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Try saying it, you'll find it cathartic - a 6 cylinder FI 4l 10:1 compression ratio engine with a modest amount of boost (12 psi) will deliver the performance of a 6 cylinder NA 5.5l 13.3:1 compression ratio engine.
So as I'd guessed earlier, your real argument comes down to you simply wanting more power. Turbo can make more power out of smaller displacement- no kidding!
I can understand trying to swing the debate away from throttle response- I think you now recognize the inherent delay as a boosted motor builds power from its unboosted compression ratio to the boosted effective one. That delay not only takes time but it effects the faithfulness of response- as Walter put it he'd stab the throttle the first time and get too little, then the next tine get too much. That delay can spice things up, but alone is enough reason for many to walk past the turbo as a technical solution in a no limits car givin the option.
On your numerical argument, however, I'll pose a question.
You have two options: option A is a 3000 lb, 700 hp normally aspirated car with a 350 lb engine- revs to 9k and has the same power to weight engine as the 918.
Option B is a 3070 lb car with a 600 hp, 400 lb turbo engine. This is the same power to weight engine as McLaren's been putting in their newer Turbo cars because frankly if we used Porsche's turbos we'd need to add another 100 lbs. So we have 100 less hp, 50 extra lbs from the engine plus another 20 lbs because the gearbox needs to be uprated to handle the extra torque.
You're arguing for the lower powered, heavier, less responsive car B. Why?
(1) I have no need to steer anything away from anything - on track there is no discernible lag that impacts on performance - 18k to 19k data points attest to that along with a lot of seat time.
(2) Yes turbos can make more power from lower displacement because the effective compression ratio is higher than a NA engine even at very low levels of boost - thats why they can be incredibly responsive and do more work in less time
(3) The torque "curves" derived from modern turbocharged cars are contrived to be flat via a series of controls from ECU to engine. This is done to deliver a linear response.
(4) From a brute performance perspective it is the ability to generate power "under the curve" - basically all else being equal - torque wins out.
(5) I'm not arguing for a heavier less responsive car - I'm arguing for a better balanced all round package. Theres a whole world of metallurgy and materials science that could and should be in play.
(6) Good luck with your incoming GT3 - the .1 engine was/is a lemon/ time bomb, hopefully the next one will be better. Time will tell.
(7) I suspect he "purists" have won out in the short term - however, like the LMP1 victory it is Pyrrhic in its form.
1)there is no discernible lag that impacts on performance
And how do you explain the fact that drivers like Walter Rohrl disagree?
Originally Posted by randr
(5) I'm not arguing for a heavier less responsive car - I'm arguing for a better balanced all round package.
But you are, whether you realize it or not... Better balanced how? If the NA car is significantly lighter it will have superior cornering and braking. Less engine weight almost invariably leads to a better weight distribution- literally better balance. You're saying that despite both of these you'd take the heavier and significantly less powerful car? What are you getting in trade that's worth that sacrifice in your mind? Engine flexibility is nice, but dual clutch transmissions make it far less valuable than it once was- even if you deal with the lag is it really enough?
Bring grand touring, emissions or fuel economy into the equation and we'll have a different discussion, but you should rethink the idea that turbos are "technically superior" for performance reasons. They are the future, but due primarily to regulations rather than performance merit. If you doubt this consider- the 9A2 in a 991.2 GTS has a significantly worse power and torque to weight ratio than the antiquated, 2 valve, non direct-injection, 11:1 compression pushrod V8 in the last generation Z/28 (2014). How's that for progress?
The article just after that one on the 919 gives fascinating hints into the pace of progress they are making, particularly on the efficiency side of the turbocharged internal combustion engine. They finally admit to using "jet ignition" which has been largely responsible for the massive improvement in fuel efficiency (and hence power as they are fuel flow restricted) in F1 over the last few years.
Jet ignition is essentially a small pre-chamber where fuel and air are mixed, ignited and then squirted into the cylinder already burning to ignite the rest of the mixture. This creates extreme swirl and mixing, allowing for a very late ignition and ultra-fast combustion. An older example of this type of system, we won't see Porsche's for some time:
This method helps ward off pre-ignition/ detonation, allowing them to run a very lean mixture. A side effect, however, is very high pressures within the cylinders- similar to those experienced in diesel engines. The high pressures are good in that they improve efficiency, but bad in that they require much stronger components than is typical for gasoline engines. The result, however, is a gasoline engine operating at diesel levels of efficiency while retaining the power density and ability too rev of gasoline.
Rumors are that these race engines are now mid 40s to possibly 50% thermal efficiency by themselves and well over 50% when combined with the heat recovering MGU in the exhaust. That's hugely better than the best street engines (the Atkinson cycle in the Prius just manages 40% peak while a Ford Ecoboost Turbo is 32.5%) while still managing 10x the power density. Amazing progress over the last few years, and all it took was the right incentive system.
