Some of you asked about the G8 exhaust system - this is the answer I received back.

Quick answer is the Commodore exhaust and G8 exhaust are different. The G8 exhaust is about an inch or so longer, so using a Commodore exhaust system will put the heat right into the fascia causing some deformation. The G8 features the L76 V8 engine with Active Fuel Management which uses different mufflers and has some other parts that the Commodore doesn't use. Bottom line recommendation is not to use a Commodore exhaust system on the G8.

Some of you asked about the G8 exhaust system - this is the answer I received back.

Thanks.
I wonder if the G8 \ Pontiac people took the opportunity to
"tune" the sound louder than the Australian laws apparently allow...
Since they had to make changes anyway.
- Ray
Had to change my new 2007 Corvette's exhaust - too quiet...

Some of you asked about the G8 exhaust system - this is the answer I received back.

Wow thanks DY for looking into that.

Yes DY thanks for the info. on the exhaust. I too definitely hope they tuned it to make it louder.

I can't wait to Mod!

Is the G8's exahust still a true dual exahust? It is not just a Cat Back dual correct?

You could cut up a Commodore exhaust and weld in some extensions. Wouldn't be too terribly difficult for a decent shop to do.

You could cut up a Commodore exhaust and weld in some extensions. Wouldn't be too terribly difficult for a decent shop to do.

I was thinking the exact same thing, but will wait to see what some manufacturers come out with like Borla and Magnaflow and even some smaller companies. Once they can get their hands on a vehicle to do some mock ups, we will start seeing stuff on the US market and not have to pay outrageous prices for Aussie stuff. Although the Aussie stuff is great and sounds awesome to boot.

They probably had to retune it for the AFM. Similar to the exhaust on my Grand Prix GXP, Pontiac had to use special mufflers to mask the "helicopter" sound the engine makes in V-4 mode.

Is the G8's exahust still a true dual exahust? It is not just a Cat Back dual correct?
I beleive the 2 CATS flow to a center single dual in/out muffler and then split back to a resonator on each side that the quad tips attach to. If so, it should be easy to replace the center single unit with 2 smaller high flow mufflers and a bit of pipe. Or, you might just replace the muffler with straight pipes and let the resonators try to quiet things enough to sneak past the lawmen.:angel:

Resonator?????? Please say yes, Please say yes, Please say yes!!

"H" or "X" pipes???? Please say No, Please say No, Please say NO!!



S.F.

Resonator?????? Please say yes, Please say yes, Please say yes!!

"H" or "X" pipes???? Please say No, Please say No, Please say NO!!



S.F.
The picture I recall seeing had a short CAT left & right just after the manifold. Those 2 flow to a single LARGE oval muffler/resonator with a total of 4 in/out pipes which split out to the small resonators at the rear to which the quad chrome tips are attached, 2 per side. If you kept the center unit (ACK!) it would act somewhat as an X or H as it would allow exhaust from both headers to mix before exiting to the separate resonators.
My thoughts run along these http://www.jegs.com/webapp/wcs/stores/servlet/product_10001_10002_744882_-1_10265 one on each side to replace the single stock muffler. :eek2:

Or, it may have been a dream......lot's of G8 dreams lately.

The picture I recall seeing had a short CAT left & right just after the manifold. Those 2 flow to a single LARGE oval muffler/resonator with a total of 4 in/out pipes which split out to the small resonators at the rear to which the quad chrome tips are attached, 2 per side. If you kept the center unit (ACK!) it would act somewhat as an X or H as it would allow exhaust from both headers to mix before exiting to the separate resonators.
My thoughts run along these http://www.jegs.com/webapp/wcs/stores/servlet/product_10001_10002_744882_-1_10265 one on each side to replace the single stock muffler. :eek2:

Or, it may have been a dream......lot's of G8 dreams lately.

Assuming that GMNA keeps Walker as the supplier for the resonator (same as GTO) and does not change its internal design, the above statement is false. The resonator as used on the 05-06 GTO allows for NO mixing of the exhaust gases between left and right banks.

Enter exibit "A" : http://ls2gto.com/forums/showthread.php?t=114481&highlight=resonator+final+report

S.F.

