Early 930 CO% settings?

[jryerson]

Does anyone know the proper CO% setting for a early 3.0 Turbo?

My 77 930 is at around 4.25% CO with 80HC and CO2 is 6.2.

The PO had a 1 bar spring put in with SSIs and dual exhaust, the last time the car was worked on over a year ago the tech put it rich to help detonation probably at high rpm but the car is very slow off idle and is bogged down till above 2300rpms, mini-vans ride my tail til then.

I am thinking the rich CO setting is causing this but I don't want to grenade my motor by setting it too lean either, I was thinking more around 2% CO.

At around 2000rpm the CO% is at 4% as well.

Any ideas appreciated.

[john walker's workshop]

4% generally works. stock early turbos are as you describe. high geared 4 speed, and low compression engine = minivan bait for a few seconds. SC cams liven them up nicely, as well as a K27.

[jryerson]

Thanks John,

So I should just leave it then?

[Sameer]

I set my CO between 3.5% to 4% and set my Andial FEC at third step.

I would also do and A/F ratio using a wideband. You should see between 11.8-12.5 under full boost for a healthy A/F ratio.

[mmastro]

Mine's at 3.8% ...that's with the mods listed below. No minivans in sight!..

[jryerson]

Thsnks guys,

maybe I'll lean it just a tad around 3.8%.

[john walker's workshop]

3.8, 4.0, really not a helluva lot of difference.

[RarlyL8]

Maybe my CIS is getting old and less responsive to adjustment but I can't tell a difference between 2% and 4%.
It runs the same in that range. More will set off the idle hunt and less will lean it out to where the engine runs hotter. I've also never been able to adjust 0.2% increments. About +/-0.5% is the best it'll do.

[beepbeep]

As far as I know, CO-adjustment mostly influences idle settings, so adjusting CO from 4 to 2 or 3.5% won't do anything to CIS ability to supply fuel at boost.

My CO was 0% but car still run slightly rich at boost. It's emission thing only.

[john walker's workshop]

an emission thing, as well as a smooth idle and somewhat better low end response, like when you take off from a stop.