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    Cayman S engine

    It has been well discussed here at Rennteam that the Cayman S's 3.4- liter flat-six engine is mildly tuned or detuned to keep the Cayman S from stealing sales from the more profitable 997.

    Here are the facts:

    Boxster S, Cayman S, 911 Carrera

    Camshaft adjustment:

    VarioCam, VarioCam Plus, VarioCam Plus

    Bore:

    93 mm, 96 mm, 96 mm

    Stroke:

    78 mm, 78 mm, 82.8 mm

    Displacement:

    3.2- liter, 3.4- liter, 3.6 liter

    Power output:

    280 hp, 295 hp, 325 hp

    Volumetric efficiency:

    88.1 hp/l, 87.1 hp/l, 90.4 hp/l

    While the Cayman S's flat-six engine is 200 cc larger than the Boxter S engine, has VarioCam Plus, 997 cylinder heads, 997S profile camshafts; it produces only 15 hp more, and its volumetric efficiency decreases from 88.1 hp/l to 87.1 hp/l.

    Chip tuners are currently developing chips for the Cayman S. Has anyone at Rennteam used a tuning chip on any Porsche?

    Re: Cayman S engine

    Quote:
    HHG said:While the Cayman S's flat-six engine is 200 cc larger than the Boxter S engine, has VarioCam Plus, 997 cylinder heads, 997S profile camshafts; it produces only 15 hp more, and its volumetric efficiency decreases from 88.1 hp/l to 87.1 hp/l.


    If you were able to increase efficiency to the same level of the 997 (90.4 hp/L), you would gain 11 hp, not exactly earth-shattering. I would skip the chip. 11hp is not worth losing your warranty...

    Re: Cayman S engine

    Torque and the torque/rpm profile are just as important for normal driving as power, if not more important.

    Re: Cayman S engine

    Quote:
    KenH said:
    Torque and the torque/rpm profile are just as important for normal driving as power, if not more important.



    True, BUT, power and torque are interdependent, because the more power an engine can produce, the greater potential torque it can generate for rotation to turn the wheels via the transaxle. Since power = force exerted over a given time over a distance (or in this case, force exerted for rotation), and torque = the product of force and lever-arm distance producing rotation, for a given drivetrain with a transmission and transaxle, the greater the potential power generated, the greater the potential torque produced. This is also dependent on engine rev's, so torque tends to peak before power does for each gear. So, all things being equal for the CaymanS, if peak HP is limited, then peak torque will be, as well, which will limit its performance. Perhaps the automotive technical experts (Fritz, et al) can jump in here, as well.

    Re: Cayman S engine

    Quote:
    KenH said:
    Torque and the torque/rpm profile are just as important for normal driving as power, if not more important.



    The torque curve is flat from 4400 to 6000 rpm (252 lbft). Porsche must have programmed the engine management system to limit the top power to the lowest possible output across this band (4400 to 6000 rpm) or lower.

    Re: Cayman S engine

    Quote:
    HHG said:
    Quote:
    KenH said:
    Torque and the torque/rpm profile are just as important for normal driving as power, if not more important.



    The torque curve is flat from 4400 to 6000 rpm (252 lbft). Porsche must have programmed the engine management system to limit the top power to the lowest possible output across this band (4400 to 6000 rpm) or lower.



    KenH,

    I am not canceling my Cayman S order nor am I going to put a tuned chip in it. I have my on reasons for liking the Cayman S and outrunning a 911 is not one of them. If I wanted to do that, I would have ordered a Z06.

    Re: Cayman S engine

    Quote:
    HHG said:
    I have my on reasons for liking the Cayman S and outrunning a 911 is not one of them. If I wanted to do that, I would have ordered a Z06.



    Good point.

    Re: Cayman S engine

    Quote:
    Al Pettee said:
    Quote:
    KenH said:
    Torque and the torque/rpm profile are just as important for normal driving as power, if not more important.



