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Old 08-23-2009, 04:52 PM   #18 (permalink)
Dieselman
EcoModding Lurker
 
Join Date: Jan 2009
Location: Uk
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Quote:
Originally Posted by Christ View Post
The idea with a turbo is that even when the manifold is under vacuum, the exact same circumstances (normally) without a turbo would put the manifold under higher vacuum.

The reason most people don't recognize this as boost is b/c the boost gauge is still in vacuum.
Quote:
Originally Posted by Ptero View Post
Any turbocharged engine has forged pistons and lower compression,
You are both thinking of petrol engines, whereas the O/p has a diesel so no intake vacuum (due to no throttle) and probably the same CR as a N/A diesel engine.

Ptero is correct about a smaller turbo creating greater boost at low revs but will ultimately restrict airflow at higher outputs.

I have found the best results for economy on a diesel without an instantanious on board fuel computer is to use an EGT gauge..high temps = high fuel usage.

This might be further improved with a boost gauge as well, as it may be better to run a higher gear under boost and higher EGT than to run in a lower gear.
It's really interesting seeing what affects the EGT, for example blocking the EGR valve made about a 50 degrees C reduction, lagging the exhaust manifold brought this back up again which improved turbo pressure and response.
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