Hib Halverson

Has anyone here, swapped the exhaust mid-section on a '12 or '13 for the no-cat mid-section on an '11?

skxf430

Good question as I was wondering the same.

But, wouldn't you have to change the manifolds and downpipes as well? The H pipe section between the years are different.

Hib Halverson

My understanding is that 06-10 Z06 uses an H-pipe but 11-13 uses an X-pipe and 12-13 has four cats.

Also Jason Harding at Katech told me he thought backdating to an 11 midsection was a bolt on but then Justin Abbott at Zip Products told me it was not.

What we need is a photo of an 11 mid-section. Anyone have one?

Halltech

In July 2010 the 2011 GMX-245 LS7 was SAE J1349 re-certified at 505/470, but made the 470 at 4400 rpm vs. 4800 rpm and the 505 HP at 5800 rpm vs. 6300 rpm.

GM claimed wave mixing and back pressure change in the exhaust (mid-pipe change) as their reason for the updated certification.

Obviously the mid pipe "wave mixing" resulted in the same certified power as the 2005 dyno of the GMX-245 LS7 SAE J1349, but at 400 rpm sooner for torque and 500 rpm sooner for horsepower. You have to wonder what the horsepower number was at 6300 rpm, since I have verified that the cams for 2006 and 2011 are the same part number. (Thanks to Glass Slipper)

For a mere $1000 you could have the full dyno pull for your wall.

By the way, the SAE Re-Certification stated 505@4800 rpm for the HP!! Obviously a typo. Had to be 5800 rpm.

I'm not sure, but did the extra cats happen in 2011 or 2012?

Hib Halverson

That's one of the statements I've heard before...from Zip Products.

Not buying until I see pics.

Might have to go back to Plan A which was Sawzall the 2nd set of cats out then weld in sections of 3-in tubing.

MTPZ06

Yes...don't think he has the car anymore, but you need the earlier cats and mid-pipe to make the swap work. I think his username is something like MarkRx?

Here's a link to an article that explains the revisions, and there's a picture (second picture) that shows how the mid-pipe wont mate up to the newer cats. http://api.viglink.com/api/click?for...13687564409017

z51vett

It could be as simple as measure and cut the extra length out and weld the ends that bolt up back on the 2011 pipe.
z51vett
Doug

z51vett

That will work for sure don't know if I want to cut my 12 zo6 exhaust up without cats you may set code or worse null warranty if heads drop a valve.I would want to keep stock exhaust around in that case and put it back on before going in for engine replacement just saying safe than sorry.
z51vett

Hib Halverson

The second set of cats are not monitered.
If I made a claim they'd not notice the two missing cats but my engine will not suffer valve guide issues.

Hib Halverson

What's your source for that information?

I'm interested in confirming that with GM Powertrain PR as my '12.
FYI, my 12 made peak power at 6100 on one run and 6200 on the other.

Who at GM made that claim?

Four cat systems are only on 12s and 13s.

Hib Halverson

Thanks, "MTPZ06", for posting that. Pics are worth tons of words.
An 11 mid-section won't fit, even if the connections were right.
Case closed
Back to my plan A.

Bedouin

Hib, look closely at the top pic of the '12-'13 system & see how the '12-'13 bolt flanges(square-ish) are mounted on the x-pipe, & the flanges with open bolt holes(roundish) are mounted on the header/downpipe side.

Now see the bottom pic of the pre-'12 system where the bolt flange is on the header/downpipe side & the female flange is on the h/x-pipe side.

The bottom pic is an h-pipe, but I'm almost certain the pre-'12/13 x-pipes had the same flange set-up as earlier the earlier h-pipes.





Here's another close up of a pre-'12 system;



Last clarification...I don't think the more important ball & socket interface has changed, just the clamps have been reversed. The cork-type gasket is still on the 'Ball' end of the cat'd downpipe, & the x-pipe still has the 'Socket' end on it. In short, you could still sawzall & add clamps, but at least now you know what you're dealing with.

Halltech

GM Powertrain letter to SAE.

The exhaust was changed in the 2011 Z06. You would think that if the extra cats came in 2012 that they would have asked for re-certification again. They did not.

I would prefer not to names on the forum.

I have the actual GM Powertrain cerfication request and report. It was the July 13, 2010 SAE Certification Letter back to the originator of the request. It's all in the Level 1 report. Level 2 would have the full pull, The caveat here is the Level 2 report is $1000, as I mentioned.

Halltech

Hib, SAE will not allow reproduction of their testing. I will be happy to provide you with my information offline.

Thanks,

Halltech

That sucker must weigh a ton! The Akra mid pipe weighs 9lbs in Titanium.

No cats though.

Minkster

Be great to know what the peak numbers were....

Halltech

I agree. The request made it clear that the "backpressure" had changed, which could only come from a couple more cats, and the "wave mixing" which was likely other mid pipe changes.

The testing was for the 2011 Z06 platform for sure.

Minkster

That's what I have, a '11 Z06/Z07.

MTPZ06

It has...it's reversed. The earlier cats had the doughnut, and the mid-pipe was flared. Now the newer cats are flared, so the doughnut is at the the mid-pipe end. What I don't know is if its integrated into the mid-pipe? Regardless; I suppose if one were handy and wanted to, they could shorten the earlier mid-pipe and then find a pair of doughnut gaskets the right size and taper to mate old mid-pipe to new cats. I imagine this is possible... Fabing this set up is not ideal for guys that want to run the Akra Ti system obviously, so the earlier cats are the only way to go.

Halltech

Here's the rub with re-certification. Once the original numbers are reached, it make no difference to SAE at what the rpm the numbers occur, the platform passes. GM is not required to say anything to the public at large. In other words, the re-cerification dyno has to hit at least 98% of the original to re-certify. All is well, and mum is the word. If for whatever reason it did not pass, then back to the drawing board. Imagine if it only hit 500 HP and they had to publish that for the 2011 Z06.

In this case, 100% validation occurred but at 400 rpm and 500 rpm sooner. Just an educated guess would tell me 515 or so is where the needle would have stopped at 6300 rpm vs 5800 rpm. If there was a good enough reason, we could buy the Level 2 test, but it is a moot point now.

Why didn't GM tout the new higher numbers? It was probably a marketing thing with so many Z06s left on dealer showrooms, they would instantly have doomed the sales of those leftovers. Personally, I think if the hp did increase, it was from lower backpressure and wave mixing, maybe higher flowing cats? I really don't know.