Do I need a standard back exhaust box to make lambda work?

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Sun Dec 13, 2015 10:07 am

The tester isn't necessarily talking rubbish guys - Larger bore, free flowing exhaust systems can actually cause the emissions to go out... Difficult to know in this specific case of course, just off description.

Has it previously (and genuinely) passed MOT's with this exhaust set up?

mercutio · Post by **mercutio** » Sun Dec 13, 2015 11:00 am

should be able to pass with whichever back box buddy it could be anything causing it to fail an exhaust leak could do it a dodgy O2 sensor, no oil change, blocked air filter, fouled plugs or bad wires or even tappets

when was the last real service?

prelerepairman · Post by **prelerepairman** » Mon Dec 14, 2015 11:44 am

I'm an A8 .
Yup a Hacksaw'll sort it but I've got the same system and the back pressure's the problem....ALLEGEDLY
Think I'll buy a cheap standard back box (90 quid) and adapt to fit my SS pipes...then remove after test.

prelerepairman · Post by **prelerepairman** » Mon Dec 14, 2015 11:46 am

wurlycorner wrote:The tester isn't necessarily talking rubbish guys - Larger bore, free flowing exhaust systems can actually cause the emissions to go out... Difficult to know in this specific case of course, just off description.

Has it previously (and genuinely) passed MOT's with this exhaust set up?

Yes that's my worry as much of this car was botched before I got her.

mercutio · Post by **mercutio** » Mon Dec 14, 2015 5:17 pm

does it have a cat fitted?

prelerepairman · Post by **prelerepairman** » Tue Dec 15, 2015 11:23 am

Yes of course..It's a 1999 model so no cat, no mot.

Post by **vanzep** » Tue Dec 15, 2015 2:30 pm

Im sure you said it was an aftermarket cat and that could be an issue if its old and a bit knackered....
Your welcome to borrow the aftermarket one i have here for your MOT if that helps any - its 355mm long and is made by Klarius it looks fairly new and is in good condition. Think its about £90 new so again probably no great shakes when compared to a genuine Honda one but it might be better than what you have.

prelerepairman · Post by **prelerepairman** » Fri Dec 18, 2015 11:15 am

Quick update. New standard back box fitted. Car still fails CO : 0.64 instead of 0.68 (shd be 0.3 or less) AND now the lambda fails at 1.043. Car wasn't super hot.. Going to try a cat next then there's only the lambda sensor to try.........
Of course oil/filter and plugs done before all this.

Post by **Vtecmec** » Fri Dec 18, 2015 11:23 am

mercutio wrote:when was the last real service?

Do this.

chrismc · Post by **chrismc** » Fri Dec 18, 2015 1:06 pm

Isn't a sensor quicker/cheaper than splitting the system after trying to find an A8 Cat?

This is given A8 cats are not interchangeable with any other H-series cats....

Can't say I'm at all shocked the backbox made no difference. I did warn you...