Porsche Central Featured Vids
...well, here it is, a new feature of Porsche Central - the "PC feat. vid section", every now and then it´ll feature a new video, announced in "Porsche News"...
we decided to post the links in "Down&Up" - i hope everyone understands that we can´t post the vids directly in PC due to bandwidth limits... __________________________________________________ ___________ vid from 01012005: :arrow: link HvS from SA´s driving the Tech Art GT Street for the Supertest at HHR and NS... ...the GT Street is based on 996TT, unlike the GT Street S which is based on the GT2, but has no AWD. at 1.3bar max boost it delivers 620hp/850Nm is able to reach 60 in under 4 seconds and 125 in under 12secs, on the test day temps had been kinda high an therefore not the very best conditions for a turbo engine, it did it in 4 flat and 11.9... the time of 1:12,3 @ HHR was driven with the normal spec Conti Sport Contact 2, so again, the time could be even better there - approx. 1sec. mechanical grip at front is nearly perfect for narrow track like HHR, so hardly any understeering noticeable, grip at the rear is a bit weak due to the normal Conti´s, also braking performance could be better - for the test at NS Conti delivered a sport version of the Sport Contact 2, compareable to the Pilot Sport with N2 secification from Michelin, and with that tyre especially braking performance but also overall handling had been significantly better, HsV guessed that this tyre version should be approx 5 sec faster than the HHR one... time at NS: 7:43 8) ...more to follow :wink: |
Absolutely brillant video of course, the Gt Street is a mad car with RWD of course! :D And 7:43 is still a damn good time :D
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Nice video st-anger thanks for sharing that. Those are some incredible times even on inferior tires. So is the “Pilot Sport with N2” a semi racing slick type tire?
St-anger, the Tech Art runs boost at 1.3 bar and when I looked back to the PC “Model section” it indicates that the Porsche based 911 runs 1.65 bar at maximum power. It was my understanding that they way most tuners increased their power output above that of Porsche’s is by running higher boost with modifications that allow the running of higher boost pressures. In the Tech Art case how are they able to run lower boost pressures and still increase the horsepower by 200 bhp :? ? |
…nope, Michelin´s semi slick is called Pilot Sport Cup, e.g. on the ///M CSL, the PS N2 is the standard tyre for the std. Porsche models, “N2” is just the Porsche specification code, Michelin´s manufacturing this tyre for PAG only, just like the “N0” for the CGT…
well, here we have to differ between absolute and relative boost pressure, i´m talking about relative pressure – the pressure to the normal atmospheric pressure, so 1.3bar, sure there are cars like GT2 which run at 2.0+ pressure but this is absolute pressure then… a normal TT´s running at ~0.85bar, a GT2 ~ 1.0 bar – nevertheless, see pic down there, shows a ~560hp TT running at “only” 1.1bar at full speed: http://www.is-mad.com/upload/[email protected] …basically u´re right, “just” increasing the boost is an easy way to increase power – but this is not the very best way, here in Europe it´s very popular to tune TDI´s, so diesel cars, with a re-mapped ECU, increasing boost ~0.3 – 0.5 bar, more fuel and re-mapped fuel ignition times, but this is the worst thing one can do – such tuning won´t last very long without an efficient cooling system, so bigger intercooler and reworked air supply is a definite MUST DO then, most, better said nearly ALL tuner won´t mention that – unfortunately… note that any boost pressure increase is extremely stressful for the engine, the turbo itself is spinning with higher revvs – due to the higher pressure ratio between turbo inlet gate and outlet gate the turbo has to spin twice the speed than with normal boost pressure - also it´s important not to have a depression inside the air box, most cars have some mbars depression, here it´s good to replace airflow parts to bigger one´s so that more air can flow, the intercooler temp is higher – again, note that ~10°C lower intercooler temp is replacing ~50-60mbar boost pressure -, combustion temp. and pressure as well as exhaust temps are increasing to critical levels resulting in a higher strain for engine, turbo, exhaust system and especially cylinder-head gasket. … well, it´s getting complicated now I think… :roll: serious tuners like TechArt definitely install a proper cooling system but again, they´re also after keeping boost pressures low, there´re some ways to gain power with turbo engines without increasing the boost too much, like bigger ports and valve opening times and travel. well, in the end this is a EXTREMLY complex topic and I have to admit that i´m not familiar with all the details i´m afraid… Quote:
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Thanks st-anger. That makes a lot of sense. When I first read 1.3 bar I thought that was relatively high. At least I knew it was in comparison to 930’s :P .
