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Exhaust tailpipe exit and the effect on sound.

Brian_Innes

Member
Recent discussions elsewhere on this forum have focussed on video clip spy shots of 718 GT4 and Spyder mules circulating various tracks during development testing. The various test mules have been shown fitted with both central and widely spaced exhaust tailpipe exits. Subsequently much controversy has ensued as to the influence of the exhaust tailpipe exits and the sound emanating from them. Whether the central exhaust exits are exclusive to the flat-4 turbo, and the spaced out exhaust exits apply only to the flat-6 is a moot point indeed.

With this in mind, I thought it would be helpful to post my past experience of an exhaust tailpipe modification which I applied to my 2010 987.2 Cayman S. Following an advert on the USA Planet-9 Cayman website, I purchased a Dream 2 Velocity Exhaust Twin Tailpipe from the company of the same name owned by Jim Love. From memory it cost around £200 including shipping and import taxes to the UK. According to the advert blurb, the Dream 2 tailpipe, greatly improved the exhaust gas flow at exit point from the mufflers on the 987.2 DFI Cayman and Boxster. This was achieved by fabricating a more rounded flow-efficient route for the exhaust gasses after leaving the mufflers. On the stock twin tailpipe, there is a marked conflict of exhaust gasses meeting head-on from each muffler before being forced by back pressure through 90 degrees to the exhaust exit. The advert blurb also claimed a much improved exhaust note and greatly reduced gas-flow back pressure at exit point.

The Dream 2 tailpipe was made of a very solid steel construction with larger diameter twin pipes. The unit was not chrome plated nor corrosion protected in any way. Fitting instructions were included and I had the job done by a local garage workshop. I made the decision to take my chances with my new car warranty and fit the modified tailpipe.

The results were amazing. I could hardly believe the difference this made to the sound of my 987.2 Cayman S. Gone was the tinny rattle of the standard chromed twin tailpipes. Now, when I blipped the throttle, the exhaust note was deeper, more rorty, and had a delightful burble on the overrun. On two separate occasions, one while participating in a charity supercar event, and the other while boarding the Eurostar Channel Shuttle on my way to France, people already familiar with the sound of a flat-6 Porsche, approached me and remarked they had never before heard a Cayman sound quite so delicious.


The point of this post is to maybe shed some light on the impact of exhaust tailpipe exists on exhaust gas harmonics. I am not an acoustic expert, but I cannot help but wonder if during the months of track testing development mules with various engine and exhaust configurations, Porsche R&D engineers have experimented with improving the exhaust sound of the flat-4 turbo engine. During my Stuttgart factory visit last September, I did manage to extract confirmation from the very knowledgable tour guide, that Porsche R&D were currently testing both flat-4 turbo and flat-6 normally aspirated engines for a future model in the Cayman and Boxster range.

It could be therefore, that the position of the exhaust tailpipes and the sound emanating from them on Porsche test mules, gives no guarantee as to the type of engine fitted.

I shall leave it there for others to pick up, as I am sure will happen.

For your interest, the photo below shows the Dream 2 Velocity twin tailpipe which was a very successful modification to my 987.2 CS. After 10,000 miles of UK and Europe driving the lack of corrosion protection began to take its toll. It was removed from my car prior to sale.

Brian

 
The stock exhaust tip arrangement causes the exhaust pulses from each bank to collide head on before exiting at 90 degrees through two tail pipes. Brian’s pictured one and mine (pictured below) have more of a merging of pulses which seems to produce more sound, in my case rather offsetting the advantage of fancy downturn tips.

B41973-EE-1019-48-F7-8190-EA28-F7-A6-BA91.jpg


 
Ralph,

That's an unusual design - presumably the perforated sections face down?

I've always thought of exhaust design as much an art as a science but I'm sure the exhaust system suppliers have plenty of analytical tools to hand. The designs of the tailpipes you and Brian have fitted certainly look far less restricitve than Porsche's standard arrangement which has always seemed odd to me, but no doubt developed by experimentation to achieve the desired sound.

Seeing those tail pipes reminds me of the period in the '60s when Peco Boosters were an essential fitment by aspiring boy racers..!

https://www.ebay.co.uk/itm/PERIOD-1960-039-s-CLASSIC-CAR-PECO-EXHAUST-SILENCER-BOOSTER-UNIT-MINI-MG-FORD-/122469041482?_trkparms=aid%253D222007%2526algo%253DSIC.MBE%2526ao%253D1%2526asc%253D20150519202351%2526meid%253Df3efa1f897944adfa39fab3162897dbc%2526pid%253D100408%2526rk%253D6%2526rkt%253D6%2526sd%253D192074465387&_trksid=p2047675.l2557&nma=true&si=9O996PPx%252BpfNfbC6b1SOpcjOsyk%253D&orig_cvip=true&nordt=true&rt=nc

Jeff

 
Interesting post and nice to hear someone stating the correct word ‘sound’ as opposed to ‘noise’ as is more commonly used...

(i.e. Noise is unwanted sound).

 
pse_SC said:
Interesting post and nice to hear someone stating the correct word ‘sound’ as opposed to ‘noise’ as is more commonly used...

(i.e. Noise is unwanted sound).

Yes, I stand corrected as I have noise [:D]

Jeff, indeed the Cargraphics’ tips face down in situ.

 
The original mini was definitely "mini". I cannot get over how small they actually were. Must have been the most modded car of it's time. Loved mine to bits. Did look at buying another not many weeks ago but I am just put off regarding the soundness of the vehicles after all of these years.

Ray

 
Ray said:
Peco exhaust for the Mini. What memories.

