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Best exhaust for SC'd NSX?

Originally posted by NSXTC:
The Tubi system is not a dual exhaust, and it still uses the cats. What, other than the promised "Ferrarri 355-like" sound and big price tag sets it apart from all the others? If it's just a question of mystique, I think I'll pass...I am an NSX owner you know!
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No, the Tubi exhaust is not a dual exhaust... did you think somebody claimed it was? You might be an NSX owner but you still don't get it... you should probably "pass".
 
I have owned the Gruppe M (version 2) exhaust system for several months now, and I can just say that it is, arguably, the BEST sounding exhaust system out there right now. I really don't care what those other vendors say
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but this observation, however subjective it may seem, was reaffirmed at the last NSXPO at Road Atlanta. Coming down (or up) the front straight at Road Atlanta, going up that hill, the exhaust system just produced a very high pitched sound, described by others as Formula One-like. My car is supercharged (Gruppe M), and whether this had anything to do with the sound, I am not sure, but the combination sure sounded great.

In contrast to what was posted previously, the price of this exhaust is not over $3200, but $2670 (including shipping from Japan, US shipping to be added). It retails in Japan for about $2800, without overseas shipping to the US, but I am able to negotiate a good deal with Gruppe M for US owners, and just passing the savings on to everybody who wants the best <g>. Group buys are also possible, with substantial additional savings.

The exhaust system comes with specially designed catalytic bypass pipes which combine the front and rear header outlets into one, and bolts on to twin mufflers that lets exhaust out through dual tips (version 2), or in its current configuration, single oval tips (version 3) each side. This design achieves two things: it allows for the right amount of backpressure to help produce more low end torque than any other exhaust system, and it combines the front and rear exhaust pulses to simulate a much higher pitched exhaust note. Gruppe M also spent a ton of R&D into the internal design of the muffler units, to further enhance the sound.

Construction is top notch, welds are impeccable and are of F1 quality. The Gruppe M seems to be really strong, and seems to withstand the rigors of forced induction extremely well. In Japan, it has been in use for several years without any problems, including supercharged cars.

I am hoping to have some sound clips available soon on a website somewhere, but here's a review posted by one of the owners.
http://www.nsxprime.com/ubb/Forum13/HTML/000071.html

More references upon request.

Regards,

Alex

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AV Motorsport
Importer of Gruppe M and other fine Performance Parts from Japan
Cell (562)896-6399
Voice/Fax(562)690-8479
Email [email protected]

[This message has been edited by GruppeMUSA (edited 24 November 2001).]

[This message has been edited by GruppeMUSA (edited 24 November 2001).]
 
Alex,

I know there were some problems with fitment on the GM V2, like it was leaned more towards one side rather than centered. Has this been addressed/resolved with the new V3 system?

Is it a design flaw or car specific problem?

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Richard
NSXTASY
 
To debunk a myth, adding forced induction to a naturally aspirated engine will not, in and of itself, cause a muffler to blow out. If this happens, it is pure coincidence.

From an engineering perspective, a pistoned engine is nothing more than a reversed reciprocating air compressor. Compressors do exactly as the name implies - they *increase* the system pressure of whatever gas is being compressed. (The opposite of this is an expander. Turbo-expanders are used in gas processing plants, that result in *reducing* system pressure.)

On a normally aspirated engine, the suction pressure at the air intake is 0 PSIG. The discharge pressure at the muffler tip as the expanded gas is released back to the atmosphere is again, 0 PSIG. There is slight manifold vacuum upstream of the intake valves and there slight header pressure downstream of the exhaust valves. This has to be, for the thermodynamics of engine combustion to work. But on a practical sense, there is no measurable amount of gas pressure within the muffler. Unless - you jam a potatoe in the muffler tip. Remember that high school prank? The muffler would split open because the system gas pressure had nowhere to go.

Adding forced induction - regardless if by a turbo or a super will increase the system pressure on the intake side of the engine. But guess what? The muffler tips are still open to the atmosphere, so the system pressure within the muffler is still the same as if the engine was naturally aspirated. (Ok, there is an infintesimally small increase in pressure, but not enough to split a muffler can.) What has changed, however, is an increase of combustion gas mass flowrate passing through the muffler. However, with the relative size of the muffler tip openings compared against the gas flowrate, there is not an attributable pressure increase that results in muffler failure.
 
You're forgetting the most important element - heat.

*****

Actually, the incremental exhaust temperature resulting from forced induction is well within the fatigue strength capabilities of stainless steel. If a weld were to fail, most likely, the heat-affected-zone (HAZ to the material scientists) was too brittle. A cause of this is too high a heat input during the weld process.
 
