Infiniti G35 Tuning:
How To Bolt On Over 40 Wheel Horsepower

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Next I installed MotorDyne Engineering’s 5/16’’ plenum spacer kit and MREV2 lower intake manifold. The MREV2 is based on a non-RevUp manifold that has had an airflow restriction removed, while the plenum spacer simply increases the manifold’s volume. Again, installation was very simple, and MotorDyne supplies very detailed instructions so you really can’t get it wrong.

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This combo of MotorDyne intake manifold upgrades proved to be very effective, increasing peak power by 10whp and 13.7wtq. But what really stands out on this graph is the huge jump in mid-range torque in the 3,500 to 6,000 RPM, with gains over 20-wtq in places. This really delivered a huge improvement in throttle response and acceleration on the street and at the track. I would argue these two mods are your best bang for the buck in VQ tuning if you’re staying NA like I did.

The Stillen HFCs I was supplied with were prototype units so not very pretty (and thus I didn’t take any pics of them), but they were very effective on the dyno, as you’ll see below.

Next I decided to change out the OEM headers for Stillen’s ceramic-coated headers, along with Stillen high-flower catalytic converters. Be warned, though, that changing the headers on a G or Z is a bit of a nightmare. There’s so little space between the frame rails and the headers that getting at the nuts that hold the headers to the block is pure torture. I think it took us (meaning Sasha from OnPoint and I) a good 4 or 5 hours to swap the headers. The HFCs are a piece of cake by comparison, simply replacing the OEM cats that sit between the headers and cat-back exhaust.

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As you can see from the dyno graphs, the headers (top graph) really improved high RPM power thanks to its equal-length primaries and merge collector, but as a trade-off we did lose some mid-range torque. The Stillen HFCs (bottom graph) also gave the upper rev range a boost, making the last 2500 RPM extremely useful around the race track, while recovering most of the torque lost by the headers. Together these mods provided a 18.6-whp gain while losing 1.7-wtq, but I think you’ll agree that for track purposes gaining that much top end is more than worth losing a tiny bit of torque for.

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MODIFICATIONS WHP WTQ WHP/WTQ GAINED
Stock 221.8 215.2
Stillen cat-back exhaust 230.3 223.2 8.4 / 8
Stillen intake 235.5 226.6 5.2 / 3.4
MotorDyne spacer/MREV2 245.6 240.3 10.1 / 13.7
Stillen headers 253.6 230.2 8 / -9.9
Stillen catalytic converters 264.2 238.4 10.6 / 8.2

 

In the end, the power gains from this combination of intake and exhaust upgrades is really quite impressive. Total horsepower on the dyno increased by almost 43-whp and torque by just over 23 lb-ft.

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This certainly delivered much improved throttle response and acceleration in every gear and across the entire powerband, making it a lot more fun to rip around on the street. But how did it impact on lap times around Toronto Motorsports Park? Not as much as you’d think, with lap times dropping to 1:28.142-seconds, a full second a lap quicker than stock. Which just goes to show, it isn’t easy going faster on power alone. For lap times to really drop, the G35 needs some wider wheels, stickier tires, brakes that can take the heat, and a suspension designed to better control its considerable mass.

The rest of the G35 upgrade stories are located here:

G35 Tuning: Big brakes make a difference

G35 Tuning: Adding grip and saving time

G35 Tuning: Ditching the V-LSD for a proper diff

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21 Comments on "Infiniti G35 Tuning:
How To Bolt On Over 40 Wheel Horsepower"

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Jerzyiroc
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Check engine light come on when you swapped the header?

JosePerez9
Guest

Did you have to tune your car at all?

Peter Tarach
Admin

Yes, the car was tuned.

Goga
Guest

And without tune does the mods have any +hp?

Rheison
Guest

What tune did you do and is this the non-Revup engine? you mentioned using nonl-Revup plenum I have the none revup and want to find a place to do tune.

DavidPratte
Guest

Jerzyiroc  no sir, never had any CEL issues with the headers.

Nick
Guest

What headers did you use I’m looking change my whole exhuats just bought my g35 3 days ago

DavidPratte
Guest

JosePerez9  nope, stock tune. We always intended to do some tuning but never got around to it.

Schmidtty
Guest

Could you send me a link where you found the catalytic converter, or does the full exhaust system off of the stillen website come with the Cat. Thanks!

DavidPratte
Guest

Schmidtty  I got the cats separately from Stillen (they were prototype pieces at the time), but I’m sure you should be able to order the Stillen system complete with cats now.

Schmidtty
Guest

DavidPratte one last question, i really like the noise the Godspeed Catback exhaust makes. do you know/have an opinion on it?

DavidPratte
Guest

Schmidtty sorry, I’ve never tried or heard the Godspeed catback on a G35.

UrielYairHernandez
Guest

i have a 04 g35 coupe do they have a rev up engine or how can i check

DavidPratte
Guest

UrielYairHernandez  the RevUp came in the ’05 to ’07 G35 coupe 6MT, so if your car is an ’04 you have the non-RevUp 280-hp engine.

tamaz0125
Guest

How much did each mod cost? You say these are affordable,but that’s a relative term.

DavidPratte
Guest

tamaz0125  if you follow the links in the story they’ll take you to the manufacturer pages with pricing. Cost is certainly relative, but for non eBay parts that are designed, tested and built in America, I consider these parts very good value. The Japanese equivalents tend to be a fair bit more expensive.

Dustin Matthiessen
Guest

You said you car came stock with 220 hp. That seems low for the g35. My 05 is suppose to be stock with 290 or so. Why the big difference?

Guest
Guest

He was mentioning WHP which is different from HP, he said it was 220Whp which is around 280hp

Alix singh
Guest

Whp is different than crank power in g35 the vq35 out puts about 280 crank and 220ish whp

Joseph Michelini
Guest

He stated wheel horsepower, meaning 80 percent of bhp… that is why it is lower, because on average you lose 20 percent from the crank to the wheels.

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