Rejetting a 34 PICT-3 for 1776cc

You don't need an AFR meter. Just tweak the PICT up in the usual way. That'll be good enough

 

The colourtune is sort of useful but again only for idle or light load running if you can see the glass part of the setup while the engine is running - the spark plug is quite deep down the hole on the aircooled engines , so it is going to be hard to see under the tinware.


I have that JK single quiet pack stainless exhaust, the sensor is fitted on the top of the collector just about 50mm from the flange.

The setup I use is permanent, the sensor is mounted on approximately 1 metre of wire, it connects to a controller box in the engine bay, and then there is an extension cable to the dash which is carrying digital data. In fact, if you extended the wiring using e.g. trailer board wiring it should work over the 5 to 6 metres between the sensor and the controller.

It is based originally on a PLX Devices wideband setup, but like Trigger's Broom, there is now no PLX hardware left in the setup.. the dashboard display was destroyed by shorting 12 volts onto some low voltage wiring when I set fire to the bus, and my custom control box in the engine bay is now controlling an LSU4.9 sensor rather than the older LSU4.2 sensor with PLX computer that PLX sold me about 10 years ago. These days if you buy a PLX devices wideband setup it also uses the LSU4.9 latest generation sensor.

A wideband sensor indicates whether the engine is running anywhere from rich 10:1 to lean 20:1 , including the optimum 14.7:1 for combustion, and the optimum 12.5:1 for cooling an aircooled engine (they are partially cooled by the evaporation of the fuel.. ) .

A narrowband sensor has a limited range around 14.7:1, basically telling you to go richer or leaner in a fuel injection system, without telling you exactly how rich it is. Historically narrowband sensors appeared first, then narrowband sensors with heaters for stability, followed by two generations of heated wideband sensors that use electronic feedback tricks to turn a narrowband sensor into a wideband sensor.

Killers for the wideband sensor - water vapourising off the sensor while the sensor is at 600 degrees C.
Heating the sensor with the exhaust while the power is off on the sensor.
Rich running covering it in soot.
So what I do is wait 30 seconds after powering up, assuming by then the engine is running and the exhaust pipe has already warmed up so water is not being spat out.

I dont think that putting it too close to the exhaust end of things is really an issue - the earlier narrowband sensors were heated by the exhaust alone.
Air mixing at the tailpipe limits how close you can go towards the tailpipe, so somewhere on the silencer box could also work.

 

Then sir, why is your engine sad ?

The further you move from stock , pushing things to their limit, the more likely it is that the setup is not quite right, and that at the very least going to a rolling road to get it set up could be a saving in the long term.

 

It`s sad for the first time in decades - give the bloke a break

 

...or a tacho, oil temp/oil pressure gauge, or CHT gauge, but they are useful.
Just researching the subject at the moment. No plans to attach an AFR anytime soon but may be a project for later. In the meantime, I need to work through a few minor problems starting with ensuring the exhaust is leak-free.

 

Oil temp, oil pressure is useful to have...if your engine's in reasonable shape

 

A lot of people spunk a lot of money on non useful /non essential shiny stuff , a couple hundred quid on a AFR set up that you can sell on or use to monitor isn`t a bad investment.
I used one with my twin dells and a fab bit of kit ... now part of my FI setup on my 914 .. you could spend £300+ on a 123 dizzy or just use points or shiny breather boxes that have no use .

 

Points are, generally, crap. Why do you think they invented electronic ignition?