I know there are lots of topics about Sport Chrono on the 997 TT...Not interested in starting a discussion about who likes the dash clock, why you cannot just do a DME flash, etc....Just curious to know if anyone knows how the 10 second over boost is achieved?

Not that it is a big deal, but I was just wondering for my own knowledge and curiosity..

Thanks for any thoughts.

PS...I already know and understand all of the changes that occur with the chrono sport button depressed ( PASM, PTM, Shift mapping, throttle response, etc.)

 

floor it.

 

Have you got SC and cant acheive the full 1.2 boost on gauge?

 

OK...I did not ask my question correctly.....I know how to use it, and get the arrow on the dash, get the boost, etc.....Yes...It works great!

I am wondering how (mechanically / technically) the extra boost is achieved? Do the variable veins lock open on the VTG turbos? Does something happen with a diverter valve? etc.. I am just interested in understanding HOW it creates extra boost...Strictly form a "wanting to understand the mechanics" aspect.

Thanks!
DC

 

A quick Google search landed me to the Porsche website offering the following:

Under full acceleration, the ‘overboost’ function provides a temporary increase in available boost pressure of approximately 0.2 bar. The overboost is applied across the low and medium rev ranges, briefly raising the standard 650 Nm of torque to as much as 700 Nm.

So, seems to simply increase the boost pressure by .2 bar -- that's it.

 

Boost is regulated by the wastegate which is controlled by the wastegate actuator. When you push the button, it signals the wastegate actuator to stay closed at higher pressure and 10 s.

 

VTG turbos have no wastegates...

 

Opps (vtg's right), I stand corrected...then membrane actuator of some sort that controls the vanes.

 

Thanks guys! That is what I was interested in, just understanding how it works.

Thanks..

Also..TTdude I love this!

"Officer, I wasn't speed'n but I sure was pass'n some that were"

DC

 

Just curious, on your digital boost gauge readout, not the moving line gauge, does yours get to 1.2 bar in SC mode? and 1.0 in normal? Assume yours is stock tune and stock exhaust?
Both my gauges seems to only show up to .09 in both normal and sport c modes. Still feels fast tho. Ive got stock tune with a tubi but am doing tune soon.

 

I don't have SC so my guage will not read above 1 bar no matter how much boost is delivered beyond that. Before my flash, I could not even get to 1 bar. Now I routinely peg at 1 bar but in actuallity the pressure is more like 1.2 bar (my guesstimate).

 

Hi TT and thanks. When my car was at P last week I had them check the boost and gauge thing out and they said all was fine but I wanted to check with other owners just incase i was being fed BS. P said i needed to be stretching it right out in 3rd, 4th on a track at high revs to acheive the 1.2 readout on the gauge which sounded odd to me. I get to give it full in 3rd up to 5k rpm but run out of road and still only .9 on gauge in SC. Logically the adjusting vanes of the VTG turbo's would provide a fast build up to 1.2 without any fuss. Thats the beauty of VTG. Maybe it is just P's stock tune and the way it is set to only deliver full boost up high.
On the Proto tune i should have it in shortly so i'll see if that crazy gauge reads differently. Hopefully it will show BIG numbers.
Cheers.

 

Hey Speed, Your situation is not unusual. Check out post #14 https://www.6speedonline.com/forums/...ost-works.html No worries, the Proto tune should take care of it. Cheers.

<TABLE id=post1750665 class=tborder border=0 cellSpacing=1 cellPadding=6 width="100%" align=center><TBODY><TR><TD class=thead><TABLE class=transp><TBODY><TR><TD class=normal align=left><!-- status icon and date --> 03-23-2008, 05:00 AM <!-- / status icon and date --></TD><TD class=normal align=right>#14 <SCRIPT type=text/javascript> vbrep_register("1750665")</SCRIPT> </TD></TR></TBODY></TABLE></TD></TR><TR><TD style="PADDING-BOTTOM: 0px; PADDING-LEFT: 0px; PADDING-RIGHT: 0px; PADDING-TOP: 0px" class=alt2><!-- user info --><TABLE border=0 cellSpacing=6 cellPadding=0 width="100%"><TBODY><TR><TD noWrap><!-- google_ad_section_start(weight=ignore) -->Porsh997TT<!-- google_ad_section_end --> <SCRIPT type=text/javascript> vbmenu_register("postmenu_1750665", true); </SCRIPT>
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</TD><TD width="100%"> </TD><TD vAlign=top noWrap>Join Date: May 2007
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</TD></TR></TBODY></TABLE><!-- / user info --></TD></TR><TR><TD id=td_post_1750665 class=alt1><!-- message, attachments, sig --><!-- message --><!-- google_ad_section_start -->ummmm 1.2 bar!! I HAVE NEVER SEEN THIS IN MY CAR!! max was 1.0 sport mode with a sport techart exhaust ( i laso tried fabspeed straight pipes). I feel the response quicker but no figures that i can really relay on. I live in Qatar sea level weather for the peast few months been very nice between 10-20C degrees...although i have been told by few people i raced that my car was so far the fastest 997TT they raced!<!-- google_ad_section_end -->
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Hehe...sure are some funny posts on that particular thread TT and, the Proto, yep that will surely cure....and cant wait! Hey the gauge is never my focal point anyways ...usually going too quik .

 

To be honest I never looked. People drive like granny's here, so when I do punch it, I have to watch for the turtles. I will check next time I do it and let you know what I get.

Take care,
DC