Failed MOT on 996TT with modified Exhaust !

[Jon Luik]

Hi Guys

Just tried to put my 996TT through its first MOT and it failed !

1. Exhaust Emissions. The CO is 0.61% Vol but needs to be less than 0.30%.

The Exhaust is not a standard one, its was installed by PSI motorsport. Any suggestions ?

2.The car is a left hand drive and failed on the fact that the rear fog lamp is incorrectly mounted to the left side (should be rightside) Any suggestions ?

Many thanks.

[Steve_M]

Can't really help with emissions. You'll probably have to put the exhaust back to standard for the MOT

As for the fog light, I have previously had this problem on a different grey import car and I wired up the right hand reversing light as a fog light, you lose a reversing light but the fog light is intergrated into your light cluster and looks a lot better than an extra fog light stuck on.

[silver993tt]

If you then put the sports exhaust back on after the MOT you'll invalidate the MOT from that point onwards.

[cyrus1971]

just take car to a more "friendly" MOT station use to performance cars, tell them what it failed on and why you are there. RHD rear fog is a blank so 15 Min labour to swap them over thats all and could do yourself very easilly.

[big.bad.wolfie]

Surely this emission problem is a sign of something else? A too richly running engine ie. fueling problem etc.

[cyberface]

big.bad.wolfie said:

Surely this emission problem is a sign of something else? A too richly running engine ie. fueling problem etc.

I agree - 'just' a sports exhaust should make little change to emissions (and certainly shouldn't make the car run too rich).

If the cats have been removed then that's a different matter - and it'll be tricky getting through an emissions test without catalysts...

Has the ECU been modified? Many turbo chip jobs overfuel to help prevent detonation.

[Paul Tolliday]

I owned an Elise S1 bought from a dealer with a sports exhaust fitted. Come the first MOT it failed on emissions. Turns out the sports exhaust does not have a cat and sends reading all wrong. My mate did the MOT so I ended up with a certificate. When I went back to the dealer they told me Elise owners put a standard exhaust back on for MOT and then change back to their sports exhaust!! I'm not that enthusiastic so I sold it! Don't expect this is the case with yours though!!

[993rsr]

When I imported my 993GT2 with Roock exhausts and cats it had to be SVA tested - failed on emissions badly. Fault was not the exhausts but the map. Remapped and sailed through on the emissions.

Sounds like a crappy PSI map to me.

[911 habit]

I just had my 996 TT MOT ok, with a DMS map and Fabspeed cats & exhaust. Emissions were up over the previous year when all was std. but still well within the limits.

Does the sports exhaust you have include up rated CATs? If you have a mod’d chip map, it will have been most likely developed with a full sport exhaust and bigger CATs.

I had a 996 c2 chipped with just the back boxes changed on the exhaust and not the cats, this failed a MOT on emissions, because the chip map was over fuelling and the std cats weren’t big enough to cope. Changed the CATs and it fixed it.

[Jon Luik]

Thanks for your answers, guys.

The work done to the engine includes the following:

• Reprogramming the Motronic ECU-241 electronic accelerator unit• Sports air filter • Sports clutch• Stainless steel sports exhaust and catalytic converter, with original outlets• 2 KKK 24 Turbo• 1 Fuel pressure regulator

May be it could be the ECU or Cats ?

[ninemeister]

Probably Cats if they are 100 cell units, but more likely to be mapping faults if they are 200 cell.

Make sure that the engine and exhaust is red hot for the test, this may affect the reading enough for you to scrape through.