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Re: Car & Driver's 997TT -Many Pics and Info-
Quote:
Isaac said:
How often can I hit that button? Like after the 10 sec, can I hit it again and then again....? As the engine can handle 600hp (eg modified 996TT) without problem, it shouldn't be a problem, right?
Well it seems to me that it comes on only during wide open throttle and then it automatically lasts for 10 seconds, then it shuts off. I wonder if there is a time limit before it can be used again.
Re: Car & Driver's 997TT -Many Pics and Info-
Quote:
W8MM said:
I'm not very familiar with the exact circumstances under which specified power ratings are measured. The folowing is pure speculation:
What if the 997TT engine is specified @ 480 PS for steady-state power output? This would be AFTER the 10 seconds had elapsed. What if the extra .2 to .3 bar of boost during the 1st 10 seconds is in ADDITION to the 480 PS rating?
By definition, maximum engine power is measured at a given engine speed, the top of a "peaky" power curve. The engine has to be running at this speed at the instant of the measurement, which is probably what you meant by "steady state".
Max power is generally at an engine speed well above the max torque engine speed. For the 996 TT engine the torque curve was flat-topped over a wide rev band, but it dropped off well below the max power engine speed.
Quote:
W8MM said:
Wouldn't this arrangement make WAY over 500 PS during "boost phase"?
People should wait to see exactly how this works before bad mouthing how "underpowered" the 997TT will be. Particularly for stop-light grand prix!
Best acceleration is achieved by running the engine at highest torque output speeds (rpm) possible, by choosing the best available gear ratio for the momentary road speed. This means that max. acceleration at any given speed will generally be achieved at engine speeds below that at which max power is achieved. So you would not normally use max power in the stop-light Grand Prix.
If, as I believe, overboost has generally been used up until now to increase torque, then boost level would already have dropped off to "normal" value by the time an engine gets to max power rpm, so overboost feature would not increase the max power output.
Re: Car & Driver's 997TT -Many Pics and Info-
Quote:
fritz said:
If, as I believe, overboost has generally been used up until now to increase torque, then boost level would already have dropped off to "normal" value by the time an engine gets to max power rpm, so overboost feature would not increase the max power output.
Fritz,
I guess I didn't make myself completely clear.
AFAIK, the overboost scenarios with which I'm familiar increase the boost by some amount all across the RPM range. Perhaps the increase is not by the same amount at every engine speed; maybe more excess boost lower in RPM and less boost increase at higher engine speed.
What I'm wondering is if the 10-second boost increase condition is "in session" during the dyno runs to certify the pferde staerke values, or whether the "official" dyno-run data is taken after the boosty trick has timed out, and run its course.
Is that better?
Re: Car & Driver's 997TT -Many Pics and Info-
Quote:
W8MM said:
Fritz,
I guess I didn't make myself completely clear.
AFAIK, the overboost scenarios with which I'm familiar increase the boost by some amount all across the RPM range. Perhaps the increase is not by the same amount at every engine speed; maybe more excess boost lower in RPM and less boost increase at higher engine speed.
What I'm wondering is if the 10-second boost increase condition is "in session" during the dyno runs to certify the pferde staerke values, or whether the "official" dyno-run data is taken after the boosty trick has timed out, and run its course.
Is that better?
Gottit!
Whilst I also don't really know for sure, I always thought of overboost as being a "temporary" thing to increase torque at more moderate rpm, to facilitate overtaking, for example. When first such systems where introduced (in the mid-80s?), I doubt that control systems were sophisticated enough to allow the variable boost levels you describe.
But, as I think you said, we're just speculating.
As far as the 997 TT's system is concerned, we'll just have to wait until more information is released.
Re: Car & Driver's 997TT -Many Pics and Info-
Quote:
fritz said:Quote:
W8MM said:
Fritz,
I guess I didn't make myself completely clear.
