R or GT4

[Porsche911R]

Mid engine love, they are all great cars.
I love my trio, cannot place one above another, drive one and it feels great, give one a rest and move to another and that feels great.
The biggest thing for me though is the R feeling on the road esp in this cold wet weather, the feedback is really good the GT4 cannot match it, that is the one thing you notice more going back to the R, maybe GT4 owners who sold up their R's just forget how good the steering was.
And if they own a Merc as the main car a GT4 will feel like it has mega steering ;-)
The GT4 steering is fine, don't get me wrong, it's only when you go back to the R you think wow, this is really good.

[Jabbah]

isaldiri said:

and I don't get why some people eulogise about revving out the 3.4 when power flatlines at about 6500 just like the gt4 tbh...

Because it is about the torque at the wheels that produces acceleration. The engine torque may drop off after a certain rpm but as it is going through a gear box to the wheels (a torque multiplier) the torque at the wheels is still greater than shifting up a gear where the engine torque will be slightly greater but wheel torque lower due to the gearing.

Here's a graph I found that illustrates the point (not a Porsche but the principle is the same):



At no point at any particular speed is the torque at the wheels in one gear lower than the torque at the wheels in a higher gear.

Edited by Jabbah on Thursday 9th February 16:57

[isaldiri]

Porsche911R said:

The 3.4 also drops off but not so fast and it's not a GT car.

The Porsche fake dyno plot is a est imo and there are 40 or 50 GT4 dyno graphs which show peak to be at 6.5k revs and a hugh drop off after.

Sense of perspective perhaps needed.

This is the BGB one taken from rennlist.

STOCK GT4 ON THE MAHA DYNO MAKING 386 HP & 307 LB/FT @ THE CRANK:


the falloff starts from 7400 quite sharply but it falls off by perhaps 10hp from 6500 to 7400 rpm. Not quite what I'd consider a 'huge dropoff after'.

Jabbah said:

Because it is about the torque at the wheels that produces acceleration. The engine torque may drop off after a certain rpm but as it is going through a gear box to the wheels (a torque multiplier) the torque at the wheels is still greater than shifting up a gear where the engine torque will be slightly greater but wheel torque lower due to the gearing.

Here's a graph I found that illustrates the point (not a Porsche but the principle is the same):

At no point at any particular speed is the torque at the wheels in one gear lower than the torque at the wheels in a higher gear.

While I don't disagree with that (although I think it's power that is the key rather than torque as far as acceleration is concerned), are you so sure the Cayman R never has any crossover in any gear? The gearing is iirc identical to the gt4 but it has smaller wheels as well. Also the gt4 crossover point isn't well before the redline but maybe a few hundred rpm so it's not exactly shortshifting at the mythical 6.5k rpm either.

[Jabbah]

isaldiri said:

While I don't disagree with that (although I think it's power that is the key rather than torque as far as acceleration is concerned), are you so sure the Cayman R never has any crossover in any gear? The gearing is iirc identical to the gt4 but it has smaller wheels as well. Also the gt4 crossover point isn't well before the redline but maybe a few hundred rpm so it's not exactly shortshifting at the mythical 6.5k rpm either.

In a given gear peak acceleration is at peak torque of the engine. Acceleration is proportional to the force applied (f=ma) where torque is the rotational force. Power is just a function of torque and rpm. I'm not sure there is no corssover. If there is, it is more likely to happen in the higher gears as the ratios are closer. Should be fairly trivial to work out if the gear ratios are available given the torque and power curves that have been posted.

[GT4P]

Jabbah said:

Should be fairly trivial to work out if the gear ratios are available given the torque and power curves that have been posted.

All gear ratios and final drive are the same for 987.2 and 981 3.4 engine and gt4

[Porsche911R]

isaldiri said:

This is the BGB one taken from rennlist.

.

Peak BHp is still at 6.5k revs ! so while it shows less of a drop off you are just backing up my point.
The torque drop off is massive though still.
So if you change later you are getting less BHP then the other side of the rising graph and much less Torque.

The whole point also was the GTS engine has a better top end, people are talking about this being a "special engine" and reving it out.

when it's quite clear you don't have to and in a GT car the GTS lump would have been a better fit.

As I said on my very 1st post no car is perfect there are plus and minus for every car, BUT when you say ANY minus point about any car it seems to upset people !

Edited by Porsche911R on Friday 10th February 08:51

[isaldiri]

Porsche911R said:

Peak BHp is still at 6.5k revs ! so while it shows less of a drop off you are just backing up my point.
The torque drop off is massive though still.
So if you change later you are getting less BHP then the other side of the rising graph and much less Torque.

Your point was that the drop off was 'huge' in hp and one should shortshift at 6.5k. It's about 10hp from 6500rpm to 7400rpm. Changing at 7400-7500 drops you to maybe 5000ish rpm which is a part of the curve that shows more power than below that. You might make a decent case of shortshifting at 7500 than 7800, at 6500 it's senseless unless you just wanted to do so for the sake of it.

