Crown

Board: Porsche - 911 - 997 Language: English Region: Worldwide Share/Save/Bookmark Close

Forum - Thread


    GT3 115 bhp/L

    Stupid question I'm sure, but can anyone please explain to a layman like me why a GT3 with a 3.6L engine can produce 415bhp (115bhp/L) and a Carrera S with a 3.8L engine can only push out 355bhp (92bhp/L). Even with the Porsche Powerkit the Carrera S only goes up to 99bhp/L.

    So what 'magic' has Porsche used to achieve this in the GT3?

    By the same measure a 3.8L GT3 should push out 440bhp given the same 115bhp/L. Makes me feel very short changed on my 355bhp 3.8L Carrera S!

    Re: GT3 115 bhp/L

    BTW - my Audi S3 (1.8L 250bhp) pushes out 140bhp/L so I'm sure the Turbo has a lot of tuning headroom too!

    Re: GT3 115 bhp/L

    More aggressive cam profiles, better flowing heads, etc.

    Re: GT3 115 bhp/L

    I think what this shows is that Porsche is designing to a market. If Porsche wanted more hp out of the CS then I'm sure they could do it. Really what we all want it for every model to have more hp then anything and everything else out there. As we all know this is not Porsche's thing....

    Re: GT3 115 bhp/L

    Quote:
    Alex (UK) said:
    So what 'magic' has Porsche used to achieve this in the GT3?


    The way to do that (other than forced induction) is with revs. GT3 revs to 8,400 and has the necessary hardware (like Titanium conrods) to do it. Carrera/S only revs to 7,200...

    Re: GT3 115 bhp/L

    Quote:
    bstew said:
    I think what this shows is that Porsche is designing to a market.



    Of course they are!

    Getting more peak HP out of a given normally aspirated motor ordinarily means giving up some low-end torque.

    If the low-end torque goes away, one will have to "row the gear box" harder to take full advantage of any increased power. It changes he personality of the car, making it more peaky and less "luxurious" to drive.

    Unless one likes to shift as a hobby, the extra peak power doesn't always translate into increased performance. One has to integrate the area under the torque curve between the shift points in RPM to see how much velocity will be gained in a given gear.

    It's easily possible for an engine with a broad torque curve (and lower peak power) to out accelerate another with a peaky torque characteristic if the shift points or the transmission gearing are not perfectly suited to the situation.

    All these BHP/liter comparisons are great entertainment for bench racers, but the real world is so much more complicated.

    Re: GT3 115 bhp/L

    Quote:
    Grant said:
    The way to do that (other than forced induction) is with revs. GT3 revs to 8,400 and has the necessary hardware (like Titanium conrods) to do it. Carrera only revs to 7,200...



    So does that mean the 997 GT3 revs much higher than the old 996 GT3 given that produced 381bhp?

    I guess it's a big combination of things if not...

    Re: GT3 115 bhp/L

    Actually, your table clearly shows that Porsche is offering lots of choices to the market on how much power, and in what configuration, you want.

    You want more power, you pay more money.

    Re: GT3 115 bhp/L

    I realize bhp/L is not the best measure of how tuned a car is (especially for non-normally-aspirated cars) but just for my own curiosity I looked up some others for comparison:

    I have greyed out the Turbo cars as they don't really count...

    Re: GT3 115 bhp/L

    Quote:
    Alex (UK) said:
    Quote:
    Grant said:
    The way to do that (other than forced induction) is with revs. GT3 revs to 8,400 and has the necessary hardware (like Titanium conrods) to do it. Carrera only revs to 7,200...



    So does that mean the 997 GT3 revs much higher than the old 996 GT3 given that produced 381bhp?

    I guess it's a big combination of things if not...


    Yes, the original GT3 (99-01) revved to 7,600 or 7,800 (don't remember) for 360hp and the MkII revved to 8,200 for 380hp and the 997 revs to 8,400 for 415hp. Certainly, there are other improvements, but since they kept the displacement the same, the revs are the biggest improvement (along with more compression and better breathing).

    Re: GT3 115 bhp/L

    Interesting thanks Grant

    Re: GT3 115 bhp/L

    Quote:
    Alex (UK) said:
    Interesting thanks Grant


    No problem. Also, it should be noted that getting more power out of a motor like a GT3 is not as simple as raising the electronic rev limit.

    Revs create alot of stress in a motor. I believe that the forces created are related to the moving mass times the square of the speed of its parts (a motor that revs twice as high will have 4 times the stress, assuming everything else is equal). So, the engineers need to make large strides in reducing the mass of the moving parts to accommodate the higher piston speeds without causing additional stress (and shorter engine life).

