[Diy_efi] O2 sensor sensitivy speed

Bruce nacelp at bright.net
Fri Apr 26 23:11:30 GMT 2002


From: "Kenny" <watson at iamfun.com>
Subject: Re: [Diy_efi] O2 sensor sensitivy speed
> Easier to use an EGT gauge in each exhaust manifold
> runner imo. Also the critical time where uneven
> cylinder filling will cause serious problems is
> generally above 3k.

How do you tell a timing from a fuel problem using EGT?.

> >Given the proper mechanical answers, I think
> > the gains with it are minimal.
> Depends on the application. With race engines,
> detecting uneven air distibution into each intake
> runner/cylinder is very critical. High end engine
> managent systems are built with functions to trim each
> cylinder independently for good reason imo.

Yep, feature creep sells 90% of any *new and improved* product line.

> >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?.

> > And that's
> > mostly about timing (given
> >the proper mechanicals).
> Isn't it easier to re-trim the injector duty cycle to a
> single cylinder? retarding a single ignition event to
> attempt to avoid detonating seems odd to me when
> richening the mixture to the offending cylinder is
> significantly easier. If ignition advance is the issue
> then it has to be retarded to all cylinders. Letting
> the other cylinders have optimal timing and controlling
> the single detonating cylinders mixture will indeed
> result in performance increases dependent upon things
> like the intake plenum's overall design for example.

Isn't best to design things so that all cylinders contribute equally?.
Individual cylinder trimmings are just covering up for other malfunctions.
I don't see where one is easier then the other, the trick is figuring out
which cylinder to work with.  And now that I think about it some, I think
timing would be the better answer.  It's easy to swap injectors around,
given a set that have been flowed,  then use the timing as a stop gap.   I
think using fuel control is alot of work to cover other problems, when a
simple injector swap would answer the fuel delivery.
  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.   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>).
Bruce

> -Kenny



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