CO2 emissions / testing...

October 03, 2020, 06:26:08 PM

The 205 is possibly due it's MOT in just over a month if the testing authority here decide to re-introduce them for its class of vehicle (car over 4 years old)

They pulled a fast one a week or so ago on owners of cars that were at 4 years, bringing back the testing of those vehicles at very short notice and catching some out... I'm hoping that'll not happen to me, but as they've shown form for it I can't take the chance and am preparing her regardless or not of getting a further MOT extension..

Anyhow, wee car's been completely gone over recently and everything is spot on with the one exception of the emissions.

The last MOT (of approx 18 months ago) shows she passed with a reading of 2.4% (3.5% being the threshold)

I've read (could be a crock, so not taking it as gospel) that 1 to 2% is expected for the GTI engine with 1.5% considered ideal if it's an older engine (which presumably they all are now!).

When a garage checked her again this week she came back at 5.6%, though that was very easily brought back down to 2.4% again using the correct setting up process, (Haynes and others) and not just fiddling around with the various screws.

So I'm happy the cars set up right and has never in my time had some of the common idling issues these cars can apparently suffer from.

If it turns out that I don't have to test her until next year that reading may again drift so I picked up one of those Gunson gas testers (digital type - G4125) and I can do it myself in future.

It's not quite plug'n'play... you need to be very particular about how you set it up and use it, plus it's got an advertised accuracy of +/- 0.5% meaning if you're hovering about the threshold it could be a problem.

Anyone else used these / have longer experience of them?

I'm consistently getting 2.4 to 2.8% with it while keeping the settings perfect.

If the higher one is out 0.5% the wrong way, that's very close to a fail... do you find them accurate / your readings match the MOT readings?

Separately... any one use the emission reducing additives, some even advertise as being specifically for pre-MOT use?

Re: CO2 emissions / testing...

Reply #1 – October 03, 2020, 06:32:29 PM

Give it the old 'Italian Tune Up' and see what it's at!

Re: CO2 emissions / testing...

Reply #2 – October 03, 2020, 06:47:38 PM

That's the way I always drive it, maybe if I took it a bit easier instead!

Re: CO2 emissions / testing...

Reply #3 – November 20, 2020, 10:35:37 AM

Going to resurrect this one in light of having just put the car through the MOT.

Since the original post I got the CO down to 1.3%... partially because of some further tweaks not mentioned above and partially because I've better sussed how to use the Gunson correctly.

Anyhow the MOT center matched my 1.3% with their 1.320% so if you're looking to do your own checking, have to recommend the Gunson as being accurate and up for the job.

Something I can't check are the hydrocarbons.

The MOT gave them as 153 ppm and while the threshold is 1200 ppm I believe that's way too high for the normal running of even an older engine?

I've no idea if mine are good, bad or to be expected for a 30 year old non-catalyst car.

The 205 is the original Bosch L-Jetronic set up, the predecessor of what's probably in older MK2's, so not sure how that might affect things.

Any experts can shed some light?