Acceleration enrichment Re: DIY_EFI Digest V4 #450

[Phil Lamovie]

Hi All,

For a simple solution to acc enrichment start by creating a FIFO
stack of say
ten counts. Read  TPS every 10 ms. Algorithm should respond in a
linear fashion to the diff b/w first and last. Say 100% of
additional fuel for 200% change in A/D value. A single integer
value of X ms will give you an adjustable ramp rate. This is a
simple feed forward system

The harder part is to arrange a proportional decay vs rate of
change of rpm

If the engine rpm changes quickly you should decay the additional
ms proportionally if the rate of change is slow then the
enrichment should be
adjusted to suit.

Of course for an engine  that has a very poor chance of acc
quickly relative
to say a blipped throttle during a down change this is really of
little import.

On the matter of duty cycle it's more to do with lousy linearity
of an injector
at either end of the scale 0-2 ms is considers to be unusable due
to lack of repeatability. With 0.5 - 1.1 ms just to open this
gives rise to variations cycle to cycle of more than 8 %. Makes
it hard to pass US pollution laws.

At the other end of the scale the rate of collapse of the
magnetic field and the fuel pressure together with pintle bounce
mean that 90 % duty cycle could in fact mean that the injector
never closes.

F1 engine at 16,000 rpm has 3.75 ms per rev losing 0.5 to open
and 0.65 to close would give a max. of 2.6 ms. Thus one injection
per 2 revs.
And you were worried about timing the injection to coincide with
valve train events.

Be wary of any O2 sensor voltage vs  A/F ratio inferences. If you
don't correct for temp there is a drift of 1.5 A/F over 400 deg
c. And that's for the
expensive BROAD BAND device. A single wire sensor can't be
trusted
at all. For any peace of mind use a 4 Gas analyser and EGT.

Then refer to EGT and infer A/F from that.

Be sure to refer to the properties of steel/wire/bailing  in the
BLUE BOOK
to aid with exhaust mounting redesign

For the key to all things in auto tech The Bosch Automotive
Handbook

SAE  order no is BOSCH4 (4th Edition) It's blue !!  ISBN
1-56091-918-3

best $35.00 you will ever spend.

DISCLAIMER .......I am a hopeless addict of the SAE book store
and would buy everything if I could.


 Regards

 Phil Lamovie

 injec at ains.net.au

     cogito ergo zoom