a few months ago. Same sound. Sounds great when revved and at idle, but I just like the idea of a little SURPRISE! when my future Camaro is revved. :jsmile
http://www.youtube.com/watch?v=bEDbrqPvjpE

If you compare the two, the idea is to have the LT1's combustion cycle sounds blended into a hum similar to the idle of my mom's car. I'm making a huge assumption that something like the Maserati's resonator could do the trick, since it (seems to be) the primary part in the application that calms the Maserati's flow at idle--when gasses are moving slowly--and lets the barking come out when the car is revved--and gasses are moving too quickly to be calmed.

One of my friends who owned and SCCA-style raced a '95 Z28 accidentally gave me a great idea. He mentioned to me that the two pipes going over the axle is going to be an issue, as there is limited room, and since I plan on lowering mine as much as his is lowered, the dual pipes altogether could cause an issue with that. So I got to thinking... what if I stuck with the Y-pipe and single pipe? :bulb :bulb :bulb I could have the resonator mounted just after the cat as planned, and just after the resonator, the stock Y-pipe could be relocated and some straight pipe cut out! :bulb :bulb :bulb. There was no reason in my mind that I needed or wanted true-dual exhaust, I was just doing it because the resonator has an X instead of Y on it. Doesn't mean X can't connect to Y! :bulb

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Only problem with the entire plan is the lack of space there, and the... (what the heck is that piece called? panhard rod?) in the way. I see a lot of Camaros with custom suspension pieces by UMI, BMR, and such that don't even have that, so I'm not sure what to call it.

Image

Hmm...
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Re: custom Camaro exhaust idea, comments please!

Post by Brangeta » Sun Aug 09, 2009 8:10 pm

Just got a picture from someone of how the cats are laid out in the '97 Z28. Quite a bit different. Drawings will have to be modified... plan may be modified to improve ground clearance... need some time to think.
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Re: custom Camaro exhaust idea, comments please!

Post by SurfnSun » Sun Aug 09, 2009 10:35 pm

I believe the resonator will control more of the low rpm resonance at cruise as opposed ot at idle sound. I cut the resonator off of one of my civics(bad example I know, but its what Ive got) and the idle was no different but acceleration was.

I hate to sound like a broken record but alas...the LS1 has a different firing order than the LT1 hence the different sound. To me it sounds like the LS motor is also idling at a higher rpm. You will definitely achieve some smoothness in sound by an idle rpm of 1000 or 1100 vs say 750-800.

Is the exhaust layout different between the LT1 and LS1 cars? If its in the thread, sorry I missed it.

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Re: custom Camaro exhaust idea, comments please!

Post by Brangeta » Sun Aug 09, 2009 11:29 pm

You know... I'm not really sure. I've never been under my mom's SS because it's such a garage queen and has never needed any maintenance since the warranty ran out a few years ago. I also tend to hang out in the '93-'97 areas on Camaro forums, so I don't read or see a lot about them.

I would venture a guess that the stock LS1 exhaust is very similar to the '96-'97 I posted above, if not exactly like it from the cats back. Not sure if the cats are different, I'll look into it.

My mom's SS doesn't idle at a higher RPM to my knowledge, but I've never paid a great deal of attention to it.

Was your Civic very loud at idle to begin with, or after cutting the resonator off? Perhaps it sipped gas so frugally at idle that there really wasn't all that much pressure based gas movement going on--not to an extent you could really notice. I've never been a gearhead or engineer, so my understanding of what goes on in the exhaust cycle is vague.

The Maserati Gran Turismo has a 4.2L V8 with 405 hp and the S version has a 4.7L V8 with 440 hp.

I have a few engineer buddies from college I could ask to do the math for me if I knew some sort of figures or dimensions to give them, but I'm willing to bet that a 285 to 300 hp (I don't project having any performance mods besides perhaps a Callaway Honker) LT1 isn't going to be expelling gasses from the exhaust pipe at nearly the same volume as a 440 hp Gran Turismo S.

The results of following my plan could be that the car is insanely quiet and humming at even mid-level RPM... I'm not really sure. I would assume that reusing the Y-pipe and not going with true dual exhaust would maintain some of the backpressure, and perhaps not cause the resonator to resonate throughout the entire normal driving range. Wish I knew. :-Irked
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Re: custom Camaro exhaust idea, comments please!

