The 6 Best Infiniti G35 Performance Mods

Early G35 models will dyno in the 220-240whp range whereas the rev-up G35’s will dyno closer to 250whp bone-stock. With just a few bolt-on modifications we can add about 50whp on top of these numbers. However, without expensive forced induction upgrades the G35 is going to be capped around 290whp for rev-up models and 270whp for early models.

In this guide we’re going to talk about plenum spacers, intakes, headers, and exhaust upgrades, as the bolt-on mods to get you that extra 50whp. We also dig into turbo kits briefly, for those looking to add even more power.

Infiniti G35 Performance Upgrades

• Intake
• Plenum Spacer
• Headers
• High Flow Cats or Test Pipes
• Cat-Back Exhaust
• Turbo Kits

If you would rather consume this content via a video, check out our 5 Best Infiniti G35 Mods video below:

1) Cold Air Intake Upgrade

One of the simplest entry-level modifications to make is the addition of a cold air intake. Upgraded intakes add power by sucking more air into the combustion chamber. More air means more combustion and more combustion means more power. Additionally, the increased air will create some small increases to air pressure within the intake manifold and higher air pressure also results in more power.

The benefit of an intake on a stock engine is minimal, but the benefits increase as other G35 mods are added. The biggest power gains from an intake are achieved when forced induction is added, but taking that out of the picture you can expect power gains in the 3-6whp range and torque gains around 2-4wtq.

Intake Benefits

• 3-6whp gains
• 2-4wtq gains
• Increased air flow
• Cool intake engine noise
• Quicker throttle response

Power gains are going to be on the lower end of the spectrum on a stock engine but will increase towards the upper range once other mods are added.

2) Plenum Spacer Mod

Although I put this mod at #2 on the list, a plenum spacer is hands down the best mod for the G35. A plenum spacer is one of the cheapest mods and provides the most power out of all of the bolt-ons we are going to discuss.

A plenum spacer sits between the upper and lower parts of the plenum and increases the air capacity of the plenum. By doing so this also increases the airflow to the cylinders, providing more power.

Since the VQ35HR has a new intake manifold design, this modification only benefits the non-rev-up G35’s with the VQ35DE.

Plenum Spacer Benefits

• ~8whp bone stock
• Up to 15whp with intake, headers, exhaust
• ~12wtq gains
• Improved air flow
• Lower air intake temps

3) Short & Long-Tube Headers

Exhaust manifolds are restrictive because you have 3 separate exhaust ports funneling air into one chamber. This restriction increases backpressure which reduces power. Performance headers replace the exhaust manifolds. Instead of funneling air into one chamber, headers have one pipe for each cylinder. So it is three separate pipes that then meet at the connection to the cats.

If you have an intake and a plenum spacer then headers are an even more important upgrade. Once you are flowing more air into an engine you need to reduce exhaust restriction otherwise the increased volume of intake air will create even more backpressure in the exhaust system.

Headers Benefits

• 7-10whp
• Improved top-end power
• Slightly deeper exhaust note
• Lower engine temps
• Reduced exhaust backpressure

The one small downside to headers is that they will cause a drop in mid-range torque by around 8wtq. Adding high flow catalytic converters will net the torque loss out to about zero while also adding another 10whp which makes it worth it in our opinion. Therefore, we do recommend adding high flow cats along with headers to supplement the lost mid-range torque.

4) High Flow Cats and Test Pipe Mods

Following the exhaust manifold or headers is the catalytic converters. The G35 uses a Y-Pipe design in which each header bolts-up to a separate pipe that then combines into one pipe where the Y-Pipe meets the cat-back exhaust system.

You have two options here: high flow catalytic converters or test pipes. Catalytic converters are the most restrictive part of any exhaust system. Therefore removing them completely provides the most performance benefits, however, it is illegal. Therefore, high flow cats are becoming the more popular option as they keep your car legal (in most states) and still provide power benefits.

High Flow Cat Benefits

• Approx. 10whp and 8wtq gains
• Emissions legal in most states
• Minimal increase in exhaust noise
• Reduced backpressure / increased exhaust flow

Test Pipe Benefits

• Around 15whp gains
• Louder exhaust noise increase
• Biggest increase in exhaust flow
• Downside: illegal

5) Cat-Back Exhaust System Upgrade

The majority of exhaust gains come from headers, downpipes, test pipes, etc. However, for the G35 upgrading the cat-back system actually has proven to add some meaningful power.

There are a bunch of exhaust options out there. The two things to look for are exhaust style and piping diameter. For style there are dual exhaust systems and single systems. Dual systems provide better flow but also cost more. Piping diameters usually range from 2.25″ to 2.5″, with the larger diameters clearly flowing more.

Cat-Back Exhaust Benefits

• About 8whp and 8wtq power gains
• Louder exhaust note
• Increased airflow

6) Turbo Kits

We’re going to keep this one relatively short here since there is too much detail to cover on adding forced induction. Check out our 350Z Turbo Guide to get a sense of cost, power levels, and supporting mods needed to add a turbo to your G35.

Adding a turbo kit can boost power levels up to 400-450whp for VQ35DE engines and 450-500whp for rev-up engines. Power levels above this are possible but will require internal upgrades and thousands of dollars in additional mods. Entry level turbo kits are going to run you in the ballpark of $7,500 and supporting mods will run you a few thousand more.

Even for more entry level turbo additions, you will need full bolt-on mods and a combination of fueling and cooling mods to ensure proper reliability. With that being said, we don’t recommend turbocharging your G35 unless you are comfortable spending $10k+.

ECM Tuning: It’s Not Really a Thing

There really aren’t any true plug-and-play tunes for the G35. The best option is the UpRev Tuner but this requires you to actually tune the car yourself and isn’t as plug and play as something like a Cobb Accessport which no longer supports the VQ35 engines.

First of all, we don’t recommend tuning unless you are full bolt-on or running a turbo or supercharger. If you are full bolt-on and want a tune we highly recommend getting a custom dyno tune from a reputable tuning shop. Doing so can add 10-15whp which you likely won’t see from any sort of flash tune. If you are running forced induction then you will definitely need a custom tune.

Summary

The majority of power gains on a G35 can be unlocked through the intake system and the exhaust system. With an intake, plenum spacer, and some exhaust modifications you can add 40-50whp and about 35wtq to your G35 for a few thousand dollars.

The best place to start is with a plenum spacer since it is the cheapest and offers the highest power gains. Headers and high-flow catalytic converters are the second best things to add, but these begin to get a bit pricey as is the case with a cat-back exhaust system.

Without the addition of forced induction 290whp is going to be pretty close to maxed out on a rev-up engine with full-bolt ons. For VQ35DE models you can expect 260-275whp depending on which model G35 you have.