[Diy_efi] O2 sensor sensitivy speed

[Kenny]

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. 
 
> 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. 
 
> > >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.
 

> 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. 

> 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.

> 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. 

> 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. 

> 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).
 
>   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.

>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

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