FastLaneTurbo

I would hope before firing me you would have examined the facts:

The point of my post was that the 991 GT3 has been a quantum leap over the
previous GT3 mainly due to additional HP, Chassis Width, Chassis length, Rear wheel steering and Super fast Tranny with Lowered gearing. No doubt follow-on models will improve it further as springs, shocks, suspension settings and tire performance are "dialed in", but, IMHO, the RS model will be much closer in performance to the very small laptime differentials of the 997 RS-4.0 vs RS -3.8
than the much larger GT3 vs GTRS laptimes since I expect the 991 chassis of both to be very similar.

The 997 GT3RS has an average decrease of 1 Second in laptimes over the
GT3 - which I attribute mainly to its wider Chassis and Body and larger more effective Wing. It also had 15 more HP and 55 Lbs lighter weight which IMHO
played a far lesser role. Why do I say that? The Laptimes on the RS 4.0 which added an additional 50 HP (500HP) and several aerodynamic bits and pieces, were very little if any improved over the 3.8 RS Times on all the shorter tracks
we use in the U.S. and Europe. The 991 GT3 already has most of the most significant improvements which greatly improved the 997 GT3RS laptimes over
the GT3. Frankly, I hope I'm wrong since I have a deposit on an RS with my dealer, but we'll just have to wait and see.

frayed

Since folks are predicting, I'll wager 7.1x ring laptimes in the RS. Rumors during GT3 development claim .1x times were hit. Porsche is pretty good at dicing up the market with seemingly 100's of different 911 variants; I wouldn't be surprised if the GT3 was slightly detuned in order to preserve a good delta from the RS. Weight, track, downforce, power, and tire are all on the table.

And IIRC the 1.08 Hockenheim time is theoretical.

Macca

Very much agree on this. I know the GT3 was posting below 7.25 on the Ring for many laps. I think it become a bit of a marketing challenge now. If the car is 40-50lb lighter with better aero and contact patch, tweaked suspension and settings and say 30 bhp more the I think sub 7.20 will become official no problem.

I dint realize however that the official GT2RS time was 7.18...

CarManDSL

The issue is, the GT3 isn't out yet and no one has driven it yet say for a few journalists, and judging it's limitations is not realistic.

The RS as before, will be a more hard core track car. How much more in performance from the GT3 will probably be similar from 997 GT3 to 997 GT3 RS - my blind assumption based on the pecking order of the whole 911 line.

From your reasoning above, there is just too much advanced engineering and development in the 991 series as a whole to make assumptions based on your, possibly quit logical, chain of observations and conclusions. Porsche had been dropping too many surprises lately.

You said, "I hope I'm wrong since I have a deposit on an RS with my dealer". We will know in a year or so. On that note, in June 07 when I dropped into Riverside Porsche, they had a new "used" RS for sale . . . with a $50,000 premium . . . just because they could. A sad spectacle indeed. I trust your dealer will at the very least, guarantee no more than MSRP.

I suggest exercising your big grin muscles well in advance of delivery! I hate sore cheeks.

If you are right in your argument, I'll still fire you. It means you didn't work hard enough to further develop the 991 series . . . and I'm pathetically jealous as I'll just have to do with the 991S!

FastLaneTurbo

Before leaving your employ, I would patiently explain to you the prior logic I posted, and also explain why additional HP over 475 and Revs over 9,000 would likely be highly stressing an Engine of only 3.8 (or even 4.0) Liters and would negatively impact long term Engine reliability and usable track lifetime. I would remind you that our similarly stressed race engines have a recommended
track lifetime of only 30 hours at maximum HP output with few lasting over
50 - 100 hours close to 100% power output before being completely rebuilt.
I would fear our track customers, already maintenance and expense-adverse,
would complain mightily if our engines only lasted under 100 track hours.
I would then plead with you to give our 911 a larger displacement Engine with
higher Torque as used by most of our competitors. I would also point out the
high costs of adding "race-grade" body, chassis and suspension components as we have done on the RSR and GT3 Cup Cars, and ask just how many of those
cars, selling for double or triple the cost of a GT3, customers would be willing to pay for. As my final comment, I would remind you as my employer, of the magnificent performance at a highly competitive pricing level my 991 GT3 has
been.
Since this discussion, and the projected performance of the 991 GT3RS, is strictly hypothetical both of us will just have to wait another year or so to find
which of us came closer to the new 3RS's performance level, your "blind assumption" or my calculations.