    So, if you want to raise engine speed 40%, you need to cut the moving mass in half to keep the same forces on the bearings, rods, etc...(square root of 2 is about 1.4)

    Re: GT3 115 bhp/L

    F1: 3.0L . 800hp+ :-)

    Re: GT3 115 bhp/L

    Quote:
    Grant said:
    Quote:
    Alex (UK) said:
    Interesting thanks Grant


    No problem. Also, it should be noted that getting more power out of a motor like a GT3 is not as simple as raising the electronic rev limit.

    Revs create alot of stress in a motor. I believe that the forces created are related to the moving mass times the square of the speed of its parts (a motor that revs twice as high will have 4 times the stress, assuming everything else is equal). So, the engineers need to make large strides in reducing the mass of the moving parts to accommodate the higher piston speeds without causing additional stress (and shorter engine life).

    So, if you want to raise engine speed 40%, you need to cut the moving mass in half to keep the same forces on the bearings, rods, etc...(square root of 2 is about 1.4)



    ... and then, since you'll have to reinforce the bearings, rods, etc. anyway because you can't actually get there, you once again INCREASE the mass - creating more stress.

    Engineering is actually hard

    Re: GT3 115 bhp/L

    Quote:
    Jeannot said:
    F1: 3.0L . 800hp+ :-)


    Yes, and about 20,000rpm

    Re: GT3 115 bhp/L

    The 997 GT3 invested most of its "upgrades" over the 996 in terms of lowering moveable mass to allow for the engine to rev much higher...

    Most of the cars on that list need to be driven hard to extract that juice (as W8MM said). If you take two comperably powerful cars, one with low displacement and the other with more displacement, the higher bhp/l car will beat the other on a track, but for daily driving, you better be ready to either downshift a lot or keep the revs real high (GT3, Lotus, S2000)...

    Re: GT3 115 bhp/L

    It's worth noting that the Carrera/S have a totally different engine to thye GT3. More interesting though, Suzuki GSXR1000 has 185bhp from 1ltr without a hair dryer. Even better though, the BMW FI turbo cars had 1500 Bhp from 1.5ltrs with the boost wound up for qualifing!!! They were however hand grenades with the pins out!

    Re: GT3 115 bhp/L

    My dad's 3.0ltr RSR clone makes 385 hp (128 hp/ltr) at 8350 rpm and redline is set at 9100 rpm. It also has Ti con rods, Ti valves, very trick heads, a hot hot cam, high stacks, electronic fuel injection with individual injectors and the case is polished almost to a mirror finish. The engine also only lasts 45-50 hours between refreshes... I guess low stress equals long life, and a production motor can't have too much stress, what with warrantees and all. 415hp out of a 3.6ltr engine and reliability is quite a feat IMHO. Remember a Viper engine at 500 cubic inches is an 8.2 liter engine and still only makes 500hp!

    Re: GT3 115 bhp/L

    Quote:
    Mithras said:
    My dad's 3.0ltr RSR clone makes 385 hp (128 hp/ltr) at 8350 rpm and redline is set at 9100 rpm. It also has Ti con rods, Ti valves, very trick heads, a hot hot cam, high stacks, electronic fuel injection with individual injectors and the case is polished almost to a mirror finish. The engine also only lasts 45-50 hours between refreshes...


    Please post photos

    Re: GT3 115 bhp/L

    Quote:
    Mithras said:
    My dad's 3.0ltr RSR clone makes 385 hp (128 hp/ltr) at 8350 rpm and redline is set at 9100 rpm. It also has Ti con rods, Ti valves, very trick heads, a hot hot cam, high stacks, electronic fuel injection with individual injectors and the case is polished almost to a mirror finish. The engine also only lasts 45-50 hours between refreshes... I guess low stress equals long life, and a production motor can't have too much stress, what with warrantees and all. 415hp out of a 3.6ltr engine and reliability is quite a feat IMHO. Remember a Viper engine at 500 cubic inches is an 8.2 liter engine and still only makes 500hp!



    Yes please some photos!!!

    Re: GT3 115 bhp/L

    Grant, I know you have posted pics from your beauty before but would you mind putting the link to them again?

    Re: GT3 115 bhp/L

    Quote:
    rhino said:
    Grant, I know you have posted pics from your beauty before but would you mind putting the link to them again?


    Well, twist my arm

    Re: GT3 115 bhp/L

    inside

    Re: GT3 115 bhp/L

    engine

    Re: GT3 115 bhp/L

    trunk

    Re: GT3 115 bhp/L

    gearbox through rear window

    Re: GT3 115 bhp/L

    Quote:
    Grant said:
    Quote:
    Mithras said:
    My dad's 3.0ltr RSR clone makes 385 hp (128 hp/ltr) at 8350 rpm and redline is set at 9100 rpm. It also has Ti con rods, Ti valves, very trick heads, a hot hot cam, high stacks, electronic fuel injection with individual injectors and the case is polished almost to a mirror finish. The engine also only lasts 45-50 hours between refreshes...


