This is the first tuning session on my new GTR setup. While I am switching to the Motec ASAP, I wanted to do a break in tune with the Cobb Accessport on the factory ECU to make sure everything in the engine was working. Since this is a 10:1 CR motor I’ll be running it on E85+ fuels most of the time, and as such I didn’t do any pump fuel tuning past wastegate boost (12psi). Once I get the Motec setup I’ll play around a bit more with pump fuel, but E85 is my primary target.

The master calibrator and head of Cobb calibration Tim Bailey was driving the Cobb Accessport, I was on the Motec data collection, Aaron on the dyno, and Myles monitoring.

I was hoping to break over 1000whp, with 1050whp as a good place to land. I was pleasantly surprised to have little problem getting over 1100whp at only 29psi. 1000whp has always seemed like a reasonable upper end of power for a street car.

At different boost levels the power output was as follows:

12psi Pump 647whp
12psi E70 717whp
15.5psi E70 817whp
18psi E70 911whp
19psi E70 925whp
21psi E70 969whp
26psi E70 1074whp
28psi E70 1098whp
29psi E70 1130whp

With 12psi waste gate springs I can dial the power down to 700whp as needed for adverse driving conditions, and with the Motec’s throttle control system it can be dialed down even more as needed.

Power delivery at the specific pressure levels was better than I expected. I thought I would need to be at 32-33psi to break 1000whp, so I was pleasantly surprised at the efficiency of the turbocharger and the intercooler setup. 29-30psi is weak sauce boost in the GTR world, but certainly enough for a street car.

As far as torque goes, we hit 918 lb-ft at 5000rpm at 28psi, but turned down the boost a bit in the midrange while we experimented with boost and timing at higher rpm. I suspect with a harder hit in the midrange we could hit 1000-lbft, but my transmission is not really rated for that kind of torque. Based off the performance so far, I think we will be able to get to about 1200whp before running out of turbo.

The setup is as follows – ETS Precision 5858 Twin Turbo Kit with wastegates routed back into the exhaust, ETS Race intercooler, ETS intakes, ETS downpipes, English Racing built 3.8L engine with Carillo HD Rods, CP-Carillo 10:1 Pistons, English Racing heads with GSC Valves and Valvetrain, GSC S2 Cams, O-Rings, T1 AOS, T1 Oil Pan, T1 Primary Fuel Rails, ID1050X primary injectors, ID1300 secondary injectors, Boostlogic Intake Manifold and Secondary Injector Rails, Cobb Accessport with Flex Fuel and 12 injectors support, Fore Systems Triple W480 fuel pumps, ER custom fuel lines, ID750 fuel filter. I can’t say enough great things about English Racing and their support in getting all of this together. Their work was flawless with an incredible attention to detail about everything. Extreme Turbo Systems did a kick ass job building me the custom 5858 turbo kit and intercooler setup, as well as got the turbo compressor covers machined for the speed sensors. I owe a huge thanks to T1 and Tony Palo for his help in getting all of the sensor goodies, Motec goodies, fuel goodies, and engine part goodies here for the party.

I have a Motec C187 Dash installed, and an array of sensors for collecting calibration data – Air temperature and pressure pre turbo, post turbo, post IC, and manifold on both sides, EGBP pre and post turbine on both sides, EGT pre and post turbine on both sides, Turbo wheel speed both sides, coolant pressure, fuel pressure and temp, air temp across intercooler external, plus a few extra thermocouples around the engine.

I will post up a more detailed analysis of the data collected in the next few days, as there is a lot of data to dig through.

A few thoughts about the attached graphs:

Boost control was straightforward and the use of the 4-port setup allowed for 12-30psi control over a small range of duty cycles.

The secondary fuel pump turn on was a bit early for the regulator and return system, so that is something I’ll tweak over the next few weeks. Fuel pressure was solid all the way to redline, indicating plenty of fuel system reserve. ( Which I would expect with triple W480s).

The 12-injector setup worked flawlessly. You could not tell when it kicked in, and it really extended the range of the fuel system. At peak power I was only at 60% injector duty cycle, with plenty of head room for a switch to E98 and a bit more boost.

Ignition timing was quite a bit lower than I expected. The car made great power at 29-30 psi at only 15-16 degrees of timing. It feels like we are still a bit under MBT, so some more exploration is needed.

Pressure drop from the turbo to the manifold was impressively low. With turbo output pressure peaking at 32psi, post intercooler peaking at 31psi and manifold pressure peaking at 30.5 psi. That is about 1psi of pressure drop across the intercooler at 1100whp and about 92% intercooler efficiency. Pressure in front of the turbos ( indicative of intake restriction ) was peaked at -1.7psi, which is acceptable given the size of the intake tubes and the restrictions on how they can get out of the engine bay. Calibrators take note of the real PR of the turbo is not the same as the ‘Manifold Pressure’.

A special thanks to many many friends for their valuable input in putting this project together – My longtime friend and accomplice Timothy Bailey , Lucas English, Myles Kerr, Tony Palo, Paul Yaw, Michael Roark – and my many friends that support my ‘data habit’. If you don’t have a data habit, I suggest you get one. It will make you a happier person.

Apologies for the abbreviated version of the analysis, but more to come.