Cayman GT4: Where are we up 2 now? Déjà vu Edition
- Thread starter ralphmusic
- Start date
Bilko1 said:
No Chris. For homologation purposes the race car has to have the road car engine. It’s just that, unusually, the race car has preceded the road car in this case.
The evidence to date is that the development road cars have naturally aspirated 6-cylinder engines not flat-4 turbos.
Jeff
Motorhead said:
313Kw = 420hp = 425PS so I think 'only' 40hp above 380hp or 385PS of Gen 1.
Nevertheless they have got many extra horses, but from where?
The original had 200 cell cats but this was changed to 100 cell as in the new car.
82mm throttle body now v 78mm
Different intake runners
Better breathing cams
Minimum 98 octane fuel
Given road car will have 400/600 cell cats plus GPF, are we realistic in expecting 425PS on the road car?
ralphmusic said:
Depends if the Clubsport is in a deliberately low state of tune because of the BoP requirements. If so, add the cats and GPF for the road car then turn the wick up a bit. Job done.
However, given the length of time we've seen finished looking GT4/Spyder mules knocking about with no road car launch, plus the non-appearance of any GPF fitted 991.2 GT3s, maybe the GPFs are causing serious issues for NA cars.
A note of caution on the engine specs. These are the 2017 and 2018 GT4 class rules:
2017: https://north.gt4series.com/file/download/3/GT4%20European%20Series%20Technical%20Regulations%202017%20FINAL-DRAFT.pdf
2018: https://european.gt4series.com/file/download/265/2018%20GT4%20Technical%20Regulations%202018%2001032018%20FINAL.pdf
Note that the 2018 version has omitted the clause that the engine must be the original from the homologated car. Could that open the door for the Clubsport to have a different engine to the road car?
2017: https://north.gt4series.com/file/download/3/GT4%20European%20Series%20Technical%20Regulations%202017%20FINAL-DRAFT.pdf
2018: https://european.gt4series.com/file/download/265/2018%20GT4%20Technical%20Regulations%202018%2001032018%20FINAL.pdf
Note that the 2018 version has omitted the clause that the engine must be the original from the homologated car. Could that open the door for the Clubsport to have a different engine to the road car?
The regulations have been somewhat of a puzzle changing each year from 2016 in subtle ways. In 2016 when SRO first started to really promote the series, homologated cars included a 997 GT4 Cup Car model and the 3.4L Cayman Pro 4 from Pro Sport (which won in 2016). Neither of these could be called production cars.
The 2018 list of SRO approved eligible cars with RACB Technical papers can be found for now at least at https://european.gt4series.com/gb_en/cars
It is entirely possible within 2018 Regs (1.2, 1.14, 2.2, 3.3 as examples) for Porsche's base Trackday 718 GT4 Clubsport to be the homologation base car. (it can be bought by the general public).
Therefore shock/horror the road 718 GT4 can indeed have a different engine than the race car because it is not the homologation base car... hence the screaming and the gruff mules.
The 2018 list of SRO approved eligible cars with RACB Technical papers can be found for now at least at https://european.gt4series.com/gb_en/cars
It is entirely possible within 2018 Regs (1.2, 1.14, 2.2, 3.3 as examples) for Porsche's base Trackday 718 GT4 Clubsport to be the homologation base car. (it can be bought by the general public).
Therefore shock/horror the road 718 GT4 can indeed have a different engine than the race car because it is not the homologation base car... hence the screaming and the gruff mules.
ralphmusic said:
Yes, my mistake Ralph. Why can't manufacturers quote 'proper' horsepower as hp and 'metric' horsepower as PS to avoid confusion? I suppose we should now be quoting power in kW for consistency and comparison with EVs and hybrids.
Anyway, 40PS is not to be sniffed at but as you say, how much of that increase will find its way to the road car given the more restrictive cat and GPF arrangement? The last time round the road and race cars had the same power output so we'll have to see (more internet speculation fluff anticipated!).
No details on any internal mods but to me it sounds as though the engine's just a modified MA1 with a GT3 throttle body/plenum, etc. arrangement and higher lift cams giving more power at slightly higher revs and a small torque increase occuring at much higher revs (6,600rpm).
An interesting observation by Dave that the 2018 GT4 class rules have ommited the clause that the engine must be the from the original car. Surely not an oversight?
Personally I'm thankful that the cat is now out of the bag and I won't have to plough through seemingly endless drivel about the car having an F-4 turbo/GT3/3.8L-X51 engine. But maybe I'm just being over-optimistic..!
