Cayman GTS

[Mario149]

bcr5784 said:

Mario149 said:

I think this is where you're mistaken. The engine has plenty of torque, 230lbft or more at about 2500rpm - a 996 3.4 only produces about 215lbft or so at that point, and my Wayne Schofield mapped 993 NVR with a 3.6 litre engine (producing 296bhp at 6500rpm) is only producing about 190lbft at 2500rpm.

The GTS 3.4 just doesn't feel like it has a lot as the torque curve is so plump at low/med revs that there isn't, compared to older engines, as much of a "crescendo" as you work up to the power band (my 997 GTS really "suffers" from this, the power kit gives you such a walloping mid range for an NA engine with 107bhp/litre it almost feels too much). Add to that the fact that many of us may also DD a petrol/diesel turbo hatchback/saloon etc with a thunking FI produced mid range, and our bum dyno baselines are all screwed!

Torque is good at 2500 which leads you to expect it to better at 3000 or 3500 - but actually it falls off so subjectively the engine feels flat until it comes alive again at 4000. If torque gradually built up from 2500 to the peak at 4500 it would be a much nicer engine to drive at 6/7 tenths. As it is it's fine when toodling, great at 8 tenths + - but a bit frustrating in between. Notice that the 991 engine is definitely more progressive.

Bang on. But even when torque drops off a little after 2500rpm, you still have loads of it relative to the 996 and 993. So it's not lacking grunt, it's just our bum dynos getting confused as you expect the shove to build.

[Twinfan]

It's a classic tuning issue on an NA engine isn't it? Reduced midrange to give more shove up top? Quite how they get the bulge at 1500-2500rpm though is beyond my understanding! I think that's the 'bonus' that's skewing the graph and bum dyno.

[Porsche911R]

Twinfan said:

It's a classic tuning issue on an NA engine isn't it? Reduced midrange to give more shove up top? Quite how they get the bulge at 1500-2500rpm though is beyond my understanding! I think that's the 'bonus' that's skewing the graph and bum dyno.

CO2 cheating maps that's all Porsche love that dip for 60Mph testing lol

[Twinfan]

Of course, can't believe I didn't twig that! A simple re-map should fix it easily then if someone can understand the ECU.

[Porsche911R]

Twinfan said:

Of course, can't believe I didn't twig that! A simple re-map should fix it easily then if someone can understand the ECU.

would you be tempted with 380 BHP the 981 platform is very easy to tune to 380BHP or do you think you will go for a GT4 ?

[bcr5784]

Twinfan said:

It's a classic tuning issue on an NA engine isn't it? Reduced midrange to give more shove up top? Quite how they get the bulge at 1500-2500rpm though is beyond my understanding! I think that's the 'bonus' that's skewing the graph and bum dyno.

As I understand it this is done by having variable (dual) length inlet manifold tuned to boost torque at low revs. This is a very common mechanism. In theory you could have an infinitely variable length and that would allow a more progressive torque curve - but that is mechanically difficult. There may as suggested be some mapping issues - but the fact that the 911 doesn't suffer the same dip suggests there is more to it than that.

Edited by bcr5784 on Thursday 20th July 10:18

Edited by bcr5784 on Thursday 20th July 10:19

[Twinfan]

Porsche911R said:

would you be tempted with 380 BHP the 981 platform is very easy to tune to 380BHP or do you think you will go for a GT4 ?

I won't be taking the extended warranty on my CGTS as I have Zunsport grilles fitted, and there's no chance I'm not protecting the radiators/condensors.

I'm taking a GT4 out at PEC next month just to satisfy my own curiosity, but I'm not going to be buying a 981 GT4 nor will I be butt kissing my OPC for a 718 GT4 allocation. I don't go on track so there's no point.

My current plan is have my CGTS tuned when the 3 year warranty is up, if I can find a reputable place to do it. At the same time I'd get larger brakes fitted too. I think the 991.1 Carrera S or 981 Spyder setup will fit as I think my front 330mm setup is the rear of those cars. I'd just need to get a new front setup and master cylinder? All guesswork at the moment, but I have my fingers crossed. The Spyder has a 340mm front and the Carrera S a 350mm front.

A better breathing engine and larger brakes would totally complete the car for me.

[Porsche911R]

Twinfan said:

I won't be taking the extended warranty on my CGTS as I have Zunsport grilles fitted, and there's no chance I'm not protecting the radiators/condensors.

I'm taking a GT4 out at PEC next month just to satisfy my own curiosity, but I'm not going to be buying a 981 GT4 nor will I be butt kissing my OPC for a 718 GT4 allocation. I don't go on track so there's no point.

My current plan is have my CGTS tuned when the 3 year warranty is up, if I can find a reputable place to do it. At the same time I'd get larger brakes fitted too. I think the 991.1 Carrera S or 981 Spyder setup will fit as I think my front 330mm setup is the rear of those cars. I'd just need to get a new front setup and master cylinder? All guesswork at the moment, but I have my fingers crossed. The Spyder has a 340mm front and the Carrera S a 350mm front.

A better breathing engine and larger brakes would totally complete the car for me.

the nice thing about the 981 is the bigger 911 caliper just bolts straight on, unlike the 987 platform which is hassle.
jens is the tuner of choice imo.

[Twinfan]

Porsche911R said:

the nice thing about the 981 is the bigger 911 caliper just bolts straight on, unlike the 987 platform which is hassle.
jens is the tuner of choice imo.

Superb - do you think switching the 4-pot 330mm to the rear and adding a 6-pot 350mm front will work then? Any other changes required e.g. master cylinder?

