Exhaust haze under hard acceleration?
06-25-2007, 05:01 PM
#1
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Exhaust haze under hard acceleration?
Having been waiting at the front of the queue for a light to change, while idling for a minute or two, I accelerated up to 7,000 rpm in 1st before changing up. I glanced in my rear view mirror and noticed what I can only describe as a trail of haze from the rear of the car. It didn't look like blueish smoke from burnt oil (I'm familiar with what that looks like from some older cars I've owned!).
Could it have been unburnt fuel, or perhaps it was just dust kicked up from the road (it's been fairly dry here lately)?
Car has ~3700 miles on it.
Anyone else noticed this?
TIA
Could it have been unburnt fuel, or perhaps it was just dust kicked up from the road (it's been fairly dry here lately)?
Car has ~3700 miles on it.
Anyone else noticed this?
TIA
06-26-2007, 06:12 AM
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It's not from the A/F ratio, it has more to do with FSI itself.
In order to minimize fuel dillution and oil wash from the cylinder walls, the FSI cars inject early at higher RPM's. The specially shaped combustion bowl on the top of the piston shields the combustion walls from excess fuel wash.
This early injection tends to increase the soot.
Drive behind an RS4 when they punch it. You'll see what I mean.
This early injection tends to increase the soot.
Drive behind an RS4 when they punch it. You'll see what I mean.
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06-26-2007, 08:19 AM
#8
Re: More reading...
Verr
However, if you read through the Powerpoint slides you'll find that soot for GDI occurs in the stratifed mode, not the homogeneous mode.
PM characteristics of GDI
? Stratified operation improves fuel economy, increases PM
? PM during homogeneous operation is comparable to PFI
gasoline vehicles
? Most current development takes homogeneous approach
However, if you read through the Powerpoint slides you'll find that soot for GDI occurs in the stratifed mode, not the homogeneous mode.
PM characteristics of GDI
? Stratified operation improves fuel economy, increases PM
? PM during homogeneous operation is comparable to PFI
gasoline vehicles
? Most current development takes homogeneous approach
06-26-2007, 10:36 AM
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homogeneous = lambda 1 = stoich A/F ratio. No soot there. When you go WOT, that changes.
I'm serious, you need to see how much soot an RS4 kicks out under WOT. I think you'll be surprised.
