Individual Cylinder AF Adjust, was: NTK wb-sensor price

[Axel Rietschin]

----- Original Message -----
From: "Lasse Langwadt Christensen" <langwadt at ieee.org>
To: <diy_efi at diy-efi.org>
Sent: Tuesday, February 05, 2002 22:03
Subject: Re: Individual Cylinder AF Adjust, was: NTK wb-sensor price

> maybe I'm missing something but wouldn't measuring the "gas transport
> time"
> be as simple as running the engine, skip one injection event and measure
> how long it takes before the sensor shows lean?
> repeat for different rpms, cylinder, etc.

...probably, but I just ask myself, why would you want to do so? Apparently
there is a lot of cylinder to cylinder variation and no two cycles are the
same (at least Heywood says so, see Sec. 9.4.2). By trying to be super
selective you may end up trying to correct for something that already
happened and will most certainly not happen again in the immediate future,
one single cylinder apparently being able to randomly jump over a few "AFRs"
from one cycle to the very next all by itself (for various reasons well
beyond ECU control, for example the mixture composition in the vicinity of
the spark). I suggest that you may well end up making things worse by trying
to adjust the fuelling this way (I actually made some tests, if you are too
"nervous" in the control loop (lots of P-gain, trying to react as fast as
possible) it never stabilizes. I got better results (as far as "mixture
stability" goes) with gentle correction and some filtering to actually
smooth thing out)

Also knowing the transport time is useful for adjusting datalogged traces
for example, but it won't help you a lot as far as closed-loop fuelling goes
(except that the more of it, the more gentle you must be in the correction),
of am I missing something?

just my 0.02 ?
Axel



----- End of forwarded message from owner-diy_efi at diy-efi.org -----
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org