The Top 6 Infiniti G35 Performance Upgrades. Powered by the VQ35DE engine, first gen G35’s produced from 2003-2007 ranged from 260-298 horsepower. The G35 received a facelift in 2007, as well as minor engine modifications that increased power to 306hp. The new engine was dubbed the “Rev-Up” engine and was assigned the VQ35HR code.
Early G35 models will dyno in the 220-240whp range, while rev-up G35s will dyno closer to 250whp. While these power figures aren’t bad for a naturally aspirated V6, the G35’s 3,500lb curb weight can make it feel sluggish.
Bolt-on mods can add 40-50whp to the G35 for performance enthusiasts or those looking for a little more power. Unfortunately, because the VQ35 engine is naturally aspirated, exceeding that power level will necessitate forced induction, which will cost you close to five figures. This guide will cover turbo upgrades briefly, but if you are serious about adding forced induction, I recommend reading our 350Z Turbo Upgrade Guide. We don’t yet have a turbo upgrade guide for the G35, but because both the G35 and the 350Z use the VQ35DE and VQ35HR engines, the guide is still applicable to the G35.
G35 Performance Upgrades
Among the best Infiniti G35 performance upgrades are:
- Intake
- Plenum Separator
- Headers
- High Flow Catastrophes or Test Pipes
- Exhaust with a Catalytic Converter
- Kits for Turbochargers
1) Upgraded G35 Cold Air Intake
A cold air intake is one of the simplest entry-level modifications to make. By sucking more air into the combustion chamber, upgraded intakes increase power. More air means more combustion, which means more power. Furthermore, the increased air pressure within the intake manifold will result in some small increases in air pressure, and higher air pressure results in more power.
On a stock engine, the benefit of an intake is minimal, but the benefits increase as other G35 mods are added. The most power gains from an intake are obtained when forced induction is used, but without it, you can expect power gains in the 3-6whp range and torque gains in the 2-4wtq range.
G35 Upgraded Intake Advantages
- Gains of 3-6 watts
- 2-4wtq increases
- Improved air flow
- Engine noise on intake
- Enhanced throttle response
Power gains will be on the lower end of the spectrum with a stock engine, but will rise to the upper end with other mods.
Recommendations for Intake Systems
- Overall winner: aFe Takeda G35 Intake
- G35 DC Sports Intake is the best bang for your buck.
The Takeda intake system from aFe is the best value for money on the market. At $265, the intake is reasonably priced and easy to install. The installation is extremely simple and can be completed by any novice. aFe claims 16whp and 19wtq gains, but these figures are exaggerated and unrealistic.
If you want a more affordable option, the G35 DC Sports Intake is the best bang-for-your-buck intake with reputable reviews. At $150-$200, this intake is ideal for those on a tight budget looking for the same performance benefits. The most noticeable difference between the two intakes is the piping finish and how the intake appears in the engine bay. Both perform the same function and provide the same benefits.
2) G35 Plenum Spacer Modifications
Despite being ranked second on the list, a plenum spacer is without a doubt the best mod for the G35. A plenum spacer is one of the cheapest mods and provides the most power of any of the bolt-ons we’ll cover.
The VQ35DE engine has a terrible plenum design that restricts airflow. The intake plenum is the section of the intake manifold that collects and distributes all of the air to the cylinders. It has “runners” that branch off of it to supply air to each cylinder. The space between the plenum and the first two runners on the VQ35DE is so small that it restricts airflow and reduces power.
A plenum spacer sits between the upper and lower parts of the plenum and increases the plenum’s air capacity. This increases the airflow to the cylinders, resulting in more power.
Because the VQ35HR has a new intake manifold design, this modification only applies to non-revved-up G35s equipped with the VQ35DE.
Plenum Spacer Advantages
- Bone stock 8whp
- With intake, headers, and exhaust, you can get up to 15whp.
- 12wtq increases
- Improved air flow
- Reduced air intake temperatures
MotorDyne G35 Plenum Spacer is a recommended plenum spacer.
