Nissan vs. Porsche 997tt redux
01-29-2008, 11:32 PM
#1
Rennlist Member
Thread Starter
Nissan vs. Porsche 997tt redux
Spoke to a true Porsche tuning expert today who tells me a few things.
1. No 997tt tested to date on the dyno produces the advertised torque figures in the lower part of the rev range.
2. No 997tt SC tested to date provides overboost for the full ten seconds
3. 997ttSC overboost does not immediately come back after the first (nearly) 10 second blast until temps internally fall to predetermined safe levels. It's duration is then limited by temperature climb.
This suggests a reason that the GTR seems to get comparitively stronger as the laps go by- namely the Porsche is losing power due to heat build up. One of the American mags noted that pehnomenon, but didn't give the explanation.
My concern is that the SC function, coupled with brake torquing, is designed to give an artificial, fleeting advantage in 0-60 and 0-100 testing, but this vanishes on a track with multiple sequences of straight line acceleration. it also raises some concerns about the true value of variable vane turbo technology.
It is also disappointing that we may be at the end of the era of conservative power claims by Porsche, as the SC is more of a gimmick than a true power increase.
I'm bracing for the assault that is anticipated. AS
1. No 997tt tested to date on the dyno produces the advertised torque figures in the lower part of the rev range.
2. No 997tt SC tested to date provides overboost for the full ten seconds
3. 997ttSC overboost does not immediately come back after the first (nearly) 10 second blast until temps internally fall to predetermined safe levels. It's duration is then limited by temperature climb.
This suggests a reason that the GTR seems to get comparitively stronger as the laps go by- namely the Porsche is losing power due to heat build up. One of the American mags noted that pehnomenon, but didn't give the explanation.
My concern is that the SC function, coupled with brake torquing, is designed to give an artificial, fleeting advantage in 0-60 and 0-100 testing, but this vanishes on a track with multiple sequences of straight line acceleration. it also raises some concerns about the true value of variable vane turbo technology.
It is also disappointing that we may be at the end of the era of conservative power claims by Porsche, as the SC is more of a gimmick than a true power increase.
I'm bracing for the assault that is anticipated. AS
01-30-2008, 08:10 PM
#2
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Rennlist Member
Rennlist Member
This is to be expected since the VTG turbos are more sensitive to heat than a non-VTG turbo. The best way to maintain the advertised power of the VTG's is to reduce backpressure, which in turn will drop the EGT's to a safer level and allow more sustained power. I can tell you that on track my 997tt loses no power lap after lap even in the heat of July in Houston, but I have a free flowing exhaust and run 104 octane as added protection
01-30-2008, 09:09 PM
#3
Rennlist Member
Spoke to a true Porsche tuning expert today who tells me a few things.
1. No 997tt tested to date on the dyno produces the advertised torque figures in the lower part of the rev range.
2. No 997tt SC tested to date provides overboost for the full ten seconds
3. 997ttSC overboost does not immediately come back after the first (nearly) 10 second blast until temps internally fall to predetermined safe levels. It's duration is then limited by temperature climb.
This suggests a reason that the GTR seems to get comparitively stronger as the laps go by- namely the Porsche is losing power due to heat build up. One of the American mags noted that pehnomenon, but didn't give the explanation.
My concern is that the SC function, coupled with brake torquing, is designed to give an artificial, fleeting advantage in 0-60 and 0-100 testing, but this vanishes on a track with multiple sequences of straight line acceleration. it also raises some concerns about the true value of variable vane turbo technology.
It is also disappointing that we may be at the end of the era of conservative power claims by Porsche, as the SC is more of a gimmick than a true power increase.
I'm bracing for the assault that is anticipated. AS
1. No 997tt tested to date on the dyno produces the advertised torque figures in the lower part of the rev range.
2. No 997tt SC tested to date provides overboost for the full ten seconds
3. 997ttSC overboost does not immediately come back after the first (nearly) 10 second blast until temps internally fall to predetermined safe levels. It's duration is then limited by temperature climb.
This suggests a reason that the GTR seems to get comparitively stronger as the laps go by- namely the Porsche is losing power due to heat build up. One of the American mags noted that pehnomenon, but didn't give the explanation.
My concern is that the SC function, coupled with brake torquing, is designed to give an artificial, fleeting advantage in 0-60 and 0-100 testing, but this vanishes on a track with multiple sequences of straight line acceleration. it also raises some concerns about the true value of variable vane turbo technology.