Just curious even when set up “properly” with the modifications you mentioned (i.e. larger intercooler, cams and port & polishing ect.) will a turbo running 1.3 bar have less reliability and require more maintenance / replacement than a 996TT or GT2? I guess what I am asking is there a way to safely run higher boost pressures and not sacrifice reliability? |
Wow! Great vid, that is a beast. :D
Thanks st-anger, and thanks for all the background info on the Porsche, very interesting. 8) |
Thanks st-anger, downloading it now - should be great. :D
EDIT: just finished watching, and another big thankyou. :D I love this car, and in yellow it sure looks nice.....0-200 in 11.9s is impressive, in that time my car would only just have got past 100kmh. :( |
great video st-anger! i think the hockenheim footage was great! and a very impressive NS time indeed... tho i must admit, i dont know much about tire ratings... i would've thought it would be a lot faster then an M3
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often, to increase reliability, charged engines run on lower compression ratios. with a lower compression, there is less direct stress on the internals. also, using lower compression, i think lower torque values would occur overall... cirtainly off set by the compressed air. as st-anger was mentioning, a turbo would have to spin at much sustained higher velocities, further increasing heat in the turbo charger through friction with itself primarily. often aftermarket tuning will run larger turbos runing lower rpm's for the same mb levels at the sacrifice of lag vs. higher power ratings... albiet turbocharging technology has come a long way to reduce lag times in a variety of ways... i think vovlo had a variable compression ratio in one of thier inline 5 turbo motors... higher compression at low rpm for increased torque, and throttle responce, and lower compression once boost is built up. it is my understanding that flow charactaristics in most production intercoolers are not designed for much higher then stock ratings, particularly for prolonged use. 'heat soak' is less noticiable at lower densities, and flow rates... but the intercoolers' rate of thermal reduction is reduced by things such as internal low pressure zones, and low fluid flow areas... think of it somehwat like a vortex that gets larger with more pressure, and more heat that reduces the efficiency of the whole. all to often, aftermarket supercharging kits in particular advertise 'bolt on' when really, this is far from the best option... but this is also true of turbocharging as well. when increasing the air density, inherently heat will occur... added heat, added pressure... which then leads away from an optimum burn, and runing extra rich. this also makes sence when comparing engine re-mapping to turn up the boost with otherwise stock configurations. eventually, turning the boost up beyond injector, fuel pump, and pressure regulator capacity would cause extream lean burns, and damage the tops of cylinders and heads along with power losses... |
..you´re welcome guys :D
...a special THX to nthfinity THAT´S what i´ve been asking for and that´s all i´m expecting from PC visitors - great contribution and effort - hope that some other´s will do so in the future as well - there´ll be quite some more vids in here :wink: |
Great info nthfinity as usual :wink: . I still wasn’t clear though. Are you saying that there is no way around the lower reliability of turbo charging a car? I am not referring here to bolt on components but tuners like Ruf or RS Tuning that perform complete conversions.
