Question about JE pistons on CIS

[mca]

Just curious, but how is it that the JE pistons work with CIS?

They don't have that smooth dome like the original Mahle pistons.

I thought that the Mahle domes were shaped this way to "swirl" the air and fuel for better combustion? Are the JEs just as good despite their very different dome shape?

[id911T]

I'm sure that some will say otherwise, but there are plenty of older cars that run CIS and don't have the swirly domes from the factory. VW, Audi, and Volvo to name a few.

[GothingNC]

Don't know, but they look nice

JE 9.7


Original

[Eagledriver]

I doubt you would notice a problem with a different piston dome shape.

-Andy

[TomCounihan]

I asked this very same question to JE directly this week. The response I got was:

"We make a round dome as we don't know
what the end customer will be doing with the piston.
We can and do make a slant dome on request .....Some engine builders request this type of dome on a
engine with single plug ignition. The idea is that the slant on the side
of the dome will push the fuel/air mix toward the spark plug. We can
make a custom piston for anyone that wants this. The custom pistons cost
a little more than our catalog parts."

[rvanderpyl]

Well I think the critical thing for CIS is the Cam profile, not so much the pistons, although the Porsche design works to promote better mixing and burning, so a regular JE dome probably won't burn as cleanly.

[timc]

I'd always read the swirled dome'd pistons were made for CIS to provide even combustion. I think using anything else with CIS, and the stock cams is a gamble.