Jeff
Ref your last line above - precisely my point in my post last night, and quite the opposite possibility to that which Jeff suggests in the last para of his last post above. I think the loose racing/homologations rules allow the GT4 road car (if there ever is one!) to be different to the 2019 clubsport. My money is still on a turbo due to emissions. I'll leave my drivel at that.ralphmusic said:
I raised the change in the rules on the Rennlist forum and got utterly ignored/snubbed - it’s a pretty unfriendly place! However one of the guys tcsracing is adamant that the engines will be the same - he has two 718 gt4 CSR and has had several 981s.
he seems a most credible source.
as for the power Jens Ehresmann provides a Cargraphic tune - 420 hp with 200 cell cats. C440hp without cats.
BGB motorsport in US offers various tunes including the above in the US.
Dundond motorsport offers a package called D4. 991.2S plenum, GT3 throttle body, long tube manifolds, revised intake tubes (they call them intake runners) GT3 main exhaust and adaptor tubes with 200 cell cats. Plus a tune this provides c395hp at the wheels. Higher without cats.
so the power is there. The Dundon package removes the torque dips in our standard engine.
now all this comes from treading their various posts and adverts oR Website, I have no hands on experience. Several on here I understand have run the car graphics package And can provide real commentary.
If new GT4 is a 3.8 with improved power I am going to stick with mine and upgrade using the Cargraphics package in soetember when my warranty expires. At c7k Euros this will be much cheaper than the buy a new car at a premium because I can’t get on the GT4 list alternative !
he seems a most credible source.
as for the power Jens Ehresmann provides a Cargraphic tune - 420 hp with 200 cell cats. C440hp without cats.
BGB motorsport in US offers various tunes including the above in the US.
Dundond motorsport offers a package called D4. 991.2S plenum, GT3 throttle body, long tube manifolds, revised intake tubes (they call them intake runners) GT3 main exhaust and adaptor tubes with 200 cell cats. Plus a tune this provides c395hp at the wheels. Higher without cats.
so the power is there. The Dundon package removes the torque dips in our standard engine.
now all this comes from treading their various posts and adverts oR Website, I have no hands on experience. Several on here I understand have run the car graphics package And can provide real commentary.
If new GT4 is a 3.8 with improved power I am going to stick with mine and upgrade using the Cargraphics package in soetember when my warranty expires. At c7k Euros this will be much cheaper than the buy a new car at a premium because I can’t get on the GT4 list alternative !
^^^
I have Ehresmann kit on mine since 2015, see Modified Section of Forum (“Modifying a 981 Cayman”, I think)
I have Ehresmann kit on mine since 2015, see Modified Section of Forum (“Modifying a 981 Cayman”, I think)
Bilko1 said:
Chris,
Although it may not be the cleanest engine in the sports car line-up compared with the latest batch of turbos, it's a DFI engine with efficient cats and a GPF so it should meet the latest emission regs quite easily (if not then Porsche are really going to be in trouble with the 992 GT3). So although I'd never rule out the possibility of the road car having a turbo engine I think it highly unlikely given the extensive development time and effort spent to date, let alone the significant cost implications.
Also, back in April a friend and I did a frequency analysis on various sound clips from some videos of GT4 and Spyder road car mules which indicated a naturally aspirated 6-cylinder engine signature and I've not seen or heard anything since then that indicates Porsche have changed tack to an F-4 turbo.
I think the biggest question mark is still when we're likely to see the road car. Although Geneva would be an ideal opportunity there's still the possibility that it will be a MY2020 car, perhaps with an announcement at the Frankfurt Motor Show in September.
As always, just my tuppence worth of course.
Jeff
Jeff,
I thought that DFI fuel systems were worse for emissions of certain particulates hence the need for GPFs
"Particulate emissions were not initially regulated for gasoline engines since conventional port fuel injection (PFI) engines do not emit a significant amount of particulates. However, gasoline direct injection (GDI) engines, have become a key technology - enabling CO2 emissions to be lowered while improving torque and power output. But, they are reported to emit more of the smaller more concerning particulates compared to conventional PFI engines."
I thought that DFI fuel systems were worse for emissions of certain particulates hence the need for GPFs
"Particulate emissions were not initially regulated for gasoline engines since conventional port fuel injection (PFI) engines do not emit a significant amount of particulates. However, gasoline direct injection (GDI) engines, have become a key technology - enabling CO2 emissions to be lowered while improving torque and power output. But, they are reported to emit more of the smaller more concerning particulates compared to conventional PFI engines."
That's right Ralph - particulates are more of a problem with DFI engines (think diesel); hence the need for the GPF.
