My regular ride is an 05 plate Scania 420. On the dash next to the traction control & exhaust brake switches is the “white smoke reducing” switch. According to the handbook it is to be used while idleing during warm up or in stationary traffic, it also warns that when used exhaust noise is increased & engine temperature may rise. It will automatically turn off untill it cools a bit.
I tried it, yes the exhaust makes more noise plus the idle speed fluctuates as it turns on. But waht is it really doing? How does it work? Can it improve mpg in town?
triple-tango:
My regular ride is an 05 plate Scania 420. On the dash next to the traction control & exhaust brake switches is the “white smoke reducing” switch. According to the handbook it is to be used while idleing during warm up or in stationary traffic, it also warns that when used exhaust noise is increased & engine temperature may rise. It will automatically turn off untill it cools a bit.
I tried it, yes the exhaust makes more noise plus the idle speed fluctuates as it turns on. But waht is it really doing? How does it work? Can it improve mpg in town?
All it’s doing is putting the exhaust brake on, reducing the flow and warming up the engine quicker.
Oh thanks, I’ve managed to ignore that button for about 6 years and not ever considered why it might be usable. Now I’ll start fiddling with it for no other reason than because it’s there and I’d never thought of doing so before 
I reckon there’ll be a lot of Scannie drivers doing the same tomorrow 
Thanks for the info Weeto.
Now I’m gonna go in 10 mins early cos I cant wait to press it again.
Pressed the button many times, never made a scrap of difference, its supposed to be a white smoke limiter (should have had that when forced to drive Gardners) but seeing as i’ve never seen a trace of white smoke in thousands of cold starts from Scanias can’t work out why they put the thing in.
I think it takes the edge off (already sluggish) performance, noticed the switch down presumably left on by previous drivers and after switching off the truck seemed livelier, might be wishful thinking mind.
That button in ours is for the ejector seat.
only works when the park brake is on. it just puts the exhaust brake about half on so putting a bit of weight on the engine and warming up faster. handy when the night heater packs up. leave engine running all night,flick the switch on and set blower to number 1.
One of our mechanics said it wastes more fuel when turned on ■■ I take it he is ■■■■■■■■■■■■ lol
white smoke = steam■■? something wrong
why cooling the engine would reduce fuel
One of our mechanics said it wastes more fuel when turned on ■■ I take it he is [zb] lol
of course it will use more fuel.
Simply putting some extra load on the engine will increase fuel consumption.
only going to be a tiny amount though.
It’s there for when it’s really cold. The white smoke is completely uncombusted diesel expelled when the engine is turning over (but not firing) before it starts. As described, it restricts the exhaust flow and thus increases the temperatures in the combustion chambers.
You shouldn’t need to use it in the UK unless the weather is exceptionally cold.
cieranc:
That button in ours is for the ejector seat.
that button in mine changes the truck 2 a bus so i can drive in the bus lanes
Thought it was a frilly curtain adjuster!