New exhaust and manifolds/hi-flow cats on my 987.1

[Jon Jon]

Hi Guys

I've just posted this on Boxa.net but thought I'd put it on here just in case it's of interest to anyone who doesn't go on that forum.

In the summer I fitted to my  Boxster 3.2S a Milltek cat back system which I bought from Design 911:

http://www.design911.co.uk/fu/prod131574/Sports-Ex...

and then a couple of months later a pair of manifolds with hi-flow (200 cell) cats from Top Gear:

https://www.topgear.co.uk/by-manufacturers/porsche...



These are my thoughts:

The exhaust;

I've always been a bit disappointed with the sound of the Boxster when the hood is down. To me it sounds a bit like a lightly souped up 4 pot hatchback with a leaky exhaust. So, I decided to fit a sports exhaust. With a budget of around a grand, I was unable to go for the fancy switchable types. There was an exception to these high cost switchable exhausts however. This was produced by Top Gear and cost just under a grand. With a lack of reviews on the latter though, I went for a Milltek owing to their reasonable reputation and I liked the look of its fancy pipework. Fitting it was fairly straight forward. It took me six hours but if I did it again, I'd probably do it in under three. Build quality was generally good. However, one of the 90 degree bends was slightly more on one side than the other. This has meant that lining up the tail pipes was more of a challenge, but not impossible.

Once installed, the car had a much sportier sound but still didn't sound special or like a high performance sports car. Additionally and as appears to be the case with nearly all aftermarket exhausts for the boxster, with the hood up it moderately droned in the 2-3000 rpm range. With the hood down it didn't. In fact with the hood down it was still too quiet but with the hood up it was marginally too loud. It still sounded like it had a leaky exhaust  when driven passed parked cars at low-ish revs with the windows wound down, although slightly less than before.

The Hi-flow cats / manifolds;

So, the next logical step seemed to be the fitment of hi-flow cats to give the car a bit more fizz in the sound department. I came across the Top Gear ones which at £485 for the pair was a bargain. Build quality was pretty good and they fitted into place fairly well although I had to loosen all of the exhaust's clamping brackets so that it's overall width could be increased slightly to make a good fit. This was straight forward. What wasn't however, was the removal of the two lamda sensors from the original left hand cat and the not insignificant problem of dealing with two snapped manifold to cylinder head studs. This meant that a job that I had planned to take a couple of weeks of just spending the odd hour here and there took three months. So, unless you really know what you're doing, make sure you have access to a back up car if you are car dependent.

The results?

Well worth it. With the hood up it still drones a bit. If I only ever drove the car with the hood up then I would keep the standard exhaust. With the hood down however, it now sound like a highly strung sports car that howls on the over-run, is very beefy if a constant speed in maintained in the 2-3000 rev range and super car-ish if taken up to the red line. The leaky exhaust sound still lurks in the back ground (yes, I have checked that it isn't actually an exhaust leak) but this is mostly drowned out but the increased exhaust volume. On the latter point, I've observed quite a few 911 996's and 997's as well as a few boxsters make this sound and it seems to be a Porsche thing. Power wise I've no idea. I'll get a dyno run done in a few months time but seeing as I haven't done a dyno run before, it'll be fairly meaningless.



Anyway, I hope this info is of some help to anyone thinking of changing their system.

Regards

Jon

[Jon Jon]

Photo of one of the manifolds.

[Maldini35]

Thanks Jon - I've fitted a Dansk back box to my 986 S and was a little disappointed with the sound.
I think I'll try the Top Gear cats too.

Cheers

[edc]

Maldini35 said:

Thanks Jon - I've fitted a Dansk back box to my 986 S and was a little disappointed with the sound.
I think I'll try the Top Gear cats too.

Cheers

Dansk do a variety of exhausts from standard replacement to loud. If all you want is sound for your 986 then a Carnewal mod or bypass is the most cost efficient way.

[Adamdove987]

Bit late in the game..
I have the top gear catless long tube headers with agency power exhaust and I too have an "exhaust leak sound" but only starting off from stop and under load obviously..
I did however remove both manifolds and found one was leaking a bit (oem gaskets with copper gasket spray). So I cleaned it up sprayed it again and retorqued.. Still have the same sound.
I'm convinced it's the sound of the engine with the header shape, size etc.
I don't have any other Porsche in my area to go by is the problem.
Could u get in touch with me please. I have a couple small questions?

[Jon Jon]

Hi Adam
Cheers for the reply. A mate of mine has a 987 with sports cats and exhaust and his makes the same sort of leaky exhaust sound and so like you say, it seems to be a characteristic of our engines.. Shame.

Jon