Cayman GT4: Where are we up 2 now? Déjà vu Edition

[MrDemon]

Yes, a strange rule but the argument appears to be that owners of old cars know how to take good care of them and don't use them much.

Mind you, driving an unmodified and original 40-year old car in modern day conditions could be a bit scary..!

Jeff

40 is not that old and while a 91173 RS might have been looked after, most others will never see a ramp

MOT is handy to let people know who do not have ramps that their brake lines have corroded, won't be long till we see a death from a >40 car due to not being road worthy imo.

 

[Twinfan]

Back on topic, there's a lot of fluff on other sites regarding the fitment of gasoline (petrol) particulate filters (GPF) possibly having a detrimental effect on performance. Whilst Porsche probably could meet the more stringent particulate requirements being introduced this September without GPF, as a safety net it seems most likely that they'll feature on all petrol engined vehicles when the lines are reopened after the annual shut-down.

The GPF will introduce only a minimal additional backpressure (something like 0.1lbf/sq inch I believe for a clean GPF), so it's effect on performance is likley to be minimal and offset easily by a DME tune bearing in mind the fact that the engine won't be let off the leash by Porsche anyway. More problematic could be the packaging, with the limited space available and relatively short exhaust pipe runs - will they use a single GPF or have a GPF for each bank? It will be interesting to see what's lurking behind the GT4's bulky rear diffuser..!

Oddly enough it's the introduction of direct fuel injection on petrol engined cars which has led to need for GPF. Although offering improved fuel consumption and reduced emissions, the downside with direct injection is particulate emissions, which traditional indirect fuel injection petrol engines don’t produce. The plus side is that the GPF is very effective at capturing particulate matter (~99%), doesn’t increase fuel consumption and is simpler than a diesel particulate filter because it won’t clog up in urban running as the exhaust from a petrol engine is hot enough to allow the filter to clean itself without any extra help.

So that's all good then..!

Jeff

I did some research and found similar info, but it doesn't explain why the next BMW Z4 will 50bhp less for the EU when compared to the US. That's a massive difference that seems to be down to emissions and the addition of a GPF. Can we expect the same from Porsche?

https://www.autoblog.com/2018/06/03/2020-bmw-z4-prototype-first-drive-roadster/?guccounter=1

 

[ralphmusic]

And why might one believe a journalist?

 

[Twinfan]

I can't see why they'd make up a 50bhp difference, but I guess they could!

 

[Motorhead]

Yes Dave, I was surprised to read that. I don't know if there is always a difference between the two markets but the EU and US have different emission requirements, so different ECU tunes are likley and maybe fuel consumption is more of an issue for European markets. All engines will be turbocharged, so power tweaks will be relatively easy to accomplish.

As for mag speculation, as usual we'll have to wait and see what materialises when the new Z4 arrives on these shores.

Jeff

 

[Motorhead]

Just to follow up on this, I see that VAG has dropped the power of its flagship Golf R and SEAT Leon Cupra cars to appease the new WLTP emission rules, so no doubt Porsche will be in the same boat in having to introduce more restrictive exhaust systems and modified engine tuning.

It’ll be interesting to see how the mods pan out across the Cayman range. We think that we know what the new GT4 will sound like but we’ll have to wait and see if the modified exhaust on the turbo cars addresses adverse comments made by some commentators.

Jeff

 

[ralphmusic]

Strange drop in power given both Golf and Cupra are both turbos which can be "easily" be tweaked.

Mercedes have offered their GPF equipped 500S mild hybrid model for the last couple of years with a turbo 4.0L V8 putting out 435HP plus electric 22HP motor. So maybe petrol engines need turbos or larger capacity to offset GPF effect.

Perhaps Porsche should enlarge the current GT4 engine to 4.0L?

 

[Twinfan]

Shoving a GPF in the exhaust has to have an effect on gas flow, so I'm not surprised power is affected. It's not much, but it'll affect the sound too so I think it explains the "different" sounding GT4 and Spyder mules.

