How do I correlate AFR to CO content...?? using a LM-2...

[911 tweaks]

maybe I am mixing apples & oranges here, but, I am trying to set AFR on a 3.2L to 12-13...I understand that stociometric(sp) of 14.7 is perfect and it equals 1 per the instructions with my LM-2 unit...
I have read & been advised that at idle speed of 900-1k rpm's I want my AFR measurement to be around 12-13...
What does a CO reading of 2-2.5% equate to in terms of AFR...??
Thx, Bob

[356RS]

Co% 2 = 13.77 afr; co% 2.5 = 13.56 afr.

[911 tweaks]

thx Mark...is there a conversion factor or a way I can convert afr to Co...??
What would the Co be for a 14.7 afr...??
Also, what is the afr for 1% Co; 1.5% Co and 3% Co...??
Thx Mark...these appear to not be linear...??
Bob

[356RS]

Bob, I have a CO% / AFR Table that I can e-mail to you. The CO for 14.72 AFR is 0.1 CO%. The AFR for 1% CO= 14.11; 1.5% CO= 13.94; 3% CO= 13.38

[911 tweaks]

Thx Mark...please email me the table at bobf@design-associates-ne.com...

Basically, I am having trouble setting the mixture on a 1984 3.2L Carrera...my LM-02 initially had issues & was found to have a faulty cable for the o2 sensor...I found 1 vacuum leak & fuel pressure reg was bad...still experiencing a low idle speed & very lean mixture readings at a warmed up idle with mixture screw turned all the way in...when I drive car & put it under load = accelerate, the afr goes to 1 to 4 afr's...at idle or coasting it is 18-21 afr...

Any ideas on what to check...?? I have checked ALL vacuum hoses & ALL sensors on engine & all "seem" to be working w/in spec...

Thx, Bob

[AlfonsoR]

I copied this from BemariM3Ex: http://www.bemarim3ex.com/demos/repair-new-bemarim3ex-141/39-afr-vs-co-table.html

%CO AFR
0.1 14.72
0.2 14.54
0.3 14.42
0.4 14.34
0.5 14.28
0.6 14.23
0.7 14.21
0.8 14.17
0.9 14.15
1 14.11
1.1 14.09
1.2 14.04
1.3 14.01
1.4 13.98
1.5 13.94
1.6 13.89
1.7 13.86
1.8 13.82
1.9 13.8
2 13.77
2.1 13.73
2.2 13.69
2.3 13.63
2.4 13.59
2.5 13.56
2.6 13.54
2.7 13.49
2.8 13.45
2.9 13.41
3 13.38
3.1 13.34
3.2 13.31
3.3 13.27
3.4 13.24
3.5 13.2
3.6 13.15
3.7 13.12
3.8 13.08
3.9 13.03
4 13
4.1 12.96
4.2 12.93
4.3 12.9
4.4 12.86
4.5 12.83
4.6 12.8
4.7 12.75
4.8 12.7
4.9 12.66
5 12.64
5.1 12.59
5.2 12.54
5.3 12.51
5.4 12.46
5.5 12.43
5.6 12.4
5.7 12.37
5.8 12.3
5.9 12.25
6 12.25
6.1 12.22
6.2 12.18
6.3 12.13
6.4 12.1
6.5 12.09
6.6 12.03
6.7 12
6.8 11.96
6.9 11.93
7 11.89
7.1 11.86
7.2 11.82
7.3 11.79
7.4 11.76
7.5 11.72
7.6 11.69
7.7 11.65
7.8 11.61
7.9 11.58
8 11.54
8.1 11.5
8.2 11.46
8.3 11.43
8.4 11.4
8.5 11.36
8.6 11.32
8.7 11.28
8.8 11.25
8.9 11.21
9 11.16
9.1 11.12
9.2 11.08
9.3 11.05
9.4 11.01
9.5 10.97
9.6 10.94
9.7 10.9
9.8 10.86
9.9 10.82
10 10.79

[304065]

Remember that the stochiometric mixture of E10 will be richer than pure gasoline.

[911 tweaks]

304065...good point...how do I factor your input = E10 fuel these days into the tables here...??
Thx, Bob

[al lkosmal]

Why not just change the mode of the LM-2 so that you can read AFR directly? Or am i missing something here?

regards,
al

[911 tweaks]

...you are right Al...however, I am having trouble...STILL...with my brand new LM-2 unit & trying to figure it out...I am as certain as possible that the engine is sound but for the life of me I cannot adjust the fuel mixture then the idle...ARGHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH...

I am about to run over the f'ng pos unit... :-) But I wont...it will probably turn out to be me not understanding something & I cannot figure this thing out...!!!

I think I need to find a local speed shop that has a known good exhaust reader so I can set mixture & then idle...

I found several cracked vacuum hoses...replaced them...fuel pressure reg was bad...replaced it... new spark plugs...I checked ALL sensors & w/in range per bently...just installed a cat bypass pipe as cat was plugged & still better but not correct mix & idle...

Anyone want to take a stab at this with me using my LM-2...I have the tail pipe clam that Al K. suggested to get & the rpm clamp...

Just when I thought it was going to get easy I am hitting my head against a wall...

[Dr J]

911 tweaks:

I have had an LM-2 sorted out and running on my car continuously for over a year with the O2 sensor on my cat bypass. I would be happy to help you out. Email me or pm me.

[911 tweaks]

pm sent to DrJ...thx

[911 tweaks]

Thx again John...you were a great help...best of luck with your work in FL... Bob

[Dr J]

My pleasure. Hope you get the rest sorted out and can enjoy the car.

[911 tweaks]

...FINALLY found out what it was...it is going to sound quite obvious...intake runner seals dried out ~ cracked = leaking air...!!

I sprayed carb cleaner around the base gaskets & no idle spike...I initially sprayed a shot into the air box & the idle spiked so I knew the engine would spike "IF" a leak where sprayed...nope...

A buddy told me that carb cleaner is not as volatile as it used to be...try brake clean...so, we gave the intakes a shot with brake clean and WHAM...SPIKE...

Thought I would pass this along so others are not fooled when trying to perform a similar diagnosis...

Thx again everyone... Bob

[Dr J]

Congrats!