MotorDyne has the best plenum spacer for the G35 on the market. The spacer adds 5/16″ to the plenum and is the simplest kit to install when compared to other options on the market. Installation should take no more than an hour and is simple enough for beginners. At $250, this mod offers the best value per horsepower gain of any G35 mod. MotorDyne claims 11-13whp gains, which we believe to be true.
3) Upgrades to the VQ35 Performance Headers
The exhaust manifold is the first part of the exhaust system in the VQ35DE/HR engines. It connects to the engine’s exhaust ports and collects exhaust air, which it directs to the catalytic converters. There are two exhaust manifolds, each with three cylinders. Each manifold has three pipes, one for each cylinder, which combine to form a single pipe.
Exhaust manifolds are constrictive because they have three separate exhaust ports that funnel air into a single chamber. This restriction raises backpressure, reducing power. Exhaust manifolds are replaced by performance headers. Headers have one pipe for each cylinder instead of funneling air into one chamber. So there are three separate pipes that come together at the connection to the cats.
Backpressure is reduced by giving each cylinder its own pipe. Less backpressure equals more power and cooler engine temperatures.
If you already have an intake and a plenum spacer, headers are a must-have upgrade. Once more air is flowing into an engine, exhaust restriction must be reduced, or the increased volume of intake air will create even more backpressure in the exhaust system.
Advantages of G35 Performance Headers
- 7-10whp
- Increased top-end power
- Exhaust note is a little deeper now.
- Reduce engine temperatures
- Exhaust backpressure has been reduced.
The one minor disadvantage of headers is that they reduce mid-range torque by about 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. As a result, we recommend installing high flow cats in conjunction with headers to compensate for the lost mid-range torque.
Recommendations for Headers
- Best Overall: Tomei V2 or aFe Power Twisted Steel (Both Short-Tube)
- DC Sports G35 Headers on a Budget (Short-Tube)
- PPE Long Tube Headers are a money saver.
- G35 Headers Upgraded – Best Infiniti G35 Mods
Short-Tube vs. Long-Tube
Only the exhaust manifold is replaced by short-tube headers. They then connect to the y-pipe that houses the catalytic converters. Long-tube headers replace the y-pipe and eliminate the catalytic converters entirely. As a result, they are a hybrid of headers and test pipes. They are illegal outside of racing applications because they remove your catalytic converters.
Long-tube headers are quite expensive, but the removal of the cats provides additional power benefits. Long-tube headers are an option if you intend to add headers and test pipes. However, if you want to keep your car legal and keep the stock cats or upgrade to high flow cats, you must use short-tube cats.
4) Modifications to the G35 High Flow Cats and Test Pipe
The catalytic converters are located after the exhaust manifold or headers. The G35 employs a Y-Pipe design, in which each header bolts to a separate pipe, which then merges into a single pipe where the Y-Pipe meets the cat-back exhaust system.
High flow catalytic converters or test pipes are your two options here. The most restrictive component of any exhaust system is the catalytic converter. As a result, removing them completely provides the greatest performance benefits; however, doing so is illegal. As a result, high flow cats are becoming more popular because they keep your car legal (in most states) while still providing power benefits.
The Advantages of a High Flow Cat
- Gains of approximately 10whp and 8wtq
- Most states allow emissions.
- Exhaust noise is only slightly increased.
- Backpressure reduction / increased exhaust flow
Advantages of Using a Test Pipe
- Gains of around 15whp
- Exhaust noise becomes louder.
- The greatest increase in exhaust flow
- Downside: illegal
G35 High-Flow Catalytic Converters at Their Finest
- ISR Efficiency
- MotorDyne
- Technology by Berk
- The AAM Competition
We will not “recommend” any test pipes because they are illegal. If you go this route, keep in mind that you can use either short tube headers + test pipes or long tube headers. With recent EPA crackdowns, finding catless options is becoming more difficult, and finding a shop to install them for you is even more difficult. If you go the catless route, plan on doing this upgrade yourself.
