Dual Fuel Exhaust Smell

[Citroënbender]

I’m poking at this ute with dual fuel conversion (Prins SVI). It appears to be changing over correctly.

What’s puzzling me is, it doesn’t seem to have the exhaust smell I associate with LPG when it’s running on gas. The characteristic gassy odour I recall with old Falcon taxis, and forklifts at the markets.

Do vapour injection gas systems never develop that odour in the exhaust gases? Or does it just take time to purge the petrol fumes from the catalytic converter?

[AMB]

When the exhaust smells like gas, it means its not being burnt completely, either just running poorly for various reasons or just adjusted too rich. Vapour injection is a bit better at getting right, but its the same with old school mixer systems. Most of my cars have been mixer systems, and whenever I've started to smell a hint of gas I know something ain't right. The older impco systems were intentionally adjusted to run rich at idle, so that it wouldn't lean out when accelerating (ie. no backfire on take off). That's why you could always smell unburnt gas, they were set up that way, to run rich and not use the O2 sensor when idling. Running a bit rough and prone to backfire? Then adjust it even richer, who cares about spewing raw gas out the exhaust.
That was the easier more foolproof way, but I used to set up mine to idle off the O2 sensor, and there was no smell of gas. With the egas system, its always cycling on the O2 sensor and there should be no smell of gas at idle.
In other words, you cant smell the exhaust in your SVI system because its running properly. The characteristic smell you remember from days of old, was from cars that weren't running properly. A good setup shouldn't smell like gas. No different to petrol really, if you can smell petrol something ain't right.

[Citroënbender]

Thank you. I’d assumed the exhaust gas smell of old was due to a heavily rich condition.

So, if there’s no real change in exhaust odour from petrol to LPG it’s making whatever use it can/does off the oxygen sensor, then? 314K, might still be on the original front oxygen sensor, too.

[Crazy Dazz]

I too recall the "gas" cars of old. Smelt like they were running on baked beans.

I've always figured this was a combination of lack of emission-control, bad tuning, and poor quality gas.
Modern cars with cats, etc, don't have the smell.

Back in the day, LPG was literally the crap they used to burn in the flare at the oil refinery. So it probably contained a lot more sulphur.

[Itsme]

Originally Posted by Crazy Dazz

I too recall the "gas" cars of old. Smelt like they were running on baked beans.

I've always figured this was a combination of lack of emission-control, bad tuning, and poor quality gas.
Modern cars with cats, etc, don't have the smell.

Back in the day, LPG was literally the crap they used to burn in the flare at the oil refinery. So it probably contained a lot more sulphur.

Gas did have a lot of crap & tar in the mix of it, probably still does, my BIL use to install & service gas systems & converters, the amount of crap residue I've seen in them is amazing, anywhere from tar, wax & metal fragments etc.
Probably the reason why the decline in gas powered vehicles these days.