Bearing surfaces in current production turbo engines

Breaking news, useful data or technical highlights or vehicles that are not meant to race. You can post commercial vehicle news or developments here.
Please post topics on racing variants in "other racing categories".
roon
roon
412
Joined: Sat Dec 17, 2016 6:04 pm

Bearing surfaces in current production turbo engines

Post

Given that current-era production petrol turbo engines are smaller while developing peak torque at lower engine speeds, have any interesting or significant advancements been required for journal, oiling and bearing designs? Are they just built more like diesels these days?

63l8qrrfy6
63l8qrrfy6
368
Joined: Wed Feb 17, 2016 8:36 pm

Re: Bearing surfaces in current production turbo engines

Post

The short answer is that no major changes have been required to accommodate higher torque at lower engine speeds. Keep in mind that the "lower" peak torque speed of the petrol engine in this case is still closer to the peak power speed of a comparable diesel engine.

I think that the ban on lead in automotive engines has had a much larger impact on bearing materials and bearing design in general.

Lead/copper/tin/indium alloys were excellent bearing materials (for example all F1 manufacturers still used them) as they offer great embeddability (debris retention), conformability and emergency running capability (low oil film thickness) with fairly good fatigue strength.
These have now been replaced by sputter AlSn alloys which tend to be very hard and have very good fatigue strength, however they are very poor at dealing with debris and have poor running-in characteristics. They usually require a very well controlled crowning to avoid seizures due to edge loading. All bearing manufacturers now offer polymer overlays tailored for particular applications (start-stop, high speed running) which have their own disadvantages, most notably being poor thermal conductivity (typically dealt with by adding Al flakes).