With the talk about “explosive” turbo engines I thought I would share some development which I am doing with my 997GT2.
Too much explosive power in a 2WD 911 means traction problems in first and second and sometimes third gear.
If you watch the vid clip in the first post on this thread you can see my GT2 being outrun by a manual 997 turbo (tuned with about 650PS) up to about 140mph (225kph) this is because it is very difficult to launch a RWD 911 which has over 900NM or torque and 800hp.
The problem is exacerbated by the programming of modern turbo engines which adjusts the throttle to improve turbo lag which in effect can give the motor 100% throttle when one only depresses the throttle pedal by 60%. If you look at the table below you can see how this strategy works. In higher gears it works really well but in first and second it means it is impossible to feather the throttle and have any meaningful input in how much torque is going to the tyres !
I thought what I needed was reduced torque/power in first and second gears but unfortunately the 997 programming does not do this as standard. My tuner believes he has identified a table which will allow torque reduction as a percentage (of maximum) by gear position between 4 (user inputted) rev bands.
So I have the first revision now uploaded to the ECU and have been testing extensively on different surfaces. The new program reduces torque in second by 80% up to 6000rpm then it is back to 100% so in theory my maximum torque should be about 740NM up to 5000rpm then rising thereafter.
The reality is not quite what we wanted, checkout the vid and the flashing TC light. This is on smooth warm surface with decent traction.
https://youtu.be/hgwwkwf6mfc
I have done lots of data logging to try and ascertain what is happening in particular by watching the boost and TBH I can’t fathom it, I think there is less torque than before but before it was completely ridiculous with zero traction and now it is just ridiculous. The next settings will I guess be down to 60% and maybe 80% from 5000rpm and if that totally neutered it then we will end up with a third revision hopefully spot on.
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997 GT2 2014 3.9 Mezger, 800PS @ 1.2 bar
993 Turbo, 2006 built 3.8, 577PS/797NM, 1440kg DIN