Installed a Wideband AFR-gauge today. Some observations...

[BigBlockMopar]

I recently bought an Innovate MTX-L AFR gauge in preparation for a future MegaSquirt installation.
Today I was able to hook it up into my '73 Dodge Dart and check it's readings at various rpms and engine-loads.

Now remember, this car runs on propane, so a "15.5:1" A/F ratio is supposed to be the 'stoichiometric' ratio here.

Some interesting stuff surfaced (for me):
Idling: 14.5 - 15.5
No-load high rpm: 14.5 - 15.5
Throttle release from high rpm: upto 22+

During driving I noticed the following:
Steady speed: 14.8 - 15.0
Steady speed, with very little extra throttle: 14.0 - 14.5
Normal acceleration: 16.0
Firm acceleration: 17.0
When I squeeze the PCV-line to the carb closed, the AFR drops to 13.0.


I've also shot some video of the motor running with the car standing still in Neutral (around the 2:00 mark I put the car in Drive)

[Barry Donovan]

cool gadget.

so you learned your pcv works an idle seep (excellent)
..and the fuel is in good control after letting off.

I still have to guess without that stuff.
wideband it is not cheap from what I can find.

[TheSilverBuick]

Your accelerations look a bit lean, but otherwise everything else looks good. With out knowing the true properties of propane, I'd "expect" the acceleration numbers to be a few points below 15.

[BigBlockMopar]

The basic ratio's are pretty much the same for regular fuel; Rich at idle and acceleration, Lean at cruise.
Somehow I have got to 'reverse' the current situation on my car now.
Although I'm a bit hesitant to do 'major' adjustments on the engine, as it starts well within 2 seconds of cranking, every day, summer or winter. Is always easy to drive with no issues at all, and it does about 17mpg on the highway.

Tuning/adjusting an LPG system is very limited aswell.
There's only a sort of 'idle-setting' and a 'powersetting' in the 'mixer', with is mounted on top of the regular 2-bbl.
And there's some more precise adjusting possible inside the liquid-to-vapour convertor by altering a certain spring height. But that's only minimal.