O2 sensor.

Finally got the wideband O2 sensor up and running on the SD1 - prior to fitting the MegaSquirt. Thanks to Longlife in Carshalton for doing the job

- after I'd put the boss in the wrong place so the cable got fouled. ;-)

Driving back from there - with the original EFI, obviously, but the Tech Edge unit fired up, the display showed it on the rich side of stoic almost all of the time. When cruising at 30 I'd have expected it to lean out a bit. Anyone know what should be expected at idle? No cat, of course. Seemed to be pretty rich at about 12.8 or so.

Reply to
Dave Plowman (News)
Loading thread data ...

less than 1

Reply to
Mrcheerful

I initially thought you meant the CO level, but if you meant the stoichiometric ratio is 12.8 then that is way too rich, as I am certain you know that 14.7 is right and more is too lean.

Reply to
Mrcheerful

It's an SD1, did they ever run lean ? :-)

Reply to
Duncan Wood

Before cats, the ratio did vary by quite a bit. But I can't find out from what to what. A cat can be damaged by the wrong ratio - which is what killed off lean burn engines.

Reply to
Dave Plowman (News)

The injection ones were notorious for it. Presumably to give the best cruising MPG.

Reply to
Dave Plowman (News)

The spec for that is 1.5 +/- 0.5% CO.

Reply to
Dave Plowman (News)

"Dave Plowman (News)" gurgled happily, sounding much like they were saying:

I thought it was high NOx levels which did for lean-burn, but that's another story...

Reply to
Adrian

All I can find here is 14.35:1 for part throttle cruise, 11:1 for full open, so 12.8 seems a little rich, but the rolling road is surely beckoning?

Reply to
Duncan Wood

A bigger issue was that cats just don't work with the any ratio other than stoichiometric. Almost every engine ever built before then ran on the rich side.

Reply to
Duncan Wood

No point since I'm changing to the MegaSquirt - this is the readings with the standard injection. However, I fitted a new pump at the same time and haven't checked the pressure. I have an adjustable regulator and it could have been set to compensate for a clapped pump.

Reply to
Dave Plowman (News)

They certainly had a quite wide spread. Most leaned off considerably at cruise.

Reply to
Dave Plowman (News)

In message , "Dave Plowman (News)" writes

Think it was more like a cat won't work with a lean burn engine, you need a certain amount of unburnt fuel and oxygen in the exhaust gas to keep a cat lit up and working efficiently. Lean burn engines produce more NOx which is a nastier pollutant than CO.

Reply to
Clint Sharp

NOX comes down again when it's truely "lean of peak" like a Wright R-3350 was taken by the flight engineers 60 years ago to get a Lockheed Constellation across the Atlantic - normal fuel burn would have seen them ditching dry and empty. The technique was developed by Charles Lindbergh in P38's during WWII, low revs, high boost, running lean nearly doubled the range. Temps go up as it's leaned out from

14.7:1 but past 16:1 they come down again. That drop in temp means no more NOX than at a cool rich setting.

formatting link
I read somewhere years ago that the original Euro emmision cat law only required a cat if a Lambda sensor was fitted but I've never been able to confirm it. Really stupid Eurocrats got us stiffed as a cat don't work until it hot and the lambda don't either but once lambda is working the cat wasn't really needed back then at Euro I. It is for Euro IV.

Reply to
Peter Hill

Found one figure - seems 12.5:1 is ideal for maximum power.

Reply to
Dave Plowman (News)

yebut you always want to be rich rather than weak for max power, a bit too rich will only lose a tiny bit of power, while the same amount too weak loses lots. Hence a richer mixture for power, cruising can be much leaner as you will only be using a very small amount of power.

Reply to
Mrcheerful

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.