Good CO Meter

[Carlito]

Hi guys,

I have a '74 911 with a '78 sc engine and am trying to tune it. The guy I bought it from did a lot of jerry rigging. For instance, the distributor vacuum line had a chunk out of it, and it was tuned to run like that. It was in rough shape, did the body and paint myself and it looks nice, now for the mechanical. I've replaced most of the old lines and it was running, albiet poorly. New ignition system, fuel filter, oil etc. Now it starts and dies. I think it was timed and tuned so out of whack from factory that this is the cause. I'm going to do the valves, time it correctly, but I need to get this CIS correct so it stops surging. My question is: What is a good, economical CO meter or device to tune the CIS injection system of a '78? I'd like to spend less than 200. Also the adjustment screw does seem to work, but does not click. Is this normal?

-Carlito

[fanaudical]

I'm in a similar situation and am trying to learn my way out of it. First, I recommend browsing through here:

CIS Primer for the Porsche 911

The section on "Testing" has some good recommendations. It seems to me that pressure test gear is initially more important than a CO meter. (You'll use the pressure test gear to get things running; once running, the CO meter helps you get it running well.)

I haven't bought one yet, but am considering this (based on feedback here on Pelican):

Gunson | G4125 | Gastester Digital

If you find a different CO meter, please post info.

Neither of the adjustment screws (idle or mixture) appear to click on my CIS.

[redstrosekNic]

+1 on the Gunson. My '75 mixture screw does not click.

[Nickshu]

I have a Gunson gastester. Works great. $200 new on ebay. There's really no other CO meter out there at that price point.

[dicklague]

CO is very 70s.

Wideband oxygen sensors have ushered in the world of very accurate AFR readings.
AFR is basically the same and can be converted

Here is a link to a discussion on this.

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

Why not get a good AFR instrument like the Daytona-Sensors WEGO IV that our sponsor her sells. I have one installed permanently in my MFI 1973 and it is just plain indispensible.

You can buy cheaper and less versatile AFR instruments from lots of sources, but I love the WEGO unit. It saves 2 hours of AFR data, which is AFR, RPM, Vacuum/MAP. and a time line.

Here is the conversion chart.


%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

[BisimotoJulio]

A data-logging wideband sensor kit that I have personally used and have had great luck with is the AEM Electronics UEGO failsafe gauge kit. This system contains an on-board data logger for logging over three hours of data recording for AFR's, vacuum and even boost pressures with its included Bosch wideband sensor and map sensor. The digital display gauge can be also mounted in your vehicle and will display the same parameters live for instant reference. Best of all they retail for only $299, but I happen to have a couple in stock that I can let go for $279 shipped to the Continental USA. P.M. me for details.

For more information, check out this link: 6speedonline.com AEM Electronics Wideband FAILSAFE Gauge

[matt demaria]

Nice number scale.
Not accurate.

[dicklague]

Originally Posted by matt demaria

Nice number scale.
Not accurate.

What is not accurate? The table, or the AEM wideband?

[kugelfischer]

This is the commonly accepted AFR to CO conversion table.