AFAIK, the overboost scenarios with which I'm familiar increase the boost by some amount all across the RPM range. Perhaps the increase is not by the same amount at every engine speed; maybe more excess boost lower in RPM and less boost increase at higher engine speed.
What I'm wondering is if the 10-second boost increase condition is "in session" during the dyno runs to certify the pferde staerke values, or whether the "official" dyno-run data is taken after the boosty trick has timed out, and run its course.
Is that better?
Gottit!
Whilst I also don't really know for sure, I always thought of overboost as being a "temporary" thing to increase torque at more moderate rpm, to facilitate overtaking, for example. When first such systems where introduced (in the mid-80s?), I doubt that control systems were sophisticated enough to allow the variable boost levels you describe.
But, as I think you said, we're just speculating.
As far as the 997 TT's system is concerned, we'll just have to wait until more information is released.
While this is all mere idle speculation (the best kind of speculation
), I bet overboost will be programmed in to the Bosch-Motronic ECU engine map, for specific torque gains at specific rpm's (and gears), rather than being driver-controlled (independent of the right foot throttle control at given rpm's and gears ).As an aside, I assume the difference between the C&D claim of 473 peak HP and the "rumoured" 480 is that 480 is in "PS" units (German for Pferdestaerke or "horse strength"), the DIN (Deutsches Institut fuer Normung) unit mathematically different from the British HP unit or now the SAE (Society of Automotive Engineers) net HP figure (flywheel HP, with accessories included with standard intake and exhaust systems). I believe it was in 1992 when the PS unit was rendered obsolete by EEC directives, replaced "officially" with the metric kilowatt (kW), but since people have a ready familiarity with "horsepower," it is still used for markting purposes-as we all obsess about 500HP on a 997TT.
Since 1 PS = 0.9863201652997627 SAE hp (give or take a few trillionths of a point
), 480 PS = 473.4 SAE hp, and voila, the 997TT gets the "rumoured" 480 "horsepower" in German Pferdestaerke , OR 473 SAE ponies. This post begs for Fritz's erudite contribution
Re: Car & Driver's 997TT -Many Pics and Info-
Quote:
Turbo Al said:
This post begs for Fritz's erudite contribution
Don't tell him I told you this, but after looking up "erudite" in the dictionary, fritz said he wasn't even going to try to live up to that, mumbled something about having to make an early start tomorrow, chickened out and went to bed.
He was in such a hurry, he forgot to log out.
fritz's dog
Re: Car & Driver's 997TT -Many Pics and Info-
Quote:
Turbo Al said:
While this is all mere idle speculation (the best kind of speculation
I agree, Al. I also think the 10 second limit is going to be irrelevant in most cases.
I think each time you shift and release the gas, the 10 sec. limit is reset. I think it's very difficult in a car like the 997TT to be on full boost for 10 seconds straight, unless you floor it in 6th gear from a low speed (not good for acceleration anyways). So, you should be able to go through the gears without losing the overboost, as long as you shift correctly and not at a premature rpm. I guess, you might stay at full boost in 6th gear for over 10 sec. if you try to go 190mph. Then the overboost might cut-out (got to preserve the highest top-speed for the 997TTS and GT2...)
Re: Car & Driver's 997TT -Many Pics and Info-
Quote:
Grant said:Quote:
Turbo Al said:
While this is all mere idle speculation (the best kind of speculation
I agree, Al. I also think the 10 second limit is going to be irrelevant in most cases.
I think each time you shift and release the gas, the 10 sec. limit is reset. I think it's very difficult in a car like the 997TT to be on full boost for 10 seconds straight, unless you floor it in 6th gear from a low speed (not good for acceleration anyways). So, you should be able to go through the gears without losing the overboost, as long as you shift correctly and not at a premature rpm. I guess, you might stay at full boost in 6th gear for over 10 sec. if you try to go 190mph. Then the overboost might cut-out (got to preserve the highest top-speed for the 997TTS and GT2...)
