Technical Support

Many Eurojet related products are sold for off-road use only. All performance modifications and installations are at the customers own risk. Eurojet holds no responsibility either implied or otherwise for mechanical, electrical or other failure when using any aftermarket performance products. Items sold for off-road use only are illegal in many states and provinces and are intended for racing vehicles which may never be used on a public road.

By purchasing any aftermarket performance product, the customer takes full responsibility for any use, and/or misuse of the product and agrees that Eurojet  holds no responsibility for any consequences, legal, or other, of such use and/or misuse.

Technical Documents

MK6 GLI Exhaust Dyno Sheet

MK6 Gen2 Exhaust System White Paper

MK6 Gen2 GTI Exhaust Installation Instructions

MK5 GTI Gen2 Exhaust System Installation Instructions

MK5 Rabbit 2.5/MK5/MK6 2.5 Golf Exhaust Installation Instructions

Questions? We've got answers.


PCV Systems

Intercooler Systems



What’s the basic theory behind an exhaust system on a turbocharged car?

For simplicity’s sake, we’ll refer to the “exhaust system” as everything post-turbo all the way to the tips at the bumper. An exhaust system is a coordination of carefully measured out bends, engine harmonics, and design that eliminates backpressure from the system on turbocharged vehicles.

Our goal is to design and deliver a clean-running, aggressive but non-intrusive, power producing exhaust system…We feel we do a damn good job of it.

One very important factor on a properly designed system is the downpipe design. Elevated exhaust gas temperatures (EGTs) can severely hinder performance, so you want a system that does not restrict flow within a close proximity of the turbo. Why? Because the harder the turbo runs, the hotter the EGTs become. High EGTs cause stress to the system, damage and warp the exhaust flanges, and can eventually cause catastrophic failure if left unmonitored.

This means that you want a port-matched flange with a downpipe that exits the turbo as straight as possible to allow the exhaust gases to exit as fast as possible. Now, a straight pipe isn’t possible in most cases unless you’re running it straight out of the hood like a drag car, so bends will be necessary. With that in mind, you want gradual bends with the least amount of interference or changes in direction and no sharp angles to allow the gases to exit. Changes create “hot spots,” choke up the system, cause premature wear, and hinder the overall performance of the engine.

Our mufflers are designed based on OEM parameters, but with our own proprietary inclusions. We use an E3 high-temperature fiber that is far superior to the regular short fiberglass fibers that most manufacturers use to reduce costs. This ensures longer life, reduces noise, and increases acoustic insulation. The muffler can handle sustained temperatures of 1,200° F, with intermittent temperatures of 1,600° F. Maximum temperatures these mufflers will see in your application should not exceed 700° F.

We also incorporate hangers and flex sections to absorb vibrations that increase the lifetime of the exhaust system.

Lastly, a performance oriented exhaust system is a foundational part of the modification process. As your horsepower increases, the need to exhaust gases is also increased. The OEM pipe size and catalytic converters are design for OEM power levels. If you plan on going faster, you’d better plan on getting our exhaust.

Why choose 3" diameter for your system?

There is a VAST difference between naturally aspirated (NA) and turbo exhaust design. The design of turbo exhaust systems is completely counter to that of NA design. NA is based off of velocity, utilizing it to scavenge cylinders during the blowdown process. To increase the velocity on NA systems, the diameter is tapered and reduced in size, which creates backpressure within the system. It's a delicate balance on NA design; go too big and velocity and the scavenging effect is lost, go too small and backpressure is killing all the gains made by velocity and scavenging.

With that said, turbo exhaust design squashes everything that we just talked about. In turbo cars you want as much velocity created within the turbo manifold as possible (within safe boost levels, of course). The faster the velocity, the faster the spool of the turbo. The faster the spool of the turbo, the faster you need to eliminate the exhaust.

In a turboback system, you want the least amount of backpressure as possible. This is why you see many race cars and drag setup with the downpipe rifling out the hood or poking out of the fender. It's actually functional, not just badass. The intent is to eliminate all pressure post-turbo to make the best use of the pressure that has been built up within the manifold. Get those gases out ASAP!

Less Pressure Post Turbo = Maximum Boost Response = Increased Velocity throughout the RPMs.

