# Turbocharger Effective Range



## Supermint1 (May 8, 2010)

TURBOCHARGER EFFECTIVE RANGE: I have a 2.8TDI engine that is lugging along about 5500kg of motorhome. I have a turbocharger boost gauge fitted which indicates 21psi of boost at max output. I also have cruise control fitted and notice that when maximum boost is achieved there is still quite a bit of pedal left but no further power increase seems apparent after the tubo has peaked. The Fuel injection system is of the pre common rail hydromechanical type. My question is, is there any effect on fuel consumption if the accelerater is floored past the point of max boost? [align=left] :idea:


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## TDG (May 26, 2009)

Supermint1 said:


> TURBOCHARGER EFFECTIVE RANGE: I have a 2.8TDI engine that is lugging along about 5500kg of motorhome. I have a turbocharger boost gauge fitted which indicates 21psi of boost at max output. I also have cruise control fitted and notice that when maximum boost is achieved there is still quite a bit of pedal left but no further power increase seems apparent after the tubo has peaked. The Fuel injection system is of the pre common rail hydromechanical type. My question is, is there any effect on fuel consumption if the accelerater is floored past the point of max boost? [align=left] :idea:


If you're using cruise control how do you know how much loud pedal it's demanding :?: 
In answer to your question, if no more power is available, increasing throttle will have no effect on fuel consumption :wink: 
Some systems produce max boost before max power in which case a variable geometry turbocharger or a blow off valve is required to prevent the cylinder head being blown off as the power increases 8O 8O


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## Supermint1 (May 8, 2010)

Thanks for that. As the cruise control is cable operated on the throttle I can feel the continuing downward movement of the pedal after max boost has been reached. Do I understand you to imply that further boost would utilise this remaining power at the top of the power curve?


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## TDG (May 26, 2009)

Supermint1 said:


> Thanks for that. As the cruise control is cable operated on the throttle I can feel the continuing downward movement of the pedal after max boost has been reached. Do I understand you to imply that further boost would utilise this remaining power at the top of the power curve?


My expertise is with very large diesel engines (>100,000 hp :wink: )so I don't pretend to be a great expert on automotive engines but the principles are the same  
You can't go increasing the boost pressure above the design value because it is likely to result in unacceptably pressure in the cylinders :evil:


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## Supermint1 (May 8, 2010)

*TURBOCHARGER EFFECTIVE RANGE*

I take your point. I guess the difficulty in judging the merits of any power upgrade is finding out what the design pressure is and what is safe. I read on a Fiat engine forum that the existing Fiat 2.8 JTD engines are tuned to 122 ps in some European countries and up to 135 in others

Many thanks for your input


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