> > Rolf <r...@winmutt.com> wrote: > > > > Boost starts building at ~1800rpm, 1500rpm is where I am > > out of stall, ymmv on an automatic. More boost does mean > > you are burning more fuel automatically because of the > > ALDA on those cars equipped with them, the electronic IPs > > are a different beast altogether. Engine efficiency does > > not equal MPG as does optimal not equal minimal.
> Curt Raymond wrote: > > Have you done any actual testing to prove this theory? Its > just that your suggestions go against everything I've ever > read about diesel theory and my own results. Unfortunately I > don't have any results involving a turbo so my ideas are > totally based on NA engines but I do have a good feel > (150,000 + documented miles) for how the NA engines perform > in 190Ds and 240Ds. At a give RPM and a given fuel rack position on an engine with an ALDA adding boost will increase the fuel used. But that's not how most of us drive because we don't directly care what the power output is, we regulate the RPM against the load by changing the fuel used. With the turbo contributing generously, more heat energy from the fuel is turned into torque. So if you were to compare the fuel rack position on an engines with a matching load and RPM once with turbo and once without the non-turbo run would have the rack delivering more fuel. The ALDA would notice the lack of boost and decrease the fuel delivered. Still, the amount of fuel required by the non-turbo run would be more than the turbo despite the ALDA allowing more fuel. That's because the turbo increases efficiency, the fuel needed to maintain RPM at that load will be _less_ with the turbo because less heat is wasted. Add to the confusion the torque curve, the efficiency curve, air resistance curve, etc and it's pretty complex to try to calculate. However, efficiency _does_ "equal" MPG. The problem is trying to get the dozen other factors to match so apples are compared to apples. -- Philip, with some spreadsheets to help with the calculating _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
