Discussion and questions related to the course Engine Building Fundamentals
Hello! So I just want to make sure I have a correct understanding. From your discussion about the 4G63 engine, my understanding is that it is more beneficial to keep the stock (shorter) stroke and increase the rod to stroke ratio (by using a block with a higher deck surface and a longer rod) than it is to increase the stroke (and decrease the rod to stroke ratio in doing so) for a higher peak torque at a high RPM range.
Also, why does reducing piston speed to and from TDC (do to a higher rod to stroke ratio) increase cylinder pressures?
Also, now I know compression ratio would not be affected if you use a block with a taller deck and the stroke stays stock, but the volume of the area where combustion happens will be different with the piston at TDC. Will this affect anything? Sorry, I hope my questions don't sound too wonky.
There are several different, but related, things there. Not familiar with that engine, but some general comments about the subjects.
Normally, the larger the engine capacity, the better for power as the bang is bigger - which is why people use stroker crankshafts and bigger bores, where practical, I guess there are some instances it is less effective, but can't think of one, off hand.
Anyway, was working on a long essay and found this while looking for referral material - it does a much better job than I can, here.
I expect you will still have questions, but should have something to refer to now, so we're on the same page. Oh, with a longer rod:stroke ratio, the piston spends more time close to TDC and there is a higher average pressure during the piston stroke. It may not seem much, but it all helps. Also less force on the bore surface from the piston.