It is obvious that higher boost and for that matter higher horsepower creates greater strains on the mechanical components of a car. But does lowering the temperature with larger intercoolers and other changes (i.e. stronger connecting rods, valves or whatever else they might do) that tuners make when increasing the boost offset the damaging affects of higher boost? Do Porsche engines come from the factory engineered to sustain the higher stresses that tuners place on them or do owners of tuned Porsches have to accept the fact that there is a trade off for the higher performance in the form of lower reliability? |
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i dont think it matters so much weather its just turbocharging a car, or other performance upgrades which would degrade the motor more rappidly even naturally aspirated. from reading material i have had, the highest performance motors seem to be designed to last 50,000 miles, unlike normal cars engines wich are now designed to last sometimes 200,000+ miles with proper maintanence. Quote:
unfortunately, heat isnt the only problem, as you mentioned. increaced power will induce much more stress all the way from the motor mounts/chassis, right through to the wheels, and everwhere in between. so replacing an iron connecting rod with a titanium one, forged sleves, will allow for extending the life of the part under higher strains, and make it more reliable. even further, sometimes a gain in performance is a trade off in material used to strengthen, or lighten... for example, Aluminum needs to be 4x thicker then steel to maintain the same strength. also, when mixing metals in an engine, advanced corrosion occurs at the contact points... so Titanium touching iron would corrode much faster then Iron touching Iron. Quote:
but costomers... and more often, tuners know that there is definately a trade off between product life, and increasing power. in the most extreme cases, a race car is basically designed for everything to work for one weekend. if a part is suspect to failure, then cirtainly extras are on hand... but a daily driver such as a 911 turbo is designed to last a great deal longer, and a variety of driving habbits and styles... the race car is just designed for where it is at, at any moment. cirtainly, everything in the race car is built with the utmost strength, and use of lightweight components, where there are more compforts in street cars, and lower tollerences at the cost of longetivity. one thing that really amazes me is how high the bar has risen in the last 5 years alone in high performance cars. who would have thought there would be so many cars available today with 400+hp? has materials cost finaly come down? or perhaps it has been the invention of new materials, computer modeling and simulation such as seen in finite element analysis programs? sorry for the lenghty responce... but i hope that makes some more sence. [/quote] |
…definitely, a customer can´t expect that his 650hp tuned engine will last as long as the 420hp one…
nevertheless, Porsche parts, and I think everyone who´s into automotive engineering will agree, are probably the best one´s in terms of reliability even when used at the racetrack, sure we had the PCCB issue, but well… :wink: so especially the engines and drive train parts are NOT sold at the peak of their potential, the have “quite some” potential left for some light modifications, nevertheless, PAG sent out “some” letter to “some” tuners because of the Cayenne – u know that there´re versions with 700hp and to say it, the 955 is NO sports car, so there were some major concerns on safety and reliability – I mean Porsche has to defend a reputation… …to quickly answer your question nthfinity – you´re right, production nowadays is way more efficient, new production processes are introduced – there´re own departments only dealing with such issues – and especially quality in production and materials are better, Wiedeking launched a major quality project in 02 resulting in cars like the MkII GT2 ( 483hp std. ) with slightly over 500hp tested on the rig… 8) |
Thanks for sharing nthfinity. Really insightful and interesting 8) .
I was really surprised to see that aluminum was weaker than steel. Had to look it up and your right steel can withstand 4 times the sheering forces than aluminum. I was really interested in your comment concerning some reading that suggested that extremely high performance engines are designed to last 50,000 miles :( . Could you provide some more detail on what you learned from the reading. Are they referring to McLaren F1’s BMW type engines and similar high powered supercars like the CGT or are they including in that GT2, 996 TT and GT3 RS engines? I’m not sure about the reliability of the more modern 911 engines but I know that the 3.2L engine was good for at least 200,000 before requiring a rebuild. Although it only produced 231 bhp in European specs. Quote:
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Wow it took me a really long time to write my response and after I posted it I realized that st-anger had already made some comments :oops: . That is a sure sign that life is getting a little too busy.
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i remember some time ago in PN, St-anger mentioned something about an 800 hp CGT... but i havent seen anything yet... it is crazy enough to think that Koenig placed a bi-turbo system in the high-strung F50 motor for an additional 350hp... i would be thinking that the 5.7 liter v10 may be able to do that more reliably naturally aspirated...? modify the heads and cams... shorter connecting rods... and without any added torque (mabey less) it could freely rev to 10,000rpms mabey?... to me, this might be a good option when comparing to the added stress in the drivedrain compared to the high torque values when turbocharging. Quote:
also, the stress over time causes micro fractures that build up, and eventually lead to a single part failing one time... then another part failing another time... so usually, its not just one part that will cause an early demise to an engine... it may be ball berring in a turbo one time, a tie rod another and so on... i think often, before massive mechanical failure, smaller failures would cause power losses. Quote:
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