[AWSAWS]

Just went out for lunch. Came back to my office where there's a round about. A guy in an Audi decided to go when he should have waited and put his foot down to keep ahead of me.

I think it was an A4 Avant, similar to the BMW tourers. The fuel was just pouring out of the exhaust all over the road. Not a light stream but like a hose.
That can't be good for the mpgs! I also wonder what impact poring diesel all over the road has on the environment? For one it must be dangerous due to causing skids. Can't help but think though putting out diesel all over the place is far worse than CO2, water and soot.

I wish now I'd told the guy but I imagine alot of cars are tuned rich like this.

[un1eash]

You sure it was fuel and not just water? Diesel would throw out black smoke.

[Russbmw]

It's just condensation/water. Usually get loads build up if you only do short journeys, so it never really gets hot enough to evaporate it all.

[AWSAWS]

Originally Posted by Russbmw

It's just condensation/water. Usually get loads build up if you only do short journeys, so it never really gets hot enough to evaporate it all.

The amount that was pouring out, it's hard to imagine it's water but I do wonder how it could get through the cats etc. Maybe it was a petrol. There was no smoke tbh.

[djgandy]

Originally Posted by AWSAWS

The amount that was pouring out, it's hard to imagine it's water but I do wonder how it could get through the cats etc. Maybe it was a petrol. There was no smoke tbh.

The amount of petrol you actually use when driving along is tiny. You'd be flooding the engine with fluid and it would just not run if you were leaking a lot of petrol.

[The0pportunist]

Spotted the same thing coming out of a 2014/newer shape 3 series, 320d i believe. I did manage to let the chap know though..

I'll try dig up the dashcam footage if anyone fancies a look.

[Russbmw]

Originally Posted by AWSAWS

The amount that was pouring out, it's hard to imagine it's water but I do wonder how it could get through the cats etc. Maybe it was a petrol. There was no smoke tbh.

It wouldn't get through the cats, as it'd ignite in the cat, over time likely melting the innards - certainly popping and backfiring if even a small amount unburnt fuel got through.

Liquid coming out of an exhaust is water vapour produced from combustion/condensation build up. That much fuel would never pass through an engine, mainly because the engine simply wouldn't be running if that were the case.

The Mazda rotary engines were renowned for many engine quirks/ faults, one of which was the passing of unburnt fuel into the exhaust and cat due to dying ignition coils. The cat would glow red hot due to the fuel then burning in the exhaust, eventually needing cat replacement. Even when that happened, no fuel "poured" out of the exhaust.

[alex-qts]

water / condensation for sure. As already mentioned, any unburnt fuel entering the exhaust would ignite the minute it touched the hot exhaust manifold popping and banging, or if it made it that far the cats would do the same, eventually killing them.

My 335i pops a bit on over-run, or if you tip the throttle a tiny bit and back off. Interesting, as I thought direct injection engines would be more precise that that. Not complaining though, I wish it did it more often like the N55's, together with that duramax-style engine and turbo sound

[AWSAWS]

Originally Posted by djgandy

The amount of petrol you actually use when driving along is tiny. You'd be flooding the engine with fluid and it would just not run if you were leaking a lot of petrol.

At regular speed yes but when booting it the consumption goes up alot. I don't know how much exactly.

Now I know this guy didn't have water injection (or at least assume it's very unlikely) but the amount of liquid that can pass through an engine is quite amazing.

At 4000 rpm, a speed it wouldnt take long to achieve in 1st gear, the engine is doing nearly 67 revolutions a second.

These cars have water injection and may well be decatted but look how much liquid they can pass through the engine without hydrolocking.

I suspect the guys car could have been cold as he's just come from an office car park. So I don't know if fuel could pass through a cat in a cold state. Yes he could have driven in and driven out with a warm car.

Anyway I'll assume it's water vapour then that settled in the exhaust. Thanks

[un1eash]

The first video isn't water injection, they just filled the exhaust with water, says so in the comments.

[djgandy]

^^

Liquids don't compress (not in an engine anyway). The valves are relatively tiny too. You'd never get that much fluid through them. The water is just sat in the backbox or wherever.

[alex-qts]

Surely it would hydrolock (https://en.wikipedia.org/wiki/Hydrolock) the engine if that much water even came close to the cylinders...

Squirted it up the exhaust pipes, seems to be a big thing on youtube for some reason...

[AWSAWS]

Originally Posted by djgandy

^^

Liquids don't compress (not in an engine anyway). The valves are relatively tiny too. You'd never get that much fluid through them. The water is just sat in the backbox or wherever.

Yeah I understand the physics. I missed the comment about pouring the water in with a hose. I was looking for an old scooby clip that seemed to have similar results. Don't see it anymore.

On my water\meth kit the pump can flow 4.9 litres a minute. The dual nozzles limit flow to 1.26 litres a minute. That's actually not that much.

Next time I'll hold a lighter under that Audi and confirm water or not.

[IanS100]

Quantities of neat petrol entering the CAT would destroy it fairly quickly and there'd probably be flames shooting out of the exhaust when it ignited.