    True, BUT, power and torque are interdependent, because the more power an engine can produce, the greater potential torque it can generate for rotation to turn the wheels via the transaxle. Since power = force exerted over a given time over a distance (or in this case, force exerted for rotation), and torque = the product of force and lever-arm distance producing rotation, for a given drivetrain with a transmission and transaxle, the greater the potential power generated, the greater the potential torque produced. This is also dependent on engine rev's, so torque tends to peak before power does for each gear. So, all things being equal for the CaymanS, if peak HP is limited, then peak torque will be, as well, which will limit its performance. Perhaps the automotive technical experts (Fritz, et al) can jump in here, as well.



    Actually, engine power is a function of engine torque by way of the equation HP = Torque(lb-ft) x RPM/5252. Looking at the equation closely, one can see that engine torque is always greater than engine power at engine speeds below 5252, engine torque and power are always the same at 5252 rpm, and engine power is always more than engine torque above 5252 rpm. Since it is engine torque (not power) which accelerates the car, the shape of the torque curve does effect the rate of vehicle acceleration. All the engine features Porsche adds with multi-stage intake tracts, variable valve timing and variable valve lift are all made to manipulate (flatten) the engine torque curve to maximize performance.

    Re: Cayman S engine

    Quote:
    Geza said:All the engine features Porsche adds with multi-stage intake tracts, variable valve timing and variable valve lift are all made to manipulate (flatten) the engine torque curve to maximize performance.



    The torque curve is flat from 4400 to 6000 rpm (252 lbft). If Porsche programmed the engine management system to flatten the engine's torque curve to maximize performance, why don't we see the same flat torque curves on the 997 and 997S?

    Re: Cayman S engine

    Geza said:Since it is engine torque (not power) which accelerates the car,

    I don't think that's an accurate statement.

    Re: Cayman S engine

    Quote:
    LowPolarMoment said:
    Geza said:Since it is engine torque (not power) which accelerates the car,

    I don't think that's an accurate statement.



    It is an accurate statement. Torque is actually what people "feel" when there is any reference to engine "power". The engineering equation in which horsepower is actually a function of torque is indeed correct.

    Re: Cayman S engine

    Quote:
    schao said:
    Quote:
    LowPolarMoment said:
    Geza said:Since it is engine torque (not power) which accelerates the car,

    I don't think that's an accurate statement.



    It is an accurate statement. Torque is actually what people "feel" when there is any reference to engine "power". The engineering equation in which horsepower is actually a function of torque is indeed correct.

    Geza didn't say that torque accelerates the car. He said engine torque. Going from 0-100 mph is a function of weight and horsepower. Torque isn't in the equation. What you feel in the small of your back is related to the torque at the rear wheels, not the torque of the engine. The difference is in the gearing. If you had two engines that produced the same horsepower but one did it at twice the revs but with half the torque, you could compensate with gearing. Engine torque is not what accelerates the car, it's rear wheel torque.

    Re: Cayman S engine

    Quote:
    LowPolarMoment said:
    Quote:
    schao said:
    Quote:
    LowPolarMoment said:
    Geza said:Since it is engine torque (not power) which accelerates the car,

    I don't think that's an accurate statement.



    It is an accurate statement. Torque is actually what people "feel" when there is any reference to engine "power". The engineering equation in which horsepower is actually a function of torque is indeed correct.

    Geza didn't say that torque accelerates the car. He said engine torque. Going from 0-100 mph is a function of weight and horsepower. Torque isn't in the equation. What you feel in the small of your back is related to the torque at the rear wheels, not the torque of the engine. The difference is in the gearing. If you had two engines that produced the same horsepower but one did it at twice the revs but with half the torque, you could compensate with gearing. Engine torque is not what accelerates the car, it's rear wheel torque.


    Erm... correct me if I'm wrong, but torque is a rotational force. Accelleration = Force / Mass. So pretty much Accelleration is directly related to torque. Engine torque.. wheel torque... splitting hairs I think. Isn't Power = Torque * Revs? Or something like that! (So the more torque you produce at higher revs, the more power you get)

    Re: Cayman S engine

    The comment I was addressing was that engine torque, not horsepower, was responsible for acceleration. Clearly, it's horsepower, not engine torque. You can dial in the rear wheel torque with gearing in spite of the engine torque. Perhaps my example wasn't as clear as it could be. Imagine two engines that produce the same torque but one produces less horsepower. Which one wins the race?

