USA / MSO Exhaust Swapout

I quite enjoyed this one, after initially fitting the Exhaust Valve Controller this was a lovely next-step in working on the McLaren.

As I mentioned on the Valve Controller page, after a while I quickly realised that there was no scenario where I ever 'closed' the valves. So when I discovered that there was a direct-fit and McLaren branded exhaust replacement, that not only improved the sound but significantly reduced the weight - and it did not affect warranties or anything, I absolutely had to swap it out!

exhaust-part

Part Codes:

Fitting It

It's really not that bad, it took me about 3 hours, it easily would have been less but I was ultra-careful and had to faff about getting some alignment sorted with the exhaust tips.

First you get the engine cover off, couple of bolts, tape up the edges so you don't clatter it against the spoiler, and then pull it out. Then you can unbolt the upper part of the heatshield and view the exhaust itself:

exhaust-1

Now you can disconnect the exhaust valve connectors (x2) and work around undoing the bolts that hold the exhaust itself in place. Take care not to drop the bolts, or washers (or your socket) as once these go into the undertray you have an entierly different job on your hands!

With the final bolts and clamps undone, the exhaust section lifts out easily. On mine (i think a spider thing) there are also two hosts that pull air into the exhaust from the roof storage area. Either something to do with drying the roof when it has been stowed when wet - or - some part of the noise-making system that the non-spider ones have (which is essentially defunct on the spider as you just open the rear window).

That then lets you compare the components like so:

exhaust-2

As you can see, the heatshields are almost identical - I just got the matching one as it doesn't have the big holes in the top for the valves and that kinda felt like the right thing to do in case it later started to melt the paint off the engine cover...

Finally, slot the new one back in, and bolt it all back up!

exhaust-3

You can make some mild adjustments to the angle of the exhaust at this stage, to get the tips aligned with the engine cover. So before you do the heatshield up (like I did...) do have a quick test-fit of the engine cover and make sure you are happy first.

The final job is to tie up the exhaust valve controllers out the way, so you just need to unclip them off the old exhaust (electronic part only) and then find a suitable place in the wings to store them securely. Some people bolt them up on a spare set of bolt holes, but i only heard of this method after doing mine. So the ones on my car are just tied up with an X of cable ties around the wing support struts. This avoids having to modify the ECU to code them out, and it also keeps things warranty friendly by not modifying the electronics with 3rd party disabling plugs (which you can buy instead).

Can't say I can feel the weight saving, but the sound is much improved - mentally, it's definitely faster too...

Oh, and there is a full album of photos here

Alignment Of Exhaust Tips

When you do the test-fit of the engine cover to make sure the tips are where you want them, if they do need adjusting then it is basically a case of slackening off the bolts and clamps a little so it can wiggle around. There is flex in both the T brace itself (between the two main pipes) also and most of the holes for mounting the exhaust are oversized compared to the bolts that bo in them (along with big washers).

The combined movement in all these places lets you shift it around a bit, and 'bend' the pipe angles. Be sure to slaken off the large exhaust clamps first as most of that movement comes from there.

All of these can be done ONLY while the upper heatshield is out of the way - as I found out afterwards 😭

Additionally - please do remember to torque up the bolts when it's all aligned, otherwise your flames may escape in unwanted places...