And how do you explain the fact that drivers like Walter Rohrl disagree?
But you are, whether you realize it or not... Better balanced how? If the NA car is significantly lighter it will have superior cornering and braking. Less engine weight almost invariably leads to a better weight distribution- literally better balance. You're saying that despite both of these you'd take the heavier and significantly less powerful car? What are you getting in trade that's worth that sacrifice in your mind? Engine flexibility is nice, but dual clutch transmissions make it far less valuable than it once was- even if you deal with the lag is it really enough?
Bring grand touring, emissions or fuel economy into the equation and we'll have a different discussion, but you should rethink the idea that turbos are "technically superior" for performance reasons. They are the future, but due primarily to regulations rather than performance merit. If you doubt this consider- the 9A2 in a 991.2 GTS has a significantly worse power and torque to weight ratio than the antiquated, 2 valve, non direct-injection, 11:1 compression pushrod V8 in the last generation Z/28 (2014). How's that for progress?
I understand exactly what I'm saying - its much easier if you deal in facts.
(1) McLaren 570S power to weight 395 HP/tonne, torque to weight 428Nm/tonne
(2) 991.2 GT3 power to weight 340 HP/tonne, torque to weight 321Nm/tonne
(3) McLaren 3.8l twin turbo
(4) Porsche 4l NA
(5) McLaren weight distribution 42 front 58 rear
(6) Porsche weight distribution 37 front 63 rear
(7) I never said anything about the 3800lb Z28........and of course a 7l V8 engine delivers more power and torque than a 3l twin turbo and of course being a heavyweight it can't corner for long, its brakes go off and its tires melt - its not relevant to the discussion at any level.
To put it simply - the weight "penalty" of 100lbs or so, if the engine is placed ahead of the rear axle, is off set by the benefits of substantially improved weight distribution, coupled with considerably improved power and torque to weight ratio. Simple example above. It can be done - easily.
As I said previously, its pretty hard too get me interested in a GT3/RS - theres too little evidence of steps forward. In fact I'd take an Austin Healy 3000 and join the historic circuit before buying one of the current GT offerings.
To put it simply - the weight "penalty" of 100lbs or so, if the engine is placed ahead of the rear axle, is off set by the benefits of substantially improved weight distribution, coupled with considerably improved power and torque to weight ratio.
Got it. So if you spend money on an expensive carbon chassis you can afford to put in a much heavier, less powerful Turbo engine in it. Makes perfect sense, and now I can see exactly why you'd want that over the same chassis with a lighter, more powerful normally aspirated engine. Crystal, thanks.
The engines aren't much heavier and the power to weight benefits are clear, obvious and well demonstrated.
The torque curves and power under the curve relative to weight are clear. Its even self evident in some significant forms of motorsport.
(1) F1 - turbo
(2) WRC - turbo
(3) GTpro - turbo
Power to weight - torque to weight - weight distribution (if placed ahead of the rear axle as Porsche do in the RSR) - the facts are against you.
I have amply demonstrated this through everything from
(1) 18k to 19k data points from a 2-3-4 track that show throttle response on track is a non-issue
(1) calculations demonstrating power under the curve relative to weight
(2) calculations that show effective compression ratios under mild and moderate boost
(3) given you examples of various different cars and data for those cars including Maha dyno results
(4) and the same for a current GTS and GT3 highlighting the disproportionate losses that high revving cars achieve
(5) and even simply contrasted a Mclaren 570S with a .2 GT3.
(6) Porsche themselves have moved the engine to the middle in the RSR.
(7) The Porsche sports car line up is dominated by turbocharged cars.
(8) The next big release from Porsche will be the GT2 RS - you guessed it turbo charged.
(9) The NA GT division cars didn't place at Le Mans in either GTEpro or GTEam - its not a BOP conspiracy
(10) The NA GT division cars are sitting dead set last in the WEC GT class.
(11) Only two SP9 class 991 GT3 R cars finished in the top 20 at the Adac24Hr Rennen
Journos - give me strength. Some of them can heel and toe they even post videos of themselves doing this. Priceless. I think I'll buy you a pipe and some string backed gloves - the EVO guys will appreciate you - oh I forgot, most of them ran after the advertising dollars and advertorial pay at drivetribe......I drove a Golf GTI this week......Journos
Petevb - you and I will never agree on this - Currently I track three cars, I binned another one into a wall this year. Our perspectives are clearly totally different and driven by different motivational factors. So lets agree to disagree bearing in mind I still own two Porsche sports cars
I can understand trying to swing the debate away from throttle response- I think you now recognize the inherent delay as a boosted motor builds power from its unboosted compression ratio to the boosted effective one. That delay not only takes time but it effects the faithfulness of response- as Walter put it he'd stab the throttle the first time and get too little, then the next tine get too much. That delay can spice things up, but alone is enough reason for many to walk past the turbo as a technical solution in a no limits car givin the option.