Nizer

3.8 and 4.0 Mezger's made 450 and 500 HP, with the additional 50hp gain of the 4.0 attributed roughly 50/50 to displacement increase and volumetric efficiency gains. I would assume that the 9A1 being a more modern design benefit from advances in reduction of parasitic and frictional loss among other things. Throw the higher redline and DFI in the mix and the new motor should in theory have a lot of development potential.

Looked at another way, the 3.8 Mezger with volumetric efficiency gains of the 4.0 Mezger would make approximately 475hp, and this is without DFI and extra revs of the 9A1 engine, not to mention other engineering advances.

Macca

Nizer. I agree they must have left something on the table for the 991 GT3RS or at the least later .2 gen variants.

However understanding where the extra power it might be is difficult. If we assume for a moment its not displacement then we have the following data points.


The 991 GT3 is 475 PS (469 bhp). The 3.8RS is 450 PS (444 bhp) and the 4.0RS is 500 PS (493 bhp). Torque is 325 lbft/ 3117lbft & 339/lbft respectively.

AP states in two different interviews that the 991 GT3 475 PS is conservative and s closer to 500. Im not sure why he would say that and Im not sure why Porsche would do that....has me puzzled.

The 991 GT3 has a 12.9 compression. the 3.8RS is 12.2 and the 4.0RS is 12.6

If we assume the displacement remains the same the I think we also have to fairly assume there really isnt any further they can push compression either on pump fuel. This leaves intake manifold, ECU, cam and exhaust. If we assume minor tweaks in all three then I suggest 20 PS maximum will be achieved and perhaps up to 7 lbft torque.

My belief is they will keep capacity at 3.8l for this generation and use some of whats been left on the table (i.e. not included in base 991 GT3 published figures) to give a marketing figure of 500 PS. If the above were to be true then it would also be possible to get a base 991 GT3 up to around these numbers with a few manifold side and exhaust side aftermarket improvements.

In terms of rpm I dont believe they will go above 9000. If they did I dont see any benefit. As we know from the 991 GT3 power/hp curves its really all over by 8250 rpm (peak hp) and although its advisable to have up to 500 rpm "headroom" on the engine then really theres no point shifting above 8750 in reality although it sure makes a nice noise form 8500-9000. Again my guess is they will move the peak power up to around 8500 but again leave the 9000 limit.

There is no doubt that they probably overshot the mark a little with the 991 GT3. I guess there were so many changes they never knew where they would end up and its probably made the job of creating an RS that little bit harder. The RS will be fatter again, lower cd but more downforce. The extra aero with a little weight reduction, a touch more power and some additional rose jointed suspension tweaks etc should see a 3-5 second advantage on the Ring time, although again I would suggest this is also manipulated as I have it on good account the 7.25 range and below was achieved during testing with the GT3.

I do agree that the new engine has better future potential than the Mezger. I personally believe however they had in mind an optimum displacement of 4.0l and what we are seeing here is just a squeeze on the 3.8L displacement to get every ounce out of it before they transfer to technology to the 4.0L platform in the generation 2 variants. They never do everything all at once. I think the 4.0L displacement increase will finally bring us more torque which IMHO this engine still needs a good dollop more of. Im thinking 340lbft+

Macca

P.S. In terms of performance parameters of the new 991 GT3/RS I think we are also very much underestimating the role the new 7 speed PDK plays in optomising best use of the performance on tap. I expect that the nominal 25 bhp increase of the 991 GT3 over the 997.2 GT3/RS is not enough to explain the almost 15 second reduction in Ring time, especially given the 75lb weight deficit between teh two models. Sure we can conclude the improved chassis dynamics, longer wheelbase, RWS and electronic diff all help with the time but I suspect at least 5 seconds of this is to do with the PDK now it has 7 linear ratios (no override) stacked into that 8750 rev band with a computer or two synchronizing the systems (PTV, e diff, dynamic engine mounts, RWS) to make best effect of it. I guess what Im saying here is stuff the same PDF-S into the 997.2 GT3RS and you would be seeing an immediate 5 sec improvement in ring time even on the older gen engine and chassis....

CarManDSL

Let's revisit this in a year.

It's a date!

Macca

We wont have to wait that long hopefully...

