Lambda Readings

[Mazda Ebrahimi]

Doug Robson wrote:
> 
> Mazda Ebrahimi wrote:
> >
> > Doug Robson wrote:
> > >
> > > Hi All
> > > is the relationship between lambda and A/F always 14.7 or is there some
> > > sort of relationship, because on the weekend i adjusted the fuel table
> > > in my race car down fro L.95 to L.9 and it felt like a 10% power drop
> > >
> > > ??
> > >
> > > also does the 4 wire Heated ($350) sensor do the temp correction or does
> > > the ecu do it
> > >
> >
> > 14.7 only produces good power if you have excellent air / fuel mixing.  As others have
> > commented, theoredically you should get more power going slightly rich, because the
> > vaporization of the extra gasoline should cool the charge down.  Here are a couple of
> > questions that come to mind:
> >         Does the system currently run open loop?  If so, when you have A/F set to 14.7,
> > have you verified stoichiometric operation by monitoring an O2 sensor or CO reading?
> > Maybe the problem is that in case of the open loop system there is an inherent error in
> > the air mass calculation.
> >
> >         How sure are you about your A/F cylinder to cylinder?
> 
> Now im really confused
> My lambda number comes from Autronic SMC ecu
> the program allows users to choose A/F type input or O2 exhaust input.
> the out put is always a number like A/F 12-15 ish. and i divide mine by
> 14.7
> 
> I cant gaurantee the individual a/f except to say that the plugs all
> look very similiar
> The same sensor ( literally) is used by a friend in a mote m4pro system
> and works fine
> 
> it sits 1 foot after 4 -2 1 collector
> 
> how do i verify the a/f on the way in?? is that what you mean
> 
> regards
> 

That is what I mean.  I wasn't sure if you had an O2 sensor on the engine or not.  If 
you can monitor the O2 sensor, and it reads between .4 to .5 volts while your indicated 
A/F is 14.7, then the indicated A/F is correct (as verified by the O2 sensor), so that 
is not your problem.

Since your spark plugs are good, then you shouldn't have a MAJOR distribution problem.  
If nothing else has changed, you should have made slightly more power at A/F = .9*14.7 = 
13.2, although I don't know how much "slightly" is.  I think that depends on your 
specific fuel system (i.e. type and location of your injectors) and how well fuel is 
atomized.  I know others reading this disagree.  

Anyway, if you have good distribution (probably the best way to check is to measure 
exhaust temps or exhaust CO cylinder to cylinder), you should experiment with A/F to get 
max power.  I don't think the numbers people generally throw around (like 12:1 for peak 
power) are set in stone.  But before you take my advise too seriously, I should caution 
you that I have little experience with gasoline (most of my work is involved in natural 
gas and propane engines).  It'll be interesting to see what other explanations there are 
for a power loss at Lambda =.9 compared to Lambda = 1!

Best Regards
M. Ebrahimi