It's not about a plus or minus point about a car but rather more about some of your 'alternative facts'.....

[Jabbah]

Ran the numbers using the graph posted earlier for the GTS and the gear ratios for the Cayman S from http://press.porsche.com/vehicles/2014/2014_Cayman...

These give:

	Ratios			Torque
Final	3.89	Total	Peak(420)	7400RPM(360)	Red line(310)
1st	3.31	12.88	5408	4635	3992
2nd	1.95	7.59	3186	2731	2352
3rd	1.41	5.48	2303	1975	1700
4th	1.13	4.40	1846	1582	1363
5th	0.95	3.70	1552	1330	1146
6th	0.81	3.15	1323	1134	977

Total ratio is gear * final. Torque is engine torque * ratio. Engine torque is value in brackets.

So peak BHP at 7400 rpm is always better for acceleration than peak torque in the next gear up. You are better off going to the red line in 1st and second, but third is slightly lower, probably switch over point is ~7600rpm. 4th and higher have a large deficit at the red line.

[Porsche911R]

isaldiri said:

Your point was that the drop off was 'huge' in hp and one should shortshift at 6.5k. It's about 10hp from 6500rpm to 7400rpm. Changing at 7400-7500 drops you to maybe 5000ish rpm which is a part of the curve that shows more power than below that. You might make a decent case of shortshifting at 7500 than 7800, at 6500 it's senseless unless you just wanted to do so for the sake of it.

It's not about a plus or minus point about a car but rather more about some of your 'alternative facts'.....

Have you got any timed plots to back up what you are saying ? because you cannot say "its senseless" without proof to back up such claims. (The plot above already shows a 7k shift being faster)

The drop off is hugh on the Torque side, and you need Torque to push you though the air, not BHP.
at 7.5k revs you could be circa >60lb/ft down ! (it's hard to tell)

I don't have plots either bar the 3rd party graph above which DOES back up a 7k shift was faster.

we agree peak BHP seems to be at 6.5k, what is not clear without testing in real life is the real fastest place to change gear, because Torque is needed for acceleration.

I'll do plots in March(as I have all the timing gear) and get some real figures up.

[franki68]

Thread has become a cure for insomnia.

Original OP...try both and buy the one you prefer ffs.

[isaldiri]

Porsche911R said:

Have you got any timed plots to back up what you are saying ? because you cannot say "its senseless" without proof to back up such claims. (The plot above already shows a 7k shift being faster)

The drop off is hugh on the Torque side, and you need Torque to push you though the air, not BHP.
at 7.5k revs you could be circa >60lb/ft down ! (it's hard to tell)

I don't have plots either bar the 3rd party graph above which DOES back up a 7k shift was faster.

we agree peak BHP seems to be at 6.5k, what is not clear without testing in real life is the real fastest place to change gear, because Torque is needed for acceleration.

I'll do plots in March(as I have all the timing gear) and get some real figures up.

Torque at the wheels is what drives acceleration which takes into account gearing and speed, not engine torque. I'm too lazy to redo the maths but the crossover point on the gt4 only takes place pretty close to the rev limiter. It is absolutely not at 6.5k rpm. It's really simple maths basically as torque and power are directly linked despite what you seem to think. I'll leave it here to spare everyone else.

[Nosliw]

It's been interesting reading all the articles / comments on the various Caymans. I've personally owned an R , GTS , and GT 4 all from new and found that they were equally enjoyable in there own right . The R and GT4 were good as real drivers cars because of the manual gearbox, however the GTS with PDK was also good but in a les involving mode . The main difference to me was how the cars have evolved in all areas culminating in the GT 4 being the ultimate current version of the Cayman as a pure drivers car, and it's this progression that will keep me interested if and when the next GT model comes along and it will certainly be on the shopping list. I appreciate the R and GT 4 being touted as long termers or investments for some , for me they came and went without all that and I had a lot of enjoyable miles driving them. Good to see some others appreciating these special cars . 👍😊

[braddo]

Jabbah said:

In a given gear peak acceleration is at peak torque of the engine.

Err...

[kilarney]

This is also why I'd have preferred to see the GT4 with a 3.4 lump but the same 380-ish hp output. It would push the power towards the top of the rev range, made it more toppy, which is my preference.


Its why i prefer the 3.8 lump with ipd and cobb intake but without the longtube headers which is a solid 400 + hp and the top end to which you refer without dramatically increasing the mid range. End of the day only GT4 and Spyder got a 3.8 and thats what makes them special or call it unique the rest had a 3.4 even if was enhanced but that makes 987 R more like GTS in todays speak.

A 997 RS 4.0 revs lower than a 3.8 but we all know which is viewed as the special one.

[Jabbah]

braddo said:

Err...

Hmmm... If there were no other forces acting on the car such as drag and friction.

[GT4P]

The first picture is the 997.2s ,then GT4 then CR all pictures from official brochures funnily you never here of anyone complaining about the 997.2s power dropping off at 6500rpm ! If the 3.4 had 380hp at 7.5k revs then would not the long gearing be even more of a problem?

[GT4P]