Obviously I am having trouble expressing myself. I have used my magnificent drawing skilz here.

Ok, no skilz at all. Just think of the large center 4 port muffer with both L&R exhaust coming in, mixing, and then L&R exiting to small resonators at the rear.
:drool:

Obviously I am having trouble expressing myself. I have used my magnificent drawing skilz here.

Ok, no skilz at all. Just think of the large center 4 port muffer with both L&R exhaust coming in, mixing, and then L&R exiting to small resonators at the rear.
:drool:


I completely understand what you are saying however I am stating to you that your information is incorrect. Again, assuming the G8 has a resonator, it is still built by Walker (the exhaust supplier to Holden) and its design is similar to the resonator on the GTO then there is no "mixing" of exhaust gases. If you follow the link I posted above you will see photo's and a detailed explanation of the resonator and what it does and does not do.

My post to DY was meant to show that I am eagerly wanting to know if the G8 in fact has a resonator. I wish to know this because I build custom H-Pipes to replace the resonator on GTO's and would like to do the same for G8's.

The question is "is it there?" not "how it works" as I am very, very well versed on the subject. A search of my screen name on ls2gto.com will confirm.........

S.F.

I completely understand what you are saying however I am stating to you that your information is incorrect. Again, assuming the G8 has a resonator, it is still built by Walker (the exhaust supplier to Holden) and its design is similar to the resonator on the GTO then there is no "mixing" of exhaust gases. If you follow the link I posted above you will see photo's and a detailed explanation of the resonator and what it does and does not do.

My post to DY was meant to show that I am eagerly wanting to know if the G8 in fact has a resonator. I wish to know this because I build custom H-Pipes to replace the resonator on GTO's and would like to do the same for G8's.

The question is "is it there?" not "how it works" as I am very, very well versed on the subject. A search of my screen name on ls2gto.com will confirm.........

S.F.
OK. What is the advantage of H or X pipe over just 2 totally separate L & R muffler/resonators?

OK. What is the advantage of H or X pipe over just 2 totally separate L & R muffler/resonators?

The original H pipes were for folks making 500+ crank who were running afoul of noise regs with true duals. Google David Vizard and read up.

On both the Right and Left bank of Chevy smallblock V8s, one pair of cylinders fire sequentially in the firing order. On the LS series it is 1-3 on the left side, I forget on the right, IIRC 4 and 6.

At the n00b level, the sequentially firing pair creates a "slug" of exhaust gas relatively dense compared to the rest of the gas flow. Having and H or X in place allows the double weight slug to use both "halves" of the exhaust system, with the general assumption that each half is ready to handle the regular flow. So the double weight slug uses both sides....

Sorta. The wave dynamics of the system are significantly more complex, math classes I didn't do real good at in college.

At the end of the day, if you are making 500+ horses at the crank you will _probably_ need an H or X to help keep your system quiet. Under 500crank, you _may_ install an H or X, if you like the sound.

Personally, and this is just opinion, I really like the sound of true duals with no H and no X.

Drive train loss for the VE will _probably_ be 15-20%. About. So if you are shooting for more than 400 horses at the drive wheels, there is probably an H or X in your future for technical reasons.

Probably 91-93 octane, an LS2 cam and a tune will be ~~about~~ the upper limit for not thinking seriously about a crossover pipe.

I should re-iterate there is nothing wrong with putting an H or X pipe on a two cylinder dirt bike making 12 horsepower. Power gains may not be measurable, but it won't hurt anything if you like the sound.

And we don't know how well or poorly the stock exhaust flows yet. From what I have seen on the Ozzie boards, dual 3" is the rule, but come on.

Here is a link to a reputable exhaust copmponent manufacturer.

{edit soon}

Whoa. That sucked. Somewhere on the onternet is a page describing what size pipe can flow how much gas and therefore supporting how much horsepower. When I find it I'll link it.

Thank You. :thumbsup:

Update: I got to examine 2 888 GT's today and have confirmed the exhaust layout. The G8 has a rather large resonator just like the 05-06 GTO's so I'll be designing/building H-pipes for it. Also, the G8 use modular bolt on muffler assemblies (axlebacks)just in front of the rear bumper cover just like the 05-06 GTO's so I'll be designing and building performance axlebacks as well.