Can you get Jens' tuning in the UK or will I need to go to Germany?

[Twinfan]

Twinfan said:

Superb - do you think switching the 4-pot 330mm to the rear and adding a 6-pot 350mm front will work then? Any other changes required e.g. master cylinder?

For anyone interested, I've done some Googling and swapping the front brakes to the 6-pot 340mm setup from the 991.1 Carrera S is a dead simple bolt on job. No master cylinder upgrade is needed and the parts required are:

99135140301 Left Front Brake Disc (340mm x 34mm)
99135140401 Right Front Brake Disc (340mm x 34mm)
99135142313 Left Front Brake Caliper (6 piston red)
99135142413 Right Front Brake Caliper (6 piston red)
99135558103 Brake Pipe Left
99135558203 Brake Pipe Right
99160917100 Brake Pad Wear Indicator Left & Right
99906705309 Front Caliper Mounting Bolt (M12 x 1.5 x 85)
99135194902 Front Brake Pad Set

The rear is the issue. The Carrera S calipers won't fit the Cayman uprights and the existing front calipers don't work on the rear due to the different piston thickness required. The best option for swapping both front and rear calipers is to use the Porsche PCCB calipers and fit aftermarket steel discs and pads along with the PCCB braking software.

A bit of shame it's not as simple as I hoped, but there are still a good couple of options.

[Mario149]

bcr5784 said:

Twinfan said:

It's a classic tuning issue on an NA engine isn't it? Reduced midrange to give more shove up top? Quite how they get the bulge at 1500-2500rpm though is beyond my understanding! I think that's the 'bonus' that's skewing the graph and bum dyno.

As I understand it this is done by having variable (dual) length inlet manifold tuned to boost torque at low revs. This is a very common mechanism. In theory you could have an infinitely variable length and that would allow a more progressive torque curve - but that is mechanically difficult. There may as suggested be some mapping issues - but the fact that the 911 doesn't suffer the same dip suggests there is more to it than that.

Edited by bcr5784 on Thursday 20th July 10:18

Edited by bcr5784 on Thursday 20th July 10:19

I seem to remember reading somewhere that it was a specific limitation of the intake system of the Cayster due to it being mi-engined. I have a feeling that even Ehresmann's packages have the dip. Actually, found it here:

https://www.facebook.com/9x1.org/photos/pcb.511341...

[Twinfan]

Mario149 said:

I seem to remember reading somewhere that it was a specific limitation of the intake system of the Cayster due to it being mi-engined. I have a feeling that even Ehresmann's packages have the dip.

Looks like you're right. So my plans for a straightforward brake and engine upgrade sound like they're really not worth the bother!

[JasonSteel]

bcr5784 said:

JasonSteel said:

what exactly happens warranty wise if non N rated tires are fitted?

If you sell it via the dealer he will want you to pay the cost of N rated tyres (he can't sell it with warranty otherwise) and if you want warranty work which is any way related to the suspension they could prove iffy.

so as long as i keep the current tyres, i can put those back on if i ever sell back to the dealer. and i guess if i did have a suspension issue then i could switch tyres before reporting... a royal PITA but a way around it none the less?

are either the Goodyears or the MPSSs quieter than the Pirellis at motorway speeds (especially on concrete sections)?

[JasonSteel]

Twinfan said:

I'm taking a GT4 out at PEC next month just to satisfy my own curiosity

slightly OT but is there a 'proper' track element to the PEC day? do you get to do some laps at full speed around a track or is it 'just' sliding around small circuits at low speed on a slippery surface?

[bcr5784]

JasonSteel said:

slightly OT but is there a 'proper' track element to the PEC day? do you get to do some laps at full speed around a track or is it 'just' sliding around small circuits at low speed on a slippery surface?

Yes there are two tracks to go on. Both a bit Mickey Mouse though - you won't get out of the third gear.

[Twinfan]

bcr5784 said:

Yes there are two tracks to go on. Both a bit Mickey Mouse though - you won't get out of the third gear.

Indeed, but very similar to road rather than track driving which is what it was designed to be.

[bcr5784]

Twinfan said:

Indeed, but very similar to road rather than track driving which is what it was designed to be.

True to a point, but there aren't any (say) 80-90mph sweepers, which I would have liked.

[PhantomPH]

bcr5784 said:

Twinfan said:

Indeed, but very similar to road rather than track driving which is what it was designed to be.

True to a point, but there aren't any (say) 80-90mph sweepers, which I would have liked.

That would require a completely different facility, I think!

Arial view for anyone interested: https://www.google.co.uk/maps/place/Hangar+Straigh...

ETA: That shot is a little older, but it gives an idea of the scale and layout of the place - which is to say not huge and lots of low gear corners. Looks very pleasant tho - just wish it wasn't so far away from me otherwise I would happily go for a play.

Edited by PhantomPH on Friday 21st July 09:37

[Koln-RS]

PhantomPH said:

That would require a completely different facility, I think!

You just need to go a few hundred meters over to the Silverstone GP or National Circuit - lots of space to play with a GT4 on the limit

https://www.youtube.com/watch?v=ZiWcTv3-nZI

Edited by Koln-RS on Friday 21st July 10:25

[PhantomPH]

Koln-RS said:

PhantomPH said:

That would require a completely different facility, I think!

You just need to go a few hundred meters over to the Silverstone GP Circuit - lots of space to play with a GT4 on the limit

https://www.youtube.com/watch?v=dT1aNQA8wVQ

Obvs - but that's not Porsche's facility.