AFR rich when letting go of throttle

Propane, Butane, LPG, GPL, C3H8, C4H10
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robin_chevelle
Posts: 5
Joined: Wed Nov 16, 2016 11:44 am
Location: the Netherlands

AFR rich when letting go of throttle

Post by robin_chevelle »

Need some help and advice.
My chevy Van with a 383 small block stroker Impco 425 mixer single fuel model e vaporizer does run very good.
0 to 60mph goes in 6.5 seconds, car is 2200kilo (th350 transmission and 3.08 rear end gearing).
Just did a very long drive of 2172 kilometer and used only 418 liter of propane. About 1 liter for 5.2 kilometer or 12.2mpg. Did not drive faster then 65mph.

But every time I accelerate from let's say 30 to 50mph or with 50% throttle or more, I reach the speed I want, let go quite a bit of the throttle the AFR goes very, very rich for a couple of seconds and then goes back to normal.
It does this for some time now and I don't know how that's possible.
Cruise AFR is 16.5 WOT AFR is 14 Idle AFR (below 900rpm) is rich at 14 because of the PCV, when I close is it's better, when I adjust is and make it leaner, the cruise AFR is also much leaner and I'm afraid is going to get to lean.

Did try to adjust the idle and wot mixture screws this weekend, but it does not fix this problem.
Am I doing something wrong? Or is this normal behavior?
'70 Chevelle SS396 - 4L80e - 3.55 - gasoline
'77 G20 Van - 383ci - th350 - 3.08 - propane

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