JUN AUTO GT SURGE TANK FOR MITSUBISHI 4G63 LHD EVO7-8 2015M-M003

 

JUN AUTO GT SURGE TANK FOR MITSUBISHI 4G63 LHD EVO7-8 2015M-M003

This is a high-performance intake manifold / surge-tank assembly developed by JUN Auto Mechanic for the 4G63 turbo engine in left-hand-drive Mitsubishi Lancer Evolution VII–VIII (CT9A). 

JUN lists the 2015M-M003 specifically for LHD Evo 7–8 applications. 

🧠 What the surge tank actually does

Think of it as the air-distribution chamber between the throttle body and the four 4G63 cylinders.

Turbo → intercooler → throttle body → JUN surge tank → runners → intake valves

The key engineering problem is air distribution. A highly tuned turbo 4G63 can demand substantially more airflow than the original intake system was designed around.

JUN’s philosophy is interesting: bigger isn’t automatically better.

• Too small: pressure distribution between cylinders can become less uniform.
• Too large: pressure fluctuations become excessively smoothed, reducing the beneficial inertia/ram effect.
• Correct volume: balances plenum pressure stability with useful pressure-wave behaviour. 

🔬 Why JUN’s internal design matters

JUN describes its surge tanks as being designed around several variables:

Collector/plenum volume + runner cross-section + runner length + engine displacement

The internal geometry is intended to promote efficient air entry and distribution rather than simply creating a large empty chamber. 

JUN specifically discusses a curl/funnel-shaped internal form intended to improve the efficiency of air entering the runners. 

For a 4G63 being pushed toward serious boost and high RPM, that can mean a more suitable airflow architecture than simply enlarging the factory manifold.

⚙️ Important installation requirements

This isn’t a simple bolt-on replacement where you retain every factory component.

JUN states that:

• Injector and throttle body are NOT included.
• It cannot be used with the stock ECU.
• Intercooler piping must be prepared separately.
• The kit requires a suitable throttle-body arrangement. JUN’s documentation identifies the relevant throttle-body adaptation, while current specialist listings specify a Nissan N15 70 mm throttle body for this application. 

So this part belongs much more naturally in a properly engineered 4G63 build than a basic street modification.

🏁 Evo VII vs Evo VIII

The application is particularly interesting because the listing covers:

Application	Engine	Chassis
Evo VII	4G63T 3rd generation	CT9A
Evo VIII	4G63T MIVEC	CT9A
Steering	LHD only	—
JUN Part	2015M-M003	—

Specialist fitment data confirms Evo VII 2001–02 and Evo VIII 2003–05 applications. 

🔥 Where it makes the most sense

I’d classify the 2015M-M003 as a high-output airflow-management component, not a cosmetic intake upgrade.

Best matched with:

Large turbo 4G63 → high-flow intercooler → 70-mm-class throttle body → JUN surge tank → appropriate injectors/fuel system → standalone/programmable ECU → calibrated ignition & fueling

The surge tank itself doesn’t create horsepower in isolation. Its value is that it can become part of a better-controlled intake system when the engine’s airflow demand has moved beyond the factory hardware.

⭐ Technical verdict

Area	Rating
Air distribution potential	⭐️ ⭐️⭐️⭐️⭐️
High-RPM airflow	⭐️⭐️⭐️⭐️⭐️
High-output 4G63 suitability	⭐️⭐️⭐️⭐️⭐️
Street plug-and-play practicality	⭐️⭐️
Motorsport/tuned-build suitability	⭐️⭐️⭐️⭐️⭐️
Installation complexity	⭐️⭐️⭐️⭐️
Rarity	⭐️⭐️⭐️⭐️⭐️

The big story: JUN didn’t simply make a larger intake manifold. They engineered the plenum volume, runner geometry and airflow path as one system. 

That is why the 2015M-M003 is particularly interesting to serious CT9A 4G63 builders.

One important current-status point: JUN officially discontinued its 4G63 GT Surge Tank production in February 2022, and JUN’s current catalogue marks 2015M-M003 as discontinued.  

This makes genuine examples considerably more interesting to collectors and period-correct Evo builds.

JUN AUTO GT SURGE TANK FOR MITSUBISHI 4G63 LHD EVO7-8 2015M-M003