Citroen Picasso... with overboost...
Is this switchable in somw way, or just marketing speak for a medium pressure turbo?
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Is this something you've seen in an official Citroen ad?
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Yup, a current terrestrial TV ad.
I believe that overboost means that there is a short term gain in power and torque. Presumably the oil and cooling system is not up to a constant increase.
I wasna fu but just had plenty.
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Not seen the Citroen ad, but I can tell you what overboost is.
Boost is what you get from turbocharging an engine, theoretically by cramming the air fuel mixture in at above atmospheric pressure. Boost is measured in atmospheres, 1 atm equating to 14 pounds of air pressure per square inch (i.e., normal atmospheric pressure). So maximum boost of 1.5 atm means the mixture is being forced ito the cylinder at 21 psi.
The turbocharger is engineered to add additional pressure up to a pre-determined limit, beyond which a valve (known as a wastegate) opens and relieves the pressure. Overboost allows that limit to be exceeded for short periods under certain circumstances either to improve torque under certain conditions or outright power.
In this case, it sounds like they're trying to boost sales more than anything else...
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Think of it like an electrical appliance. We've all seen the power data as in max power rating = x, max continuous power rating = y (where y < x)
As MO says this is the same, the turbo boost is set to a level of whatever the engine will stand for long periods. By some means that boost pressure can be raised for a time.
Citroen claim "An overboost function integrated with the engine management system provides additional bursts of torque over a short period, for overtaking or in emergency situations."
Not just limited to Citroen eg TDCi Fords (including mine) it allows "overboost" for about 30 seconds.
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Thanks for your replies people, sounds like Citroen have chosen to make a point of a feature I was unaware of. Presumably this is purely a software change that could be added to most engine management systems, at the cost of a some extra engine wear.
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This is what Citroen say about it. I assume this is a turbo diesel engine?
"The fantastic new 1.6HDi 16V 110hp engine combines the power and driveability of the latest common-rail diesel technology with enhanced acoustics and vibration control, while ensuring a significant reduction in fuel consumption and emissions. An overboost function integrated with the engine management system provides additional bursts of torque over a short period, for overtaking or in emergency situations."
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