Looking for info/help on system from '01 Chev Metro for an airplane

This system and motor are being used in a homebuilt airplane that also has a turbo added. We think the issue (mid RPM surging) is O2 related, but not 100% sure. The exhaust had to be shortened for use in the airplane of course and modded for the turbo, but the problem is the rpms surge at part throttle. The OEM O2 sensor is the basic on/off style but it works backwards to most. I doubt it needs the sensor heater, but wonder if maybe a wide range sensor would cure the problem. This is about the last thing needed to make it run right for flying.
The laptop reads it as running too rich. Any ideas?

Can you give more specifics about the system in question? The Metro is a Suzuki built vehicle with a Japanese sourced controller. GM never equipped the Metro with a turbocharger. Are you using the stock controller? How are you tuning for positive intake pressure?

MAP sensor was changed to wideband to account for the positive manifold pressure. Suzuki used the same setup with turbo. It's only boosting 5 to 7 psi and the surge happens before it even spools up.

It's been difficult determining which US model to use for comparison to your setup. I used an 87 Chevy Sprint turbo which uses an airflow sensor rather than a MAP sensor. In that application it doesn't look like Suzuki / Chevrolet used the same engine computer for turbo and non turbo engines. Often when you try using a non turbo controller with boost you'll find it delivers too much spark advance. The problem can be aggravated by changing airflow or pressure sensors as now the ecu believes there is less pressure and / or airflow than what's actually being delivered. Too much advance can cause surging.

If you suspect the oxygen sensor placement is causing issues try disconnecting it to see how the engine runs. You don't need to run closed loop. Some of the early Japanese EFI systems were pretty primitive. You might be able to build a small circuit which generates 0 - 1V adjustable by potentiometer to provide a signal on the O2 signal line to keep the ecu from illuminating the check engine light. This circuit could double as a manual adjustment to overall fueling.

01 metro could only be the 1.3 4 cylinder.... i didn't think those ever came with a turbo, even from suzuki(or in the case of the canadian market, the pontiac firefly).

but if it did come so equipped, then i would grab the PCM and associated sensors from the factory boosted application, assuming they didn't change heads/pistons and stuff to change compression.

using a 2BAR MAP sensor in place of a 1BAR.... so when you key-on, the PCM thinks the barometric pressure is around 50kPa, delivers way too much advance if the spark advance is based on speed-density instead of MAF... i can see a few issues popping up here.

It appears Suzuki / GM sold a version of this car with turbo worldwide up to 91 or 92 but I can only find service literature on the turbo version from 87. Pistons do appear to be different and there's a turbo sprint ecu on Ebay now so there's a difference in at least 87.

If this system is MAP based then BARO updates could be so far off it's not funny. First, the aircraft engine is subject to BARO changes much more often than the ecm is programmed to check for. Second, if the ecm updates BARO at WOT, with a manifold under boost and the MAP calibration for one BAR, who knows what you'll get.

IMO if this system is MAP and doesn't have the turbo controller the best approach is to use a one BAR MAP with check/bleed valve combination plus extra injector controller. If pressure above 1 BAR is experienced, the check valve seals the MAP line off from manifold pressure, and the bleed valve opens the MAP sensor to atmospheric pressure. At least that way the ecu will be able to control fuel and spark accurately when there's no boost.