Milltek Full Exhaust & Cat Bypass for BMW 3 Series E30 M3 (1987-1992) – Maximum Flow, Motorsport Use
This is Milltek's large-bore downpipe and de-cat for the BMW 3 Series E30 M3. It replaces the factory downpipe with a larger-bore pipe and removes the catalytic converter entirely, clearing the single most restrictive point in the exhaust for the biggest flow gain available at this position in the system. It's usually fitted alongside a Stage 2 remap, since the ECU needs to be told to expect the different readings the lambda sensors give once the cat's gone. It's offered in non-resonated or resonated versions, so you can pick the setup that suits how the car's used.
It's built for owners already committed to a serious power upgrade rather than a casual bolt-on, so pair it with the matching Milltek cat-back system for the full effect.
Because it removes the cat, it's intended for off-road and competition use. A de-catted car will fail an MOT emissions test and isn't legal to use on UK roads.
Specifications
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System Type: Full System (including Cat Replacement Pipe)
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Pipe Diameter: 63.5mm (2.5")
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EC Approved: No
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Race System: Yes
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Fitting Time: approx. 2 to 2.5 hours (Milltek figure)
Key Features
- Made from T304L aircraft-grade stainless steel, which is anti-magnetic and resists discolouration
- Mandrel-bent pipework keeps a constant diameter through every bend for unrestricted flow
- 63.5mm (2.5") pipework
- Removes the factory catalyst for maximum flow (off-road and competition use only)
- Resonated (quieter) or non-resonated (louder) versions
- Designed, developed and manufactured in the UK by Milltek Sport
Fitment
- BMW 3 Series E30 M3 (1987-1992)
Not suitable for: the BMW 3 Series F80 M3 & M3 Competition Saloon (Non OPF/GPF Models Only), which needs the Milltek Downpipe & De-cat BMW 3 Series F80 M3 & M3 Comp Saloon Non OPF/GPF 14-18; the BMW 3 Series F30 328i M Sport Automatic (without Tow Bar, Non-xDrive & N20 Engine Only), which needs the Milltek Downpipe & De-cat BMW 3 Series F30 328i M Sport Automatic (without Tow Bar, Non-xDrive & N20 Engine Only) 12-15; the BMW 3 Series G80 M3 & M3 Competition S58 3.0 Turbo (North American/ROW Non-OPF/GPF Cars Only), which needs the Milltek Secondary Catalyst Bypass BMW 3 Series G80 M3 & M3 Comp S58 3.0 Turbo (North American & ROW Non-OPF/GPF Cars Only) 21+.
Installation
Milltek quotes a fitting time of approx. 2 to 2.5 hours. This work involves removing parts close to the turbo and engine, so we recommend fitting by a specialist with a ramp and suitable software support.
Upgrade Further
Also available from Milltek for this car: Milltek Full Exhaust & Sports Cat BMW 3 Series E30 M3 87-92.
What's the difference between the resonated and non-resonated versions?
The resonated version adds extra silencing for a quieter, more refined tone. The non-resonated version leaves it out, so it is louder and more aggressive.
Does it fit the BMW 3 Series F80 M3 & M3 Competition Saloon (Non OPF/GPF Models Only)?
No. For that car, choose the Milltek Downpipe & De-cat BMW 3 Series F80 M3 & M3 Comp Saloon Non OPF/GPF 14-18.
Is it road legal?
No. Removing the catalyst means the car will fail an MOT emissions test, so it is for off-road and competition use only.
Do I need a remap?
A suitable remap is strongly recommended, as the engine management needs to account for the change in flow and sensor readings. Speak to your tuner before fitting.
Will removing the cat cause a warning light?
Without suitable software it is likely to, as the ECU expects the readings a working catalyst gives. This is why Milltek pairs it with a remap.
How long does it take to fit?
Milltek quotes approx. 2 to 2.5 hours.
What is it made from?
T304L aircraft-grade stainless steel, which is anti-magnetic and resists discolouration better than lower grades.
Is there a warranty?
Yes. Milltek products are covered against defects in materials and workmanship. Contact us with your order number if you have a problem.
