View Single Post
      09-25-2013, 04:09 PM   #8
Major General
NISFAN's Avatar
United Kingdom

Drives: BMW M2
Join Date: Aug 2012
Location: Bedford UK

iTrader: (0)

Originally Posted by Needsdecaf View Post
It would appear not to however, no ? That is certainly true when it comes to N/A emgines, but we are talking FI here.

It is significant because it should be much freerer revving than the lazy n55.
Originally Posted by Boss330 View Post
In a NA engine more so than in a Turbo'd engine. You can compensate for less torque from the engine by adding boost so that it makes up the torque deficit when on boost.

But a comparable engine, but with longer stroke, would make more torque under same boost conditions. Or the same torque with less boost.

But I'd rather have a bit higher boost to compenaste the torque lost due to shorter stroke and the higher rpm/lower piston speeds possible on a short stroke engine.

It should feel much more alert than a "lazy" N55 335i.
None the less, stroke length has the same effect in FI as NA. Obviously the torque is still good despite the reduced stroke, but as you say this is likely to come from higher boost.

A side effect of the short stroke, is the cylinder pressure will still be very high at end of stroke, which means more pressure to power the turbo.
Appreciate 0