McLaren 600LT Exhaust 'MSO' vs. Standard Valved

If you own a 600LT you’ve probably heard there is a 'MSO' exhaust and wondering if you should upgrade. Let's clarify one thing before we get started, a lot of people mistakenly refer to the US valveless system as the "MSO exhaust," but that’s not actually correct. The valveless version is just the standard US spec exhaust, not an MSO upgrade, the US have less stringent noise and regulatory requirements to the UK and in turn do away with the valves of the standard UK Mclaren 600lt.

With that correction out of the way let’s break down the two different systems.

The Standard Valved Mclaren 600LT Exhaust: A Dual Personality

The stock exhaust on the 600LT in the UK (and other regions with stricter noise regulations) is a valved system, meaning it has flaps that open and close depending on the drive mode and throttle input.

• In Comfort mode or at low RPMs, the valves stay closed, keeping the car relatively quiet for daily driving.
• In Sport or Track mode—or when you push the throttle hard—the valves open up, letting out more of the engine tone.

This system gives you the best of both worlds—quiet when you need it, loud when you want it. It’s perfect if you daily drive your 600LT or don’t want to wake up the neighbours every time you start the car on an early morning Sunday run.

That said we don't generally buy a 600LT to be quiet and sensible :)

The US Spec Valveless Exhaust: A Bit Louder Less Weight

In contrast to the UK 600LT exhaust the US spec version has no valves and is a straight pipe system which has no back box. Best shown in the comparison pic below.

Key Differences vs. the UK Valved System:
No exhaust valves – Unadulterated sound through out not only just in certain driving modes or high rev range.
Lighter weight – No valve mechanism and no back box means weight reduction. You dropping in the range of 8kg.
No software changes needed – The car doesn’t need ECU updates or remapping. This is just dealers in the UK creating fear and doubt.
Pure, unrestricted sound – Slightly louder and sharper than the UK-spec system.

If you install the US-spec exhaust on a UK car, it’s a simple swap. No ECU updates, no remaps, no hassle. Just unplug the valve solenoid, tuck it away neatly inside the car, and you won’t have any warning lights or issues. It’s a completely plug-and-play upgrade.

The "Warranty Void" Debate – Dealer Fear Tactics vs. Reality

If you're in the UK and thinking about installing the US-spec valveless exhaust, you may have heard conflicting opinions about warranty concerns.

Some dealers will fit it for you with no questions asked, while others act like it will immediately void your entire warranty.

The truth? It’s just a back box.

• It doesn't bear any upstream issue to the engine, ECU, or any other components.
• It has zero impact on reliability or mechanical components.
• There are no known cases of a McLaren warranty being voided purely for fitting this exhaust.

Some dealers just don’t want to deal with modifications and will use fear tactics to discourage owners from making changes. If you’re unsure, speak to an independent McLaren specialist like V Engineering—they’re true experts who understand the car inside and out, rather than just repeating “computer says no" which is often the usual dealer response.

Final Thoughts

The 600LT sounds incredible no matter which exhaust you run, but if you’re after the full, unrestricted experience, switching to the US spec valveless exhaust is the easiest way to unlock more drama. It’s a straightforward swap, doesn’t require ECU changes, and is as close as you’ll get to a race car soundtrack on the road. Well until you also upgrade the cats to sport cats anyway :)