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I've noticed when starting from the engine cold at about 10 C that just after cranking the AFR spikes up briefly. I have seen AFR swing up to 22 for about 3 seconds then settle down to normal. I heard of a suggestion to add a feature to extend cranking fuel for a few revolutions after cranking is complete. Would that be feasible?

[video][/video]

https://sourceforge.net/p/rusefi/tickets/324/

Any idea what parameters we would need?
Simplest model would be
1) threshold CLT temperature - only activate below certain CLT
2) after cranking taper down time, in seconds
3) extra fuel, milliseconds, right at cranking to running transition, with taper down to zero after "cranking taper down time, in seconds"

Or do we know if anything more complex is needed?

Any chance we should not do anything since that's just AFR sensor not running properly, or any chance we should not do anything since this is totally not a big deal at all?

The perfect solution would probably be a 2-D table with CLT on the Y-Axis and Engine cycles on the X-Axis or vice versa. The cells contain enrichment percent.

BUT: I'm not terribly concerned about a few millileters of fuel we might waste right after starting, so I'd opt for a simpler solution for now: Two parameters- max percentage (right after changing from 'crank' to 'run') and a duration in engine cycles. Linear interpolation of the percentage between crank-to-run switch and the final cycle. When the engine is warm we'll likely need less, but who cares....

Post startup enrichment is pretty common...

extra% vs CLT is very simple. works fine.

Some systems adjust the target lambda / eq mix. Some add %. As long as you're not trying to pass emissions you can be very crude.

So a simple CLT based formula for initial enrichment? Like (TargetCLT- ActualCLT) * factorX = initial enrichment percent
Add a number of cycles for enrichment and we;re good to go. Three parameters total. Should be fairly easy.
I like the idea of adjusting the target lambda. Seems cleaner somehow.

blundar wrote:Duration: till warmed up, although a lot of OE's kill the enrichment when they go closed loop.
Amount: max 25-30% for gasoline, typically tapers to 2-3% at 10deg below "warmed up"
special case for ethanol due to low vapor pressure and negligible vapor pressure when cold.

Wait a second, that sounds like warm-up enrichment (like 60 seconds or more). I think the proposal here was a much shorter much crueder enrichment for the first ~one? ~two? seconds of running.

Unless that all we need is to increase the enrichment number of the current warm up implementation?

Yes, we're talking about immediately after startup. Only a few seconds until things have stabilized in the intake area.

My bad... I misunderstood at first reading. There are typically two enrichments:

1. long term CLT vs. enrichment (I described previously, not what was being discussed)

2. short term "post startup" enrichment immediately after crank (what the topic was, I missed it first go)

#2 is implemented in several ways elsewhere by OEMs

-Linear decrease of crank pulse over N cycles where CLT vs. N table defines number of cycles to remove fueling completely
-post startup adder with table of CLT vs. pulsewidth in ms, numeric value for number of ms/cycle to drop out each cycle
-table of "desired fuel" vs. CLT, essentially the above but fits within an injector model to allow the same moles of fuel to be delivered with different injectors
-Common to have different settings for E0 and E100 with linear interpolation based on ethanol content

Some considerations are that this stuff is generally *relatively* constant with respect to physical engine present. It's also a relatively constant AMOUNT OF FUEL present. If your model can somehow be affected by injector size (i.e. deliver the same number of moles of fuel with different injectors that are properly calibrated) you'll find very little adjustments need to be made to the section.

Did you record a datalog?
Would be nice to see how everything is interacting when it goes lean.

This log shows an example of what I'm talking about, it's not always this bad and depends on air temp:
http://rusefi.com/forum/viewtopic.php?f=3&t=660&p=21330#p21265

This is not a high priority request, but here is what it looks like, AFR spike in the first 3 seconds after cranking

creepy how it goes lean like that

Try to get the car to do it again and check fuel pressures.
I think it might be something to do with that. Maybe pump/filter/etc. Could be a red herring.

Also see if you can let the wideband preheat before you start it, maybe its just the sensor getting hit with the hot exhaust gasses.

Could also be something along your intake path. Maybe a leak of some sort. dont think so.

Just somethings to potentially waste your weekend