[scarceller]

The SC is a bit more tricky to properly tune and fuel because of 2 reasons:

- No air flow compensation for IAT or Altitude. That air plate and funnel measures Air Flow not Air Mass and the system has no compensations built in. Keep in mind that air becomes lighter (less dense) as IAT goes up and also as Altitude increases. This means that as it becomes lighter your mixtures will get richer. So as you climb in altitude you will get richer, and on a hot day you also will be richer compared to a cold day. Simply cold air at sea level is the best for these motors or any motor. Because of this lack of compensation you can't afford to go lean in cold temps so you MUST set mixture for a target no more than 13.0AFR at sea level and 0C temp this gives you the safety margin you need for cold temps and low altitudes. But it's a compromise that as IATs go up and Altitude increases your AFR goes down. Simply go back to physics 101 with law of gasses and you can run the numbers, you'd be surprised how much the density of 1 Liter of air changes by simply increasing IAT from 0C to 40C and/or going from 0ft to 6000ft elevation.

- Next reason the SC is tricky is it has no computer controlled timing to correct ignition across all engine conditions. If recall I think the SC engine runs about 25deg adv ignition at WOT above 4000RPMs and that's the factory spec. But you can easily run 30deg adv safely with 93 octane fuel so long as the AFRs stay in the 12.5 to 13.0 range. You really need a load dyno to find peak torque for a given RPM. I'd lock the dyno in at 4000RPMs pull a quick WOT pull for 5 seconds and record torque at the stock 25deg ign. Then increase adv to 27deg and repeat, then 29 and so on. But you need a good knock sensor to be sure you don't have detonation, although the torque number will also drop significantly with knock. My bet is you'll find optimum ignition possibly as high as 35 deg!

Here's some other thought exercises: All the early cars 1968-1973 ran ignition of 30-35deg advance and these motors had much smaller bores. Engine dynamics follow a rule of thumb that as bore increases so does ignition advance if nothing else changes. It simply takes longer for the flame front to reach the edges of the cyl. This means that these motors lost efficiency as they increased bore! It makes no sense for a 2.2L engine to be at 35deg ign while the sister 3.0L engine is at 25deg. For some reason the factory detuned the 3.0 and 3.2 engines.

Taking a well running 3.0L and installing a decent WBO2 meter and then a few dyno pulls at 4000, 5000 and 6000RPMs will show what ignition the motor wants, once you know this a good distributor shop can build the curve for the distributor.

I've also had the idea for a very cool project, take a 3.0L and install the 84-89 motronic system into it and tune it. That would result in a very interesting engine with proper timing for all conditions.

One last thought: my personal 3.2L Euro engine runs 30 deg advance without issue and I hold my AFRs at 12.8 across the RPM range at WOT. The 3.0L engine should easily tolerate the same ignition as the 3.2L in theory. And my engine is a Euro with higher compression running at 30 deg on 93 octane fuel.