MFI Q's

Thank you both and I will do so. Read it twice at least, at the very least I'll know what the shop does.

I got my 'snail' air flow the other day and got around to using it. First thing was cleaning the air screws. Rice's #41 drill is 30mm which I don't have. If you want to go that route get a long shank bit or use duct tape so you don't lose it. I went the Q Tip route, you have to cut the tips off. #2 & 3 I didn't do since I didn't want to lose a spring and the motor will be coming out anyway later. Other than some carbon they were all fine. #1 cylinder was about 10% over the other's flow rate. Fiddling with the air screw didn't change it. Funny thing is +180 <210 I get a static idle.. <180, hand throttle. Heat hose to the MFI is fine. I'll get around to buying an exhaust gas analyzer. My guess is the thing is running slightly rich which I prefer to lean.

For MFI to work well you have to have the supporting systems, engine, and MFI setup within spec.
Then you can start tuning. I am not a professional engine tuner. I have setup and tuned a few MFI systems. I use the following points and triangulate.

1) Data:
- Exhaust: CO, CO2, O2, HC (readings at part load & idle)
- Airflow: stacks at 3,000 rpm and idle
- Milage experience: Cruising and stop & go traffic
- Engine: Temperature, how quickly does engine return and settle to idle rpm?

2) Visual: Spark plugs and tailpipe
3) Sound: Does engine sound happy, any misfires, consistent idle, popping or backfires?
4) Feel: How does it drive during transition to full load, start off, cruising, during throttle lift?
5) Smell: How does the exhaust smell?

I use a 4-gas analyzer that can be attached while driving. Folks use wideband O2 sensors, but my sense is those are directionally right, but specifically wrong. These MFI engines have high valve overlap and, at least at idle, there is going to be more O2 in the exhaust stream, which will indicate a leaner condition than might actually be the case. I largely ignore AFR/Lambda, and focus on CO and CO2, with an eye to where all 4 gases are falling. I have not been able to use AFR as the sole metric to produce a good outcome.

Just my experience.

Bert