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Porsche 911 Turbo/GT2 vs. GT3

post #1 of 52
3/9/10 at 3:20am
Thread Starter 
I haven't been able to find a satisfactory answer to this, but if the GT3 RS is such a beast, why is the GT2 or Turbo so much faster in a straight line? (I get that performance doesn't equal straight-line speed.) Why couldn't they just make the GT3 as insanely fast as a Turbo?
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post #2 of 52
3/9/10 at 3:52am
Quote:
Originally Posted by leftover_salmon View Post
I haven't been able to find a satisfactory answer to this, but if the GT3 RS is such a beast, why is the GT2 or Turbo so much faster in a straight line? (I get that performance doesn't equal straight-line speed.) Why couldn't they just make the GT3 as insanely fast as a Turbo?

An insanly fast car is even more insanely difficult to control in a curve....straight line speed is cheap...holding that same car thru a turn....priceless.

Regards.
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post #3 of 52
3/9/10 at 4:21am
Also to be in the gt3 class I think is must remain normally aspirated.
The turbo/gt2 kill it in a straight line because they have two turbo's, however, either way you look at it Porsches don't tolerate idiots,
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post #4 of 52
3/9/10 at 4:30am
Quote:
Originally Posted by leftover_salmon View Post
I haven't been able to find a satisfactory answer to this, but if the GT3 RS is such a beast, why is the GT2 or Turbo so much faster in a straight line? (I get that performance doesn't equal straight-line speed.) Why couldn't they just make the GT3 as insanely fast as a Turbo?
Do you mean, technically/engineering wise why is it slower? Or philosophically, why does it exist? It's technically slower because it doesn't have a turbocharger (or two). Thus, it has to 'make due' with what, 380 hp in the last version and 450hp in the new version. This, compared to 475hp in the 996 and 520 hp in the 997 versions of the GT2. And one of the key ingredients in acceleration is horsepower. Along with traction, and weight. The GT2 has more horsepower, the Turbo has both more horsepower and better traction. It's philosophically slower because Porsche needs a base vehicle to homologate their successful racing business, and most of the classes they race in will not homologate a Porsche Turbo. So as long as they want to beat up on unibody BMW M3s and V8 Ferraris, they have to build a racy, naturally aspirated car. Turbo 993s used to occasionally race against Vipers, Corvette C5Rs, Saleen S7s, etc and (at least in the US) . . . didn't fare very well. This does, of course, have as much to do with who writes the rules as the technical capability of a certain platform.
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post #5 of 52
3/9/10 at 12:13pm
Lots of positive attributes on a track don't play so well on a real-world freeway
And every aspect of engineering has trade-offs, so no one perf car is unquestionably superior in all (or even most) scenarios

GT2 and TT have far more tq than GT3 for real-world mid-range accel
GT2 has more tq than TT but more turbo lag
Many track drivers don't like turbo lag/nonlinearity as it can upset chassis balance; and need less tq on a track when driving cars at higher RPMs (in a different style than on public rds)
Some lighter cars w/super-precise steering and chassis calibrated for smooth twisties or tracks prove shaky/non-confidence-inspiring in high-speed stability on a real-world freeway w/bumpy stretches, damp patches, crosswinds, narrow lanes, other cars nearby, etc
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post #6 of 52
3/9/10 at 3:18pm
Quote:
Originally Posted by sw20 View Post
Lots of positive attributes on a track don't play so well on a real-world freeway
And every aspect of engineering has trade-offs, so no one perf car is unquestionably superior in all (or even most) scenarios

GT2 and TT have far more tq than GT3 for real-world mid-range accel
GT2 has more tq than TT but more turbo lag
Many track drivers don't like turbo lag/nonlinearity as it can upset chassis balance; and need less tq on a track when driving cars at higher RPMs (in a different style than on public rds)
Some lighter cars w/super-precise steering and chassis calibrated for smooth twisties or tracks prove shaky/non-confidence-inspiring in high-speed stability on a real-world freeway w/bumpy stretches, damp patches, crosswinds, narrow lanes, other cars nearby, etc

Good explanation.

I would also add that NA is quicker to respond to inputs and accelerates much quicker coming out of a corner. Get in a track with a series of twisties and the turbo can never quite build it's boost and by the time they are out of the twisties it's lost 30 ft to the NA car.
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post #7 of 52
3/12/10 at 1:31am
Quote:
Originally Posted by turboman808 View Post
Good explanation.

