MOT failure. Help please

[Graham]

My '93 manual NSX has just failed it's MOT due to it's Carbon Monoxide reading being 0.638, which is higher than the 0.3 max limit. The Lambda reading was just in at 1.03 (limit is 0.97 to 1.03).

I bought the car with a stainless steel exhaust fitted and a different air intake, conical in shape and far smaller than the standard black box. I've no idea if these mods make a difference.

Does anyone know what components or settings can be changed or adjusted to bring it into spec, please?

[amo]

hi mate what if you give it a good hard run clear what crap there is in the exhaust

thx amo

[m666 edd]

Does it have the catalytic converters still? Sounds like they may have been removed.

[Graham]

Spot on edd! Just spent an afternoon underneath it. No cats ! I do have the old exhaust system which came with the car so I'll try an refit it and get it re-tested.

Can't legally give it good blast as it's out of MOT, amo. I could take the long route on the way to the re-test I guess. He He !

Can the system be re-tuned to compensate for no cats? I know absolutely nothing about emissions, I'm a nuts and bolts kinda bloke.

[m666 edd]

The job of the catalytic converter is to get rid of Carbon Monoxide so unless the old exhaust system has them attached to it you'll be needing to get hold of a set.

They'll look similar to:
http://www.nsxprime.com/photopost/data/500/IMG_9239-OL.jpg
(these are aftermarket cats)

At the moment you'll have straight through pipes with no bulges.

[Graham]

Yep, the new system has no bulges. The old system has cats but God only knows how effective they were. They still have the complete mesh inside them. If I get an MOT with them, I'll try to get them off the old system and put them in line with the stainless steel exhaust. They're so rusted though, I may mangle them trying to detach them.

Those in the picture look nice. Any idea how much they cost?

[m666 edd]

Might be worth sticking the whole original system on just to get the MOT sorted then try and separate them after. Get some stainless nuts and bolts for future ease of use while you're at it.

No idea about them cats on the pic. I just googled an image :)

[Kaz-kzukNA1]

Hi, all.

Please and one more time, please, do not use the combination of commonly available 304 Stainless bolts AND Stainless nuts on any parts getting heat/vibration especially on the exhaust/header.

It will 100% seize and anyone working on your header/exhaust area will struggle to remove them.

At least, please try to use different family of stainless (4xx and 3xx) if you still want to use the stainless bolts and nuts.
It is best to use standard Fe bolts and nuts unless they are used at the spring loaded oval gasket point.

Some of the car manufactures go even further.
For example, on our later NSX models, Honda decided to use specially treated nuts (black coloured) at the header-engine head connection point for the very reason as above.

I always use this nuts when I have to replace them when working on the header/exhaust area.

It would be much easier to break the standard Fe bolts and nuts if we had to work on the header/exhaust area. Cheaper to get hold of initially and saves the labour charge in the future.

304 stainless changes its characteristic with heat/vibration/force. If you have aftermarket header/exhaust, try touching it with the magnet. You'll find the magnet will stick at the bent section, vibrated area and so on even it looks like a single tube.


Regards,
Kaz

[Senninha]

No idea about them cats on the pic. I just googled an image :)

Here's all you need to know ... can be ordered direct from Prospeed on NSXPrime.com http://www.nsxcb.co.uk/testvb/showthread.php?t=4978&highlight=ponies

Hope this helps and you get your MOT sorted

regards, Paul

[TheSebringOne]

Hi, If it helps I think theres a second hand pair on Ebay that off the exhaust and in good condition? HTH

[mutley]

I must have been lucky, as my car is a '92, I passed emission test without cats. I still have my original system too, but I had to grind off the old bolts as there was nothing left of them.

Jim

[NSXGB]

...I just have a very understanding MOT inspector. :D

[m666 edd]

I think it's just any car manufactured August 1992 and later require catalytic converters for the MOT.

[Graham]

Hi, If it helps I think theres a second hand pair on Ebay that off the exhaust and in good condition? HTH
Any chance of the link to the cats on ebay please? All I seem to be able to see are for the 3.2 litre engine.

[nigel]

No matter what combination of bolts and nuts used ALWAYS use High Temp Anti-Sieze, the GOLD coloured stuff, sometimes goes by the name C5-A Anti-Sieze depending on the brand.
It won't gurantee they will always come back off but more times than not they will.

Cheers
nigel

[AR]

Graham you are not to far, if your cats are buggered and you need to borrow a set I can lend you mine for the MOT.

Cheers,

AR

[AR]

Can't legally give it good blast as it's out of MOT, amo. I could take the long route on the way to the re-test I guess. He He !


As far as I know if you are booked for MOT then you can be out of MOT. I am not a lawyer etc etc, but I have been there with other cars and they have allowed me to come back next week.

Hope that helps,

AR

[TheSebringOne]

Sorry Graham, I can only currently find 3.2s, It was a while back when I thought I saw ones for a 3.0.

[Graham]

Graham you are not to far, if your cats are buggered and you need to borrow a set I can lend you mine for the MOT.

Cheers,

AR
Thanks for the offer AR, I'm going to try to fit the old system today and hope to get a retest on Friday. If all goes tit$ up I'll come back to you.

Actually the headlights are apparently too low, probably because the previous owner had bigger wheels on the front. I'll try and find the adjusters for that too.

[NSXGB]

Actually the headlights are apparently too low, probably because the previous owner had bigger wheels on the front. I'll try and find the adjusters for that too.

Are you sure they have not been adjusted from the centre console and just need switching back?

[Graham]

Are you sure they have not been adjusted from the centre console and just need switching back?
The centre console thingy is set to 0 so I presume that's the highest headlight setting. Just found the page in the manual and I've turned the screws a bit and brought the beams up. I never knew there was a minimum height, just a maximum height so you didn't dazzle anyone.

The old exhaust system is back on now, after a day of struggling, luckily with the help of a friend. The cats leaked but I've bunged up the hole with some exhaust gasket sealant. I'll try for a retest on Friday.

If it passes I'll get two new cats anyway and I think I need a new pipe with the flexible piece in it, that crosses under the engine sump. The old one is a bit blowy. I gummed that up too. I'll get some decent bolts while I'm at it, like Kaz recommends.

If it fails I'll get back to AR over in Cardiff. I'm off on holiday soon, so worst case scenario means I'll be turning up to Japfest in VW Passat !!!!

[AR]

Fingers crossed for you but if you get stuck get in touch.

[Graham]

IT PASSED. YEEEEEHAAAAAH.

I'll still get some stainless steel cats for the new exhaust system and fit the good stuff back on, but at least I don't have a gun to my head any more. At least I might get to Japfest in a Japanese car now.

Thanks for all the advice,

Now on with all the other problems. Oh well the summer's coming !!!

Cheers

Graham

[m666 edd]

Good to hear.

[AR]

Good to hear, forget the Stainless cats, just get your straight pipes back on until next year.