[TitaniumTT]

Originally Posted by RETed

This is why I don't like widebands...

If you read the FSM, it tells you to adjust everything possible until idle is highest.
The FSM does not mention anything about AFR's or widebands - you don't need it accord to what Mazda recommends.

A lot of things can affect wideband AFR's, and it's not going to be identical for all engines.
Most have reported that anywhere between 12.9 to 12.5 is about normal.
The engine just doesn't like idling any leaner than that - probably due to the fact that atomization is very poor at that low RPM's.

Bottom line...adjust AFR's until idle is highest; don't adjust idle trying to hit some target number.


-Ted

Speaking on that atomization point, since I've changed to my new injectors (WAY better atomization across the board) I can idle my engine MUCH leaner. My spark also has something to do with it as well I'm sure.

Originally Posted by classicauto

Shouldn't be smoking at 12.

10, yes perhaps. But not idling at 12 or even high 11. What colour is the smoke? fuely smell?

Depends how much premix you're running. When I first started my car up this year I went with some Idemitsu pre-mix @ 1/2 oz/Gal (what they rec) and the OMP working as well. So basically I over oiled the engine for about 1/2 hour idle after sitting stationary for about 5 months. After I added some gas without premix, the smoke went away, AFR's didn't change much at all.

Originally Posted by NoDOHC

I have found that it is more about your manifold vacuum than anything (Idle AFR).

It has been a little while since I did this, so I have tried to indicate the accuracy of the numbers listed.

Ignition Timing (BTDC) Manifold Pressure at Idle (kPA relative) Idle AFR
20 -75 to -80 12.2-12.7 *These are very close
15 -70 to -75 12.5-13.0 *These are also very close
10 -65 to -70 12.8-13.2 *More of an estimate on the AFR, vacuum is right
5 -60 to -65 13.0-13.5 *Pretty accurate (ran for a while at this)
0 -55 to -60 13.4-13.8 *Ran for a few minutes only
-5 -50 to -55 13.7-14.4 *Ran for weeks
-10 -45 to -50 14.4-15.0 *Was running at 14.8, closed loop until my fuel system gave up the ghost from the E85.

This was all with a 15 degree split.

porting plays a HUGE role in that as well