The Lotus Grand Tourers

OpticalBoffin wrote:Mine failed the MOT a few weeks ago and the readings were CO:3.48% HC:351ppm. When I finally got it retested yesterday, (and passed) the readings were CO:3.07% and HC:456ppm without it having covered any miles in between.

I've had it SORNed this month as I've been unable to tax it without an MOT but come July it will be back on the road and the first thing in needs is a good long run to clear it out.

Andrew

I would assume this has a lot to do with what conditions and temperature your carbs were originally set up in. Conditions may have been closer to the day they were set up second time round.........or they let engine warm up properly 2nd time round

Having stood over the shoulder of my MOT man last time it went for a test, I was ASTOUNDED how inconsistent the readings were. Even without fiddling or adjusting anything, it seemed to vary by 30% or more from one test to the next.

Luckily the guy was on my side (he likes the car, he commented on how often he spotted me driving around!), and was happy to spend far longer than he should helping me tinker and re-test until we got the "right" result.

I should say that this was after a session a Ricky Gould to get it all set up and running right - so I was suprised it was failing at all, until we spotted that one of the vacuum hoses had come loose. All good after that!

Just been MOTed for this year (straight pass, in spite of having wrong dizzy - see thread in Electricals about that damn AB14)

2013 (162791 miles) : CO : 1.766% vol HC : 303 ppm

2012 (150236 miles ) : CO 0.78 % vol, HC 83 ppm
2011 (139532 miles ) : CO 1.34% vol, HC 211 ppm
Engine rebuilt at approx 121k miles in 2010
2009 (113768 miles) : CO 1.94% vol, HC 455 ppm
2007 (90727 miles) : CO 1.86 % vol, HC 497 ppm

The increase for this year (and low reading in 2012) may have something to do with fixing some exhaust leaks before Xmas.

Mine passed the MOT today also.
Advisory on front ARB bushes.

Annual update. MOT passed with no advisories.

176195 miles. CO 2.55%, HC 640 ppm

Notes - idle is a little fast and carbs are definitely slightly off at the moment.

Feb 2013 - Co2 0.617% HC 462ppm

Feb 2014 - Co2 0.180% HC 876ppm - advised too low

Have opened all 4 mixture screws 1/4 turn since the last results - will go for another test in the next few weeks.

Mark.

PS. running on V-power unleaded.

CO 2.69% HC 1029 - passed again.

CO 2.69% HC 1029 - passed again.

.................................Mileage
CO 1.11% HC 465 ; Nov 2013 84203
CO 1.20% HC 455 ; Sep 2012 83005
......................Sep 2011 82398
CO 3.22% HC 125 ; Oct 2010 82070
CO 3.11% HC 246 ; Feb 2010 81643
......................Jan 2009 80914
CO 0.12% HC 107 ; Feb 2008 80499
CO 0.07% HC 31 ; Nov 2006 79074
CO 2.03% HC 854 ; Oct 2006
CO 0.08% HC 34 ; Oct 2005 74500
CO 0.50% HC 927 ; Oct 2004 71921
CO 0.32% HC 201 ; Nov 2003 68121
CO 2.44% HC 138 ; Jul 1992 42417

There's a nice little history list for you
2005-2006 yoyo is interesting

Hawaiis0 wrote:.................................Mileage
CO 1.11% HC 465 ; Nov 2013 84203
CO 1.20% HC 455 ; Sep 2012 83005
......................Sep 2011 82398
CO 3.22% HC 125 ; Oct 2010 82070
CO 3.11% HC 246 ; Feb 2010 81643
......................Jan 2009 80914
CO 0.12% HC 107 ; Feb 2008 80499
CO 0.07% HC 31 ; Nov 2006 79074
CO 2.03% HC 854 ; Oct 2006
CO 0.08% HC 34 ; Oct 2005 74500
CO 0.50% HC 927 ; Oct 2004 71921
CO 0.32% HC 201 ; Nov 2003 68121
CO 2.44% HC 138 ; Jul 1992 42417

There's a nice little history list for you
2005-2006 yoyo is interesting

Yes. Not necessarily a yo yo in your actual emissions. It's quite possible that their own calibration (or methodology) is lacking ...esp if you made no changes between readings.

Hi all. Mine passed yesterday.
CO 3.27%
HC 1171 ppm
39557 miles.
Carbs could still do with a tweak though.
It failed in September due to burning it's own hole in the ozone layer.

Thanks to lotus-e-clan for the very easy to follow guide on setting the carbs.

http://www.lotusexcel.net/phpbb/viewtop ... =carb+sync

Passed MOT again, today. after 540+ miles of motorway driving in the last couple of days and no time to do any checks or prep. before the test this morning. Figures to follow after I've picked it up.

Edit : The numbers :

Miles : 184086 (barely 8k since last one - I'm slipping!)

CO : 2.16
HC : 421

Advisory - slight leak from exhaust centre box (probably where it caught on the ramps in the hotel car park on Sunday night - again!)

I am at a bit of a loss as to the purpose of this thread though it has shown that a well maintained high mileage engine seems to get results that as are as good as well maintained lower mileage engines, if there is deep unrevealed search for some facts or figures I would love to know what they are. for what it is worth the first test of the lotus bits 2.5 engine was.
% CO 3.275
ppm CO 381
lamda 1.362 what is this?.
air-fuel ratio 20.029
% CO2 9.50
% vol O2 6.41

alanbell wrote:I am at a bit of a loss as to the purpose of this thread though it has shown that a well maintained high mileage engine seems to get results that as are as good as well maintained lower mileage engines, if there is deep unrevealed search for some facts or figures I would love to know what they are. for what it is worth the first test of the lotus bits 2.5 engine was.
% CO 3.275
ppm CO 381
lamda 1.362 what is this?.
air-fuel ratio 20.029
% CO2 9.50
% vol O2 6.41

Yes the 1.3 lambda and AFR of 20 represents the same values and are MASSIVELY lean.

They are the sort of figures you only tend get on the over -run AND then you'll get loads of popping and banging in the exhaust (depends on overlap of the cam) caused by the unburnt fuel escaping into the hot exhaust.

I know that sounds counter- intuitive (lean ratio with unburnt fuel) but it's almost impossible to set enough advance to completely burn an AFR of 20 hence it might be VERY lean but it won't burn off a pin point spark but it does when it hits the large surface area red hot exhaust manifold.

Any way those data in the previous post have no proper context so are pretty pointless. Assuming no jet changes, you need to quote the AFR along with rpm, throttle position, and ignition advance (and any inter-cylinder ign scatter, if present). For a given real ratio of air and fuel you will see a range of AFR readings across a range of ignition settings. ie if the ign is too advanced or retarded for a given fuel charge you will get unburnt fuel and achange in AFR reading to match.

(somehow the above reply got posted in a break-away thread by mistake - when it was meant to follow alan's post within this thread )

alanbell wrote:I am at a bit of a loss as to the purpose of this thread though it has shown that a well maintained high mileage engine seems to get results that as are as good as well maintained lower mileage engines, if there is deep unrevealed search for some facts or figures I would love to know what they are.

Historical record of figures for carburetted engines more or less as they left the factory, since we are often told that they can't pass emissions tests without tweaking - something I've never had to do.