What is the difference between your street and race series downpipes?
Street series downpipes include a catalytic converter. Race series downpipes do not. Race series downpipes are not legal in most states and for racing use only. Check your local emissions laws to see if a catalytic converter is required in your area before ordering. Our downpipes are all modular in construction allowing you to change configurations at any time.
What is the difference in sound between your street and race series downpipes?
The race series downpipe will be louder than the street series downpipe in every case. When not using a catalytic converter you will hear more turbo noise, more burbles, and an overall louder exhaust note. The street series downpipe is toned down in comparison to the race series downpipe. All the sounds are still there, just toned down.
What kind of cat are you using on your street series downpipes?
We are using a Magnaflow high-flow cat. It uses a 400 cell ceramic catalyst. The honeycombs are not interwoven, they are straight through in design. Magnaflow catalytic converters offer a lifetime warranty and have been proven to be incredibly reliable.
Will your downpipe cause a CEL?
Race series downpipes WILL cause a CEL.
Street series downpipes MAY cause a CEL.
We have had a 75% CEL success rate with our catalytic converter choice. None of our local test vehicles using our street series downpipe have reported a CEL. We have found that 25% of our internet customers have reported a CEL with the street series downpipe. Race series or street series, the CEL can be avoided by using an angle block adaptor on the second oxygen sensor. To learn more about CEL fixes please read our Test Pipe FAQs.
Will my current cat-back fit your downpipe?
mk4 1.8T Downpipe
Using our stock sized adaptor almost any aftermarket cat-back will bolt-up using the stock band clamp. Almost every cat-back exhaust on the market has been designed with a reduction to stock pipe size in order to bolt-on to the stock downpipe with ease. To find out if your aftermarket cat-back will bolt up please contact the manufacturer. If the cat-back system bolts up using the stock band clamp it will fit perfectly with our downpipe and stock sized adaptor.
TT 225 Downpipe
All current aftermarket cat-backs available for the TT 225 have been designed to install at the stock band clamp with no modification. Our downpipe includes a 2.55" stock sized adaptor to allow installation of your stock cat-back or any aftermarket cat-back exhaust. No 3" cat-back is currently available for the TT 225. If you are building a custom system we can provide you with one of our 3" flanges for $15.
How do I connect my 2.5" or 3" cat-back to your mk4 1.8T downpipe?
Ideally if you have a 2.5" or 3" cat-back you should connect to our downpipe without any restriction. If your 2.5" or 3" cat-back has been designed to install with the stock band clamp it will install flawlessly with our stock sized adaptor. The downside to this is a significant reduction in pipe size at the clamp. To avoid restrictions we offer a 2.5" and 3" adaptors. In most cases something will need to be modified to install a 2.5" or 3" cat-back with no restriction. Let's discuss...
There are easily 30 different cat-backs currently available for the mk4 chassis. There is no way we can offer an adaptor for every 2.5" or 3" exhaust out there. In most cases, something will need to be modified in order to connect your 2.5" or 3" cat-back to our downpipe. In some cases no modification is necessary.
If your cat-back has a reduction pressed into the piping...
Most cat-backs have a reduction pressed into the start of the piping. You will need to cut this reduction off and extend either the cat-back or our adaptor. We recommend extending our adaptor and saving the reduction for later sale of the exhaust. A sleeve clamp will need to be used to connect the cat-back to the adaptor.
If your cat-back includes a separate reducer...
Some cat-backs are cut short and include a clamp-on reducer which slides into the stock sleeve clamp. In this case either the cat-back or our adaptor needs to be extended. We recommend extending the adaptor and using a sleeve clamp to connect the cat-back to the adaptor. Save your cat-back's reducer for later sale of the exhaust.
Every cat-back is different!
Please be aware that every cat-back differs. Our 2.5" adaptor measures 2.5" OD. Our 3" adaptor measures 3" OD. Measure your cat-back! Aftermarket cat-backs can range from 2" to 3" using every pipe size in between - even metric. Every install is going to be different. In most cases we recommend modifying our adaptor. At any time a new adaptor can be purchased to suit a new cat-back or return to stock. If in doubt, seek professional help!
Can you recommend a 2.5" sleeve clamp?
