991 GT3 vs Carrera S Engines- differences
01-20-2015, 05:34 PM
#31
Nordschleife Master
In my view,the conclusion of this thread is that the 2 engines share quite a few more components than AP was babbling about...the reasons are many...cost comes to mind...That doesn't mean the GT3 engine is not good. Hell,the Carrera engine is pretty good so far! It's interesting to see how Porsche is going to proceed with their motorsport program and this " new " RS engine. I guess we'll find out soon enough...
01-20-2015, 05:39 PM
#32
It's about money. Mezger water cooled engines were low cost developments as they'd been developed 20 years ago. But given their manufacturing cost they were too expensive to make. The new DFI engines are also expensive, but not like the Mezger. I bet the new DFI engines were tested for Motorsports, I bet they had issues. Otherwise they would use them and really advertise them to up the 991 GT3 "race engine."
So what's up? Sharing components is the best way to drive costs down, the 9A1 does that. BMW left the race engines home, now Porsche is doing the same. BMW has turbos, guess what's next...
In truth, this is the way the market is going, GT3 does not mean sports car that can be tracked. It now means, deviated stitching, and funky electronics that are easily DDed. Oh, you can take it of the track.
Bottom line is Porsche needs to make money and this is the way to do it, I'm sure it's not what the core engineers want to do. But orders come from up top. Porsche also knows that whatever Kool-Aid they serve, it will run out of it in record time.
So what's up? Sharing components is the best way to drive costs down, the 9A1 does that. BMW left the race engines home, now Porsche is doing the same. BMW has turbos, guess what's next...
In truth, this is the way the market is going, GT3 does not mean sports car that can be tracked. It now means, deviated stitching, and funky electronics that are easily DDed. Oh, you can take it of the track.
Bottom line is Porsche needs to make money and this is the way to do it, I'm sure it's not what the core engineers want to do. But orders come from up top. Porsche also knows that whatever Kool-Aid they serve, it will run out of it in record time.
01-20-2015, 05:53 PM
#33
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Time will tell how well the 991 GT3 engine holds up on track, but I've made my bet that Porsche won't risk their reputation by producing something which doesn't cut it. And of course we do have a good warranty which covers track use.
01-20-2015, 06:05 PM
#34
Race Director
I certainly did take my time. I am not an an engineer but can follow drawings. Something certainly does not jive. I am not taking issue with Pete' s analysis. Contrary, what I am trying to understand is why if the two motors are that similar why is their performance so dissimilar? I stand by my two observations but can add a third: that the parts that are different are really critical to performance and the ones that are the same are either over engineered or not as critical. So maybe the motors are similar in a number of parts but very dissimilar in a number of very very important ones. One could argue that it is not how many parts/components are similar/dissimilar but which ones. Absent that what gives?
The fact that it is not motorspots proven is a separate issue altogether. What this requires is a ceteris paribus analysis to see what causes "essentially" similar motors to have such different performance.
Finally how come we see the motorspots press continue to make reference to what, at least numerically, could be shown to a fallacy?
The fact that it is not motorspots proven is a separate issue altogether. What this requires is a ceteris paribus analysis to see what causes "essentially" similar motors to have such different performance.
Finally how come we see the motorspots press continue to make reference to what, at least numerically, could be shown to a fallacy?
IMHO, to focus on the use of similar but relatively insignificant parts as the final yardstick to measure the two engines, is misleasing.
01-20-2015, 06:49 PM
#35
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Thread Starter
This is what I take away:
The block, main bearings, etc was far, far over-engineered for the base models, it was clearly designed with Turbo power and likely 600+ hp in mind. Thus every base Boxster has a far heavier, bigger, beefier bottom end than needed, but if it's also cheaper no one cares (and most don't have a clue).
Other parts like the generator have similar requirements across all engines- all street cars require about the same amount of power, need reliable knock sensors, etc. These parts work, they are proven, and they are relatively cheap due to volume. The only reason to change these items would have been to reduce weight, and that desire didn't rise high enough on the price/ performance scale to warrant it.
The intake, head and internals (crank, pistons, rods) were clearly revised for power, which in a normally aspirated engine is simply a function of airflow. Maintain airflow at increased revs and you get more power. The GT3 gets a power bump of 19% over the Carrera S or 11% vs the GTS. It's no coincidence that the GT3 also redlines 15% higher, 9000 rpm vs 7800.
To spin these extra revs and not float valves, entirely new rocker cam heads were required. Titanium rods and an upgraded crank were needed to prevent the pistons from stretching the rods and departing the block at 9000 rpm. Not cheap parts, not easy to get right, but simple in concept.
Finally the oiling system was revised to support all this. The true dry sump reduces windage, unlocking a little more power, but more consistent oil flow and higher pressures were likely required to hit the durability targets at the engine's higher RPM and the car's higher cornering G force. The cooling system was also upgraded as required to deal with the extra heat and perhaps revs.
Thus it's a pragmatic and efficient upgrade, made possible by the modularity and flexibility designed into the 9A1 platform in the first place. From the outset the engine was designed with ~600 hp in mind, so it's no surprise it got there. The fact that it's significantly lighter than the equivalent Mezger is a bonus. The fact that it's less modular and tunable than a Mezger is a negative to many of us, but probably a positive to Porsche.
The result won't break any records as far as power to weight ratio is concerned. Where the 918 optimizes every component from the block down and has budget to spend, this engine borrows from whats there, and some of the shared parts are relatively low-rent. Part of the reason the 918's engine makes nearly 2x the power per pound, but also part of the reason the 918 is not exactly cheap.