I agree with Andy... From my experience, I never heard of a muffler "coming apart" due to forced induction or NOS. I never hooked up an EGT to a NSX but have to my mustang, the temp sat around 1,400 degrees at the headers primary tubes. I NEVER had problems with mufflers on my car. Measuring the temp at the muffler should be a lot cooler due to distance and heat dissipation from combustion chambers. If a muffler is stainless steel 100%, there should not be a problem UNLESS the muffler is of poor quality (welds and construction), then and only then I could see a muffler rattling. Just because a muffler costs ~10 times more than it SHOULD doesn't mean it is of quality...
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IMO I think mufflers and headers are outrageously priced!!
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Not to change the subject but.... Hence, why Mark is HONEST to sell a SC that is reasonably and realistically priced than the other companies out there. GO MARK!!!!

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Kenji Ligon
91 Red CTSC NSX

[This message has been edited by Attitude Adjuster (edited 24 November 2001).]
 
Andy --

It's not just the welds, but the packing material and packing material hangers. Case in point... the B&B Triflo exhaust.

I agree with your point on the welds, I doubt that welds on the exhaust would be a source of problems on forced induction.

-- Chris

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SoS_logo.gif

www.ScienceofSpeed.com - Click for more info
 
It's not just the welds, but the packing material and packing material hangers. Case in point...the B&B Triflo exhaust.

*****

Right, I have had problems with the RM DTM (although corrected by B&B) with welds when my NSX was still a virgin ;D, err, naturally aspirated.

The point NSXers must keep in mind - we are "pushing the envelope" as we increase HP levels +33% over stock. That said, problems of one kind or the other will manifest.


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Happy VTEC-ing :)
 
I know the manufacturer, but I'm not telling.
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That looks sweet John! Looking forward to seeing and hearing it at the meeting in December.
Maybe I'll have my 4.55 R&P installed by then. It's already sitting in my trunk. More rides anyone?
 
Originally posted by ANYTIME:
Just trying to help out the local NSX community in getting a unique, dyno tested, lifetime warranteed product. If anyone has any suggestions anything in particular that they would like, feel free to contact me or post replies.

Cordially,
John Richards
Any updates on this system ?
The pictures look like the Corsa C5 ones -- looks good!
 
The exhaust will be under sound and dyno test THIS week. If the current configuration passes the required 92db sound limit(This is maximum sound levels on the street,per manufacturer). One or both of the exhausts will be at the Dec 20th CalCoastalNSX meeting. Most likely it will be the street version that retains the cats. The track version which eliminates the cats will be somewhat louder and doesn't fall under the sound limit rule. If the street version is not finished in time for the meeting, the track version will be there. Similar to Mark Basch's way of thinking, the exhaust and headers are going to be tested on many cars(supercharged and NA) before any product gets sold. Tuning and dyno tests to squeeze every last horsepower out of the exhausts and headers are the main goal, with sound being a close second. The focus of designing the exahaust was to have a tuned system that produces "real world" dyno results, with a lifetime guarantee even with forced induction. One other goal is to have a BaschBoost supercharged car fitted with the exhaust for a dyno run before and after. Chris, are you listening?

Best regards,
John Richards
 
From a quick search of the web, it looks like Laguna Seca's noise limit is down to 90db. I suggest the track version be engineered with that in mind:
------- http://www.cfra.net/Race_Team/races/2001feb22_th.htm

Qualifying went well as everybody got used to their dry tires and the mostly dry track. June had to lug it past sound check between turns 5 and 6 as she was already black flagged twice for exceeding the 90 dB sound limit. Just over halfway through the session a sudden downpour came over the track and caused many drivers to have a moment before they realized what was happening. Many drivers pulled in knowing even if they could stay in control, their times weren't going to get better


Originally posted by ANYTIME:
The exhaust will be under sound and dyno test THIS week. If the current configuration passes the required 92db sound limit(This is maximum sound levels on the street,per manufacturer). One or both of the exhausts will be at the Dec 20th CalCoastalNSX meeting. Most likely it will be the street version that retains the cats. The track version which eliminates the cats will be somewhat louder and doesn't fall under the sound limit rule. If the street version is not finished in time for the meeting, the track version will be there. Similar to Mark Basch's way of thinking, the exhaust and headers are going to be tested on many cars(supercharged and NA) before any product gets sold. Tuning and dyno tests to squeeze every last horsepower out of the exhausts and headers are the main goal, with sound being a close second. The focus of designing the exahaust was to have a tuned system that produces "real world" dyno results, with a lifetime guarantee even with forced induction. One other goal is to have a BaschBoost supercharged car fitted with the exhaust for a dyno run before and after. Chris, are you listening?

Best regards,
John Richards
 
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