CO2 (and NOx?) emissions are lower than for PFI, so now that Porsche are incorporating particulate filters in the exhaust I can't see there being a problem meeting emission limits. Incidentally, I believe Audi use both port and direct fuel injection on some of their engines, switching between the two depending upon operating conditions.
Jeff
CO2 (and NOx?) emissions are lower than for PFI, so now that Porsche are incorporating particulate filters in the exhaust I can't see there being a problem meeting emission limits. Incidentally, I believe Audi use both port and direct fuel injection on some of their engines, switching between the two depending upon operating conditions.
Jeff
Steve Brookes
Moderator
ralphmusic said:
I don't see it as underwhelming. I see it as typical generation to generation improvement that we have come to know and love Porsche for. I guess we may even see the road car with a little less power because a 40 hp increase between generations is unusual for Porsche.
Steve Brookes said:
Steve, I think that is fair but the first generation race car, for that is what we are talking about was very much a simple start point. Whilst the new version has a well reworked engine with more power, I didn't expect it to be heavier, and I did expect a big improvement in aero. As they made the recent RSR race cars almost mid-engined in order to fit a decent diffuser and underbody, I would have thought there would be a step change on the GT4 Clubsport also.
Steve Brookes
Moderator
Ralph, I should have said that I was only judging the changes made to the engine/power. Personally I like the look of the new front on the clubsport. Looks really purposeful as a race car in my eyes. I would not be surprised if we see a lot of praise in how the new clubsport and road car actually drives when folk finally get behind the wheel (not that the current one is bad at all in my biased opinion!). I remember the much tutting and moaning from people about the Cayman R when it was announced..."parts bin special", etc. Then people drove it and soon realized that it was actually very, very good. I would not be surprised to hear the same when the new GT4 properly arrives.
Steve,
Good points, the engine is the bit I did not really get initially. It is a new (to GT4) crankcase which means most likely they have upgraded most components within a budget that is significantly lower than the GT3 series engines. I assume they have also adopted the later cylinder liner technology so there might be real gains from lower friction losses. I am sort of surprised they did not use the multi-value GTS plenum since I thought that would have given more flexibility on tuning power and torque curves. I wonder if the small torque gain is reflective of a PDK torque limit but there is a lot more produced by the 718 GTS which has PDK.
Good points, the engine is the bit I did not really get initially. It is a new (to GT4) crankcase which means most likely they have upgraded most components within a budget that is significantly lower than the GT3 series engines. I assume they have also adopted the later cylinder liner technology so there might be real gains from lower friction losses. I am sort of surprised they did not use the multi-value GTS plenum since I thought that would have given more flexibility on tuning power and torque curves. I wonder if the small torque gain is reflective of a PDK torque limit but there is a lot more produced by the 718 GTS which has PDK.
Ralph,
Like you I was somewhat surprised by the engine spec. No doubt it’s been updated but I’m not certain that it actually is a new block/crankcase - the bore and stroke appear to have been carried-over from the 981 (although there’s some confusion with published data) and I would have thought it would have been simpler just to use a version of the GT3’s 4.0L block rather than probably have two sets of castings. So it looks to me very much like an updated MA1 base engine with a modified intake system and high lift cams, although I’m sure that’s an oversimplification.
I’m sure the PDK transmission is more than capable of handling more than than the additional 3lbf-ft of torque produced by the new engine but I don’t know how marginal the manual Getrag transmission is on torque.
Jeff
Like you I was somewhat surprised by the engine spec. No doubt it’s been updated but I’m not certain that it actually is a new block/crankcase - the bore and stroke appear to have been carried-over from the 981 (although there’s some confusion with published data) and I would have thought it would have been simpler just to use a version of the GT3’s 4.0L block rather than probably have two sets of castings. So it looks to me very much like an updated MA1 base engine with a modified intake system and high lift cams, although I’m sure that’s an oversimplification.
I’m sure the PDK transmission is more than capable of handling more than than the additional 3lbf-ft of torque produced by the new engine but I don’t know how marginal the manual Getrag transmission is on torque.
Jeff
Jeff,
I think our views on the manual box are probably coloured by the 3rd gear failures, the cause of which was gear/shaft attachment rather than a fundamental gearbox torque limit. One has to think/hope all OEMs would run with over engine power spec drive train components, else there would be endless warranty claims and for Porsche, restrictions on track use.
I think our views on the manual box are probably coloured by the 3rd gear failures, the cause of which was gear/shaft attachment rather than a fundamental gearbox torque limit. One has to think/hope all OEMs would run with over engine power spec drive train components, else there would be endless warranty claims and for Porsche, restrictions on track use.
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