Unmodified I maintain I'd rather have this GT3 motor than the Mezger all else being equal. Modified the Mezger is a better platform currently, and likewise for race use that may still be the case. Rumors of test engines blown up trying to make the 9A1 durable for racing persist, and it sounds like they've had a difficult time getting to where they want to be on the track. They will get there, the only question is will it be with this platform, or the next evolutionary step forward?
The block, main bearings, etc was far, far over-engineered for the base models, it was clearly designed with Turbo power and likely 600+ hp in mind. Thus every base Boxster has a far heavier, bigger, beefier bottom end than needed, but if it's also cheaper no one cares (and most don't have a clue).
Other parts like the generator have similar requirements across all engines- all street cars require about the same amount of power, need reliable knock sensors, etc. These parts work, they are proven, and they are relatively cheap due to volume. The only reason to change these items would have been to reduce weight, and that desire didn't rise high enough on the price/ performance scale to warrant it.
The intake, head and internals (crank, pistons, rods) were clearly revised for power, which in a normally aspirated engine is simply a function of airflow. Maintain airflow at increased revs and you get more power. The GT3 gets a power bump of 19% over the Carrera S or 11% vs the GTS. It's no coincidence that the GT3 also redlines 15% higher, 9000 rpm vs 7800.
To spin these extra revs and not float valves, entirely new rocker cam heads were required. Titanium rods and an upgraded crank were needed to prevent the pistons from stretching the rods and departing the block at 9000 rpm. Not cheap parts, not easy to get right, but simple in concept.
Finally the oiling system was revised to support all this. The true dry sump reduces windage, unlocking a little more power, but more consistent oil flow and higher pressures were likely required to hit the durability targets at the engine's higher RPM and the car's higher cornering G force. The cooling system was also upgraded as required to deal with the extra heat and perhaps revs.
Thus it's a pragmatic and efficient upgrade, made possible by the modularity and flexibility designed into the 9A1 platform in the first place. From the outset the engine was designed with ~600 hp in mind, so it's no surprise it got there. The fact that it's significantly lighter than the equivalent Mezger is a bonus. The fact that it's less modular and tunable than a Mezger is a negative to many of us, but probably a positive to Porsche.
The result won't break any records as far as power to weight ratio is concerned. Where the 918 optimizes every component from the block down and has budget to spend, this engine borrows from whats there, and some of the shared parts are relatively low-rent. Part of the reason the 918's engine makes nearly 2x the power per pound, but also part of the reason the 918 is not exactly cheap.
Unmodified I maintain I'd rather have this GT3 motor than the Mezger all else being equal. Modified the Mezger is a better platform currently, and likewise for race use that may still be the case. Rumors of test engines blown up trying to make the 9A1 durable for racing persist, and it sounds like they've had a difficult time getting to where they want to be on the track. They will get there, the only question is will it be with this platform, or the next evolutionary step forward?
Last edited by Petevb; 01-20-2015 at 07:25 PM.
01-20-2015, 07:22 PM
#36
Race Car
A propos the last sentence of Petvb's post-
"New" engines under the turbos and for non turbos too- per a very good automotive journalist:
http://www.motorsportmagazine.com/ro...-future-plans/
"New" engines under the turbos and for non turbos too- per a very good automotive journalist:
http://www.motorsportmagazine.com/ro...-future-plans/
01-20-2015, 08:12 PM
#38
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01-25-2015, 04:03 PM
#39
[QUOTE=Petevb;11971990]
This is what I take away:
The block, main bearings, etc was far, far over-engineered for the base models, it was clearly designed with Turbo power and likely 600+ hp in mind. Thus every base Boxster has a far heavier, bigger, beefier bottom end than needed, but if it's also cheaper no one cares (and most don't have a clue).
--------
It would be interesting to know if the block was machined differently in anyway or if machining tolerances were different between the Carrera's and the GT3
This is what I take away:
The block, main bearings, etc was far, far over-engineered for the base models, it was clearly designed with Turbo power and likely 600+ hp in mind. Thus every base Boxster has a far heavier, bigger, beefier bottom end than needed, but if it's also cheaper no one cares (and most don't have a clue).
--------
It would be interesting to know if the block was machined differently in anyway or if machining tolerances were different between the Carrera's and the GT3
03-19-2018, 12:04 AM
#42
Thanks for posting.
What I see here are two totally different engines that only share not important things like accessories, screws, bushings, etc. Major components that define engine are different. Engine block, cam shafts, pistons, main shaft, main bearings, piston rods, whole oiling system, etc. are all different.
Where are the similarities? I don't see them.
What I see here are two totally different engines that only share not important things like accessories, screws, bushings, etc. Major components that define engine are different. Engine block, cam shafts, pistons, main shaft, main bearings, piston rods, whole oiling system, etc. are all different.
Where are the similarities? I don't see them.
03-19-2018, 01:33 PM
#43
The GT3 engines have a very different valvetrain than the normal 9A1. The GT3 engines use a finger follower design, whereas the standard 9A1 use a valvetrain type which I can not translate to english, sorry ;D
Some parts (camshafts (new introduced DLC coating), finger followers (improved DLC coating), valve springs, piston rings, oil pump) changed from 2015 to late 2016 during production of the MA175 and M176 engines, mainly because of finger follower wear. With the revised 9R1.5 engine, they simplified the valvetrain further by deleting the hydraulic lifters (fixed finger followers). So the new engine doesn't feature hydraulic lash adjustment but requires less exotic materials (DLC coating).
Some parts (camshafts (new introduced DLC coating), finger followers (improved DLC coating), valve springs, piston rings, oil pump) changed from 2015 to late 2016 during production of the MA175 and M176 engines, mainly because of finger follower wear. With the revised 9R1.5 engine, they simplified the valvetrain further by deleting the hydraulic lifters (fixed finger followers). So the new engine doesn't feature hydraulic lash adjustment but requires less exotic materials (DLC coating).
