Carbon Monoxide meters......huh? (Mk2 GTI tuning)

[BMXJeff]

I have a low-milage (55k) Mk2 GTI 8v, just fitted 4-1 manifold and full stainless and drilled airbox and now I want to do a good tune up to get it running sweet before I mess it up again fitting a cam 

There has been throttle lag since I got it and a little judder at low rpm etc, not bad enough to make me not enjoy it but it's no where near perfect so I've been looking into doing a full timing/tune up. I understand everything to do with crank/cam timing having fitted cam belts etc before but had to do my homework for the idle and fuel/air mixture setting.

I am looking for an exhaust gas analyser/CO meter to give a more accurate tune and to get optimum performance and MPG. This is where I'm stuck.

Firstly.. According to rubjonny and his excellent guide here: http://www.edition38.com/forums/index.php?showtopic=174702 CO content should measure about 1.8%. Haynes says 1%. I'm not disputing either I just want to know is there an ideal content % or how do I find the optimum content for my car?

Secondly.. Obviously I want a CO gas meter preferably the best on the market for free, but I'll probably have to settle for the cheapest that's just about accurate enough, beaten up and second hand because it's all I can afford and it wont be used regularly enough to warrant taking out a loan. Now the main one that people recommend is the Gunson gas tester or similar (£70 at Halfrauds) with an accuracy of 0.5% and apparently quite reliable. Sounds great, but if I'm looking at rubjonny's 1.8%, a 0.5 percent accuracy is just not good enough, right? Now there are also a lot of different CO meters on the market and loads on eBay for £40+. They are handheld units that measure in PPM (parts per million) and measure up to 999PPM. Are these suitable? I read that 1000 PPM is 1% is that true? If so, these will not help me find the magic 1% or 1.8% either.


Sorry about the essay. In a nutshell what is the cheapest gas tester that is good enough for a rare tune up and how do I use it?

[rallye_golf]

Cant give you an answer I'm afraid, But I am in exactly the same boat as you.

anyone help?

[The Doc]

I have one of these - your welcome to come and use it - http://www.kane.co.uk/online-catalogue/automotive/auto-4-1-hand-held-analyser-oiml-class-1-179

[BMXJeff]

Thanks so much for the kind offer. If was was a bit nearer you I'd probably take you up on it. Looks like a solid bit of kit.

I want to get to the bottom of what I'm supposed to be aiming for in terms of CO content. Seems to be a closely guarded secret of those who actually know what they're doing under that big metal flap hanging off the front of the car

[Santiago]

1000ppm is 0.1%
10000ppm is 1%

DIY CO meters aren't really any good if you want anything more accurate than about  +/- 0.5%

1% CO at the tailpipe is about optimal on non-cat cars from an emissions/eco-warrior perspective; but a shade richer is optimal from a smooth idling perspective. Anything over about 2% is starting to get wasteful and unnecessarily poisonous.


Your best bet is to befriend someone at a garage that does MOTs and set it up there with a proper gas analyser.

[BMXJeff]

1000ppm is 0.1%
10000ppm is 1%

DIY CO meters aren't really any good if you want anything more accurate than about  +/- 0.5%

1% CO at the tailpipe is about optimal on non-cat cars from an emissions/eco-warrior perspective; but a shade richer is optimal from a smooth idling perspective. Anything over about 2% is starting to get wasteful and unnecessarily poisonous.


Your best bet is to befriend someone at a garage that does MOTs and set it up there with a proper gas analyser.

Thank you. You cleared up everything I wanted to know!

Household CO meters are useless and exhaust gas analysers are inaccurate but potentially better than nothing. Rubjonny's 1.8% content is for a smooth idle/healthy tune and Haynes' 1% content is aiming to save the icecaps.

I'd better go and get some biscuits for the local grease monkeys.

Thanks again