CO values 2.4l (idle)

[Bijan]

Hi everyone,

I just asked myself if there are any official exhaust gas CO values (idle) existing for the 2.4l? I couldnt find anything in the workshop manuals I know.

If nothing official exists: on what values are you running your cars?

Thank you

Regards
Bijan

[Georg]

My Dino 2400 is set at about 5.5 to 6.0 CO. I believe that factory setting is about 4.5 but mine does not run well that lean.

[Bijan]

Hi Georg,

thank you, mine is currently running too rich, as far as I remember about 7.5.

I will try it with 5.5. Do you measure each cylinder separately? I theoretically could measure each single cylinder through threads in the exhaust manifolds...

Thanks
Regards
Bijan

[abarth4]

Excellent thread! Way back in the day here in the USA, shops used to routinely measure % CO when testing/adjusting fuel mixture. Unfortunately that testing equipment has gone the way of the dinosaur, at least in the USA. I used to have a CO meter but nobody seems to sell/service or calibrate them any more. If you have a CO machine and place a probe in one of the tail pipes, you are measuring 3 cylinders at once (each bank) so the reading is sort of a "average" of what each cylinder is doing. You can have 1 rich cylinder and 2 leaner ones and get a number that you like, but that doesn't mean the mixture is correctly adjusted. Bijan, you are absolutely correct that you can measure each cylinder through a tap in each exhaust header. I used to do exactly that on my Fiat 124 twin cam with dual Weber IDF's. This will allow you to properly measure and set the CO percentage for each cylinder, rather than trying to rely on an average across multiple cylinders. As you noted however, this requires the addition of a port on each exhaust header pipe for a measuring point. WAY back, when I had a Bosch service center, I seem to remember the number of 1.5% being the adjustment value for a "modern" (1980's) VW Rabbit/Golf with K-Jetronic fuel injection. 5.5% CO is a big number, but we're dealing with 1960's carburation technology here. Emissions were not a thing, so a "rich" engine was a happy engine! Modern electronic fuel injection allows engine to run much leaner and cleaner than carbs ever did. Also, if you hook a CO machine up to your Dino you'll find out just how sensitive and un-repeatable the mixture adjusting screws are on your Weber carbs... There's a reason things are fuel injected these days! If Dino's had been sold in the USA, there would have been an emissions tag somewhere under the hood (bonnet) that would give the idle CO percentage. As we all know however, we never received the Dino over here! If you do modify your headers to include a test port, please keep this thread up to date. Pictures are great! Best of luck!
Charlie

[Bijan]

Hi Charlie,

thanks for your helpful reply, I had already modified the headers with ports ages ago by welding in stainless steel nuts, but I never used them since to be honest Next time I tune my carbs I will definitely measure each single cylinder. I will post an update after that.

Regards
Bijan

[abarth4]

Sounds good! Here's a tip (ask me how I know... ) The closer your sampling ports are to the cylinder head, the higher the exhaust temperature. Make sure the hose you're using to route the exhaust gas to your analyzer can take the heat.... otherwise it will melt and you'll have a mess. On my Fiat 124 the sampling ports were very close to the head, so I would screw a nipple into the sampling port, then use a short piece of special high temp hose to connect it to a reasonably large diameter piece of steel brake pipe that was 4 or 5 feet long. I would then hook this brake pipe to the CO machine hose. The exhaust gas would cool enough when it traveled through this length of brake pipe so it wouldn't melt the hose! Hope this helps!
Charlie

[2dinos]

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Infrared Industries Inc
25590 Seaboard Ln, Hayward, CA 94545
(510) 782-8100

Their FGA4000XDS is magic. It even calculates air/fuel ratio (lambda) making it nice to optimize mixture for your engine. If carbs are good, and well set,, the Webers hold their tune well.