GMON

What is the difference powerwise between the D shaped ports and the non d shaped ports. This is on a turbo engine.

Jeff20B

D shape closes more slowly and is less peaky. You might want to use the straight cut port for a more forceful pulse onto the turbo.

BigTurbo74

i know jeff20b has that style porting on one of his 12a engines. i'm a little hazy on the details but i think it has to do with making the powerband higher with more torque and/or not peak as much... anyway, here is another thread that is quite interesting but is kinda off topic to this thread. but you have to check out all of the links that are given as well.



https://www.nopistons.com/forums/index.php?...topic=35439&hl=

Jeff20B

I actually did the D shaped port on two four port 13Bs for my REPUs. I wanted a wider, less peaky power band because it's better for a truck.

suganuma

Wouldn't a sharp "D" shape help on a turbo engine as it would accelerate the flow as less gasses were there to push out effectively keeping the flow rate about the same? The sharp opening of the port would provide a "pop" or forceful push of gases towards the turbo and then gradually lessening the area of the port would accelerate the gasses still left which would help accelerate intake suction when there is some overlap.



Am I off base here?...just thinking out loud.