Locked and Loaded, Cobb Tunings Time Attack Nissan R35 GTR
By Mike Kojima, photos by Jeff Naeyaert
When the R35 GTR was launched on the US market last year, its release was surrounded with rumors and controversy. Its chief engineer publically bragged that he was designing its systems to be impossible for the aftermarket to modify. Nissan imposed draconian warranty policies in which nearly every sort of sporting driving would be recorded and become an opportunity for Nissan to void the warranty by labeling it as customer abuse.
The car initially got the reputation for being fragile and with Nissan not supporting the cars warranty when a controversial launch control feature was activated or even when the VDC system was turned off, the car initially was approached by tuners with trepidation. A very popular humorous video about Hitler's GTR getting the warranty denied was widely circulated on the net much to Nissan executives chagrin.
|One of the most stock nearly 800 whp engines you will ever see. The Nissan VR38DETT really responds to minor bolt ons and careful tuning. So far it seems pretty reliable as well. The Cobb Motorsports/GOTO racing GTR has had nary a valvecover removed in over 10 race and test weekends to date.|
Well, we have been keeping an eye on the GTR that has been campaigned by Brian Lock and GOTO racing under the Cobb tuning banner. Although the car runs in modified class, we noticed that it was starting to come together and was turning lap times just a few seconds a lap slower than the big guns in unlimited class like Sierra Sierra, Crawford and FXMD. We expected to find some really exotic hardware when we examined the car; after all we could not see how the huge GTR with its crushing weight of 3800 lbs could even come close to being competitive in any sort of racing without some exotic work. Under close scrutiny we were amazed to find that the GOTO machine is actually a pretty darned close to stock GTR. Its amazing performance has given us a new respect for the platform.
|The Harman Motive midpipe is made of rust resistant stainless steel and features TIG welding and 3.5″ tubing|
When talking to the projects head tuner, Cobb's senior tuner, Engineer Tim Bailey, we were amazed at the powerplants stockness. The Nissan VR38DETT's long block is completely stock, having nary a valve cover removed. The stock exhaust manifolds were modified by AMS to mount a pair of Garrett 2871 ball bearing turbos. The turbos breathe into Harman Motive down pipes feeding into a Harman Motive 3.5″ stainless Y Pipe. Finally the exhaust gasses vent to a simple 3.5″ stainless exhaust that exits above the rear diffuser activating its flow.
|The Harman Motive charge tube is 3.1″ in the area near the MAF sensor as opposed to the stock 2.5″. The larger diameter flows more and allows the MAF to read the higher flow volume without getting maxed out. Then the MAF compensation tables in the ECU are rescaled with the Access Port so the higher air flow can be properly metered. This trick is critical for sucessful high power tuning.|
The intake pipes feed into prototype larger diameter 3.1″ Harman Motive charge tubing whose greater flow vs the stock 2.5″ tubes effectively allows rescaling of the airflow meter compensation tables without exceeding the MAF's 5 volt limit. Harman Motive reinforced silicone charge tubes replace the ballooning prone stock rubber and plastic parts. The charge pipes feature prototype Cobb compressor bypass valves with reliable pistons replacing damage prone diaphragms. The stock injectors are replaced with huge Injector Dynamics 2200cc/min injectors and bigger prototype Cobb fuel rails to enable the use of E85.
|To ensure uninterrupted fuel flow under hard cornering a big fuel pump feeds a surge tank and another pump moves fuel from the surge tank to the engine. The surge tank ensures that the engine will get fuel even if the main pickup in the tank sucks air.|
The fuel system uses an Aeromotive fuel pressure regulator to handle the high volume of fuel flow needed by E85.
The fuel system has been converted from a dead head electronic pressure controlled system that is emissions friendly to a high volume conventional return type for the E85 fuel.
|Actual GOTO Racing GTR data logs from the Cobb Access port|
Engine management is handled by the factory ECU controlled with a Cobb Access Port interface using Cobb Access TUNER Pro software v 2.0. The Access Port gives a tuner access to all of the engines tuning parameters and provides 3D graphical mapping of fuel, ignition, cam control and every function that a tuner would need to manipulate. The Access port also does data logging to speed tuning.
|Cobb Access Port is found mounted to the rollcage door bar for easy access. The fire system activation handle and master power switch are mounted near here as well.|
It takes big power to push a 3600 lb race car to competitive speed and the Cobb equipped VR doesn’t disappoint. Tim tuned the ECU to where the car produces an amazing 788 whp on pump fuel and 721 lb/ft of torque at 24 psi of boost. When switching the car to E85 the power increased to 795 whp! At this power level, the car is still reliable; so far the stock engine has survived over 10 race weekends without flinching!