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Discussion Starter #1
In trying to better understand the exhaust set up on my 2007 Sport, I read a review of the Sport QP in EVO (May 2006) in which it is stated:

"A more vocal exhaust (thanks to bypass valves) gives the Sport GT a deeper and more distinctive voice ...."

I was communicating with Tubi Style USA as I was considering replacing the stock silencer with a Tubi style sport exhaust, and they informed me that there are no bypass valves on any of the Quattroporte models. Nothing bypasses the silencer, rather, there is an x-pipe that replaces a center muffler section. The part number is the same on the rear mufflers on the standard and the Sport GT.

(This sounds to me a little bit like another post on this site describing what Fabspeed did for someones 2005 Coupe Cambriocorsa: http://www.youtube.com/watch?v=4ntYvqp3MAI )

I would have to think Tubi is correct on this, but wonder if anyone else has any comment (other than you can't believe anything you read!)
 

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The valves were required for emission standards.

On Ferrari they reduce the exhaust output by 50% ( exhaust gas flow is through two pipes instead of four) thereby keeping gasses w/in the muffler a bit longer to ensure they are fully burned when the engine is reving below 2,500 RPM.

Above about 2,500 RPM the system opens the valves and gasses flow out of all four outlet pipes.

Most of us Ferrrai owners either have removed the valve's function (leave it open) or replace mufflers with no valves.

So, not only is the noise output level increased w/o them, engine efficiency goes way up.

They are a ridiculous excuse to keep down emissions.

They are absolutely unnecessary from a functional stand point.
 

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The valves were required for emission standards.
...
there are no bypass valves (as in the GS) in the QP that alters the exhaust notes.

tubi is correct. there is a x-pipe.
 

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there are no bypass valves (as in the GS) in the QP that alters the exhaust notes.
I am not sure this is correct as there has been discussion on other sites about the bypass vales on maserati's.

I check on that though.
 

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Here's a quote excerpt from a British publication in 2004 as they reviewed the QP:

"This is achieved with less aggressive intake cams and a longer air intake, while the exhaust is claimed to improve high-rev responsiveness – as is the fashion at Ferrari, a bypass system in the exhaust makes it sound better when you floor the accelerator. And who are we to argue?"

Quite certain they are there.
 

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Here's a quote excerpt from a British publication in 2004 as they reviewed the QP:

"This is achieved with less aggressive intake cams and a longer air intake, while the exhaust is claimed to improve high-rev responsiveness – as is the fashion at Ferrari, a bypass system in the exhaust makes it sound better when you floor the accelerator. And who are we to argue?"

Quite certain they are there.
Quite certain they are NOT there.
http://www.eurospares.co.uk/partTable.asp?M=3&Mo=636&A=1&B=36183&S=

btw what is the British publication you are quoting??
 

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btw what is the British publication you are quoting??
this is how it was listed off the other site where I searched for it:

Test Drives ----------------- FROM UK DAILY TELEGRAPH---------------

Trident missile
(Filed: 31/01/2004)
 

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Here you go:

"Even at town speeds you can enjoy the basso profundo, beat of the four exhausts if you want. In normal mode the car is rigged for silent running. But press the sport button and you open the exhaust by-pass valves to release the best in Italian automotive music."

This is from: http://maseraticlub.co.uk/trident35.htm

It's about the coupe but applicable to all Maserati's.
 

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Here you go:

"Even at town speeds you can enjoy the basso profundo, beat of the four exhausts if you want. In normal mode the car is rigged for silent running. But press the sport button and you open the exhaust by-pass valves to release the best in Italian automotive music."

This is from: http://maseraticlub.co.uk/trident35.htm

It's about the coupe but applicable to all Maserati's.

Here you go: THAT IS A GRANSPORT, NOT A COUPE.
 

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Discussion Starter #10
The valves were required for emission standards.

On Ferrari they reduce the exhaust output by 50% ( exhaust gas flow is through two pipes instead of four) thereby keeping gasses w/in the muffler a bit longer to ensure they are fully burned when the engine is reving below 2,500 RPM.

Above about 2,500 RPM the system opens the valves and gasses flow out of all four outlet pipes.
Forgive the stupid question: When you describe two pipes vs. four, are you describing the four pipes coming out the rear of the muffler, i.e. two each side? Or are you saying that there are four pipes leading out of engine all the way back to the mufflers instead of just the two that are on the QP Sport?