    Re: Cayman S engine

    Quote:
    LowPolarMoment said:
    The comment I was addressing was that engine torque, not horsepower, was responsible for acceleration. Clearly, it's horsepower, not engine torque.



    I give up, continue to think and ignore as you wish. Geza gave you the formula.

    Re: Cayman S engine

    Quote:
    LowPolarMoment said:
    Imagine two engines that produce the same torque but one produces less horsepower. Which one wins the race?



    LOL!!......OK, take two cars with the same horsepower, but one has less torque.....which one wins the race?

    Re: Cayman S engine

    Quote:
    schao said:
    Quote:
    LowPolarMoment said:
    The comment I was addressing was that engine torque, not horsepower, was responsible for acceleration. Clearly, it's horsepower, not engine torque.



    I give up, continue to think and ignore as you wish. Geza gave you the formula.

    I learned the formula 40 years ago in high school. It has nothing to do with the comment Geza made that I said wasn't accurate. There's nothing wrong with the formula but saying that engine torque and not horsepower is responsible for acceleration is simply not true.

    Re: Cayman S engine

    The E55 AMG has 516 ft lbs of torque while the M5 has 383 ft lbs of torque and is at least as quick.

    Re: Cayman S engine

    Quote:
    LowPolarMoment said:
    Quote:
    schao said:
    Quote:
    LowPolarMoment said:
    The comment I was addressing was that engine torque, not horsepower, was responsible for acceleration. Clearly, it's horsepower, not engine torque.



    I give up, continue to think and ignore as you wish. Geza gave you the formula.

    I learned the formula 40 years ago in high school. It has nothing to do with the comment Geza made that I said wasn't accurate. There's nothing wrong with the formula but saying that engine torque and not horsepower is responsible for acceleration is simply not true.



    I finished high school 35 years ago, so I guess that explains why both of us are so set in our ways?:-) Let's agree to disagree and move on.

    Re: Cayman S engine

    I know what you're trying to say, and we're all being pedants. terms like 'as quick' are misleading. Ultimately, torque produces accelleration (instantaneous accelleration) and a powerful engine can produce lots of torque at high rpm. If you neglect speed-related counter forces (wind resistance for example), a flat torque curve would produce constant in-gear accelleration across the rev range, and power would rise across the same range. I think!


    Re: Cayman S engine

    Quote:
    Geza said: Actually, engine power is a function of engine torque by way of the equation HP = Torque(lb-ft) x RPM/5252. Looking at the equation closely, one can see that engine torque is always greater than engine power at engine speeds below 5252, engine torque and power are always the same at 5252 rpm, and engine power is always more than engine torque above 5252 rpm. Since it is engine torque (not power) which accelerates the car, the shape of the torque curve does effect the rate of vehicle acceleration. All the engine features Porsche adds with multi-stage intake tracts, variable valve timing and variable valve lift are all made to manipulate (flatten) the engine torque curve to maximize performance.



    I agree Porsche engines use multi-stage intake tracks and variable valve lift to improve torque thruogh out the torque curve. But Porsche made the top of the Cayman S's torque curve flat from 4400 to 6000 rpm (340 Nm) thus limiting maximum torque. The 911 Carrera S has a maximum torque of 400 Nm at 4600 rpm. If Porsche limited the 997S's torque to the lowest point on its torque curve between 4400 to 6000 rpm, its maximum torque would be 382 Nm.

    Re: Cayman S engine

    Quote:
    LowPolarMoment said:
    I learned the formula 40 years ago in high school. It has nothing to do with the comment Geza made that I said wasn't accurate. There's nothing wrong with the formula but saying that engine torque and not horsepower is responsible for acceleration is simply not true.



    torque is one type of force
    F = MA (force is mass times acceleration)
    W = Fd (work is force applied over a distance)
    P = W/t (power is work over time)

    Therefore, torque is what is responsible for acceleration. Power is responsible for acceleration for some distance over time.

    In other words, torque gets you going, but power keeps you going.