Switchable exhausts are rumoured to be on the way out due to the emissions regulations, so I'm assuming we'll get the "quiet" setting as stock due to noise restrictions.

Will the new cars coming up lack a bit of drama and excitement due to all this?

 

[Steve Brookes]

After ChrisW's and my experience at Zolder of being kicked off for being too noisy (we didn't have the sports exhaust enabled) we both think it's about time Porsche came up with a quiet mode for the exhaust on GT cars because it's becoming increasingly difficult to use them for their intended purpose of track driving.

 

[Twinfan]

Very good point...

 

[Motorhead]

I was about to make the same comment as Steve. It's something Porsche need to consider for a track-based car - maybe they've taken it on board. Plus, I believe that increasingly more stringent noise pass-by regs have been introduced recently to add to the mix (if you want to consider "defeat devices" you only need to ponder developments when electronic throttles were introduced..!).

Incidentally a friend was talking to a SEAT salesman recently. He said that the new WLTP emission rules mean that it will be much harder for manufacturers to allow punters to cherry-pick options which affect emissions and fuel consumption e.g. sunroofs, body kits, different wheel sizes, sport exhausts, climate control(?), etc. I presume that every option will require a separate test, leading to a significant amount of additional work, and so it's likely that we'll see the introduction of option packs.

Quite how all this will affect the next GT4/Spyder is open to question. Porsche/AP's group have had ample time to get their act together on power, fuel consumption, emissions and exterior noise - subject to the usual restrictive marketing requirements - so it will be interesting to see what compromised solution turns up.

Jeff

 

[TDT]

After ChrisW's and my experience at Zolder of being kicked off for being too noisy (we didn't have the sports exhaust enabled) we both think it's about time Porsche came up with a quiet mode for the exhaust on GT cars because it's becoming increasingly difficult to use them for their intended purpose of track driving.

Agree with this - I received noise warnings, and black flagged for noise @ Goodwood on Wednesday (102db through St Marys on consecutive laps in multiple stints) and that was with PSE off also. And it was a noisy day @ Goodwood 105db.

I want go to Brands but don't think i'll be able to get on without going down the route of getting diverter pipes - which i don't really want to do.

 

[Brian_Innes]

As a "old school" track and motorsport competitor, I find all this talk of particle filters, diverter pipes, and punitive drive-by noise regs thoroughly depressing. Knockhill, like Goodwood, also has a 105db noise limit, which so far as in my knowledge, has not excluded GT4's and GT3 RS's with PSE on full blare. Long may that continue, but for how much longer?

Steve made an excellent point about exhaust noise on Porsche GT cars. What's the use of engineering a punchy exhaust howl if the cars are ultimately excluded from the tracks. I am very interested in the new GT4, but if it's going to be ham-strung by ever tighter emissions and noise regs, I'll hang on to my 718 CS.

Could it all be a cunning plan to hasten the demise of the internal combustion engine? Electric cars can be both very quick, and quiet. A sea-change in performance cars is about to dawn in my opinion. Porsche Mission E, whenever it comes to replace the current sports coupes, will be a revelation. Once they get the weight issue sorted, GT cars will enter a new era.

Make the most of our current petrol engined coupes now I say. The writing is already on the wall for their production demise. If track owners continue to enforce ever more stringent noise controls, where are all the track day enthusiasts going to go to play?

Brian

 

[Steve Brookes]

If Porsche could come up with an exhaust with 'quiet track mode' for the new GT4 that can be retrofitted to the old one, I'm sure many of us would be potential buyers. We're realistic enough to know that Porsche would charge us £2K++ for the pleasure of having one retrofitted. But it certainly beats trying to get some after market dog's dinner to hang on the back! AFAIK there's nothing currently available aftermarket for the GT4 anyway. The closest thing I can find is this that can be fitted to a GT3 (996 and 997 models I think):

http://www.actproducts.co.uk/product/si06-porsche-gt3-sliencers-pr/

I've yet to ask them if they can make a version for the GT4.

 

[ralphmusic]

Steve,

Great find although I wonder why they don't droop in use absent any additional support straps. Not sure you can fit these to a GT4 without replacing the rear tip assembly.