Now I just need a developement car...........

S.F.

To also explain the x-h pipe from another angle you also have to examine the pulses (for scavaging). The pulse is an area of high pressure. This is immeadiatly followed by an area of low pressure. Since the right and left banks fir at different times your letting the pulse from one bank cause a pressure drop in the other which speeds the pulse along and moves gasses out of the system. It plays much more into header design but is practically the same principle.

Classic BPG has agreed to allow me to take measurements of one of the GT's for my prototype H-Pipe!!! They are going to put one up on the lift for me in the morning......


Yay!

S.F.

Keep us posted, I'll be looking to make mine a bit louder. On my TBSS I just took off the resonator for sound...

Okay here's the scoop on G8 exhaust:

The system is 2.25" in diameter (05-06 GTO is 2.5") and has a very long but narrow 2 inlet/2 outlet resonator (like 05-06 GTO) with two bullet resontators a small distance further downstream and terminating with the two large mufflers by the rear facia. The mufflers are still flange mounted however they benefit from flex couplings which should reduce the amount of stress on the hangers.

The G8 specific H-pipe will be a WELDED ONLY installation as there are bends immediately before and immediately after the resonator assembly making Safe install using clamps impossible.

The G8 specific axlebacks will bolt in place just as the stocker and it looks like mufflers will be easily obtained.

Pics to follow.

S.F.

Resonator?????? Please say yes, Please say yes, Please say yes!!

"H" or "X" pipes???? Please say No, Please say No, Please say NO!!



S.F.

What effect do you expect the DOD V-4 fuel saving mode to have on the exhaust sound if you replace the center resonator after the Cat's with an H or X-pipe? Will you not hear the "helicopter" sound due to the light throttle or will it be apparent at cruising steady highway speeds 55 to 70 MPH in 6th gear? What's your experience with this?

What effect do you expect the DOD V-4 fuel saving mode to have on the exhaust sound if you replace the center resonator after the Cat's with an H or X-pipe? Will you not hear the "helicopter" sound due to the light throttle or will it be apparent at cruising steady highway speeds 55 to 70 MPH in 6th gear? What's your experience with this?


I personaly have no experience with performance exhaust on a DOD equipped motor. That being said it is a issue that Borla, Bassani, Corsa, Flowmaster and myself will all be learning about together.

Hemi Rams, Tahoe's etc.. have DOD and those guys are running performance exhaust with no issues.

DOD will only be operable under certain conditions in a very tight operating window: I.E. highway crusie. With the right kind of muffler the sound volume at cruise will be low, thus any odd harmonics from DOD operation should not be very noticeable. The instant the the gas is pressed to accelarate DOD shuts down so as the roar of the V8 sounds as it should.

S.F.

Okay here's the scoop on G8 exhaust:

The system is 2.25" in diameter (05-06 GTO is 2.5") and has a very long but narrow 2 inlet/2 outlet resonator (like 05-06 GTO) with two bullet resontators a small distance further downstream and terminating with the two large mufflers by the rear facia. The mufflers are still flange mounted however they benefit from flex couplings which should reduce the amount of stress on the hangers.

The G8 specific H-pipe will be a WELDED ONLY installation as there are bends immediately before and immediately after the resonator assembly making Safe install using clamps impossible.

The G8 specific axlebacks will bolt in place just as the stocker and it looks like mufflers will be easily obtained.

Pics to follow.

S.F.

I'm in! Do ya'll usually remove the bullet resonators as well and place straight pipes in their place?

My V4 sounds great! If it sounds this good with DOD I'll be happy!

Not mine... What can I say? I love listening to videos...

http://holeshot.com/videos/VMax4_2_DynoPull.MPG
(http://holeshot.com/videos/VMax4_2_DynoPull.MPG)

Okay here's the scoop on G8 exhaust:

....

The G8 specific axlebacks will bolt in place just as the stocker and it looks like mufflers will be easily obtained.

Pics to follow.

S.F.

