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Target AFR ?
clairetoo - 24/5/08 at 07:27 PM

I know this is a real beginners question - but I`m getting more than a bit lost......
I have an LC1 wideband Lambda setup on my megasquirted V6 , and one thing I cant find written anywhere is - if its rich , is it a higher number or lower ?
And can anyone help me with a `target AFR` table , my current one just looks total garbage (seems to have got corrupted with all the faffing about...)


mr henderson - 24/5/08 at 07:35 PM

14.7 is the ideal

More info here
http://en.wikipedia.org/wiki/Air_to_fuel_ratio

John


daviep - 24/5/08 at 08:10 PM

You actually want to be running richer than 14.7. The extra fuel cools the crown of the piston and delays detonation allowing you to get ignition slightly more advanced.


clairetoo - 24/5/08 at 08:13 PM

quote:
Originally posted by daviep
You actually want to be running richer than 14.7. The extra fuel cools the crown of the piston and delays detonation allowing you to get ignition slightly more advanced.

But............what will the AFR show if its richer ?
Will it be a higher , or lower , number ?

[Edited on 24/5/08 by clairetoo]


b184 - 24/5/08 at 08:21 PM

I would say a lower number.
Air to fuel ratio
14.7 parts air to 1 part fuel?
I could be totally wrong though


Rallye_Mark - 24/5/08 at 08:23 PM

You dont want to run at Stoichiometric conditions which is 14.7:1 approximately, or an equivalence ratio of 1. For maximum power, an equivalence ratio of 1.1 which is roughly 13.4:1, but for maximum economy you want an equivalence ratio of about 0.9, roughly 16.2:1.

This is because to provide maximum economy, all of the fuel must be combusted therefore there must be excess air available, and the opposite applies for maximum power, when you want all of the oxidiser (the air) to be combusted therefore an excess of fuel.

Hope this makes sense, Mark


piddy - 24/5/08 at 08:50 PM

quote:

Text if its rich , is it a higher number or lower ?


To answer your question the lower the number the richer it is.


mark chandler - 24/5/08 at 09:05 PM

Clare

Now its running you need to take the 0-5v output from your LC1 and wire it into your megasquirt.

Within the settings configure for wideband then go for drive datalogging.

Now load up megalog viewer and load into this your current map and the datalog file.

When you run the VE analyser in this program it will compare the datalog to the map and generate a new table based upon the logged values.

Just keep repeating to refine the map, drive about logging data and use megaview to sort it out for you.

Regards Mark


clairetoo - 24/5/08 at 09:20 PM

I`ve been working on logging it - and allmost got my head around `megalogviewer` as well
If the sun comes out tomorrow I may well be burning a lot of un-leaded now that I have sorted an on-board power supply for the laptop .


darrens - 28/5/08 at 06:06 PM

To confirm

rich = below 14.7
lean = above 14.7

To richen your VE table increase the value (i.e an increase from 44 to 54 say) and reduce to lean it out.

For motorway cruise you ideally want to be above 14.7 (how high depends on your engine tolerances) otherwise you'll be burning fuel in excessive amounts when you don't actually need it. I.e motorway cruise, no load, minimal throttle.

Cheers


[Edited on 28/5/08 by darrens]

[Edited on 28/5/08 by darrens]