Cayman GT4: Where are we up to now?
- Thread starter Motorhead
- Start date
Thankfully we seem to have exhausted the contentious subjects of slots and deposits, so it's time to get back on track.....to the car itself. The information released so far has answered many of our questions, most of which we had covered beforehand. The main surprise, I think, was the adoption of the ball-jointed and adjustable GT3 front suspension components and GT3-spec brakes, springs, ARB and aluminium sport dampers all round, the rear axle using a totally new wishbone [lower arm(s)?] and upright. The rear cross-member has, I believe, been strenghtened as well. Turbo hubs are featured and the GT3 steering system is used but with different software tailored to the GT4's mid-engine layout. GT3 Cup2 tyres are used at the front but the rears have been developed specially for the GT4. A beefed-up GTS gearbox is used with a torque-limiter [presumably via governed engine power] coupled to a lightweight DMF, similar in weight to that of a single-mass flywheel. The same ratios as those in the GTS are used but the additional torque of the 3.8L engine should help counteract the relatively long gearing. It seems as though the standard LSD is employed [PTV option] together with dynamic engine mounts [Sport Chrono option]. The BIW has been reinforced to accept both full and Clubsport Package roll-cages but the GT4's weight is similar to that of the GTS thanks to lightweight seats and wheels, despite the use of the GT3 suspension components and an additional centre coolant radiator up front. A 54-litre fuel tank is standard with a 64-litre tank being a no-cost option. Engine details are very sketchy other than it being a detuned 3.8L unit from the Carrera S. Claimed output is 385PS [380bhp] @ 7,400rpm and 420Nm of torque from 4,750-6000rpm with a redline @ 7,800rpm, but Preuninger reckons that this power output is conservative. The figures represent a useful improvement over those for the GTS: 340PS @ 7,400rpm and 380Nm from 4,750-5,800rpm. The detune is most likely derived from a DME remap but could include throttle-body/plenum mods as well, and bespoke intake and exhaust systems are fitted. Surprisingly, the 3.8L crankcase had to be modified for the engine to fit in the GT4's engine bay. I wonder if that means the crankcases in the 3.4L 981 and 991 are also different, or perhaps the 3.8L crankcase is different in some way from that of the 3.4L? I've just assumed it to be an over-bored 3.4L. Jeff
it's prob not detuned, it revs higher and where the engine is placed it needs more cooling hence the bigger side scoops. it's also got more torque lower down than the 991, so detuned to me may not be the right word, it's prob been tuned to last 200,000 miles with the air available and longer exhaust system it has over the 991 and also tuned to have that Torque lower down for that push out the bends. it also prob got 400bhp in the real world. keep that baby above 4,500 rpm and you are singing 
the GT3 I had to keep it >6k to make use of the engine, that was not easy and just frustrating. Not a bad thing on track which is where a GT3 should be, the GT4 should be dual purpose though and it looks like it will make an ok road car which then can go on track.
the GT3 I had to keep it >6k to make use of the engine, that was not easy and just frustrating. Not a bad thing on track which is where a GT3 should be, the GT4 should be dual purpose though and it looks like it will make an ok road car which then can go on track.
The power curves for the GT4 and 991S look very similar, with that of the GT4 appearing to be slightly more linear, and both engines seem to run out to 7,800rpm. Preuninger's comment that it's 385 Motorsport horsepower means that will be the guaranteed minimum. So, yes it's likely that a fully run-in motor could well develop 400PS+. The different torque characteristics are probably due to the very different intake and exhaust arrangements and, as you say, the GT4 has more torque lower down than the 991S. Coupled with its flat torque curve from 4,500-6,000rpm, this should give it very punchy performance on both road and track. Interesting to note that the Motorsport Dept. added scoops to the side intakes to capture more air, presumably because body mods weren't allowed. Jeff
For what it is worth, German tuners (using Maha) say that the 3.8L engines rarely produce more performance than spec and tend to be below, whereas the ECU throttled 3.4L tends to be slightly higher. I suspect the 'ear' intakes are simply to improve on the low air pressure around the standard recessed 981 S/GTS grills and will no doubt join 'smile' kits and dive planes as fad goodies. Fabspeed do an improved intake kit for the non-Powerkit 997 DFI and if packaging can be sorted out, something similar might become a 981 upgrade but will require an engine out install.
They really haven't sorted the Porsche Nm dip between 2,500 and 4,000 rpm. The custom tune dyno (Maha) graph below shows that the torque profile can be improved upon.