It is also disappointing that we may be at the end of the era of conservative power claims by Porsche, as the SC is more of a gimmick than a true power increase.
I'm bracing for the assault that is anticipated. AS
01-30-2008, 09:18 PM
#4
Race Director
I read the same article during the "lighting lap" competition..... I can't remember which mag it was though....it was run at VIR using the longest course they have....C6 Z06 was top dog at a 2:58.....I think 997 GT3 was second at a 3:01....then a base Z51 vette at 3:03.....the Audi R8 and 997TT were tied around 3:04....they did mention that the 997TT would loose power at the temp climbed.....but I think they said that same thing about the Mustang GT500....
Since then they ran a 08 600hp Viper and it barely beat the Z06 with a 2:57 or something like that
Since then they ran a 08 600hp Viper and it barely beat the Z06 with a 2:57 or something like that
01-30-2008, 10:57 PM
#5
Rennlist Member
Thread Starter
Despite the advertised power boost, I don't think the 997ttSC is as quick as a 996ttX50 ( I have the latter and have driven the former). The C6ZO6 does not pull harder than my car stock, but does turn in better. I think the 997tt SC owners are going to need to do somenting to get rid of engine heat to make the car run the third lap as quiclky as the first.
All coments about "sliding is not the fast way around" ignore the fact that the 997tt slides. That is the way it is set up. So you might just be saying, "the 997tt is not set up to go around the fast way". That car will get the tail out on the street, which a 996tt will not do. AS
All coments about "sliding is not the fast way around" ignore the fact that the 997tt slides. That is the way it is set up. So you might just be saying, "the 997tt is not set up to go around the fast way". That car will get the tail out on the street, which a 996tt will not do. AS
01-31-2008, 07:27 AM
#6
That was on the grand east course, which is 4.2 miles long. After reading that article, one of rennlist's very own GT3 owners (and Potomac Red rungroup regular) went out and bought a new 2008 Z06. I won't reveal his user name, but will point him to this thread so he can comment.
The 2008 Z06 is a much different car than all previous Z06s. GM seemed to get rid of that dead steering feel that all previous C5-C6 vettes had. They also fixed the axles and rear end issues over the previous two years, stopped the tops from flying off, and revalved the shocks.
To add insult to injury, "our" friend is sending the car out for coil overs, more power and better brakes... I hear there's gonna be one tricked out track ready Z06 running around Culpeper Va. real soon!
Mike
The 2008 Z06 is a much different car than all previous Z06s. GM seemed to get rid of that dead steering feel that all previous C5-C6 vettes had. They also fixed the axles and rear end issues over the previous two years, stopped the tops from flying off, and revalved the shocks.
To add insult to injury, "our" friend is sending the car out for coil overs, more power and better brakes... I hear there's gonna be one tricked out track ready Z06 running around Culpeper Va. real soon!
Mike
Last edited by Mikelly; 01-31-2008 at 07:10 PM.
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01-31-2008, 12:13 PM
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I read the same article during the "lighting lap" competition..... I can't remember which mag it was though....it was run at VIR using the longest course they have....C6 Z06 was top dog at a 2:58.....I think 997 GT3 was second at a 3:01....then a base Z51 vette at 3:03.....the Audi R8 and 997TT were tied around 3:04....they did mention that the 997TT would loose power at the temp climbed.....but I think they said that same thing about the Mustang GT500....
Since then they ran a 08 600hp Viper and it barely beat the Z06 with a 2:57 or something like that
Since then they ran a 08 600hp Viper and it barely beat the Z06 with a 2:57 or something like that
http://www.caranddriver.com/features...-lap-2006.html
In the 2007 issue, the editors were also commenting on trail-throttle oversteer issue with the 997TT.
01-31-2008, 06:56 PM
#9
02-01-2008, 12:59 AM
#10
Rennlist Member
Thread Starter
http://www.caranddriver.com/features...-lap-2007.html
http://www.caranddriver.com/features...-lap-2006.html
In the 2007 issue, the editors were also commenting on trail-throttle oversteer issue with the 997TT.
http://www.caranddriver.com/features...-lap-2006.html
In the 2007 issue, the editors were also commenting on trail-throttle oversteer issue with the 997TT.
Personally, I think the compromises in cornering speed are engineered in to give more "rear drive" feel. I tmay be the automotive equivalent of the medical joke about "looks bad, feels good- you're a vagina" I hope I have a chance to try a GT2. AS