Ray

Had to laugh at the Peco Booster quip Ray. I recall my dad had one fitted to his Vauxhall Victor.....

Like father, like son eh.... :ROFLMAO:

Brian

 
Brian,

My father wasn't interested in cars they were just a form of transport from A-B. Where I got it from I have no idea. He would look out of the window and say to my mother, "He's got that bloody bonnet up again".

Ray

 
No-one knows for sure of course Brian, but from what I've seen in photos/videos and read/heard:

* GT4 and Spyder mules have exclusively had the 'wide spaced' exhaust arrangement

* The 718 GT4 Clubsport has the 'wide spaced' exhaust arrangement and a 3.8ltr naturally aspirated flat six engine

* Rumours of a 4.0ltr naturally aspirated 718 GT4 road car are the strongest/most prolific

* No-one appears to be saying the 718 GT4 road car will have anything other than a naturally aspirated flat six engine

* Styling of the road going 718 GT4 is almost certainly going to mirror the 718 GT4 Clubsport, including the 'wide spaced' exhaust arrangement

Based on the above, not just the sound of the engines in video clips, the 'wide spaced' exhaust arrangement seems very likely to be linked to a naturally aspirated flat six engine.

In addition:

* Non-GT4 and non-Spyder 718-based mules have been spotted with the 'wide spaced' exhaust arrangement, that's true

* However, several sources are quoted as saying that a 718 Cayman 6 and a 718 Boxster 6 are under consideration with a naturally aspirated flat six engine

* So these mules may well be 718 Cayman 6 and a 718 Boxster 6 test cars

In conclusion, and based on all the available evidence, I believe the 'wide spaced' exhaust arrangement is exclusive to a new 718 series naturally aspirated flat six engine that will appear in the GT4/Spyder and the 718 Cayman/Boxster 6 modeis (if they reach production). It's not all about the sound [:D]

All in my opinion, your mileage may vary etc etc.

 
Brian

Nice to hear your thoughts on the Dream2.

I was sorely tempted to buy one last year.

I think you can get them in stainless or a chromed finish now, so in the interest of longevity I might have another look.

I have the Carnewal GT exhaust which is already rather fruity :ROFLMAO:

Was your 987.2 exhaust standard or the PSE Brian ?

 
David,

You put your point of view very succinctly, and I appreciate your comments.

I am merely a casual observer to the 718 GT4/Spyder test mule saga. I do not have your level of connected knowledge on the topic of prospective engine/exhaust configuration options for this eagerly awaited new Porsche sports car.

My opinion on the engine route Porsche may decide for the Cayster models is of course influenced by the fact I have recently purchased a new, and very expensive, 2019 GPF Cayman GTS PDK. This, as many on this forum already know, is my second flat-4 turbo 718 Cayman. I've grown to like the F4 engine for its wide torque band and drivability on the roads I know best.

Regarding the rumoured 718 Cayman 6, a model supposedly under consideration to supersede the Flat-4 turbo 718 Caysters. If this were to succeed, it would be a retrograde move by Porsche in my opinion, if only for the fact that in the case of my new 2019 GPF 718 CGTS, Porsche have clearly invested massive amounts of R&D time and money preparing the car for the current WLTP emission regulations. If indeed the flat-4t were due to be binned this year in favour of a naturally aspirated flat 6, why would Porsche have gone to all this trouble? Especially for a model with such a limited future ahead of it.

For my twopence worth, I see a convincing case for the flat-4 turbo, both as a stand alone emissions efficient, and potentially very powerful engine, and also as a supplementary power unit as part of a hybrid sports car model. For Porsche to revert to a flat-6 for the Cayster now, would be a huge PR gaff which goes against everything they have said about the F4 since its conception.

I agree it's not all about sound. It's also about emissions, power per Euro, and the prevailing environmental pressures exerted by the political and economic climate of the day.

Brian

 
Your casual observations don't match what I've heard/read, Brian. It seems most likely that the 718 Cayman/Boxster 6 would be an addition to the range and not a replacement. It's a model that would sit above the GTS and below the GT4/Spyder. It's still under consideration as a model though, and may not make production.

My guess is that the 718 base/S/GTS will continue as-is with F4T engines until the current 982 platform is superceeded, but they will be supplemented by runs of naturally aspirated models such as the GT4 and Cayman 6 as a return on investment in the new flat six engine. They will sit at the top of the Cayster hierarchy, above the F4T models.

Post-982, I fully expect the Cayster range to either disappear or become full electric like next Macan will be.

 
If as rumoured the 718 Cayman/Boxster is a runner, the hierarchy is getting a bit crowded - 718, 718T, 718S, 718GTS, 718-6, 718GT4 - perhaps taking a leaf out of the 911's progression.

Everything depends upon the GT4's pricing this time around and the 6-cylinder 718 cars could well be limited edition models, initially to test the water and maybe boost 718 sales. We'll have to await the WLTP figures to see if Porsche have managed to produce a clean and economical naturally aspirated engine to rival the F-4 turbo since a lot is at stake in that respect no matter what the F-4 turbo critics say because corporate fuel economy figures also have to be considered. It does seem an odd mix though - a stop-gap knee-jerk reaction perhaps? - when all other current Porsches (GT3 excepted) are now turbocharged.

Surprisingly, at the moment there don't appear to be any 718 succesor mules running around, although I believe that the 992 has a modular design which could allow a mid-engine development. I think we're much more likely to see a mild hybrid Cayman/Boxster before full-blown electrification, but what IC engine will be installed is anybody's guess at the moment. The motor-generator could either be installed at the flywheel position or more simply replace the current alternator but using a toothed belt drive. Battery packaging will be a challenge though.

Jeff

 

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