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    Turbo more info from Autocar

    Sincere apologies if repost, I haven't been keeping up to date with this board:

    480 hp for 1580 kg
    0 to 100 kmh in 3.8 secs
    Top speed: 310 kmh
    Torque: 629 Nm between 1950 and 5000 rpm
    With Sport chrono package overboost function: 680 Nm between 2100 and 4500 rpm!!!
    New multi plate clutch that can send ut to 100% of the traction to the front wheels (as opposed as 40% for the C4S)

    Voila!
    again, sorry if info was posted before.

    Re: Turbo more info from Autocar

    The question is: does the overboost increase power too???
    In the Lancia Delta HF Integrale, the overboost increased the boost pressure for a few seconds and of course power went up too. Theoretically, this should be the same with the 997 Turbo. I doubt that you gain 10% more horses but I'm pretty sure that you gain at least 4-5 % which wouldn't be bad either.

    Re: Turbo more info from Autocar

    It only depends if the overboost has an RPM limit or just a time (10 secs) limit.

    Re: Turbo more info from Autocar

    thanks Fanch! guess we know the data by now, but some reminder on such a nice thing as 683Nm cant come often enough!!

    Re: Turbo more info from Autocar

    Im sure a tuner will figure out how to keep the boost on permanently!!!

    Re: Turbo more info from Autocar

    i don't think that MAXIMUM power will be increased too.

    i think this overboost function was made to improve the acceleration while overtaking without shifting in a lower gear.

    if you drive @25000 rpm in fifth gear and use the overboost (+60nm) it would feel the same like driving in forth gear at that speed. so you don't need to shift...

    Re: Turbo more info from Autocar

    Thanks fanch . Good to hear from you.

    Re: Turbo more info from Autocar

    Quote:
    RC said:
    The question is: does the overboost increase power too???
    In the Lancia Delta HF Integrale, the overboost increased the boost pressure for a few seconds and of course power went up too. Theoretically, this should be the same with the 997 Turbo. I doubt that you gain 10% more horses but I'm pretty sure that you gain at least 4-5 % which wouldn't be bad either.



    if you look at the torque figures, you see that the maximum normal torque of 629nm is available at a very wide range of 1950 - 5000rpm. this indicates, that the boost is limited because a normal turbocharged engine would never make the same ammount of torque at such a wide range. and as you can see, the 680nm is just available in this range in a range itself of 2100 - 4500 which is inside of the normal maximum torque's range.



    i hope you understand, what i am trying to say

    Re: Turbo more info from Autocar

    The article in Autocar states no power gains with the torque boost gizmo.
    Which from a theoretical point of view makes sense, since the overboost torque of 680 Nm is available in a smaller rpm range, so IMO, to answer your question, YES, you gain power associated with the torque gain up to 4500 rpm but NO, peak power remains the same at 480 hp.
    Seems it's a little button that'll give you that extra Oophm... Kick in the ass kinda thing, should be fun!!!

    We'll find out soon enough anyway.

    Re: Turbo more info from Autocar

    Quote:
    randy said:
    Im sure a tuner will figure out how to keep the boost on permanently!!!



    Guys, you don't understand the "principle" of overboost.
    Some of you seem to have the feeling that Porsche somehow limits boost pressure and just "allows" the overboost function for a few seconds. The overboost has a different purpose, it is some sort of excessive boost function to allow faster passing times in certain critical situations.

    Raising the boost pressure on the 997 Turbo is no problem, the problem is that the whole mapping has to be changed, just tweaking the boost pressure won't do the job if you want to keep a good balance between performance and reliability.

    Re: Turbo more info from Autocar

    Quote:
    RC said:
    Quote:
    randy said:
    Im sure a tuner will figure out how to keep the boost on permanently!!!



    Guys, you don't understand the "principle" of overboost.
    Some of you seem to have the feeling that Porsche somehow limits boost pressure and just "allows" the overboost function for a few seconds. The overboost has a different purpose, it is some sort of excessive boost function to allow faster passing times in certain critical situations.

    Raising the boost pressure on the 997 Turbo is no problem, the problem is that the whole mapping has to be changed, just tweaking the boost pressure won't do the job if you want to keep a good balance between performance and reliability.


    I have a Porsche turbo engine in which RS Tuning have programmed overboost - What is overboost ? It starts with deciding does the motor have a predetermined peak boost level ? The answer is no not really as the boost will always vary on these Motronic cars as is reads air mass and as that changes the boost will change. Having said that there will be a DIN boost curve ie the boost curve which is given by the ECU on a full load dyno run under DIN conditions.

    For a 996tt this could be 1.0bar @ 4000rpm 0.75bar@ 5700rpm 0.8bar @ 6500rpm.
    Now overboost is the ability of the ECU to let the turbos overshoot these numbers, usually at peak torque. The boost will climb to a higher peak, say 1.3bar (on a tuned car), where it will stay for a short time. This time is determined by the onset of knock. As soon as the ECU detects knock it will bring the boost back to the original level. The ECU will also allow overboost at higher engine RPM so if you punch the throttle at 5500rpm it again will overshoot to 1.1bar (or whatever) until the knock comes (could be only for 1 sec) then brings it back again.

    This type of overboost makes the car very fast as it provides a much bigger kick in the back than the DIN dyno rated boost.

    Porsche effectively DOES limit boost - there is no doubt about that (its reasons are many, including as RC points out the onset of overboost can make the car hard to drive - my car gets a kick of 0.8G at 65mph in 3rd gear as the overboost hits 1.4bar - this is quite scary )
    The 997tt with overboost may well work in the same mode as I describe above - so it is there all the time when you punch the throttle for a number of seconds - that number of seconds will be determined by how long the motor can hold the 1.2bar (reported in Autocar) without detecting knock.

    It may well be that Bosch/Porsche have developed further this feature (which has been pioneered for Porsche turbos by Rhienhold Schmirler) and it will be controlled at WELL BELOW the knock onset level - ie it will be a set TIME limited overboost rather than a condition/input limited feature.

    Re: Turbo more info from Autocar

    any pics from the article by any chance?:)

    Re: Turbo more info from Autocar

    Thanks for this very clear explanation - now I get it

    Re: Turbo more info from Autocar

    Scan please

    Re: Turbo more info from Autocar

    Quote:
    CF said:
    Scan please



    Seriously, I would but I don't have a scanner.
    Any other UK user please? It's only a couple of pages.

     
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