Yep,
And that overboost-either pneumatic or electrical (and if the latter could it be Borg Warner's patented eBooster?)-could make for some fearsome acceleration times, especially when combined with the VTG's, sort of like perpetual dual forced induction-again, I CAN'T WAIT TO SEE THAT TORQUE CURVE on the official specs.
Re: Car & Driver's 997TT -Many Pics and Info-
sorry fritz, but that is not true. you get the maximum acceleration when the engine gives you its maximum power and you are in the best gear!
power = rpm * torque / const.
i think this makes it clear.
take an "old" 996TT. this car has 560nm from 2700 to ~4500rpm, right? so where does it accelerate better, at 3000rpm or at 4500rpm or maybe at ~5800rpm? ;-)
and this fourmular is the key to understand the meaning of torque and at which rpm you need it.
power = rpm * torque / const.
i think this makes it clear.
take an "old" 996TT. this car has 560nm from 2700 to ~4500rpm, right? so where does it accelerate better, at 3000rpm or at 4500rpm or maybe at ~5800rpm? ;-)
and this fourmular is the key to understand the meaning of torque and at which rpm you need it.
Re: Car & Driver's 997TT -Many Pics and Info-
1 nm @ 7023,5rpm = 1ps
so the constant is 7023,5
very easy ;-)
example:
100nm @3000rpm generate less power than 100nm@6000rpm
(42,7hp vs 85,4hp)
so the constant is 7023,5
very easy ;-)
example:
100nm @3000rpm generate less power than 100nm@6000rpm
(42,7hp vs 85,4hp)
Re: Car & Driver's 997TT -Many Pics and Info-
Quote:
How about this : 680 Nm - 1950-5000 1/rpm
OK, I was a bit optimistic there.
We now know that there is 562 Nm
on tap at max power 480 HP/6000 RPM
A new estimate would be 680Nm - 1950-4500.
630 Nm at 5200/RPM
600 Nm 1600/RPM
More than 600 Nm between 1600-5500/RPM
Jan 29, 2006 1:55:44 AM
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Reply to:
RC
Re: Car & Driver's 997TT Test Drive!!!! -Many PICS-
Quote:
RC said:
2. the Turbo S has traditionally always been the variant Porsche offers at the end of a model lifecycle. It will be the same with the 997 Turbo S.
Traditionally they offer it for the last year and a bit of the models production 993 Turbo S 97-98; 996 Turbo S 05-06. But what makes it complicated is that the Cayenne Turbo S is already here and we havent even had a facelift and production will only end at around 2009.
I am expecting 997 production to end in 2011, but if they bring Turbo S introduction earlier it wont be as much as the Cayenne as a 911 Turbo has a higher priority in keeping market value as they are more likely to be bought as investments aspecially a Turbo S. I still think the earliest is firs quarter 2009I think only with time we will see as Porsche is changing the traditionall product launch periods with the 9x7 model range.
Quote:
jrlcarrera1 said:
No need to get personal...or defensive
Sorry if I sounded harsh, but I hate when people complain about Porsche figures on paper aspecially Bhp. Porsche dont care about figures on paper, its the whole package that makes a fast car. Look at the Car and Driver test with the Ford GT; SL65; Gayardo(sorry aout spelling); F430; DB9 and finally 450Bhp Turbo S cab being the second lowest powerd car it was still second fastest behind the 550Bhp GT.
Re: Car & Driver's 997TT -Many Pics and Info-
Quote:
guy2 said:
look at it this way:
680nm @ 2000rpm = 193hp
680nm @ 3000rpm = 290hp
680nm @ 4000rpm = 386hp
680nm @ 4500rpm = 435hp
so the new 997TT will have more power at 4500rpm than the old 996TT at maximum power. and there are still >2000rpm left
Finally somebody who seem to understand the "potential" of the new 997 Turbo.
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