High Co Emissions

[fliprio 9]

The 205 failed the MOT this week on CO emissions being at 8%, which is little bit over the 3.5% limit, Hydrocarbons were fine at around 600ppm. Its running twin 45 Dorletto carbs and a dizzy on a GTI-6 engine.

 

I had it tuned up on a rolling road only about 6 weeks ago, and asked to make sure it could pass an MOT, speaking to the guy at the rolling road today he said that he doesn’t check the CO and just uses a wideband lamda set-up and said that they are always a pain to get down to 3.5% with most running at 4+ when at idle, which he neglected to say when I picked it up!

 

He said that if the hydrocarbons are ok, then the carbs are still in balance and it still drives perfectly fine, what can cause it to have such a high CO when it is supposedly in tune?

[mickie 3]

i said the same to the guy at motoscope.. ive got a 1.9 on twin 45s

 

he said it should easy pass an MOT now and it did with 2%

[mickie 3]

Excessive CO results from rich air/fuel mixtures

[fliprio 9]

Excessive CO results from rich air/fuel mixtures

 

I thought the HCs would go up as well if it was just a rich mixture because of the unburnt fuel?

 

Does the mixture adjustment screws adjust the mixture throughout the whole rev range, or just at idle for the primary jets?

[welshpug 1,666]

hc of 600 is still high, my 309 passed at 125 PPM + 1.5% CO.

 

 

its a standard 1.9 on Jetronic with a remanufacftured AFM.

[mickie 3]

so it seems it isnt set up all that well

[Tom Fenton 1,548]

Main cause of HC is usually either poor setup, ignition timing wrong, or a lumpy camshaft. Also ignition timing for emissions will not make the best power. So don't shoot your RR guy just yet!

[welshpug 1,666]

indeed, if it was on mappable, I'd comment that it just need mapping properly as who maps for peak power at idle...

 

but as its on a distributor so you'd be best off finding someone to get it MOT worthy at least, if not a better setup all round.

 

i'd imagine if its giving an emissions result like that its not particularly good on fuel! (great on flamed I'd bet)

 

Or if you must stick with carbs then at least get mappable ignition.

 

 

 

 

out of curiosity, what kind of figures is it producing power+torque wise? is it standard cams?

[fliprio 9]

Main cause of HC is usually either poor setup, ignition timing wrong, or a lumpy camshaft. Also ignition timing for emissions will not make the best power. So don't shoot your RR guy just yet!

 

it does pink at low RPM when in a higher gears, he said that he could stop it, but it would take a fair bit off the top end and was ok as it was.

 

he also said it was good on light throttle, a little rich on part throttle at mid revs, but spot on when WOT

 

what kind of HC would you normaly expect for a carb set-up?

[fliprio 9]

indeed, if it was on mappable, I'd comment that it just need mapping properly as who maps for peak power at idle...

 

but as its on a distributor so you'd be best off finding someone to get it MOT worthy at least, if not a better setup all round.

 

i'd imagine if its giving an emissions result like that its not particularly good on fuel! (great on flamed I'd bet)

 

Or if you must stick with carbs then at least get mappable ignition.

 

 

 

 

out of curiosity, what kind of figures is it producing power+torque wise? is it standard cams?

 

its not too bad on fuel, 200 mile round trip to Cadwell park and 100 miles on track and it averaged 23 mpg, which I thought wasnt bad

 

I managed to get it through the MOT by winding in the mixture screws and then setting them back to the same position afterwards, had to wind them a fair way in to get it to go below 3.5% though.

 

It did 170 bhp at the fly, so standard-ish power

 

if its meant to run like that, then thats fine, just wanted to make my mind up that it needed looking at again

[fliprio 9]

indeed, if it was on mappable, I'd comment that it just need mapping properly as who maps for peak power at idle...

 

but as its on a distributor so you'd be best off finding someone to get it MOT worthy at least, if not a better setup all round.

 

i'd imagine if its giving an emissions result like that its not particularly good on fuel! (great on flamed I'd bet)

 

Or if you must stick with carbs then at least get mappable ignition.

 

 

 

 

out of curiosity, what kind of figures is it producing power+torque wise? is it standard cams?

 

standard cams as far as im aware, made peak power at 6,700 RPM

[Tom Fenton 1,548]

Carbs are always a bit tricky, what you really need is to mark up the dizzy, and a friendly tester who will let you swing it there and then whilst you watch the emissions meter. Then drive round the corner and put it back where it was.

[fliprio 9]

Carbs are always a bit tricky, what you really need is to mark up the dizzy, and a friendly tester who will let you swing it there and then whilst you watch the emissions meter. Then drive round the corner and put it back where it was.

 

so it is plausable that it is supposed to be like it is and hasnt gone out of tune since it was on the RR and its just because of the ignition timing that the CO is high?

 

It still goes well and I havent noticed a drop off in power since it was set-up, or any popping and banging like it was before it went in.

 

its passed for another year anyway, so might have to upgrade to something differnt for next year

[welshpug 1,666]

i'd be sorely tempted to fit the standard intake and management, you'd get far better drivability, and vastly improved fuel ecomomy, and seemingly sod all performance loss.

[fliprio 9]

i'd be sorely tempted to fit the standard intake and management, you'd get far better drivability, and vastly improved fuel ecomomy, and seemingly sod all performance loss.

 

I had thought of that myself, and my bonnet would fit properly then as well!

 

I do like the sound of the twin 45s though, Im sure its adictive

[Anthony 1,003]

GTi-6 inlet manifolds are trumpetted (if that's a word) internally, so you do get a degree of induction bark - not as much as carbs or throttle bodies admittedly, but certainly much more pronounced than on most plenium type manifolds

[fliprio 9]

indeed, if it was on mappable, I'd comment that it just need mapping properly as who maps for peak power at idle...

 

but as its on a distributor so you'd be best off finding someone to get it MOT worthy at least, if not a better setup all round.

 

i'd imagine if its giving an emissions result like that its not particularly good on fuel! (great on flamed I'd bet)

 

Or if you must stick with carbs then at least get mappable ignition.

 

 

 

 

out of curiosity, what kind of figures is it producing power+torque wise? is it standard cams?

 

does the GTi-6 engine already have a crank sensor for running an ignition only set-up?

[welshpug 1,666]

yes, just depends if its still there from whenever the wiring loom was removed

[fliprio 9]

yes, just depends if its still there from whenever the wiring loom was removed

 

can it be used for any of the ECUs such as megajolt? makes it a bit easier if it already has a crank sensor on it, will have to have a search around on the engine tomorrow as I have no idea where it is.