FastLaneTurbo

Agreed! We're all shooting in the dark. Let's wait before speculating - (but it's so much fun)
Re the Engine output, During my last visit to the 911 Factory last September,
our guide pointed out that the factory had changed in recent years from a nominal HP rating plus or minus some modest percentage to a minimum Rating with no "minus" tolerance. In other words, every Engine is now built to a nominal tolerance that is substantially greater than the Spec HP so that even the worst Engine (presumably with all components at maximum acceptable QC tolerances) will produce its rated HP which means most engines shipped produce more HP than their "Spec HP" I've also noticed in our Porsche Region's annual "Dyno Day" that the previous MT GT models have Rear Wheel HP on the Dyno which is higher than the expected 15% to 20% Transmission losses. The Mustang Dyno showed a 996 GT3 rated at 385 HP with RWHP of 357 HP, a loss of only 7%, A 997-01 GT3 w/ 415 HP Rated and 362 RWHP, a 13% loss, and a 997 GT2RS rated at 620 HP showing 580 RWHP, only a 6% loss.

Petevb

If you dyno a "380 hp" 996 GT3 vs a "380 hp" X51 997 Carrera w/ powerkit you'll realize Porsche has been under-rating the GT3s for years. They are simply keeping the tradition.

Seems fairly clear that they have two options, increasing the RPM where peak power is made or stroking to increase displacement.

Keeping torque the same but moving peak power up by 500 rpm (from 8250 to 8750) would result in 30 additional hp. While it's not 100% clear they can do this it seems very likely: the new top end's reason for existence is an aggressive high rpm cam, and the bottom end is obviously capable based on the (relatively, vs audi, etc) low pistons speeds the car is running at 9000 rpm. Also keep in mind that removing the human from the equation has eliminated the headroom that was once needed to cover a missed shift, another reason pushing the RPMs up seems relatively straightforward. All this suggests that a 3.8L version could comfortably rev past 9000 rpm if needed, and a 9000-9250 rpm redline .1 RS with "500 hp" (really 525-530) primarily though a cam change would be my bet.

Alternatively stroking the motor, which I agree was part of the plan from the beginning, could deliver a similar increase by itself, or be combined with a shift up the RPM band to get more than 50 hp total (though the stroked motor would probably not be able to exceed 9000 rpm, one reason we may not see an increase in a .1 3.8 RS redline). Given the potential of the bottom and new top end I eventually expect to see a ~550 hp @ 8700 rpm 4 liter. The question is when we'll get to see that- I tend to agree that we might need to wait for a .2 RS.

My fear is that simply increasing the RPM on a 3.8 .1 RS will leave the large hole in torque on the lower end, making the motor significantly less suitable for pairing with a manual.

Macca

Pete. Im agreeing with you on most points here.

There is headroom in the current rpm curve to accommodate a more aggressive cam. Whilst I don't believe this alone will produce 30bhp (will need some inlet, manifold, exhaust tweaks in unison), I do agree the primary challenge is the torque peak and placement. They only raised peak torque by 7lbft over the outgoing 997.2 RS and the 991 GT3 delivers the exact same peak torque as the 991S! They have left the door open there! I believe they did this knowing that the PDK-S in the 991 GT3 will make up for this in terms of optomised/intelligent shifts....for now....

My personal belief is we will see a 3.8L with 9000 rpm redline in the RS variant same as GT3. I dont see an increase in peak rpm, its simply not needed and expensive to engineer for a simple gen 1 "hot variant". My punt is they will choose a cam/manifold/exhaust that brings the peak torque up another 7-10lbfts at maybe 250 rpm more peak (6600 rpm). I think as a compromise the true power increase will be only 20 bhp but there is already obviously some understatement with the 991 GT3 power output so maybe they will fudge it a bit to give a 500 PS headline figure.

If you couple the above with a slightly different set of 7 speed ratios and some fine turning on the PDK software (the gen 1 will be only PDK) then although these gains seem relatively small between the two cars I should think over a long course such as the North Loop we will see a 5-7 second advantage. Torque will be the key married to matched ratios and shift points.

I agree with you that a 4.0L displacement is some way off (gen 2?). This will give the torque requested but as you say will require some intensive work to make reliable without dropping the headline rpm below 9000.

It is all speculation, however it is also fun....and kills time LOL!

991 3Turbo

I think we will see Ring times in the teens before the end of the first production year. Quite attainable with all the changes.

The only way you are going to get remotely close to 20% driveline loss would be with an AWD car with a slushbox conventional automatic. Modern drivelines, as said above are much more efficient at extracting power. I am guessing with the 991 7-10% loss with the PDK. It is a remarkable transmission and it will be proven with further testing on the dyno.

frayed

PDK won't improve driveline efficiency. Performance, yes. Rear wheel hp no.

Its claim to fame is to be able to fully take advantage of a motor that is, in essence, peaky. Like my motocross bikes from long ago, it's a transmission that allows you to stay 'on the pipe'. PDK is a bit of an equalizer wrt high tq (displacement) cars.

IMO.