[jabl]

> Exhaust back pressure is not an issue at all on diesels because they all run big turbos.

Not sure what you're arguing here. Isn't it quite obvious that resistance in the exhaust system means that the engine has to do more work to push the exhaust gases out; work that otherwise could be used to turn the crankshaft. Now of course a lot of that extra energy is wasted in any case, particularly if there's nothing like a turbocharger to make use of it.

[TylerE]

Practically all diesels have turbos. You have literally have to go back to tiny tractor engines form The 60s to Find ones that aren’t. Turbos already provide a ton of back pressure. What’s downstream of that is pretty irrelevant

[jcgrillo]

My tractor from the early 00s doesn't have a turbo. Plenty of VW and Mercedes Benz cars built in the 80s and 90s don't have turbos.

Backpressure aft of the turbo is something you really want to avoid because it makes the turbine much less effective. The whole point is to use a pressure and thermal gradient to do work.

[12thhandyman]

Ford and VW put a naturally aspirated diesel into their vehicles up until the early/mid 90s.

[TylerE]

Absolutely none of which have DPFs or EGRs.

[lupusreal]

Backpressure to the turbo reduces the efficiency of the turbo, no?