Roller, due to the fact the opening and closing ramps are so quick.
Chris
cylinder pressure, if all things being equal between two engines and one had a roller and the other a flat tappet which would have the greatest cylinder pressure?
Roller, due to the fact the opening and closing ramps are so quick.
Chris
I really don`t think it would matter. Overlap may play a role on some grinds but doubtful.
Sorry Hoss, It's all about ramps.
Years ago, I did some testing back to back with identical grinds as far as lift and duration. Flat tappet versus Roller. The roller was better everywhere, especially low end. Huge difference.
No pressure difference if the valves open and close at the same time. The thing about a roller is you can open the valves sooner than a flat tappet cam.
even if the opening and closing events are the same, the flank rates of the lifters are not close. . roller is much quicker.
Chris
Originally posted by cstraub69
even if the opening and closing events are the same, the flank rates of the lifters are not close. . roller is much quicker.
Chris
Thats what I ment if the cams have the same profiles no advantage to the roller. But we all know the advantage of a roller that you can open a valve quicker and keep it open longer
hmmm.. . no the roller would have the advantage. The equivlant to a roller lobe, say 250 @ .050" the flat tappet lobe would be 270 @ .050". This is because of the steep ramps and flank area of the roller, to get the same in a flat tappet you have to have more phyiscal area due to the constraints of the lifter area.
Chris
Originally posted by cstraub69
hmmm.. . no the roller would have the advantage. The equivlant to a roller lobe, say 250 @ .050" the flat tappet lobe would be 270 @ .050". This is because of the steep ramps and flank area of the roller, to get the same in a flat tappet you have to have more phyiscal area due to the constraints of the lifter area.
Chris
You didn't understand the original question if all things are equal
Read what I wrote if the cams have the same profile
read ramps that are the same
once again If both cams have the same profile
I know that a roller can have an advantage by being able to use a steeper opening and closing ramp
If both cam lobes are cut the same, they will develop the same cylinder pressure. But this is like asking if I have an apple and an orange and they are exactly the same, which will taste better?
The roller lifters do not by themselves add any cylinder pressure. They might free up some horsepower because of reduced drag but that was not your question. As iterated above, roller lifters allow different ramp rates to be ground into the cam lobe which improves the potential to build additional cylinder pressure.
cruzer