The Brief
This 2018 370Z Nismo build shows what’s possible from a naturally aspirated VQ37 when you commit to doing it properly — engine out, quality parts, and a thorough tune.
The owner, Sam, wanted a car that could do double duty. Comfortable and refined on the street, aggressive and responsive on club track days. He wasn’t chasing a number for the sake of it. He wanted a properly engineered package that would transform the driving experience across the full rev range, on both 98 RON and E85.
That meant a full bolt-on exhaust system from headers to tips, a flex fuel conversion so the ECU could automatically adjust between pump fuel and ethanol, an engine oil cooler for sustained track use, and a custom ECUTEK dyno tune to tie it all together. The car was in the workshop for five days from drop-off to collection.
Why the Engine Had to Come Out
On paper, a “full exhaust and flex fuel kit” sounds like a bolt-on job. On a 370Z, it’s anything but.
The VQ37’s exhaust manifolds sit buried between the engine and the firewall in a tight V configuration. There is no realistic way to install aftermarket headers with the engine in the car. The factory manifolds are designed to be fitted during assembly, before the engine goes into the chassis. Replacing them with the Fujitsubo Super Ex units meant pulling the entire engine and transmission as a single assembly.
With the engine on the stand, we had clear access to both banks for the header install and could also address the fuel system work cleanly. The intake manifold was removed to replace the factory fuel injectors with a set of six reconditioned GTR35 injectors, which flow enough fuel to support E85’s higher fuel demand. The fuel feed line was replaced to suit the flex fuel kit, and the EFI Hardware flex fuel sensor module was wired in to allow the ECUTEK ECU to read real-time ethanol content.
The Exhaust System
The exhaust was built around three complementary pieces chosen for both performance and sound character:
Fujitsubo Super Ex Headers replace the restrictive factory manifolds with equal-length tubular headers. On the VQ37, headers are where the single biggest exhaust restriction lives. This is the part that demands the engine-out approach, and it’s also where the most significant gains come from.
Invidia Catted Test Pipes replace the factory catalytic converters while retaining a high-flow cat for emissions compliance. These bridge the gap between the headers and catback system.
HKS Full Dual Muffler Catback completes the system from the mid-pipe back. The dual muffler design keeps the exhaust note deep and controlled at cruise, while opening up at full throttle.
The combination gives the VQ37 an exhaust path that breathes freely from port to tip without sacrificing street manners.
Oil Cooler and Supporting Mods
Sustained track use puts significant thermal load on the VQ37’s oil system. The HKS S-Type engine oil cooler was mounted behind the front bumper bar, requiring removal of the front bar, modification of the front tray and venting for the intake pipes, and careful remounting of the crash sensor. Racework fibreglass heat shield sleeving was used to protect adjacent hoses and wiring from exhaust heat.
While the engine was out, we took the opportunity to do a full fluid service: Penrite HPR 5 5W-40 engine oil, Ryco Syntec oil filter, fresh ATF, and engine long-life coolant. Every clamp, gasket, and washer that was disturbed during the build was replaced with new hardware.
ECU Calibration
With the mechanical work complete, the ECU was removed from the vehicle and bench-flashed with a modified ROM file to unlock the ECUTEK tuning platform. This gives us full control over fuel maps, ignition timing, cam timing, and flex fuel blending.
The car received four separate tuning sessions:
Custom dyno tune on E85 to establish peak power and optimise the fuel and ignition maps across the full rev range with ethanol. E85’s higher octane rating and cooling effect allows more aggressive ignition timing, which is where the power gains come from.
Custom dyno tune on 98 RON as the secondary fuel map, so the car runs safely and optimally on premium pump fuel when E85 isn’t available. The ECUTEK flex fuel strategy blends between the two maps in real time based on the ethanol content reading from the sensor.
Cold start calibration to ensure the car starts and idles cleanly on both fuel types, particularly on E85 which requires significantly more fuel enrichment at cold start than petrol.
Road tune to refine drivability, throttle response, and part-throttle behaviour in real driving conditions outside the dyno cell.
The Results
Both runs were measured at the wheels on our Dyno Innovations dyno:
On E85: 236.7 kW @ 7,274 RPM / 346.2 Nm @ 5,140 RPM
On 98 RON: 222.5 kW @ 7,444 RPM / 327.6 Nm @ 4,994 RPM
E85 gains: +14.2 kW / +18.6 Nm
A stock 370Z Nismo makes around 253 kW at the crank — roughly 205 kW at the wheels. This build is making 236.7 kW at the wheels on E85, a gain of over 30 kW at the wheels.
What the numbers don’t show is the shape of the power curve. The torque comes on strong from around 3,400 RPM and holds flat through to 6,200 RPM before the power curve takes over and pulls hard to the 7,400 RPM peak. The result is a broad, usable powerband that hits hard on track corner exits without being peaky or unpredictable.
Even on 98 RON, the 222.5 kW figure represents a meaningful improvement over stock, and the car can run on regular pump fuel indefinitely without any driver intervention. Fill up with E85 when it’s available, fill up with 98 when it’s not. The ECU handles the rest.
What the Owner Had to Say
“After I chose to wait for some selected parts it is exactly what I asked for. I got it back and took it for a drive and boy did it transform the car. It drives smoothly and quietly; I can have an uninterrupted conversation with my wife and lightly accelerate through the rev range with elegance to our favourite breakfast bar. Then on club track days the NA engine gives instant throttle response, the engine roars and gives an intense kick in the pants upon corner exits that requires some serious throttle modulation. This is serious acceleration.”
— Sam