If you're using our 2.5" adaptor you can use an Audi TT 225 OEM sleeve clamp. The part number is 8L9 253 139A. World Impex sells this clamp for $36: Audi TT OEM Sleeve Clamp. If you are using our 3" adaptor you will need to source a 3" clamp.
Can you add a wideband bung or EGT bung?
Yes, we can. For $10 we can add an additional oxygen sensor bung for use with a wideband gauge. For $10 we can add an EGT bung at the turbo flange. Bungs will be TIG welded in a proper location that we have tested. We will have order buttons loaded for these upgrades soon...
Why not use stainless steel hardware?
Stainless steel exhaust hardware comes with many caveats. If the hardware doesn't rattle loose it will weld together with no hope of removal. Here's why:
Stainless steel expands more than mild steel at the same temperature. When your exhaust heats up, the stainless hardware expands more and can come loose. Vibrations will cause the nuts to back off within a few miles. If stainless steel hardware stays tight, it's stuck forever.
Stainless steel is known as a "gummy" metal. When stainless steel threads are torqued together tiny balls of metal snowball in between the threads and literally weld the threads together. This is called galling and can only be avoided by using plenty of anti-sieze compound. Even with anti-sieze we don't recommend stainless steel hardware.
We include grade 5 zinc plated hardware with all of our downpipes. This hardware is corrosion resistant, but like anything will eventually rust over the years. Penetrating oil will help break them loose. They may put up a fight, but at least they will come off!
Why not build the downpipe in stainless steel?
Stainless steel has it's applications, and our downpipes aren't one of them. We feel strongly about our choice to use mild steel / aluminized piping and will be honest in our explanation why.
Stainless steel has some advantages in extreme applications such as exhaust systems. One benefit to using stainless is initial corrosion resistance. Stainless piping can be polished to a mirror finish for a beautiful look in the show room. It can also save weight on a race car. Because stainless has a higher tensile strength it is possible to use thinner gauge pipe and achieve the same strength as a thicker mild steel. While these advantages make stainless steel a major selling point in aftermarket exhaust systems, the advantages are short lived and not worth the additional cost.
95% of all stainless steel exhaust systems on the market use grade 304 stainless steel. 304 is a commonly available grade which exhibits all the characteristics of stainless at an affordable price. The #1 selling point of stainless steel is corrosion resistance. Salesman will tell you that 304 will never rust. A 304 exhaust system will rust, just give it some time. Improper polishing of 304 removes the additional carbon content on the surface of the metal. Once the polishing compounds and impurities are burned off the metal is much less resistant to oxidation. A polished 304 system will turn a golden brown color after a few heat cycles and begin to rust after 6 months in a corrosive environment. Additionally, welding stainless steel can actually cause rust. When TIG welding the area on the metal directly to the sides of the weld bead are called the heat affected zone (HAZ). When 304 is TIG welded the slightest bit of extra heat will change the properties of the metal in the HAZ allowing faster corrosion.
Using thinner gauge pipe to save weight is a great idea on a race car. On a full interior or even gutted street car that mindset really isn't worth the possible risks. The only risk we're talking about is the system breaking. Fractures will happen at the weld joint in the HAZ. As mentioned above, the properties of the metal change in the HAZ weakening the metal. Besides the change in properties, the simple physics of connecting a 0.050" pipe to a 0.375" flange is asking for trouble. With the forces that are applied to the exhaust system during a hard run these connections are where the system will break. Butt welds and muffler - pipe welds can also cause problems.
VW transversely mounted motors are notorious for excessive motor movement. Everyone at 42 has their VW projects and we've all experienced broken exhaust components due to excessive motor movement and wheel hop. On a street driven vehicle why risk breaking your exhaust system? A broken exhaust is an inconvenience for you, the customer and 42.
Everyone at 42 has been building VWs and modifying them for years. Some of us have been tinkering with VWs for 10 years, while some of us have spent the last 5 building wild custom setups. We have experience using both mild steel and stainless steel exhaust components and systems. We are 100% confident in our choice of materials for our downpipes and exhaust systems. We are not going to build a product that we don't have 100% confidence in.