Post by SurfnSun » Sun Aug 09, 2009 11:55 pm

I cut the resonator off the civic b/c it was leaking....welded a test pipe back in. All it did was make the muffler buzz a little on acceleration.

I got to thinking about the Gran Turismo, my guess on the sound, other than firing order, is use of a flat plane crankshaft like the Ferrari's use. Big time race stuff that is one of the reasons they can spin 8k rpm. It also gives it that racey italian sound.

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Re: custom Camaro exhaust idea, comments please!

Post by Brangeta » Mon Aug 10, 2009 2:05 am

Revised drawing since I screwed up the cats on my first attempt since I'm wanting a '97.
Image
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Re: custom Camaro exhaust idea, comments please!

Post by Brangeta » Tue Aug 11, 2009 2:40 pm

Update:

A friend with a '99 Camaro mentioned to me that the '00-'02 Camaros came with vastly different catalytic converters than any previous Camaros. My parts manual fails to show that...
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but I'll be damned if it isn't true! I went out and managed to get my arm under my mom's 2002 SS with my camera, and sure enough, I could see enough to know it is true! The cats attach directly to the exhaust manifolds and are roughly flask shaped. In the normal location under the passenger where a large catalytic converter has always been located (see pics in previous posts), there is nothing at all to speak of!
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People on Camaro boards have told me that the cats will NOT bolt up to the LT1's stock manifolds, but no one has justified their answer as to why they could not just be welded on. Perhaps the shape is wrong. I'm completely ignorant as to why they would not work at this time. My friend with the '99 who mentioned the different cats came up with this design that I am in love with:
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The illustration isn't completely accurate to the plan that might work, so let me walk you through it.
Stock cats from a '00-'02...
the 3" pipe that leads from them...
pipes will have to be narrowed to 2.5" where they connect to the resonator as I believe that is the size of the inlets on the resonator...
resonator in the space where the cat was always located from '93 to apparently '99...
2.5" dual pipes running all the way down to a Y-pipe located just before the axle...
3" pipe going over the axle (same size as stock to my knowledge)...
stock muffler and exhaust pipes (just as I hoped I could keep).

Looks like an absolutely incredible plan. I have a friend who has a set of these stock cats in his dad's garage that he's going to take photos of and measure for me, so hopefully something using them would work. Getting the cat out from under the passenger seat and being able to put the resonator there will solve any ground clearance issues I was going to encounter!

As far as flow is concerned, compared to what the '97 Z28 is used to, which is dual cats with 2.5" pipe leading to a Y-pipe, leading to a single 3" pipe all the way down to the muffler... flow should actually be better in certain areas. My concern with the resonator is that it is made for a car with 400+ hp. If it is made for toning down the burble of a 400+ hp engine, what will it do to a 300 hp one?

My assumption is that if the exhaust gasses are flowing very easily through my considerably less restrictive exhaust plan (speaking only in reference to the 3" pipe from the cats leading to the resonator), the pressure may not be enough to pass through the resonator and NOT be resonated except at very high RPM, which could be a problem.

That's a risk/problem I'm willing to encounter, because I can always tune up the engine to 400+ horsepower if necessary as time goes by. It's a lot better of a problem than too MUCH pressure. That would be a disaster.

For reference, the compression ratios are:

Gran Turismo, 4.2L, 405 hp, 11.1:1
Gran Turismo S, 4.7L, 433 hp, 11.25:1
'97 Camaro Z28, 5.7L, 285 hp (stock), 10.4:1

Callaway C8 SuperNatural 400 (for reference), 6.27L, 404 hp, 10.5:1

If I need to increase compression, a 383 stroker ain't gonna work!

Or do these compression ratios even matter? I don't know the math, but I would assume a 5.7L V8 at 10.5:1 is actually producing a LOT more overall flow than a 4.2L or 4.7L at 11:1. Thoughts?

(link for S version's engine specs for my reference only, as it's hard to find these specs on other websites, as they don't cover the S version yet: http://www.motortrend.com/cars/2009/mas ... index.html)
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