I had been looking at a single custom rear box which would cost around £800 as Cargraphics and Design911 exhaust manufacturers' factories are near me in Devon.

The one you found is like the one below that I posted on the old GT4 thread and is used on a highly modified GT4. It allows the car to run at Brands GP, Goodwood and Thruxton. The owner, Tim, did say that induction roar was also a contributor but his add-on exhaust gets him on low noise tracks.

This year Silverstone have been warning track dayers that they monitor drive-by noise, in previous years they have never mentioned it in driver briefings.

Re Goodwood noise monitors, perhaps the one TDT refers to is the one located after St Mary's and on the approach to Lavant. On that stretch you are coming off the power at around 110 and braking to 70 mph so maybe down change noise is the issue.

 

[Brian_Innes]

To quote Steve, "A dog's dinner to hang on the back" springs to mind looking at the above photo........

Such a shame it has come to this.......

Brian

 

[ralphmusic]

The joy of normally aspirated engines.

 

[Motorhead]

Ralph,

I can recall your original posting of that pic - it hasn't improved with age..! I wonder if it's still intact or is lying on a track somewhere along with other exhaust bits?

With ever more stringent noise and emission regulations it's inevitable that probably we've seen the last of standard "rorty" exhausts. Turbos, GPFs and hybridisation are bound to have an impact on exhaust sound. Fully electric powertrains are another matter.

All's not lost though. Done correctly, it's possible to artificially enhance the in-car sound - a method which Jaguar have been using successfully across its range for a while, although not well publicised. Porsche have dabbled with it using ducted sound and electromagnet devices, with limited success.

Jeff

 

[Brian_Innes]

Jeff,

The artificial representation of in-car "sound" leaves me unimpressed and bemused. Why bother with re-created in-car sound? As time goes by, I'm getting more and more attracted to the all-electric developments. True, they may also offer synthetic in-car sounds, anything from a Flat-6 to a V8 to a V12, all downloaded on the in-car App. Take your pick.

Being from another era, I have had the experience to appreciate a variety of sublime engine and induction sounds. I can remember the mechanical banshee of a 1293cc Mk1 race Cooper S with a 4 speed "works" straight-cut gearbox and LSD howling it's way up the hillclimbs I used to do. My racing Imp also scored well with it's 9500rpm revving 998cc Hartwell racing engine. Or, moving decades ahead, to my memorable experience with the 997 GT3 RS 4.0 manual which I had the joy of driving on the Silverstone GP circuit in 2012. All are wonderful memories which I am lucky enough to have experienced first hand. They are tops among the automotive memories which I shall take to my grave.

Sadly, today's enthusiasts brought up on the over-regulated, emissions driven world, have less such memories to savour.

On a brighter note.........England are through to the semi-finals of the World Cup. As a Scot I wish you well, and it's been a fabulous performance from the England team.

Brian

 

[Motorhead]

Brian,

I'm of the same generation as you and share your opinions. However, we are where we are and have to accept an increasingly regulated vehicle environment - both on road and, unfortunately, on track too..!

I have some experience in the implementation of enhanced in-car sound systems and can assure you that, done correctly, they can indeed improve and enhance the sound quality. The word correctly is key here - Jaguar have been working in this field for many years and it's bearing fruit in their current product range, the latest I-Pace being a very good example of their research programme on interior sound for EVs. BMW on the other hand have much work to do on their rather crude implementation in my opinion.

Some advantages of using electronics and software over hardware-based systems are cost, robustness and customisation. With vehicles becoming ever more refined, manufacturers are seeking to inject more excitement into what is becoming a rather dull driving experience and, like it or not, I suspect that we're going to see increasing use of enhanced in-car sound systems.

On your final point, regardless of allegiance it's certainly heartening to see a team of relatively inexperienced young footballers (and manager) from these Islands doing well on the International stage, regardless of the final outcome. It makes a change from the demonstrable incompetence displayed by the so-called leaders of our Nation...!

Jeff