The Lotus Grand Tourers

I had a look at the plugs, they are a healthy brown colour. mike said that as the cr was 12/1 so timing was retarded, I have not any information about jets but could the cr and timing account for the very lean mixture readings at idle. the petrol was v-power.

If nothing else has been altered....Compression ratio ... Yes. You are sqaushing 9% more air into the combustion stroke compared to the original HC engine at 11:1 CR

alanbell wrote:I had a look at the plugs, they are a healthy brown colour. mike said that as the cr was 12/1 so timing was retarded, I have not any information about jets but could the cr and timing account for the very lean mixture readings at idle. the petrol was v-power.

The CR and ignition timing per se will not determine what AFR is required for idle.

However they would influence the optimum AFR for max torque for a specific engine (combustion chamber design & SCR /DCR etc will affect optimum ign timing required) - hence there is a normally accepted range of AFRs for best power and torque across a range of differnt engines - you have to find whats best for your spec.

For example my Clan engine has a SCR (static comp ratio) of 11.8 and likes 36 degrees BTDC ignition timing within the power rev range and goes like stink with an AFR of 13.2 within the power/torque rev range (5000 -9000 rpm).

This figure shows relationship between AFR and CO etc ...



This table clarifies AFR and CO% readings ....

From the table you can see it's your 3.2 CO% (AFR 13.3) that makes most sense IF that 's what you have in the max torque range....it's even OK as an idle figure, if a little rich (unnecessary waste of fuel).

A standard Excel SE with an IDLE AFR of 14.2- 14.3 (CO 0.5%) is perfectly achievable. And ideally this is what we should all aim to have come MOT time.

The AFR of 20+ makes no sense AT ALL as a useable setting (in any context!) it's completely off the scale!

MOT passed today, no advisories. Emissions data CO 2.848% HC 200 ppm

The carburettors have not been adjusted for several years and like Angus I usually run on 95 ron.

Mine Passed it's m.o.t today. No advisories.
CO 3.58% HC 224 ppm.

MOT Passed again. Emissions data : A little high this year

2.24% CO
1122 ppm HC

Yes - passed again on Saturday.

CO2 0.482 - don't think it has reached 1% in any of the tests yet!

HC 210

no advisories
Car starting and running great.

Mark.

Passed today. Gave it a bit of a carb tune before going

Co. 2.82%
HC 573 ppm

Passed the MOT today with no advisories and really good HC emissions results which have steadily improved year on year for the last 5 years, hopefully as a result of the hours of work on the carbs, ignition and vacuum pipes and not just a fluke due to the notorious inaccuracy of the testing machines.

HC 182
CO 2.15

Shaun

Passed MOT today (after a brief fail for a rear bleed nipple not properly nipped D'oh! )

CO 0.51%
HC 822 (quite a warm day)

Great news Peter. I look forward to seeing the motor out and about sometime.

KevW wrote:Great news Peter. I look forward to seeing the motor out and about sometime.

as long as it's not a Sunday

MrCoolA wrote:

KevW wrote:Great news Peter. I look forward to seeing the motor out and about sometime.

as long as it's not a Sunday

You never know...

This year's figures:

CO: 2.93
HC: 64

Carbs were rebuilt last year as they were clogged with silt.

MOT pass this morning

emissions data ;-

CO = 0.724

HC = 107



Mark.