I will be watching for the "axle back" - that was my first thought when I saw the G8 GT's configuration from underneath...
- Ray
Driving a Corvette with more exhaust changes than is sane...

I'm in!

I will be watching for the "axle back"


Just waiting for someone local to be a developement car.....

S.F.

http://i152.photobucket.com/albums/s190/angelajeanmessina/G8pics006.jpg

http://i152.photobucket.com/albums/s190/angelajeanmessina/G8pics007.jpg

http://i152.photobucket.com/albums/s190/angelajeanmessina/G8pics008.jpg

http://i152.photobucket.com/albums/s190/angelajeanmessina/G8pics009.jpg

http://i152.photobucket.com/albums/s190/angelajeanmessina/G8pics010.jpg

http://i152.photobucket.com/albums/s190/angelajeanmessina/G8pics011.jpg

http://i152.photobucket.com/albums/s190/angelajeanmessina/G8pics010.jpg

http://i152.photobucket.com/albums/s190/angelajeanmessina/G8pics013.jpg

Not pictured are the two bullet resonator just after the big oval resonators shown above

S.F.

I've delt with several trucks with DOD and the guys complain about the sound w/ aftermarket exhaust. With the stock exhaust/ intake the DOD transistion is seamless.. however just as soon as you put a catback on SOME trucks tend to change pitch and tone when DOD is active. I hope this is not the case so much with the G8

I've delt with several trucks with DOD and the guys complain about the sound w/ aftermarket exhaust. With the stock exhaust/ intake the DOD transistion is seamless.. however just as soon as you put a catback on SOME trucks tend to change pitch and tone when DOD is active. I hope this is not the case so much with the G8It is apparent on the stock exhaust, I drove one today and could hear the pitch of the exhaust change and feel a difference in the way the car vibrated..

I've listened closely to my own and have not been able to hear it. BTW.. the white looks sick on these cars ! NICE

Am I the only one disappointed with the car having 2.25" exhaust from the factory?

An intake and catback setup should REALLY wake these cars up!

Stolen Fox -

I see you're in Mansfield - that's just down the road from me. When you get all this ironed out I'll be paying you a visit. :cool:

Thanks for posting the pics. I have to give Holden credit for having a very nice-looking exhaust from the factory.

What's that rectangular hole in the large 2 > 2 resonator?

Stolen Fox -

I see you're in Mansfield - that's just down the road from me. When you get all this ironed out I'll be paying you a visit. :cool:

Thanks for posting the pics. I have to give Holden credit for having a very nice-looking exhaust from the factory.

What's that rectangular hole in the large 2 > 2 resonator?


Keep an eye out for my updates.....

The "hole" is a build sticker from Holden or Walker that is burning off.

S.F.

i have a g8 gt if i put the magnaflow cat back will have droneing?

i have a g8 gt if i put the magnaflow cat back will have droneing?

No, Magnaflow is legendary for great sound without the drone. Now if you did the 4" Magnapacks, thats a different story.......


S.F.

so guys i wanted to get the x pipe should i stay with the 2.25 or should i go with 2.50 thank you

Okay here's the scoop on G8 exhaust:

The system is 2.25" in diameter (05-06 GTO is 2.5") and has a very long but narrow 2 inlet/2 outlet resonator (like 05-06 GTO) with two bullet resontators a small distance further downstream and terminating with the two large mufflers by the rear facia. The mufflers are still flange mounted however they benefit from flex couplings which should reduce the amount of stress on the hangers.

The G8 specific H-pipe will be a WELDED ONLY installation as there are bends immediately before and immediately after the resonator assembly making Safe install using clamps impossible.

The G8 specific axlebacks will bolt in place just as the stocker and it looks like mufflers will be easily obtained.

Pics to follow.

S.F.


i cut out that large single resonator on my G8 GT and had two pipes fabricated for it. I also put two 3-chamber flowmasters in place of the back two mufflers. it does sound MUCH better however it tends to gurgle a bit when active fuel management kicks in =/ this is a problem your going to have to live with if you want an aftermarket exhaust system for this car. i did, however, notice an increase in power and throttle response. i got the car the day after it came out. hopefully this H-pipe will eliminate the gurgling...