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MAD 3.5" Fat Boy Downpipes BMW G82 M2 / G80 M3 / G82 M4

SKU: MAD-047
Price
$299.00
Currently Backordered - You can still place your order and we'll ship your order as soon as the product is back in stock!

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Installation Services

Don’t worry about the hassle — let our expert team at Forza Motorworks handle the installation for you. Our professional installation ensures everything fits and operates exactly as intended, giving you clean, factory-quality results, proper wiring or mounting, and avoiding the risks of DIY mistakes. You’ll save time, avoid frustration, and get peace of mind knowing the job is done right the first time. Contact us to learn about our installation services and enjoy a seamless upgrade from day one.

FAQ

Shipping Information
For items that are in stock, purchases made after 9am EST will be usually be shipped out in the next 1-2 business days. Please inquire to confirm lead times if you have specific time constraints. Orders will be sent via signature required at our discretion unless otherwise requested.

International Shipping
Any and all customs duties, taxes, import fees, and/or tariffs assessed in connection with the purchase shall be the sole responsibility of the customer/end user.

Return Policy
We have a 30-day return policy, which means you have 30 days after receiving your item to request a return. To be eligible for a return, your item must be in the same condition that you received it, unused and in its original packaging. All returns are subject to a restocking fee based on item and package condition. Buyer is responsible for paying for return shipping costs. If you need a return label, we will email you a return label and deduct cost from refund. Original shipping costs are not refundable. Special order items are not eligible for return.

Cancellation Policy
In order to cancel your order you must email within 24 hours of placing your order or before your order has shipped, whichever occurs first. Special order items are not eligible for cancelation.

Exchange Policy
We have a 30-day exchange policy, which means you have 30 days after receiving your item to request an exchange. To be eligible for an exchange, your item must be brand new in box. Buyer is responsible for paying all shipping costs to exchange product.

Product Description

The MAD BMW S58 3.5″ Fat Boy Downpipes are a high-flow exhaust upgrade engineered specifically for the S58-powered M2, M3, and M4 (G87, G80, G82, G83). Designed to replace the restrictive factory downpipes with free-flowing 3.5″ tubing and large-diameter bends, these downpipes reduce backpressure and optimize turbo efficiency for quicker spool, improved throttle response, and better overall performance. Built from premium 304 stainless steel with precision TIG welding, the Fat Boy Downpipes deliver robust durability and enhanced exhaust tone without compromising drivability. Ideal for enthusiasts pursuing both street and track gains, this upgrade lays the foundation for significant performance improvements, especially when paired with a high-flow cat-back system or tuning.

Fitment Notes

  • Designed to fit BMW M2 (G87) chassis with S58 engine

  • Fits BMW M3 (G80) and BMW M4 (G82, G83) with S58 engine

  • 3.5″ diameter design fits existing factory hangers and turbo outlets

  • Professional installation recommended for best alignment and safety

Included

  • One (1) MAD S58 Fat Boy Downpipe set (left and right)

  • Precision-formed stainless steel tubing and collector sections

  • Required mounting hardware for direct fitment

  • Installation instructions

Product Specs

  • Downpipe Tubing Size: 3.5″ diameter (larger than factory for freer flow)

  • Material: 304 high-grade stainless steel with corrosion-resistant brushed finish

  • Welding: TIG welded joints for strength and leak-free performance

  • Compatibility: Designed specifically for S58 engine chassis (G87/G80/G82/G83)

  • Exhaust Path: Improved free-flowing design for turbo efficiency and power delivery

Product Features

  • Large 3.5″ diameter tubing reduces backpressure and enhances turbocharger efficiency

  • Precision TIG welding ensures strong, durable joints under high heat and boost

  • Performance-oriented flow design improves throttle response and potential power output

  • Premium 304 stainless steel construction for corrosion resistance and long life

  • Enhanced exhaust tone adds a richer, more aggressive sound character

  • Direct-fit design bolts onto factory components for a clean installation