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Old 20-08-2017, 01:31 PM
h4pry's Avatar
h4pry h4pry is offline
Join Date: Dec 2005
Location: Kent
Posts: 1,334
Default The perils of a de-cat system

This is my second Coupe of which I've owned for nearly 7 years. The previous owner of this one fitted a Supersprint exhaust system in the following config:

-OEM headers with O2 sensors still in situ and no adjustment to ECU

-A seemingly generic decat mid-section (although I always thought it was SS until I removed from the car yesterday)

-Genuine stainless steel Supersprint backboxes

I was fed-up having challenges come MOT time due to the emissions issue, and I had a suspicion the car was down on power (difficult to tell when it gets infrequently driven / given full beans), so I intended to revert the whole system back to stock.

Having scoured eBay, forums and breakers yards for 6 months, nothing came up. BMW want £2600 just for the mid-section and this is an exchange price with 20% discount! So I'm up shit creak as I don't have an item to exchange, and so would be looking at well into ££££ to replace the system for new. :(

As luck would have it, a mid-section came up on German eBay for £800 - still seriously £££ but better than the alternative,so I bought in. Enthusiasm in abundance, I decide to have a go fitting it but retaining the SS backboxes.

Anyway I fitted them yesterday on my drive with no great dramas other than a few awkwardly positioned bolts. Took the car for a spin last night and OMG!!! It has at least 25% more power than previously and pulls hard all the way through the rev range in each gear.

So the moral to this long story is tread carefully with de-cat pipes, as unless they've been configured properly by a specialist, it could be a step backwards!

Here's a pic of the infamous pipes with the OEM alongside:


And gratuitous pic of the car getting treated to a tank of premium this morning.

Out: 99 S50 Titan Silver V876 KKO
In: 98 S50 Estoril.......
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Old 21-08-2017, 04:11 PM
ian's Avatar
ian ian is offline
Senior Member
Join Date: Nov 2006
Location: New Forest
Posts: 2,032

I couldn't agree more. Many a mistake has been made fitting so called "tuning parts" that screw the OEM system design.
S54 Titan Silver metallic. Black leather, most factory options including sunroof, Becker Cascade and Becker Silverstone changer.
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