Exhaust CO reading

[Gadgetman]

Does any one know what the correct CO reading at idle on a Vitesse should be, I cant find it listed??

[Pete Lewis]

its not listed for Vitesse  as there was never a spec being before the days of emission results 

eg  https://www.classiccarsforsale.co.uk/blog/advice/classic-cars-and-the-mot-test

 

from my past  work in smoke emissions   on diesels  and petrols from a faded memory  around 2.5  to 4.5  Co would be about normal get it too low and the HC unburnt goes up and driveability disappears 

if you search around for something conclusive its a bit illusive

I had some snazzy Horiba units but upkeep and calibration became a nightmare so up the tip , i could dig the gunsons unit out its dust but by the time its warmed up and stabilised we will have gone to bed 

none of my WSM give any clues neither GTS Vitesse or the 2000/2500  all devoid of clues 

set the   mixture to  its best idle condition and lean it 1/4 to 1/2 a turn from 'best '

Pete

 

 

 

[Pete Lewis]

this is later than your vitesse but comes up with the same 2.5/ 4.5  sort of result 

Pete

[NonMember]

The 2.5-4.5% spec was for late 1970s emissions rules but it's fairly typical for an engine of that sort of technology. A Vitesse will probably be happier at the 4.5 end of the range.

[Pete Lewis]

there's a balance between the CO and HC 

drop the CO   and the HC rises   drop the HC and the CO rises 

you have to settle for a happy medium

we could do with a 'medium' on here at times   Ha !!

Pete

 

[Gadgetman]

19 minutes ago, Pete Lewis said:

its not listed for Vitesse  as there was never a spec being before the days of emission results 

eg  https://www.classiccarsforsale.co.uk/blog/advice/classic-cars-and-the-mot-test

 

from my past  work in smoke emissions   on diesels  and petrols from a faded memory  around 2.5  to 4.5  Co would be about normal get it too low and the HC unburnt goes up and driveability disappears 

if you search around for something conclusive its a bit illusive

I had some snazzy Horiba units but upkeep and calibration became a nightmare so up the tip , i could dig the gunsons unit out its dust but by the time its warmed up and stabilised we will have gone to bed 

none of my WSM give any clues neither GTS Vitesse or the 2000/2500  all devoid of clues 

set the   mixture to  its best idle condition and lean it 1/4 to 1/2 a turn from 'best '

Pete

 

 

 

Thanks Pete. I was thinking 3-3.5 was about right going by the old MOT standard for 1975 ish cars as they were still twin StrombergS on the TR7 of that era!

i guess it’s a case of wind the jets up to touch the piston then back 2 turns on each, balance the carbs  with idle screws, tighten the linkage then adjust both jets equally to get the correct co setting at idle ( I’ve used the piston lift pins before but now have use of the gas analyzer !) 

I’m also going to put a Colour tune plugs in #2 & #5 cylinders to see what the mixture burn looks like!

 

 

 

[Pete Lewis]

thats a plan    the TR7 bonnet sticker also has 2.5 to 4.5 CO 

going lean is not kind to the engine , too lean = too hot  and exhaust valves will suffer 

yes the basic carb setting were purely mechanical settings prior to engine build    m gas flowed settings did not appear till the mid /late 70s 

so your idea is spot on get all things equal and the balance is as good as it gets 

pete

[NonMember]

1 hour ago, Pete Lewis said:

there's a balance between the CO and HC 

drop the CO   and the HC rises   drop the HC and the CO rises

Only under some conditions and for engines that don't tolerate lean burn. On a more modern engine (including the Dolomite Sprint!) the CO and HC both go down as you lean off towards 2% CO (but the NOx starts to go up). The increase in HC is a result of "lean quenching", where the design of the combustion chamber causes the flame front to extinguish early with a not-so-rich mixture. Hemi or pent-roof engines generally don't suffer this until a fair bit leaner.

The CO/HC balance is true of a Vitesse engine but it's a consequence of the "cleaner/happier" balance around the 3-4% CO region

[Nigel Clark]

I aim to set my GT6 for 4% CO. At 2.5-3% it feels too weak, with slightly rough idle and throttle response/acceleration not as crisp.

Nigel

[Pete Lewis]

Rob youre right but we are only talking our old engines the Vitesse was never in a emission controlled   Era 

Pete

[dave.vitesse]

From long term experience 4.0- 4.5%. You can run down to 3.5% for better economy, but the performance will be reduced. 3.0-3.5% is too weak.  Over 5.0% and you are getting too rich. I agree with Pete, the Vitesse was never in the emission controlled era. Engines designed to run at 2.5-4.5% came in the 1970's with a reduction in power. Most ran better at 3.5% than 2.5%. 

Dave