AFR's at idle

[RETed]

Originally Posted by Rotary Evolution

take his suggestion with a grain of salt, every car reacts differently to different AFRs and 16AFR cruising on most 2nd gens simply wont happen because the car will want to fall on its face to even keep up with itself, perhaps he runs a smog pump which skews his figures up or runs an AEM with a crappy bosch wideband sensor which also seems to have figures a bit off..

First, if we're going to assume the AFR #'s are off, then why even bother mentioned #'s at all?

Second, I've run a 13BT past 16.0, and it did not "want to fall on its face".
This was at 4kRPM+ and EGT's were creeping past 1,000C or over 2,000F.
The engine will push ultra lean mixtures like that but EGT's are just too hot to be comfortable.
There was no hint of lean surge - see below - and the car kept running with no hiccups.
Granted, we were cruising at a spritely speed of over 100mph on the expressway...

you don't need wideband figures at all, the engine will tell you where it wants to be because it will begin to lose power if you push the AFRs too far on the lean side, on the rich side the engine will not hate you so much before it starts losing power. when leaning out AFRs there is a radical ramp you will reach when the engine doesn't like what you're feeding it.

Those in the industry call this "lean surge".
I guess you can call it "lose power", but it's more like a hesitation.
It's more likely an ignition misfire, cause you don't have a coherent burn inside the engine.


-Ted