    Re: Cayman S engine

    Quote:
    HHG said:
    Quote:
    Geza said: Actually, engine power is a function of engine torque by way of the equation HP = Torque(lb-ft) x RPM/5252. Looking at the equation closely, one can see that engine torque is always greater than engine power at engine speeds below 5252, engine torque and power are always the same at 5252 rpm, and engine power is always more than engine torque above 5252 rpm. Since it is engine torque (not power) which accelerates the car, the shape of the torque curve does effect the rate of vehicle acceleration. All the engine features Porsche adds with multi-stage intake tracts, variable valve timing and variable valve lift are all made to manipulate (flatten) the engine torque curve to maximize performance.



    I agree Porsche engines use multi-stage intake tracks and variable valve lift to improve torque thruogh out the torque curve. But Porsche made the top of the Cayman S's torque curve flat from 4400 to 6000 rpm (340 Nm) thus limiting maximum torque. The 911 Carrera S has a maximum torque of 400 Nm at 4600 rpm. If Porsche limited the 997S's torque to the lowest point on its torque curve between 4400 to 6000 rpm, its maximum torque would be 382 Nm.



    I don't beleive Porsche consciously limits performance on either the Carrera or Cayman engines. They are extracting the most they can based on the hardware they have to work with and the time and budget they were given to develop the engines. There are so many factors (physical engine parameters) affecting torque curve, and emperical dyno testing is the only way to find out what you really have. You can do analysis and simulation, but testing is where you really see what is happening. Given another year of development, they will probably extract more power out of the engines...they are probably working on this right now.

    Re: Cayman S engine

    <In other words, torque gets you going, but power keeps you going.>

    Yeah but it's torque at the rear wheels, not torque of the engine.

    Re: Cayman S engine

    Quote:
    LowPolarMoment said:
    The comment I was addressing was that engine torque, not horsepower, was responsible for acceleration. Clearly, it's horsepower, not engine torque. You can dial in the rear wheel torque with gearing in spite of the engine torque. Perhaps my example wasn't as clear as it could be. Imagine two engines that produce the same torque but one produces less horsepower. Which one wins the race?



    It is engine torque, multiplied by gearing in the drivetrain and transferred to the road by the tires that accelerates a car. Horsepower is not involved. That being said, the horsepower properties of an engine (which are really the product of the torque and RPM properties of the engine) can affect acceleration as drivetrain gearing can be adjusted to get the most out of the engine torque properties and maximize what is transferred to the pavement.

    Re: Cayman S engine

    If an engine puts out 300 ft lbs of torque and goes through a gear reduction of 2:1 and another identical car has an engine that puts out 150 ft lbs but is geared 4:1, they'll both accelerate the same. The rear wheels dont know if it's engine torque or gearing torque. It's rear wheel torque that counts.

    Re: Cayman S engine

    Quote:
    LowPolarMoment said:
    If an engine puts out 300 ft lbs of torque and goes through a gear reduction of 2:1 and another identical car has an engine that puts out 150 ft lbs but is geared 4:1, they'll both accelerate the same. The rear wheels dont know if it's engine torque or gearing torque. It's rear wheel torque that counts.



    Agreed. Drive wheel torque is engine torque multipled by a fixed gear ratio (for each gear) minus some drivetrain loss. In a given gear, the torque curve at the drive wheels will follow the torque curve of the engine (multiplied by the gear ratio) as the engine travels through its RPM range (under full throttle).

    Re: Cayman S engine

    Quote:
    LowPolarMoment said:
    If an engine puts out 300 ft lbs of torque and goes through a gear reduction of 2:1 and another identical car has an engine that puts out 150 ft lbs but is geared 4:1, they'll both accelerate the same. The rear wheels dont know if it's engine torque or gearing torque. It's rear wheel torque that counts.


    But only instantaneously! You keep talking like Engine Torque and Power are static across the rev range of the engine!

    Consider a badly turboed small capacity engine, where the power and torque peaks right at the top of the rev-range.
    Compare that to a decent NA engine that develops the same peak power, but delivers a flatter torque curve. Which one is going to give you a better 0-100 time?

    Re: Cayman S engine

    Hey wtsnet, Geza and I are on the same page now so I'm going to quit and move on.

     
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