Can you make a 981 GT4 compete with a GT3? Our performance hungry customer was considering making the upgrade but first wanted to pursue optimization with both software and hardware. All of these upgrades were tested on the same SuperFlow dyno at JD Engineering in the Netherlands. Testing was done in three stages – stock, software, then software with hardware. All information was provided by our customer with slight editing for readability. Originally posted on Rennlist.
Dyno 1: OEM Software and Hardware
385.5 hp (manufacturer’s specification 385 hp), torque 433 Nm (manufacturer’s specification 419 Nm)
- OEM lambda value above 5,500rpm good, below that adjusted a little too lean
- Throttle valve all the way 100% open (not restricted by Porsche)
- Torque has significant dips at 3750rpm and 5000rpm
- Maximum power very early at 6,400rpm (manufacturer specification 7,400rpm) and therefore does not build up to 7800rpm
- Inlet has negative pressure from 4800rpm which is probably due to restricted throttle body/valve 74mm which is 82mm on 991.1 GTS and 991.1GT3
Dyno 2: Softronic ECU Tune Stage 1 – OEM Hardware
396 hp (+11 hp) and 452.5 Nm (+19.5 Nm)
- Torque builds up much more aggressively at low revs; you really do notice when accelerating
- More ignition advance; 25 to 30 degrees at 4800rpm. This gives approximately 30nm extra torque in the midrange and you can feel it!
- Torque and power dips at 3,750rpm and 5,000rpm all but gone
- Engine continues to lack airflow and there is under pressure in the intake at higher speeds above 5,500rpm despite professional fans placed 20cm from side air intakes
Note from Scott at Softronic: “The tune alone dyno runs could have performed better as you mentioned it wasn’t driven 30 miles or so and flashed on the dyno. This is done so the DME adapts again as when the Siemens units are flashed they basically eliminate the learned data and start over. They start out low and work there way up and typically it is about 15- 20BHP or so for the stock cars. The TQ increases also yet 10 or a bit less. Running it without the driving or learning starts out at the base for the file and increases in which the first dyno shows. The race cars with 100 octane add more yet there is more timing and TQ changes for it. ”
OEM 385pk at 6,400rpm; with Softronic tune 396pk at same RPM yet 30NM torque and impressive mid range. Engine breathes through 74mm OEM throttle body which doesn’t allow power to rise beyond 6,400rpm…
Dyno 3: Softronic ECU Tune Stage 2 – SOUL Headers, IPD Plenum, GT3 TB
This software update is made for stage 2 adjustments including Soul Performance Products Long Tube Street Headers, BMC performance air filters, IPD plenum with 82mm GT3 throttle body, and new spark plugs.
Gains: 434.7 hp (+41.7 hp) and 480.7 Nm (+28.2 Nm)
Final Gains: +52.2 hp and +47.7 Nm
Massive torque dip at 3,800 rpm completely gone; about 75 Nm gain at 5,100 rpm
- Engine delivers max power now at 7200rpm (was 6400rpm)
- Engine was previously restricted by the smaller factory 74mm air intake compared to 82mm GT3 throttle body (valve); only now does the engine also continue to gain power above 6400rpm towards redline!
- Larger aluminum IPD plenum distributes air better over all cylinders
- High flow BMC air filters give just a little more flow
- To give the engine more torque, Soul Performance Products Long Tube Street Headers with 200 cell cats were needed; great fit and finish, reasonable price and high quality 200cell HJS HD cats
- Dyno ECU logs show an improvement in air intake pressure beyond 5,500 rpm and therefore the engine breathes much better
- Ignition advance now max 33 degrees vs 25 degrees. Torque now well above 991.1 GTS and GT3!
- Around 10% more sound with PSE/valves closed; 25% more sound with valves open. Much more character, almost sounds like an engine with carburetors at times
valves open automatically at about 90mph so you have full sound control with OEM rear exhaust!
REAL-WORLD PERFORMANCE: How do these numbers compare to yours?
GT4 is good for 0-100 in 4.3 sec and 0-200km/h in 14.4 sec
In short, 10.1 seconds from 100-200 km/h
After tuning, tested on highway with Race Timer app showing 100-200 km/h in just 9.3 seconds – almost a second faster
991.1 GTS measured 9.9 seconds 100-200 km/h by Sport Auto (German) magazine
991.1 GT3 is still a step too far with 8.1 seconds but those measurements were with PDK and this car is manual…
Can you imagine yourself driving this GT4? The second best thing we can offer is this video highlighting the increase in tone from the 3.8L with SOUL Long Tube Street Headers!
Questions? Comments? Let us know!
– Mike Spock / Marketing Manager