Having gone down the all-motor, bolt-on, power-adder path with our recently retired '06 Infiniti G35 Coupe project car, we're quite familiar with the limitations of the VQ35 in normally aspirated form. Despite throwing a full complement of bolt-ons at the engine, we only bumped at-the-wheel output from 221 whp to 258 whp on U2Ndyno.com's Dynapack when it was all said and done. That's a decent gain and it helped bring the car to life quite a bit, but we got nowhere near our 300-whp NA goal, which should really be a lot easier to attain with a 3.5-liter V-6.
Of course, now that we've retired our G, an all-motor power-maker appears on the market that would've undoubtedly helped us move much closer to that elusive 300-whp mark. SG-Motorsport has been hard at work developing its new longtube headers, true race-quality pieces that have been tested and tuned on the company's Grand Am 350Z race car (you've probably already read the "I Wanna Go Fast!" story about SG's recent racing adventure on page 50).
One of the big bottlenecks when trying to make more normally aspirated power from a VQ35 is the factory exhaust manifolds. In the quest to reduce emissions, Nissan equipped the VQ with very short headers so the catalytic converters can be placed as close to the heads as possible for faster light-up time (where the cats achieve the required temperature to work their emissions-killing magic). As a result, the headers' primary runners are cut prematurely short and this forces a less efficient collector design because the primaries must come together abruptly to make space for the cats.
To overcome the design limitations of the OE headers and uncork the VQ on the exhaust side, SG-Motorsport has replaced the factory headers and catalytic converters with its race-tuned longtube headers. Beautifully TIG-welded from stainless steel and using true racing merge collectors, the SG longtube headers make zero compromises in their design. These headers are optimized for both low-end torque and high-end horsepower, the stepped primary tubes improve low-rpm engine response while the primary lengths have been tuned for optimum high-rpm output. As an added bonus, SG headers also feature slip fit merge collectors, helping reduce install time by as much as 75 percent.
Results To test SG's longtube headers, we borrowed the company's low-mileage '06 350Z Roadster. Equipped with a stock RevUp engine, a custom 3-inch diameter cold-air intake and a custom 3-inch diameter single-exit exhaust, we started by baselining the car with the OE headers. During this process we tuned the factory ECU for maximum output using an UpRev Osiris reflash that optimized fueling, ignition timing and cam timing. Strapped to U2Ndyno.com's conservative-reading Dynapack, we got a best reading of 257 whp and 239 wtq. That's some very impressive jam from an internally stock RevUp with just an intake, after-cat exhaust and an ECU reflash.
After letting the engine and stock headers cool down, we threw the Roadster on a hoist and swapped on the SG longtube headers. This job took us about four hours, less than half the time it took us to swap Stillen headers onto Project G35.
The time savings were a result of the SG longtubes having an individual tube for each cylinder that slip fits into the merge collector, allowing them to be installed without having to remove the steering shaft, lifting the engine up or doing any other hard labor often required when installing one-piece headers.
Once the SG longtubes were bolted up, the Z Roadster was loaded onto the Dynapack and the fun really began. Some intake and exhaust cam timing adjustments using our UpRev Osiris tuner were required because of the additional flow through the exhaust (and therefore through the heads), but the ignition timing and air/fuel-ratio targets stayed the same. After a few pulls, the power started to nose over and it was time to compare our gains.
The engine gained 27 whp and 15 wtq at its peak, producing a maximum reading of 284 whp and 254 wtq. Those are some very impressive peak gains, but what really impressed us the most were the consistent gains across the entire rev range. The SG longtubes made substantial power everywhere in the rpm band, averaging 15 to 20 ft-lbs of torque throughout with maximum gains of 30 whp at 6300 rpm and 22 wtq at 6000 rpm.
As impressive as these overall gains are, what really blew our minds was the sound blasting out of the exhaust pipes. The correct merging of exhaust gas pulses into a cat-less single exit exhaust resulted in an engine note that's almost F1 race car in pitch. At 7000 rpm the engine sounds like it's ripping at 10,000 rpm. It's just insane. To hear it for yourself, check out SG-Motorsport's video on YouTube (search "Sequence Garage" or go to youtube.com/watch?v=4Ap9jzeHMCY).
It's important to keep in mind that running SG's longtube headers without installing a catalytic converter in the mid-pipe means your car won't pass a smog test. But anyone with a VQ-powered race car needs to seriously consider investing in a set of these uncompromising race-tuned headers.
'06 Nissan 350Z Roadster
3.5-liter RevUp VQ35DE V-6
Custom 3" single-exit exhaust, custom 3" cold-air intake, UpRev Osiris ECU flash
Replaces the factory headers and catalytic converters
True race merge collectors for maximum torque throughout the powerband
Stainless steel tubing, flanges and collectors to ensure a rust-free life
Stepped primary tubes for improved low-end torque without sacrificing top-end power
Tuned primary lengths for improved high-rpm performance
Individual primary tubes with slip fit merge collectors cut install time by 75 percent
TIG-welded and backpurged for maximum weld strength and beauty
Bolt up to the standard Y-pipe or dual exhaust
With SG-motorsport LONGTUBE headers gains made + 27 hp + 15 torque Before 257.6 whp and 238.6 ft-lbs After 284.3 whp and 254.2 ft-lbs