I would also add that NA is quicker to respond to inputs and accelerates much quicker coming out of a corner. Get in a track with a series of twisties and the turbo can never quite build it's boost and by the time they are out of the twisties it's lost 30 ft to the NA car.

Accelerating out of corners has everything to do with torque and grip and nothing to do with N/A or Turbo. If you know how to use a turbo motor, you can keep it in the boost range and be just as responsive as N/A.
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post #8 of 52
3/12/10 at 2:03am
Quote:
Originally Posted by maomao1980 View Post
Accelerating out of corners has everything to do with torque and grip and nothing to do with N/A or Turbo. If you know how to use a turbo motor, you can keep it in the boost range and be just as responsive as N/A.

+1. Left-foot braking can help keep the turbos spooled up.

--Andre
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post #9 of 52
3/12/10 at 6:18am
Quote:
Originally Posted by A Y View Post
+1. Left-foot braking can help keep the turbos spooled up.

--Andre

?
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post #10 of 52
3/12/10 at 7:08am
He means keeping your right foot on the accelerator to keep the engine revs up, and thus the turbocharger spinning. Your left foot takes care of the braking.

Another related technique is heel-and-toe'ing. This involves using the edge (toe) of your right foot to brake, whilst using the heel to accelerate, enabling you to rev-match your downchanges and maintain a smoother balance through corners - this also allows you to keep the engine revs in the power-band whilst dropping your actual roadspeed.

There are several YouTube videos illustrating all of the above.
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post #11 of 52
3/12/10 at 7:23am
Quote:
Originally Posted by Sherlockian View Post
He means keeping your right foot on the accelerator to keep the engine revs up, and thus the turbocharger spinning. Your left foot takes care of the braking.

Another related technique is heel-and-toe'ing. This involves using the edge (toe) of your right foot to brake, whilst using the heel to accelerate, enabling you to rev-match your downchanges and maintain a smoother balance through corners - this also allows you to keep the engine revs in the power-band whilst dropping your actual roadspeed.

There are several YouTube videos illustrating all of the above.

I assume we are not talking about manual transmission? If not, these cars like the GT3 and GT2 don't rev match automatically?
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post #12 of 52
3/12/10 at 7:53am
I was talking about manual transmission. I guess some of the newer kinds of shift will do a throttle blip for you; they're not my bag, so I haven't driven one to be able to comment.

I would personally prefer a car as driver-oriented as the GT3 / GT3 RS to leave everything up to the driver. IMHO testing and practising your skills is a big part of the driving experience in a track environment. I can't honestly see why someone would choose the GT3 over the Turbo or GT2 if they're going to use it primarily for road driving.
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post #13 of 52
3/12/10 at 9:27am
Quote:
Originally Posted by Sherlockian View Post
I was talking about manual transmission. I guess some of the newer kinds of shift will do a throttle blip for you; they're not my bag, so I haven't driven one to be able to comment.

I would personally prefer a car as driver-oriented as the GT3 / GT3 RS to leave everything up to the driver. IMHO testing and practising your skills is a big part of the driving experience in a track environment. I can't honestly see why someone would choose the GT3 over the Turbo or GT2 if they're going to use it primarily for road driving.

left foot braking + blipping the the throttle without the clutch on a production car can be done, but it would be really rough on the transmission.

It sounded the like the post above was referring to left foot braking + blipping the throttle without necessarily changing gears, but that sounded weird to me, as braking + throttle should not be pressed at the same time (in gear) if you want to go fast (stopping + accelerating = extremely inefficient).
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post #14 of 52
3/12/10 at 10:34am
When looking at straight-line speed there are three main factors, BHP and drag and gear ratio's. More drag means better cornering but slower straight-line speed. And remember the faster you go the more BHP you need is exponential. 500bhp may get a M5 to 200mph, but it takes 1000bhp to get a Veyron to 250mph, yet similarly 200bhp will get an old 328 to 150mph. 100bhp -> 115mph - Most cars 200bhp -> 150mph - BMW 328 500bhp -> 200mph - BMW M5 1000bhp -> 250mph - Veyron
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post #15 of 52
3/12/10 at 10:46am
walter röhrl favors the GT3
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