So, back to the question: Why should I buy a 3" exhaust when I see advertisements that 2.5" is better? Generally, 2.5" is fine for 250 hp. If your stock downpipe is 2.40”, then what's the point in paying $1100 for a downpipe that is only 1/10" larger in diameter and needs to be mated to specific software to see the advertised gains? Meaning, if software is written for a 2.5" downpipe, then the results will be skewed for a 3" comparison on the same software…

As for 3"…for anything pushing 300 hp, 3" is your best bet. You are sub-optimal with a 2.5" downpipe with anything above 250 hp.

These are the basics of our exhaust design. We can go deeper into it if you'd like, just give us a call and talk to one of our engineers.

What is T304 stainless steel?

Stainless steel is a "steel alloy," meaning is has an alloy content of at least 11%.  Stainless steel does not corrode or rust as easily as ordinary or mild steel, but it is not "stain proof." This means that if there is a ton of salt on your roads in the winter and moisture, salt, and road grime accumulate on the exhaust system and are not rinsed off on a regular basis during heavy weather, your stainless steel exhaust system will rust and corrode. Sorry, stainless steel is not "rust proof."

Stainless differs from mild steel by the amount of alloy or chromium that is mixed with the metal. For example, when mild steel is exposed to the elements and is unprotected (meaning no coatings), moisture and grime permeate the matrix of the metal. Once this occurs, rust forms, and then it's able to spread fairly easily throughout the metal matrix. Stainless steel has enough alloy content that it creates an oxidized barrier that repels corrosion from spreading into the internal matrix.

Why is material thickness important for exhausts?

One very important thing to take into account is the thickness of material used when constructing a proper exhaust system. There are many less-expensive stainless systems on the market. However, many systems use thin-walled stainless, some with almost half the wall thickness we use in our systems.

Material thickness is not used to combat corrosion—T304 stainless steel already minimizes corrosion. Instead, this thicker material is used to keep excess noise out of the cabin. The material also ensures that the system will not deform during years of the expansion and contraction that occurs during normal operation.

Our Gen2 exhausts have a 0.065” thickness, up from 0.049” in previous systems. This thicker material reduces cabin noise and improves long-term reliability.

How does the exhaust achieve and maintain its sound quality over time?

Our goal with our Gen2 exhausts was to decrease cabin noise and bring out the European sound quality that a 2.0T produces. We improved on the following areas:

  • Pass-through area—We were able to increase the pass-through area of the core from 30% to 40% by adding internal expansion joints and superior sound-absorbing material.
  • Inlet-outlet placement—We changed from an offset inlet-outlet to a center inlet/outlet design, which provided equivalent sound absorption while ensuring consistent temperatures throughout the muffler and minimizing turbulence.
  • Anti-reversion chamber—We added an anti-reversion chamber to stabilize the long sound waves and reduce cabin drone. It has the added benefit of reducing the weight of the rear muffler without reducing the exhaust flow.
  • Tubing—We’ve increased the wall thickness from 0.049” to 0.065” to keep the drone out of the cabin and behind the car.

With these improvements, our exhausts deliver a cleaner European sound without any reduction in the exhaust flow.

Why is exhaust flow important?

Exhaust flow, measured by cubic feet per minute (CFM), is crucial to maximize horsepower and minimize turbo lag. Our Gen2 exhausts improve exhaust flow in two areas:

  • The v-band flange design was improved using a male/female flange design to ensure perfect alignment, eliminate exhaust leaks, and prevent condensation sweat.
  • We changed the radius of the bends, increasing the center line radius to increase exhaust flow. 
What is the advantage of a modular v-banded system over a slip fit system?

It boils down to precision and design. A slip fit system gives the fabricator the ability and flexibility of not having to be exact with every bend. V-banded systems demand perfection. They are precise and spot on almost 100% of the time when pulled out of our jigs. They are simple to install, the tips do not hang or fall out of place. The modular system allows for quick and easy replacements and upgrades, and allow the end user complete control over how the systems fits and looks on their car and more importantly what options they decide to choose.

How do male/female v-band flanges improve fit and simplify installation?

Gender-based v-band flanges self-align, ensuring a smooth matting surface throughout the connection. In contrast, distortion between alignments after clamping for non-gender flanges can exceed 0.25”, an issue that may not be visible because the clamp hides the misalignment.

All Gen2 Eurojet exhausts include a male/female v-band flange. This design guarantees that the joint will not leak exhaust or sweat condensation, issues that can occur with v-band connections. 

What is the advantage of a formed v-band flange over a machined flange?