Has anyone ever seen a diagram of the inside of a Tubi muffler (or other make) which would make it clearer as to how / where the bypass valves are and how they divert the exhaust in the low vs high rpm driving scenario?
 

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Discussion Starter #12
Clarification

Mark, thanks for the link on discussion! Very informative, but I wonder if you (or others) could confirm if I understood this all correctly:

The Sport GT exhaust is as follows:

Pre Cat and Cat
Pipes to X crossover (i.e. no central resonator)
Pipes from X to rear silencer (same as on standard QP)
Rear Silencer / muffler does not have any bypass valves, nor are there any bypass valves anywhere in the exhaust system of the QP Sport.

Qualitatively, to some ears, there is little difference in the QP Sport voice and volume compared to the standard QP

Replacing the rear silencer with a sport Tubi will alter significantly both the volume and quality of voice. This may or may not be too loud for driver and neighbors.

Replacement may cause some vibration percieved by driver and passengers.

Replacement may slightly increase power (HP)

Replacement of muffler should be accompanied by replacing the air filter to reap benefit of increased HP. (Hard to believe that Maserati doesn't already put in best air filter available, but that is what I have read)

Altering the exhaust in this way on a QP Sport could result in damage to Pre Cat and significant engine damage.

Thanks
 

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From what I've seen \ heard:

Normal \ Executive QP:
headers w/ integrated pre-cat
cat
h pipe
rear resonators
mufflers

Sport GT:
headers w/ integrated pre-cat
cat
rear resonators
mufflers

The only major difference is the deletion of the h-pipe, and some minor ecu changes that probably give the exhaust a different character, but like the difference between CDs and Vinyl.

NO QP has variable valving in the exhaust tract that I've ever heard of. (aside from the engine's variable valve timing, which does make a difference)

Sound differences - there is definitely a noticeable difference - the sport is raspier, but not a lot louder. I think the deletion of the H pipe is what leads to most of the extra exhaust pops and burbles due to the difference in back-pressure characteristics. (the exhaust pulses aren't shared between banks and since it fires bank-to-bank the exhaust gas has more time to pop and resonate before a subsequent exhaust pulse is sent down behind it)

Changing the mufflers to Tubi mufflers is a very noticeable difference, especially with the sport gt. The exhaust gets noticeably louder, raspier, and has more pops and burbles.

Exhaust modifications and their relationship to pre-cat damage is still untested enough that you've really only got anectdotal evidence either way. We've got one guy currently across the pond that has an unmodified car with the issue, and Buzz had an issue with breakup, with some modifications. The drop in back-pressure from heavy modifications could easily contribute to this. A car running too rich, or with a bad plug could easily be a bigger contributor.

My *personal opinion* is that tubi mufflers on a QP shouldn't cause a problem. I don't think they cause enough of a backpressure change to drastically change exhaust temperatures at the engine. I know of a couple QPs in town that have had Tubi on since new, driven year round, with no problems. Now at the same time, I know of a couple Coupes that had Tubi mufflers on them that had some problems that could have easily been caused by exhaust modifications.

I think it may be a good idea to replace your battery with an Optima red top, swap spark plugs for some premium units, use a good air filter, and always buy good gas, and you're more than likely OK. Or you can just play it better safe than sorry and never mod a thing..

(There are threads on these plugs, an optima red top model # if you search - I've heard good things about these mods anyway, and if you're spending the money on the other stuff you should start there)

Performance gains - negligible. Mostly you will feel better throttle response and a bigger smile on your face.

Threadjack:
I'm not sure if this is credible or not, but:
http://www.toptiergas.com/
 

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...Replacing the rear silencer with a sport Tubi will alter significantly both the volume and quality of voice. This may or may not be too loud for driver and neighbors.
not too loud but will certainly wake them up 6 o'clock in the morning.

Replacement may cause some vibration percieved by driver and passengers.
also vibration on all objects around you.

Replacement may slightly increase power (HP)
ermmm... yes 1 billion horse bhp... this is more psychological than factual.

Replacement of muffler should be accompanied by replacing the air filter to reap benefit of increased HP. (Hard to believe that Maserati doesn't already put in best air filter available, but that is what I have read)
the BMC air filter tend to allow more particals to enter so change oil frequently and wash the air filter often.

Altering the exhaust in this way on a QP Sport could result in damage to Pre Cat and significant engine damage.
so they say...
 
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