[Diy_efi] O2 sensor sensitivy speed

[Bruce]

----- Original Message -----
From: "Kenny" <watson at iamfun.com>
Subject: Re: [Diy_efi] O2 sensor sensitivy speed
> Quoting Bruce <nacelp at bright.net>:
> > How do you tell a timing from a fuel problem
> > using EGT?.
> Well, ideally your EGT gues should give fairly uniform
> readings. If they're giving nice reading and you're
> still detonating, you know that there is optimal
> combustion pressure in all clyinders, so you can back
> off ignition. Mixture is always tuned first with a base
> ignition map.

Wow, talk about assuming facts not in evidence.   Assuming it's a fuel
problem is an odd thing to do.  I'd rather pull a plug and see what the
problem is.

> > Yep, feature creep sells 90% of any *new and
> > improved* product line.
> Well, it's not a particularly new feature, and it is
> definitely a useful one either way.

In your opinion.
Following your logic, and a good many others SEFI has to be better then
Batch fire.  Well, maybe in general, but in my application, I run better in
Batch fire.  Hence why I qualify much of what I say.  Generalities are just
that.   Can you guarantee that it's useful?.  You say it is, but if the
mechanicals are correct, then what will it gain you?.

> > > >I'd worry more about individual cylinder tuning as a function of
detonation
> > > >control rather then just for AFR.   Yes but lean mixtures and
detonation go hand in hand.  Monitoring individual A/F mixtures and trimming
each cylinder accordingly will go a long ways toward both optimum power as
well as detonation
> > prevention.
> > And what is the usual reason for leaness being a
> > problem?

> Excessive combustion temps leading to less-than-optimum
> burn times and combustion pressures, greater tendency
> to detonate, increased overall heat stress on
> (particulary cast or hypereutectic) engine components.

You've mixed cause and effect in your answer.

> > Isn't best to design things so that all cylinders contribute equally?

> For sure, in a perfect world. And in most OE setups
> they do, but when modified intake manifolds come into
> play (as they often do in hi performance apps that
> necessitate EMS) it's nice to be able to Juggle things
> around.

If you buy into, well that's the way it is.  Hi Performance stuff should not
buy into packaging problems.  Some answers aren't easy, but they're too
often compromised.

> > Individual cylinder trimmings are just covering
> > up for other malfunctions.
> Well, I'd prefer to call them necessary evils. ;)
> Like the modified intake manifold scenario.

So a software answer to a ME fubar.  No thanks, I'll work on the ME problem,
first.   Then again some ME problems are easy to cure, since some MEs,
really don't know their subject manner.

> > I don't see where one is easier then the other,
> > the trick is figuring out
> > which cylinder to work with.
> I've never noticed any programmable syste, being able
> to retard timeing on a single cylinder basis though. If
> this is common practice then my bad.

Maybe they are popular just because too often the buying public are just
doing monkey see monkey do.   Popularity is 2/3 of what sells aftermarket
ecms.  There are some interesting quotes floating around the Net on what the
basic underlaying reasoning for aftermarkets ecms are, and none of them put
performance first.

> > And now that I
> > think about it some, I think
> > timing would be the better answer.
> Except you lower the cyl. pressures in every cylinder.
> That's my only thing.

How the heck do you get to lowering all the cylinder pressures with
individual timing control?.

> > It's easy to
> > swap injectors around,
> > given a set that have been flowed,  then use the
> > timing as a stop gap.

> Uh oh, I think we're talking about different things.
> hmm.
> >I think using fuel control is alot of work to
> > cover other problems, when a
> > simple injector swap would answer the fuel
> > delivery.
> What I'm talking about is adjusting fuel delivery by
> 10% or so. If you're using and ems you might as well
> have it compensate rather than running different sized
> injectors (if this is what you mean).

If your fueling is off by 10% your in the wrong end of the known universe.
That would be when your trying to cover a dead injector.  10% that's a
ridiculous figure.

> >   After studying the plugs out of the GN with
> > the big plenum manifold I
> > think more then ever the mechanicals need
> > optimised alot more then people
> > think.
> Agreed. Sometimes things like intake design is a
> compromise where even distribution is slightly
> compromised for lower pressure drops=> greater overall
> volumetric efficiency.

>From what I've seen it's about bean counting, or packaging.

> >Batch or SEFI is fine for getting the
> > fuel evenly distributed, it
> > the air that's being overlooked, again all my
> > opinion (some supported by own
> > little experiments <g>).
> Agree with this for sure.
> -Kenny
> AKA Captain Bondo

Bruce
   AKA Major Headache




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