Related : The Guide to the Mustang GT 5.0 Coyote Supercharger
5) Upgraded G35 Cat-Back Exhaust System
We don’t usually recommend cat-back exhaust upgrades for performance reasons. Cat-back exhaust upgrades provide little to no benefit to most naturally aspirated and turbocharged engines. The majority of exhaust gains come from headers, downpipes, test pipes, and other accessories. However, for the G35, upgrading the cat-back system has proven to add significant power.
There are numerous exhaust options available. The two most important factors to consider are exhaust style and piping diameter. There are dual exhaust systems and single exhaust systems for style. Dual systems improve flow but are more expensive. Piping diameters typically range between 2.25′′ and 2.5′′, with larger diameters clearly flowing more.
We won’t go into too much detail here because the most important factors are cost and sound. Most dual exhaust systems will provide the same performance benefits as single systems. So a lot of the time choosing the right exhaust system for your G35 comes down to sound and price.
Advantages of Cat-Back Exhaust
- Gains in power of approximately 8whp and 8wtq
- Exhaust note that is louder
- Improved airflow
Recommendations for G35 Exhausts
Keep in mind that fitment will vary depending on whether you have a sedan or coupe, as well as whether you have a rev-up or non-rev-up engine. We’ll try to lay it out in a helpful format based on price preference because there are so many options. Also, before purchasing, consider what all is required. Some of these systems include Y-Pipes, while others do not, and some require you to purchase them separately, etc.
Exhaust Systems at the Lowest Prices
- DNA Driving / Auto Dynasty (same exhaust)
- Manzo
- Spec-D
Brands with a Little More Respect
- Megan Racing
- Tanabe
- Magnaflow
Best Exhaust Systems for Performance (Most Money)
- Stillen (our favorite) (our favorite)
- HKS
- Gemini Invidia
- Borla
6) Turbo Kits for the G35
We’ll keep this one brief because there’s too much information to cover about adding forced induction. Check out our 350Z Turbo Guide for an idea of the cost, power levels, and supporting mods required to install a turbo in your G35.
Power levels can be increased by installing a turbo kit to 400-450whp for VQ35DE engines and 450-500whp for rev-up engines. Power levels higher than this are possible, but will necessitate internal upgrades as well as thousands of dollars in additional mods. Entry-level turbo kits will cost around $7,500, with additional mods costing a few thousand dollars more.
Even for more entry-level turbo additions, full bolt-on mods and a combination of fueling and cooling mods will be required to ensure proper reliability. Having said that, we don’t recommend turbocharging your G35 unless you’re willing to spend $10,000 or more.
How about G35 Music?
There aren’t any true plug-and-play tunes available for the G35. The UpRev Tuner is the best option, but it requires you to tune the car yourself and isn’t as simple as something like a Cobb Accessport, which no longer supports VQ35 engines.
First and foremost, we do not recommend tuning unless you are running a full bolt-on or a turbo or supercharger. We highly recommend getting a custom dyno tune from a reputable tuning shop if you are a full bolt-on and want a tune. This can add 10-15whp, which you will most likely not see with a flash tune. If you use forced induction, you will undoubtedly require a custom tune.
Summary of G35 Performance Mods
The majority of power gains on a G35 can be obtained via the intake and exhaust systems. For a few thousand dollars, you can add 40-50whp and 35wtq to your G35 with an intake, plenum spacer, and exhaust modifications.
Keep in mind that the power gains we quote for each mod will vary depending on the other G35 mods you have installed. In general, the more mods you add, the more benefit each one provides and the more power it generates. A plenum spacer is the best place to start because it is the cheapest and provides the most power gains. Headers and high-flow catalytic converters are the next best things to add, but they are more expensive, as is a cat-back exhaust system.
Without forced induction, 290whp is going to be close to maxed out on a rev-up engine with full bolt-ons. Depending on the model G35, you can expect 260-275whp from VQ35DE models.
While a fully modded G35 will not be able to walk on turbocharged cars, adding 40whp will really open up the car and make it a lot more fun.
