Quote:
Originally Posted by Big Dave
Anybody here think the Tier II diesels are not more efficient if you lose the DPF?
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Overall they surely are, but not just because of back pressure. Every now and then the DPF goes into a regeneration cycle to burn the trapped soot. This uses extra fuel.
Regarding back pressure, on previous generations TDIs, people gutting out everything back of the turbo and replacing it with a straight pipe have not reported increased FE. Probably because the turbo is the biggest restriction in the exhaust system to start with.