A formed V-band flange is 20 percent lighter than the machined flange. Because it is formed from tubing, the expansion and contraction characteristics are the same as the exhaust pipe itself. 

How does this fit a TSI and an FSI?

We've machined and slotted all of our flanges as well and tightened the bend and left the hangers adjustable for a perfect fitment across all transverse 2.0T motors. That's right! It fits the GTI, Jetta, Tiguan, Passat, CC…anything with a transverse 2.0T in the Volkswagen Group family and it'll mate right up.

Porting and flowmatched pipes.

Take a look at the inside of our pipes. Where possible, we port and clean all the "sugaring" that forms on the inside of the pipes during the welding process. This cleans the pipe and allows for uninterrupted airflow.

Why corrugation within the flex?

This added inner sleeve within the flex section prevents premature failure. Braided flex sections without a corrugated sleeve will "puff up" over time and restrict exhaust flow. You will not find this issue on our systems.

Why Clampco clamps?

These clamps have been proven to be the strongest clamps on the market. They're made out of stainless steel and once they're tight they're not going anywhere.

Do Gen2 exhaust components attach directly to Gen1 exhaust components?

Our Gen2 exhausts include even more features that improve sound quality, exhaust flow, and overall reliability. They may require minor modifications for compatibility with Gen1 systems.

Where are Eurojet exhausts built?

We are now building our exhaust systems in the United States to ensure quality and keep our supply line filled. This allows us to stand behind our products and offer a lifetime warranty on exhaust systems. 

PCV Systems

What is a positive crankcase ventilation (PCV) system?

A positive crankcase ventilation (PCV) or a crankcase ventilation system enables the engine components to allow pressure and gases to be routed back into the intake stream.

Combustion motors create “blow-by.” “Blow-by” consists of gases that are pushed past the pistons and piston rings, which in turn create pressure within the head and the crankcase.

These gases can be vented in two ways. One, they can be simply vented to the atmosphere, meaning there is a vent that allows the gases and pressure to be vented. Or, it can be recirculated into the intake stream.

What is the difference between a vent-to-atmosphere (VTA) and a recirculated system? 

A vent-to-atmosphere (VTA) system is the simplest of all systems, and uses a port at the block and the head to vent the gases into either a catch can or into the atmosphere. We recommend a can, otherwise you’ll be splattering gunk all over your engine bay and things will get messy.

A recirculated system is a bit more complex, but not by much. Whether you’re routing the gases through a set of baffles or catch can, or running a “draft tube” like our passage plate design on our PCV replacement systems, it’s routed from the block and headed back into the intake stream.

How is a PCV system different on a turbo engine vs. a normally aspirated (NA) engine?

Pressure, pressure, and pressure.

A turbo is increasing the pressure within the system. A PCV system is connected to the block and head and then routed back into the intake tract. The issue is that when the turbo builds pressure, it builds it within the intake manifold, causing the pressure in the intake manifold to be greater than pressure within the crankcase. This also creates pressure and pushes it back into the head. So, to avoid this catastrophic problem, our motors are equipped with a “check valve.”

Under idle, the intake vacuum is at near maximum. This is the time when “blow-by” occurs, so the check valve within the OEM system at this point in time is providing the needed restriction.

As load on the motor increases and pressure builds within the system, vacuum is eliminated from the system and pressure is introduced. At this point, the check valve closes to prevent a reversal of airflow back into the crankcase.

What makes the Eurojet PCV Link Plate unique?

Eurojet’s innovative MK5 2.0T FSI PCV Plate replaces your failing original equipment manufacturer (OEM) PCV plate with a strong but lightweight plate that not only retains the functionality of the OEM PCV plate, but also dramatically increases your flexibility when planning for future modifications. With aircraft-grade aluminum construction, it is strong and lightweight, and built to last.

What makes our plate unique is the flexible design. The system is completely modular, giving you a great deal of flexibility to configure your setup, and even to upgrade to one of our catch can setups later. Want to change can setups? No problem. Need to block off a port completely? We have you covered. Learn more.

Will the PCV kit void my warranty?

If you replace the OEM system with our PCV system, don’t expect your dealership to cover costs or provide a warranty on our parts. That means if our part malfunctions you need to contact us for a replacement, not your dealership. You also need to take into account that if you take your car into a dealership with our PCV system installed and you tell them that you’re having PCV issues they’re going to point right at the PCV plate and say “take a hike.”

Intercooler Systems

Can an intercooler be too big? 

