The stock downpipe has a double-walled tubing with an inside diameter of just over two inches. Following the restrictive downpipe section, the stock unit subjects the exhaust gases to the choking effects of the catalytic converter. After the cat, it flattens out into a section dubbed the infamous "U-Bend," which is a section of pipe crushed into a "U" shape by GM in order to fit a rear o2 sensor. This section has less volume than the same length of 2" pipe, and approaches the volume of a 1.75" pipe with the rear o2 sensor in place! Our downpipe eliminates all of the aforementioned problems! Gains of over 15HP have been seen, along with a substantial drop in knock. Most users can drop a pulley size and/or eliminate 5-7 degrees of knock. This part can typically be installed in under an hour.
Our downpipes are made from high quality stainless steel. Even the flanges are stainless, which isn't something any other company offers. All welds are held to the strictest of quality control standards to ensure a professional finish. Our Weld quality is higher than any other downpipe manufacturer. When shopping around, ask if the downpipe is 100% stainless, ask if they use stainless and for a close up shot of their welds. Compare them to ZZP's downpipes, and it will be apparent why ZZP's downpipes are leaps and bounds ahead of the competition. They are guaranteed leak free and feature high quality welds, laser cut flanges and 16 gauge metal. We have test-fitted our bolt-in pipes on both stock and modified cars with perfect fitment. Our pipes even include the slight factory angle offset on the flange.
Bolt in Off-road pipes do not have catalytic converters in them. You will need an o2 sim or PCM programming to remove the 137-141 & 420 codes. They are not legal for use on public roads. They provide maximum HP gains and minimum weight. They bolt up to a stock or aftermarket cat back exhaust system. They do not include an o2 bung for the secondary o2 sensor unless selected from the drop down. All bolt in downpipes have a 2.5" exit flange that bolts in the factory location, if you would like a 3" exit flange please select the "3" with 3" exit" option.
Bolt in with Cat downpipes can be used on stock to highly modified cars. They do not require PCM programming and are emissions legal. We use Spun metal high flowing catalytic converters. They should not void your factory warranty. They bolt into a stock or aftermarket cat back exhaust system. They include an o2 bung for the rear factory o2 sensor. All bolt in downpipes have a 2.5" exit flange that bolts in the factory location, if you would like a 3" exit flange please attach a $20 custom payment to your downpipe order and we will include the correct bolt in flange.
2.5 inch downpipes are designed for naturally aspirated applications where no loss in low end torque is desired. They can also be used in supercharge applications when the lowest possible cost is important. They come with interlock flex standard.
Interlock flex, sometimes called turbo flex is the best flex money can buy. Typically, the downpipes in our market use a single wall flex. This is durable but has a ribbed inside design that can disrupt airflow. This type of single wall flex is what people are running when you hear them complain about a whistling or ticking noise coming from their exhaust section. To remedy these issues, you can buy a double braided flex which has braided stainless on the inside, as well as outside, of the flex. The problem is that they fail very easy on supercharged cars. Interlock flex is the 3rd solution and while is costs more, it is the best. It withstands the higher temperatures of boosted applications and provides a flat smooth surface for the exhaust gas to run over. Click here to see interlock flex compared to single wall flex. Seen in the pictures below, the stock pipe narrows down to a 2" hole before lowering into the cat. This is very restrictive, causes KR, and introduces a loss of HP.
Most common downpipe gaskets can be found here, exhaust manifold to downpipe inlet gasket, downpipe to factory catback/2.5" catback gasket.
04+ Grand Prix' will require a style "B" o2 extension for the rear o2 sensor. Please use factory torque specs when installing our downpipes.
This will only fit the 3800 v6 engine, does not fit LS4 b8 cars, if you have an LS4 powered car, you would want our "GXP" downpipe instead.
This downpipe is not compatible with any aftermarket headers, it is designed to fit the stock OEM rear manifold. *Shipping charges are based on dimensional weight** Offroad pipes require PCM programming or our o2 sim.***UPS shipping only please ***IMPORTANT information concerning High Flow Catalytic converters*******
The downpipes we sell come with a high performance converter. It is OBD2 compliant but it is on the very edge of being so. The PO 420 code is set when the rear bank O2 sensor PCM thinks that the converter is not doing a good enough job. Because the stock cat is so thick and dense, it can still function when the tune is off or it gets old. An error in tuning, running too rich, having too cold of a thermostat, too cold of plugs, or an old primary O2 sensor can all affect the engine enough to set a code when using the cat. This code DOES NOT affect the way the car runs, it just sets an SES light. To fix it, you'll need that code removed from the PCM, or you can run our O2 emulator(not available for ALL vehicles), or you can clear the code and try to tune the car in better to allow the cat to operate more efficiently. This is a situation in which your cars stock sensor was not designed with your performance goals in mind. Please make your purchase with the understanding that over time, an SES light could be thrown due to the reasons stated above. This is not grounds for a warranty claim, as a repair or replace of the cat/downpipe would not permanently fix the code.
ZZPerformance will give out a $50 coupon code for returning your stock downpipe to ZZP for catalytic converter recycling. You don't even have to pay for return shipping! Simply email a picture of your cat to Henry@ZZPerformance.com and if it is OEM we will email you a UPS prepaid return label. Then put your old downpipe (or just the cat) in the package that the new one came in and drop it off at any UPS shipper (excluding the catback box due to being oversized). Then we'll email you a coupon code good for $50 off of your next ZZP purchase! Returned units can be cut up but the OEM converter must be intact. Already bought our downpipe? We'll still offer the $50 coupon code but you'll have to pay for the return shipping.
Note: We can only issue prepaid shipping labels to people in the lower 48 states, this excludes Canada, Hawaii, and Alaska.
To take advantage send to:
ZZPerformanceAttn: Cat Credit (Order #)2450 28th ST SWWyoming MI 49519
For everyone: Include your original order # and email address to send the coupon code. Write down your return tracking number for your records!
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