4-strokes obsolete? 1

[Satanicusmaximus]

Why build a 4-stroke over a two stroke? Assuming both engines utilise direct injection a 2-stroke is fundamentally better is it not?

 

[Satanicusmaximus]

That 2/4 stroke engine is a good idea. I wonder how it would work with a multi plane crankshaft.

 

[YvesLLewelyn]

To follow on from BrianPetersen's comment - this valve/port timing diagram shows there is no chance (or attempt) to supercharge the typical two-stroke diesel.

http://www.marinediesels.info/Basics/the_2_stroke_engine_explanation.htm

Maybe Satanetc. should consider a two-stroke petrol/SI engine with this type of port/valve layout. The main problem with these is that the camshaft must run at crank speed and thus work the valve gear very hard.
Possibly with four large diameter exhaust valves the lift could be very low and not overstress the valve gear? Maybe half-speed camshafts with alternate pairs of valves opening?
From memory - Bruce Crower had a two-stroke petrol engine like this.

 

[DanEE]

From the linked presentation below:

Scavenging process
The replacement of the products of combustion in the cylinder from the previous power stroke with fresh-air charge to be burned in the next cycle .
can be divided into four distinct periods
Pre-blow down,
Blow down,
Scavenging &
Additional-Charging

Slide 29 shows the port/poppet timing and, scavenging manifold, cylinder and exhaust manifold pressures versus time on a typical uniflow 2 stroke supercharged design.

http://forum.vtu.ac.in/~edusat/Prog7/tda/dp/PPt_Ch-2.ppt

 

[YvesLLewelyn]

DanEE - I can't get that link to open.

 

[DanEE]

You have to have Microsoft Powerpoint on your computer to open it..

 

[JayMaechtlen]

or the free PowerPoint Viewer, or OpenOffice.

Jay Maechtlen

http://www.laserpubs.com/techcomm

 

[YvesLLewelyn]

Jay - thank you - now it works.