    Please post photos



    Sorry, no pictures of the engine at my office, but here are a couple of it running. Though it's a little different now, we had the head aerodynamisist from Multi-matic go through the car and it's a bit wider in the front and much more streamlined. Looks like a beast now (and will still hit 172mph going into the bus-stop at the Glen)

    Re: GT3 115 bhp/L

    more

    Re: GT3 115 bhp/L

    last

    Re: GT3 115 bhp/L

    Nice! Please post engine photos too when possible - much appreciated!

     
    Edit

    Forum

    Board Subject Last post Rating Views Replies
    Porsche Sticky OFFICIAL: New 991.2 GT3 (2017) 1/3/19 8:54 AM
    Porker
    417074 5218
    Porsche Sticky SUN'S LAST RUN TO WILSON, WY - 991 C2S CAB LIFE, END OF AN ERA 12/30/18 7:55 PM
    RCA
    327559 2018
    Porsche Sticky The moment I've been waiting for... 12/8/18 8:33 AM
    Joost
     
     
     
     
     
    214852 1083
    Porsche Sticky OFFICIAL: 911 GT2 RS (2017) 1/20/19 9:53 AM
    GaussM
    212706 2772
    Porsche Sticky OFFICIAL: 991.2 GT3 RS (2018) 1/19/19 5:48 PM
    WhoopsyM
    139020 2521
    Porsche Sticky OFFICIAL: The new Porsche 992 – a design icon and high-tech sports car 1/20/19 1:25 PM
    BiTurbo
    41399 574
    AMG Sticky Mercedes E63 S AMG (2018) - Short Review (updated on a regular basis) 1/16/19 10:53 PM
    Leawood911
    39382 383
    Porsche Sticky Paint protection film 9/25/18 6:14 PM
    throt
    15056 121
    Porsche Sticky Child seats in a 991 11/29/18 3:43 PM
    RCA
    14324 35
    Porsche Sticky OFFICIAL: 992 Carrera Cabriolet 1/17/19 3:54 PM
    Lars997M
    4355 43
    Porsche Sticky OFFICIAL: The new Porsche 718 T (Boxster & Cayman) 12/29/18 7:17 PM
    spudgun
    3584 27
    Porsche OFFICIAL: 991 Turbo and Turbo S 1/4/19 7:02 PM
    Topspeed
    485823 4255
    Porsche 992 (Next 911 generation 2019/2020) Thread Closed 11/29/18 11:38 AM
    RCA
    308746 3195
    Porsche OFFICIAL: 911 R (2016) 12/31/18 2:19 AM
    DJM48
    284685 2598
    Porsche Cayman GT4 1/7/19 7:33 PM
    Carlos from SpainM
    271967 2653
    Ferrari 488 GTB/GTS 1/17/19 8:13 PM
    GoHardGT3RS
    194428 1789
    Porsche OFFICIAL: New 991.2 Turbo and Turbo S 1/23/18 12:27 AM
    RCA
    193151 1074
    McLaren McLaren on a winning streak 1/14/19 8:04 PM
    TB993tt
    188359 3331
    Others Audi R8 V10 Plus (2016 model) - Review (updated Feb 13th 2017) 12/17/18 12:42 PM
    RCA
    155678 2491
    Porsche Boxster Spyder (981) 8/31/18 10:25 AM
    WAY
    144061 757
    Ferrari Ferrari F12 Berlinetta / 599 GTO Successor 5/22/18 9:16 PM
    RCA
    112568 789
    Others VW caught cheating emissions tests 5/3/18 7:52 PM
    CGX car nut
    107400 871
    Porsche Porsche Mission E - the future of Porsche? 1/19/19 7:40 PM
    Pentium
    94625 1317
    Porsche Donor vehicle for Singer Vehicle Design 12/7/18 10:15 PM
    Boxster Coupe GTS
    68149 673
    Porsche UPDATES: 2018 Porsche Cayenne 2/6/18 2:13 PM
    RCA
    57979 423
    Others Tesla Roadster 1/19/19 10:56 PM
    DJM48
    51443 1570
    Porsche OFFICIAL: New 991.2 Carrera GTS models 11/3/18 11:09 AM
    bluelines
    47885 477
    Others Tesla Model X Thread Closed 2/23/18 3:41 PM
    RCA
    43262 1122
    AMG AMG GT R 11/30/18 4:10 PM
    RCA
    42743 605
    Lambo Aventador and SV 11/19/18 8:31 AM
    RCA
    40298 472
    274 items found, displaying 1 to 30.