Idle mixture / AFR etc

[itguy]

Hi all

I'm looking at the setup of my idle values in my VE table now.

What AFR should I be aiming for, and does it really matter? I've read the tuning manual and it suggests that I should be aiming to get the lowest MAP reading possible with the fueling VE table when fully warm at the idle points, however this gives me an AFR of 13 or so - is this too rich?

Initially I thought about using EGO correction from 800 rpm upwards (my idle is 950) and setting it to be 15.5 AFR for a nice lean idle, however the revs seem to not be too stable when doing this, presumably because its just not rich enough.

I've also got an ICV (bosch 2 wire running PWM) and have set this to closed loop mode to idle at 950 fast and slow, seems to be more settled with my 13 AFR rather than my 15.5 AFR on EGO.

Any advice would be great,

Thanks

[jonfx4com]

13 does sound a little rich, mine is happiest around 14.5.
I suppose this varies from engine to engine. How about leaning it a little and seeing if moving the advance around a little makes it steady? If not either your engine needs 13 or your EGO calibration is off.

Jon

[ptegler]

On an adjustable fuel pressure regulator.... should the pressure be set 'with' or 'without' the vacuum pipe attached??

In other words.... for a setting of 43 psi.... should it be adjusted WITH the vac attached (so the 43 is the highest pressure) or set it WITHOUT the vac attached so the 43 psi is the lowest pressure??

Paul Tegler
ptegler@cablespeed.com (ptegler@cablespeed.com)
www.teglerizer.com

----- Original Message -----
From: jonfx4com (jon@fx4.com)
To: megasquirt-tuning@msefi.com (megasquirt-tuning@msefi.com)
Sent: Wednesday, August 02, 2006 4:05 PM
Subject: Idle mixture / AFR etc


13 does sound a little rich, mine is happiest around 14.5.
I suppose this varies from engine to engine. How about leaning it a little and seeing if moving the advance around a little makes it steady? If not either your engine needs 13 or your EGO calibration is off.

Jon




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[keithmac]

I run 14:1, seems fine at that (ego active), all depends what the engine seems happiest at though.

I belive the FPR should have it`s base setting set with the vac line at atmospheric pressure, it can then account for vacuum and boost situations (alters the base fuel presure in relation to the manifold pressure so in theory the fuel delivery from the injector should not be affected by the pressure in the manifold, just it`s opening time..).