+1
Don't mean to be dismissive of others, but people who have not 'danced' with a car's throttle and steering at its grip limit mid-turn will have hard time understanding how essential it is for the throttle response to be immediate and repeatable (predicable) to within microscopic amounts of time and pedal travel.
I don't care about hp, or power/weight ratios if the best part of the experience (the mid-turn 'dance') will be even slightly compromised.
I'm with Pete on this one : I love Turbos in certain applications but I prefer NA. These engines are hands down better in many aspects,including long term reliability. Perhaps not so critical in high value applications that rarely get driven and accumulate high mileage,but more so in day to day sedans,SUVs etc. Manufacturers are getting pushed into a corner and Turbos is the cheapest way to respond while continuing the HP war. A large majority of customers do not necessarily care or understand all the technical details related to the new car they're buying. I have seen them way more interested in creature comforts,MPG and " lack of maintenance " required : they love to hear words like " lifetime " (lifetime this,lifetime that). And the salespeople are directly responsible by promoting and encouraging this type of behavior.
A family member asked me for advice in getting the new HONDA CRV. He wanted the fully loaded version. Honda promotes their new turbocharged engines. They are still selling their old 2.4(or 2.5...can't remember) NA engine on their base CRV model. I've advised him to get that one. The new engine is 1.5 L but it's running 16 PSI of boost!!! That's a lot for a stock engine! Honda builds reliable engines. I wonder how reliable this one turns out to be...
I suspect I have danced with the throttle than most here.......
Would love to see some videos.. I remember you were quite critical of Skippy in his Targa Tasmania series.. considering he was actually driving in a competitive, timed series of events and you were behind a keyboard, it would be refreshing to know that you have the expertise to back up your subjectivity....
There is no win - we have different perspectives - the gap will never close.
I provided data, real inputs and calculations - Petevb really provided very little - he did correct me on a compression ratio for a turbo engine, not that it mattered given that engine won performance engine of the year ahead of the NA mill found in the R - at the end of the day I was simply being mature and courteous. I'll be quite clear I have zero time for motoring journalists. At best they provide crude often ill informed infotainment.
If your background was in rallying (as was mine) - then you would find a lot of the statements largely typical of someone who has limited on the clock track/stage time. I mean no disrespect when I say this, most people don't do 20 plus on the clock days per year in semi-retirement (excluding set up and tuning days) and that excludes off track fun like hill climbs etc.
For all I know, he probably wants to cruise around in a manual GT3 and do a handful of "off the clock" track days a year. If thats the case great, I hope he enjoys them safely. If he wants to use it as a club level track toy even better - thats probably the target audience. Perhaps he is the epitome of the Porsche purist, the last defender of the indefensible as it were. Again, fantastic - but also not for me.
Anyhow, driving a performance car round a track is relatively easy - if you have a lot of experience and training - I still do it in my semi retirement as does my wife (we are still involved in on the clock events) - as its both relatively easy and relatively safe and to be quite clear its just as easy to balance/move a turbo charged vehicle on throttle as a NA car. Its not even nuanced - Its just a question of experience and its very easy to tell when your tires are feathering at the limit.
From my own perspective, I know exactly what I want from a performance car, I have owned and fielded two national level open class (or equivalent) rally cars (plus 8 others at different levels) - far more raw and exhilarating than any OTS GT car The GT division can't provide what I want - its not a big deal, I'll go elsewhere as many are doing.
To be frank, perhaps the bottom line is this simple - Porsche placed the engine in front of the rear axle in the WEC GT RSR.
It is Porsche that opened Pandoras box.......and like Pandoras box, all that remains is hope.
When Porsche GT division carry this design philosophy through to its logical conclusion - I may be interested, until then its a big no. However from my perspective, they will have to be quick as I'm looking at two specific events I want to do over the next three years. As it stands Porsche GT don't offer the product that I require - they can't even produce what they do offer in a timely fashion. So thats that. Nothing more to say.
06-26-2017, 10:19 AM
they even post videos of themselves doing this. Priceless. I think I'll buy you a pipe and some string backed gloves - the EVO guys will appreciate you - oh I forgot, most of them ran after the advertising dollars and advertorial pay at drivetribe......I drove a Golf GTI this week......Journos 
The GT division can't provide what I want - its not a big deal, I'll go elsewhere as many are doing.