Yes. In street-driven as well track-driven conditions an intercooler can be too big. The closer that intake temperatures approach ambient, the larger the internal surface area of the core is required. A larger internal surface area, with properly designed louvers and fins, will increase friction/drag while causing a static pressure drop.

If you simply increase the surface area, let’s say by adding another core, or by buying an off-the-shelf core and making a “kit” with your pipes, all while not properly calculating pressures and flow characteristics, don’t be surprised when optimal performance isn’t achieved.

It’s a fine line drawn by companies that market an “upgraded kit,” but are not taking into consideration the precise measuring and testing needed to design an optimal piece. Falling back on a “name” or adding another core isn’t going to do the job. Proper engineering and testing backed by precision tooling and manufacturing, however, will do the job just fine.  

What are the advantages of a bar and plate (BP) and a tube and fin (TF) design? 

Tube and fin (TF) cores are by far the weakest when it comes to strength and reliability. Because of the thin materials, stretched extrusions, and older assembly techniques, they are prone to crack, leak, and wear down over a shorter period of time when compared to a bar and plate (BP) core. 

BP cores require 5 steps for construction as opposed to 3 steps with the TF cores. They are heavier than TF cores and offer increased durability.

We focus the majority of our time on two points of the core: fins and tank design.

Fins within a pressurized system, like the inside of an intercooler, dissipate heat. They do this by “catching” passing air and then transferring the heat to the chamber wall. Then, the ambient cross flow of air cools the external fins that then cool the outside of the chambers where the internal heat is being pulled. It’s an elementary way of explaining, but you should get the point.

Three types of fins are commonly seen in the marketplace: flat, punched, and louvered.

Flat fins are seen in TF cores that are being heavily used in the VW aftermarket. However, most of the TF cores used are not using any internal fins at all, but would fall under “flat” fins both by design and by ineffectiveness. These are the cheapest and least effective fin design, but commonly used because of the cost savings during manufacturing. This design lacks the internal fins, which transfer heat to the external chamber that is cooled by ambient crossflow. This design is ineffective at lower speeds and long durations at the race track and on the street.

Punched fins are #2 on the list. They’re aptly named “punched” due to the manufacturing process. They cool better than the flat fins, but lack louvering within the internal fin structure. But, something is better than nothing in this case.

Lastly, the #1 choice for internal fins on a BP core is internally louvered fins. This type of design properly dissipates heat from internally charged air to the external fins of the core. But, there are disadvantages. The more fins, the more pressure drop. This is why proper measuring and engineering is vital during the design process. It’s insulting to the customer to just grab an off-the-shelf core, weld some endtanks on it, and then call it a “kit.”

There are many variables that you can take into account when comparing a BP and a TF core. But, when the parameters and design criteria are equal, meaning that there are equal chambers and internal fin count as well as core size, a BF will outperform a TF every time.

Why is the design of the endtanks so important?

There are two major points that should be addressed about endtank design without going into pages and pages of boring tech talk:

  • The thickness of the alloy used in construction
  • The shape or flow profile of the tank

Many companies skip the casting process and use a sheet metal constructed tank. This type of construction creates two issues. One, sheet metal is thin and aluminum is not a fatigue metal. When the metal heats and cools, expands and contracts, the durability of the metal is weakened. This is why many cracks and failures occur at the end tanks. One positive side of the thin-walled tank, however, is that heatsoak is nominal.

With our cast tanks, we use an average of 3- to 3.5-mm wall thickness. This is a good combination of thickness for durability. It is also a good thickness that avoids heatsoak on the tanks.

The most important difference in both cast and sheet metal endtanks are the flow profiles.

By design, sheet metal tanks are archaic, basic, and elementary, and shortcut the system. The square edges impede air flow, and create turbulence and eddies in the corners where cast endtanks are radiused. This in turn causes the air to tumble and cause flow issues on both the inlet and the outlets of the core.

You’ll also notice on sheet metal tanks that as oil accumulates in the core, the thin edges of the welds on the tanks will weep oil. This can be seen as little brown stains at the welds and bends of the tanks.

Cast tanks are superior in construction, they are radiused at the corners for improved flow, and have a thick enough wall to avoid cracking and weeping. Invest in a proper intercooler the first time so that you can avoid extra expenses down the road.

Why is your core so much more than "X" company's core?

Quality control backed by proper R&D vs. shortcut manufacturing and “off-the-shelf” design practices.