For us, stainless steel is not the answer. We use 14 gauge (0.075") tubing which is coated in aluminum. This is known as "aluminized" tubing and is very resistant to corrosion and oxidation. Our flex sections are 100% stainless steel. This is one area where stainless is recommended. We use Magnaflow catalytic converters and mufflers. Magnaflow uses a low grade of stainless steel for their mufflers and catalytic converters. While not a high enough grade to call them "stainless steel", they are more corrosion resistant than uncoated mild steel. Magnaflow offers limited lifetime warranties on their products and we honor their warranties. We CNC machine our flanges from mild steel. These are uncoated and will be the first thing on the system to rust. The flanges are thicker than necessary and will not simply rust to pieces. That's just not possible.
Yes, our systems will rust. All exhaust systems will rust. It's a question of how long will it take for the rust to affect the life of the system. We have discussed the vulnerable areas of a stainless steel system and have discussed the materials used to build our systems. Think about how long you plan to own your car and compare that to how long you need your exhaust system to last. Would you rather overpay for an initially more shiny system , or pay less for a stronger, more reliable system? Our systems are engineered to really fit, last a long time, and make power. Your choice.
Corrosion resistance can be had. Ceramic coating is the most durable coating process available. When ceramic coated, a mild steel exhaust system can literally last forever. JET-HOT (www.jet-hot.com) offers many ceramic coatings which we use when possible. Their sterling coating is affordable, bulletproof, and great looking. We have used JET-HOT in the past and recommend their services to anyone interested in ceramic coating. Please visit the JET-HOT website and contact them to have your system coated.
Other corrosion resistance options to exist. High temperature powder coatings can be used which will withstand 1000°. This is useful after the catalytic converter. The downpipe and cat can be heated to over 1500° during normal use. Also, high temperature paints can be purchased. If you plan to paint your system, be sure to closely follow the product's instructions. Prep the metal correctly and cure the coating and you will have no problems.
We hope this has answered any questions you may have had about stainless steel use in exhaust system construction. If you have any additional questions or would like discuss this issue further, please contact Evan via email tech@42draftdesigns.com.
On eBay I can get a downpipe really cheap. Why buy yours?
The simple answer - you get what you pay for. The long answer - there's plenty of reasons that our downpipes are higher quality than an eBay downpipe. There's almost a dozen different mk4 1.8T downpipes available on eBay. Any one comparison we make won't apply to all the available options. In a general sense, here's a few reasons why these downpipes aren't all they seem.
Most eBay downpipes are made from very thin stainless steel. We have measured less than 0.040". This just won't hold up. The majority of these downpipes have a cheated angle at the turbo flange. This makes tightening two of the four turbo bolts extremely difficult. In addition, most of these downpipes have no transition to 3.5" at the turbo flange. The exit of the turbo is 3.5" If you use a Ko3 flange with a 3" opening the exhaust gases will be hitting a 1/4" ledge on every side. The flanges used on these downpipes, if any flanges are used at all, are seldom accurate and can require grinding to fit correctly.
The welding on these downpipes is hit or miss. Some have been MIG welded and covered up with a quick finish pass with a TIG welder. Many of them are clearly improperly TIG welded. Instead of laying a bead of weld the welder simply laid down a series of tack welds to mimic a TIG bead. This holds up for shipping, but the weld penetration is far from ideal. TIG welding takes time and practice. The easiest thing to learn is a tack weld. Let your imagination do the rest of the thinking here.
None of the eBay downpipes include a catalytic converter. Those that claim to have a hollow resonator welded in to look like a cat. Some of the downpipes include a reduction to stock pipe size for a bolt-on fit. Most don't, leaving you on your own for a reducer. All of the downpipes are stainless steel (who knows what real grade?). You can learn how we feel about stainless steel above.
To sum up - just be careful. What's advertised may not be reality. You can compare the construction of our downpipe to an eBay downpipe by reading our product descriptions, checking out our pictures, and reading our FAQ. We're confident in our product and hope that is reflected in our product descriptions. Oh, and we don't charge $45 for shipping :)
Will your downpipe still fit if I change my turbo?
Probably not. Our downpipe will work with the stock K03 and K03 sport turbo. If you install a K04-001 turbo the downpipe will fit. This downpipe will not fit any other turbo configuration. The same goes for the TT 225. Our downpipe is only designed to fit the stock turbo.
Will your 3" turbo-backs be available again?
Yes! We hope to re-release our 3" turbo-backs in winter 2007.
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