3.4L is 97mm bore 77.5mm stroke 3.8L is 102mm bore 77.5mm stroke As my German friend has a 'standard' 991 3.8L Powerkit with the huge plenum installed in his 981 Boxster S PDK, I it may be more to do with the new suspension than height of engine. Ralph
Yes, that may be the case Ralph. Pity we don't yet have the full details or pics of the GT4 rear suspension arrangement. That will probably have to wait until Geneva. As to the low rpm torque bump/dip, it appears to be a feature of the DFI engine used in the 987 and 981. Any idea how it's been eliminated in the Maha tune? Jeff
The graph is for the 991 3.8L Powerkit with a custom tune that I have mentioned before. They took 3 days just getting the multiple flaps in the Powerkit plenum working as they wanted so lots of time invested. The simple answer to your question is that they are not trying to pass mpg cycle tests etc and therefore they can optimise fuelling, VarioRam,etc. They ran it up to 8100 rpm and got 450PS but are keeping to OEM rev limit. Can I refer you to https://www.porscheclubgb.com/forum/tm.asp?m=809089 which did not show the dip in my Cayman's torque. Ralph
Thanks Ralph. Yes, I recall the discussion now and the fact that your torque and power curves appeared very smooth. Porsche's curves always look very strange and lumpy to me; almost as though they test a number of engines, calculate the mean values at 500rpm increments and join up the dots..! **On the subject of engines, here's a thing: All current 981 and 991 cars use the Gen2 DFI as a base. According to press reports, the GT3 RS will use a 4.0-litre version of the new [Gen3?] engine as will the 3.0-litre [?] and 3.4-litre [?] turbocharged flat-6 engines in the revised 991.2 Carrera and Carrera S due later this year. The new 2.0-litre [?] flat-4 engine is also rumoured to be a 4-cylinder version of this engine, which would make sense from the production standpoint. This means that the 981-series cars as well as the 991 GT3 and Turbo will still be using the Gen2 engine for the time being. We have to assume that the GT3 and Turbo will be updated to Gen3 spec at some stage and we must also assume that a flat-6 will still be available in the revised 981.2 Boxster and Cayman, but will it be the Gen3 engine or a run-out version of the Gen2? I presume that the Gen3 will just be a development of the Gen2 and assume that they're dimensionally similar but a GT4 wouldn't use a N/A 3.8-litre GT3 engine and the Carrera engines would be too small a capacity in N/A form for the Boxsters and Caymans, so there would have to be 3.4 and 3.8-litre N/A versions of the base engine for the S, GTS and GT4 cars. Preuninger has said that GT4 production time will be limited and that the GT cars will be normally aspirated for at least a couple of years and we're anticipating 2-years delivery of GT4s but beyond that, who knows? I'm sure that the GT4 will be successful and will become an established part of the Cayman line-up but it's impossible to say what engine it'll have. Hopefully it'll track it's GT3 sibling and have a N/A flat-6. Just my thoughts of course. Jeff **Note: This is now the subject of a new post.
Jeff, I think we need a new thread on future Porsche engines. I thought the conventional wisdom was turbo for all but it would be good if 981.2 is a refuge for normally aspirated and (whisper it) manual as well as PDK for us faster guys. I also think the Cayman register is the new "go to" forum as the Spyder group are into sewing machines tonight.
I was on the verge of ordering a GT4 in South Africa as I may spend some time there. However, Porsche South Africa are having a laugh. They cannot commit to any slot/timing but they expect me to stump up a deposit of R100,000 (equiv to £5600) which is NON-REFUNDABLE nor interest bearing. Whilst I can fully understand that they need to cover costs should the car go into production at which point one is committed, doing so at the time of ordering is unacceptable. This behaviour by Porsche South Africa is nothing short of a joke. I politely declined.
Hardly surprising that you declined the offer Nazir. Incidentally, I read somewhere that a Swedish customer just walked up to his dealership, ordered a car and was given a build slot immediately. I suppose that it may be possible for a UK customer to do the same in Sweden or other European countries, but I'm not sure whether or not they could order a UK-spec car. Has anyone tried? Jeff
always an issue with gray imports later down the line though. all gone a bit quite on the GT4 front, dealers are holding off for the most part about telling customers until after this week end if they have a car or not. So many still do not know and I don't know of any one who has got a full order yet paying the 10% order deposit. As it stands my order is in, but no build slot and no 10% needed paying
I wouldn't think that a full UK-spec car with a UK chassis number ordered via a European PC would be classified as a grey import MrD. However, I'm not sure that the Centres are encouraged to do it these days. A shame to hear that the PCs are still dragging their feet on notifying potential customers. Presumably negotiations are still going on between the Porsche Retail Group and the factory to get as many cars as possible, bearing in mind worldwide demand for the car. Jeff
Just noticed the rather odd pricing on PCCB's for GT4. On GT3 the PCCBs were £6248 compared to £5787 on any other 991 model. On GT4 they are only £4977 which is the same price as the upgrade on any other 981, despite the fact they are the larger GT3 spec than can be ordered on other 981's.! Makes them a bit of a bargain really - if £5k can be called a bargain. []
]
I can't see the problem with a C16 UK spec European import. The biggest issue in this case might be finding a spare allocation at a European dealer, who can swing a rhd car. I bought one in a few years ago, sold it privately without problem, a year or so after that I saw it advertised for sale on the forecourt at an OPC. They didn't seem to have a problem offering or swiftly selling it on, why should they? It was rhd C16 full Uk spec and came from Germany like any other Porsche! []
]
some things are a bit funny, I quite like a nice shot, and think Steyr make nice air rifles and they are £500 cheaper in Germany, but no one will touch one in the UK if you have a fault. being in the euro zone sucks, we may as well pull out if no one likes grey imports. on a more serious note, keep thinking about changing my GT4 colour to metallic blue
Posts made and opinions expressed are those of the individual forum members
Use of the Forum is subject to the Terms and Conditions
