S3 E-Type

O2 Sensors for Carburettor Tuning
Close monitoring of each carburettor

by Dave Lacey

The nature of a V12 is that it's quite difficult to determine what each individual cylinder is doing, in fact they run quite well on 6 cylinders, so detecting 1 or 3 cylinders misbehaving is difficult.....possible...but difficult. This makes carburation rather challenging to setup. In the past, working on single/twin carb 4 or 6 cylinder engines, i have relied upon the fact that when you disturb one carburettor you can hear the difference, with a V12 thats difficult. So, having used "Colortune" devices with some success to set the mixture at idle, I was interested to understand what was going on under various load conditions. Given the layout of the V12, one carb feeds 3 cylinders & feeds into individual exhausts which join into the same 3 cylinders just before joining into one exhaust per cylinder bank. Therefore, it's possible to mount an exhaust gas sensor just before this final join and monitor the performance of each carburettor individually. The function of simple "single wire" oxygen sensors can be found elsewhere (this is a good old-car intro), and it's possible to make or buy small circuits to "sense" & display the sensor output. My plan is to use 4 of the circuits published in Silicon Chip and sold by Jaycar of Australia to monitor the 4 carbs. To do this the exhaust oxygen stoichiometry must not be "contaminated" with any air injection, so i plan to remove the whole system fitted on this US-spec E-type. There is enough space to fit the sensors into the exhaust, and i will temorarily fit the electronics behind the instrument cluster. This Photo shows the downpipe of the V12 E, there is space towards the front of the car and to the rear to install the sensors:

Some might question why i feel the need to use this "modern technology" to tune an old vehicle....well I do it because I believe it's the simplest way to do it without a rolling road. The technology is now standard on all motor vehicles, so I feel we should take advantage of whats available to make our cars run as good as possible.

Here's the new downpipe with an adapter welded on:

And here's how the sensors will fit:


Here's a view down the pipe to indicate the 'restiction' or exposure of the sensor elements:

I'll add more info to this article later on the use of this system...
O2 Sensors for Carburettor TuningAnonymous|02 Feb : 13:41

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Hi I'm Larry from Arizona,I'm rebuilding a 1971 XKE V 12 I've been told[by a head rebuilder of high repute] the air injection is necessary to keep the exhaust valves cool could this be the reason for so many valve seat and guide problems? I dont know what do you think?great site THANK you Larry

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