Grail 3-inch exhaust system suitable for BMW 1 Series M135i F20 / F21 (N55) – Exhaust Valve System

description

The GRAIL exhaust system with a 3-inch diameter is suitable for the BMW 1 Series. MThe 135i F20 and F21 with the N55 engine combines maximum six-cylinder sound with full road legality. Thanks to ECE type approval, the system is registration-free within the EU and ready to drive immediately. Handcrafted in Germany from L304 stainless steel.

The N55 inline six-cylinder engine of the MThe 135i already makes a statement acoustically – the GRAIL exhaust system unlocks the full sonic potential of this hot hatch. Powerful, clear, and with the distinctive GRAIL delta between loud and quiet.

Loud but Legal: You can choose between two control options – the original BMW exhaust valve control or the GRAIL ECE R-59 control for maximum legal compliance. Both options function flawlessly from a technical standpoint, but differ in detail in their noise measurement.

FLOW DOWN® is an official GRAIL partner in the Ruhr area and specializes in the professional installation of exhaust systems. Installation is carried out directly at our facility in Essen – cleanly, precisely, and including a functional test of the valve control.

Important: Select the correct variant in the configurator.

The GRAIL facility for the MThe 135i F20/F21 is offered in various versions. Depending on your vehicle, you must select the correct version in the configurator. If the wrong version is selected, the system will not fit – please check carefully or contact us beforehand.

You choose from the following factors:

• Flap control: Standard BMW exhaust valve control or GRAIL ECE R-59 control
• Tailpipes: brushed stainless steel or black

Note: This facility is exclusively for M135i models without a gasoline particulate filter (non-OPF) are available. An OPF variant will be available for the M135i not offered.

Unsure which version fits your vehicle? Send us your VIN or year of manufacture via contact form or WhatsApp – we'll check the configuration for you before you order.

Two control options to choose from

1. Standard BMW flap control
The flaps are controlled via the original flap control system of the MThe 135i is addressed – that is, via your vehicle's Sport mode. Technically flawless, however, the factory control is based on an older type approval with different measurement values. In the relevant speed range (20–80 km/h), the flaps can remain open longer, which means that the system may exceed current noise limits in noise measurements.

2. GRAIL ECE R-59 control (for maximum legal compliance)
The GRAIL control system automatically closes the flaps within the prescribed measurement ranges between 20 and 80 km/h. This ensures the exhaust system remains compliant with regulations at all times – even during a current inspection according to ECE R-59 standards. Anyone who... MAnyone who frequently drives a 135i or values maximum safety is on the safe side with this variant.

Highlights

• Specifically designed for BMW 1 Series M135i F20 / F21 with N55 engine
• ECE type approval – registration-free within the EU
• Choice between BMW control or GRAIL ECE R-59 control
• 3 inch L304 stainless steel, handcrafted in Germany
• FLOW DOWN® is an official GRAIL partner in the Ruhr area

Material

L304 stainless steel, handcrafted in Germany. Durable, rustproof, and high-temperature resistant. CNC-machined components ensure precise manufacturing. Acoustically tuned mufflers deliver a powerful sound without unwanted frequencies, while the flow-optimized pipework ensures ideal exhaust flow and thermal stability.

Available variants

Flap control:

• Standard BMW exhaust flap control
• GRAIL ECE R-59 control (for maximum legal compliance)

Tailpipes:

• brushed stainless steel
• black

Note: An OPF variant is available for the M135i not available – the system is only available in the non-OPF version.

use

The valve-controlled exhaust system replaces the entire exhaust system downstream of the pre-muffler. Depending on the chosen control unit, the valves are operated either via the factory BMW control unit or the GRAIL ECE R-59 control unit. No additional remote control or wiring harness is required.

Professional installation by FLOW DOWN® in Essen is recommended. As an official GRAIL partner, we know the systems in detail and ensure clean installation, correct connection to the damper control, and functional testing.

GRAIL order with installation at FLOW DOWN®

Since GRAIL systems have a longer delivery time due to production requirements, we offer a fair down payment model for orders including installation:

• Upon placing the order, you pay 50% of the investment.
• We will pay GRAIL in advance on your behalf and order the system.
• You pay the remaining amount after the system arrives at our workshop.
• Then schedule an appointment for the installation.

Important: The deposit option is only available for orders including installation and only works via prepayment/bank transfer. PayPal or other payment methods are not accepted.

Swiss suitability assessment

For customers in Switzerland: Upon request, you can receive a Swiss conformity certificate for the GRAIL exhaust system for an additional fee. If you are interested, simply contact our support team – we will clarify the details with you directly.

Suitable vehicles

• BMW 1 Series M135i F20 (5-door, without OPF)
• BMW 1 Series M135i F21 (3-door, without OPF)
• BMW 1 Series M135i xDrive F20 / F21 (without OPF)

Note: This device is only suitable for M135i without gasoline particulate filter (non-OPF). Each variant (flap control × tailpipe color) is a separate system – please select correctly in the configurator.

scope of delivery

• 1x GRAIL 3-inch flap exhaust system suitable for BMW 1 Series M135i F20 / F21 (in selected variant)
• Tailpipes in selected variant (stainless steel or black)
• When selecting the GRAIL control unit: ECE R-59 control unit
• mounting material
• ECE type approval (paper)

Information on admission

The GRAIL exhaust system has ECE type approval and is registration-free for EU vehicles. For imported vehicles with a different operating permit, please check before purchase whether registration in the vehicle documents is required. The included ECE type approval certificate should be carried in the vehicle.

All brands, model names and manufacturers mentioned in this shop such as AUDI, BMW, Hyundai, Kia, Toyota, VW, Tesla are used solely to describe the compatibility of our products . They have no connection with the respective brand owners and, unless expressly stated, they are not original parts from these manufacturers.

FLOW DOWN® is an independent supplier of tuning and accessories. The use of the brand names mentioned is for guidance only and does not constitute a collaboration, licensing or approval by the respective rights holders . All trademark and name rights are held by their respective owners.