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I far prefer lightweight and naturally aspirated from a personal enjoymeny perspective, but I do wonder if the torque point prevails. The GTS puts down a great N-ring time...if this engine was boosted to have the same power as the GT3 and put into a GT3, I bet it would have a faster N-ring time (single lap) than the Gt3 despite higher weight and more lag. Perhaps it makes up the lost time in the corners by accelerating out of them faster? And probably worse to drive for most of us! thoughts on that? The answer might be depend on whether these cars can use more closely spaced race car gearboxes vs. street ratios? Seems like this example is where there is a difference between what is optimal in theory like in a race car vs how it shakes out for a street car where there are tons of compromises.
In the example Pete provided of the two cars, not sure why the n/a has 700 hp and the turbo car only 600hp. Maybe to use currently existing engines only? The v8 from the 918 vs the v8 from the 720S seems like a fair comparison.
Finally, to some extent this convo is academic. In practice, Porsche is not prepared to put a 600hp n/a engine in the 911, so if all you care about is performance, turbo is the easier route seems like, even if not as optimized as an n/a car could be in theory. Car companies seem more interested in throwing power and torque at the cars instead of reducing weight.
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.
Combining this with independent valve control could get REALLY interesting.
With the raised compression ratios from jet ignition and infinite variability of individual valve control, we could have a 600 hp 4.0 flat six that's 20 percent more efficient than a conventional DI turbo. The best part, NO LAG.
Unless they license it from Mahle for the regular street engines (non-918 successor) with a few PAG goodies thrown in, like Ferrari did with their race engines...
Originally Posted by Argon_
The best part, NO LAG.
Moving the exhaust valves to the topside with the turbos being almost directly attached to the cylinder head (and getting rid of most of the associated plumbing...) seems to have reduced lag and decreased the gap in throttle response between the NA and turbo engines. Now we just have to wait for the 992 to actually see it?
Unless they license it from Mahle for the regular street engines with a few PAG goodies thrown in, like Ferrari did with their race engines...
Moving the exhaust valves to the topside with the turbos being almost directly attached to the cylinder head (and getting rid of most of the associated plumbing...) seems to have reduced lag and decreased the gap in throttle response between the NA and turbo engines. Now we just have to wait for the 992 to actually see it?
Probably the 992.2, as the first run uses the previous .2 generation's engines.
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.
Originally Posted by randr
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
Keep digging that hole, buddy. Rather than denigrate one of the most respected and knowledgeable members, take some notes, go to summer school, and come back ready to learn.
Originally Posted by JasonAndreas
Unless they license it from Mahle for the regular street engines (non-918 successor) with a few PAG goodies thrown in, like Ferrari did with their race engines...
Moving the exhaust valves to the topside with the turbos being almost directly attached to the cylinder head (and getting rid of most of the associated plumbing...) seems to have reduced lag and decreased the gap in throttle response between the NA and turbo engines. Now we just have to wait for the 992 to actually see it?
I believe the turbulent jet ignition diagrams that Pete included are courtesy of Car & Driver; they recently confirmed that the Mercedes Project One will feature turbulent jet ignition.
I believe the turbulent jet ignition diagrams that Pete included are courtesy of Car & Driver; they recently confirmed that the Mercedes Project One will feature turbulent jet ignition.
see HERE for info on Mahle's setup that Ferrari has been using.
turbo car and NA car are both fun on track. there is a difference in throttle response.. is it going to cause huge difference in lap times with everything else being equal, no probably not, but it is a perceptible feeling no matter how small it actually is. with that said, I prefer driving turbo cars, it is just a little more fun/challenging to me. NA is not necessarily easier, and it feels much more precise, but I am not as good at it. Perhaps the extra torque and corresponding more speed on corner exit masks some of my driving inefficiencies
IMO you can't drive a turbo car and NA car in the same way and be equally fast in both, it takes a different driving style just like a mid engine RWD car or AWD car requires different method than rear engine RWD car.
+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.
+2, I suggest him signing up for ice driving from Porsche.
Have him go out in the current turbo-ed C2 then head out in the GT3RS.
He will have a clear understanding of what 'linear' throttle respond is.
In the C2, one may not feel the on/off nature of the power on the street, but on a low grip surface, he will for sure. That car/engine combo is so horrible to drive, even the Porsche instructors hated it, they keep spinning it also. Just about impossible to hold it on a drift in a circle.
Keep digging that hole, buddy. Rather than denigrate one of the most respected and knowledgeable members, take some notes, go to summer school, and come back ready to learn..
Respect is earned and if you bothered to read what was written you would have seen that there was little point continuing a debate when our positions were poles apart. I acknowledged that. My position was based on seat time and literally thousands of data points collected on sighting laps and timed laps - where throttle opening is actually one of the variables measured........data is data.
No hole dug buddy - its simple, you want power to weight add turbo, every single WRC team gets this and has for at least 30 years, put the engine in the middle and you get better weight distribution. Porsche has been fighting a rear guard action for years - in the street cars the last roll of the dice before going inboard of the rear axle is the trickle down of RAS
Every major sports car manufacturer gets this, whether its front mid or rear mid. Look at the weight distribution of an AMG GT R/S, any McLaren, Lotus, and most Ferraris - the outlier is Porsche, and in many respects the worst performer is Porsche. Even Porsche has put the engine in the "middle" of the RSR, partly for aero, partly for tires and partly for improved weight distribution leading to higher corner Vmin (which it achieved).
+2, I suggest him signing up for ice driving from Porsche.
Have him go out in the current turbo-ed C2 then head out in the GT3RS.
He will have a clear understanding of what 'linear' throttle respond is.
In the C2, one may not feel the on/off nature of the power on the street, but on a low grip surface, he will for sure. That car/engine combo is so horrible to drive, even the Porsche instructors hated it, they keep spinning it also. Just about impossible to hold it on a drift in a circle.
My god you're serious, I'll just chuck by IR and IN licences away. Insular view ....much
06-27-2017, 11:10 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 
Respect is earned and if you bothered to read what was written you would have seen that there was little point continuing a debate when our positions were poles apart. I acknowledged that. My position was based on seat time and literally thousands of data points collected on sighting laps and timed laps - where throttle opening is actually one of the variables measured........data is data. 
Insular view ....much