Are thin piston rings worth horsepower?

[DSRE388]

I have a set of Probe FPS forged pistons in a 388 street/strip engine i built 8 years ago and it has the 5/64-5/64-3/16 ring package, you had to spend another couple hundred dollars for forged pistons with skinnier ring grooves at the time atleast for shelf pistons.
This engine made 504hp at 57-5900rpm and 500tq at 47-4800rpm
Is this too low of an rpm engine to reap any significant gains from say a 1.2-1.5 ring package?

[tenxal]

I have a set of Probe FPS forged pistons in a 388 street/strip engine i built 8 years ago and it has the 5/64-5/64-3/16 ring package, you had to spend another couple hundred dollars for forged pistons with skinnier ring grooves at the time atleast for shelf pistons.This engine made 504hp at 57-5900rpm and 500tq at 47-4800rpm
Is this too low of an rpm engine to reap any significant gains from say a 1.2-1.5 ring package?

I think so. If you want to work with the existing ring grooves, a barrel faced 5/64" moly top ring with a .135 -ishback cut, a Napier style second and working with oil ring tension will yield some nice benefits.

[BradH]

Most of the stocking BB Mopar "performance" pistons still use 1/16", 1/16", 3/16" ring packs. If I had to go custom for whatever reason, would there be quantifiable improvements from changing to a 1.5mm/1.5mm/3.0mm setup?

Let me ask another question on top of this: 4.375" bore / 3.75" stroke / 7200 RPM / some actual street use (not daily driver)... At what top ring(s) thickness is a sanity check required? If HP matters, say 700+/- at close to 7000 RPM peak. No vacuum pump or anything out of the ordinary.
- .0625 (1/16)
- .0585 (1.5 mm)
- .043
- .039 (1 mm)
- < .039?

Somebody's going to think: "Seriously, you gotta ask that?!" Ummmm... yeah.

[BILL-C]

.043, .043, 3.0mm would be my normal choice for the typical street driver. Track only car I would get a little braver and do 1.0,1.0,2.0 with a real good pan and vac pump.

[NORSK]

.043, .043, 3.0mm would be my normal choice for the typical street driver. Track only car I would get a little braver and do 1.0,1.0,2.0 with a real good pan and vac pump.

Here is one thing i don't understand
If the oil ring is a 3 piece,there would basically be no difference in resistance since it is the same 2 rings touching the wall no matter if it's a 2 or 3mm tall ring package

[BILL-C]

.043, .043, 3.0mm would be my normal choice for the typical street driver. Track only car I would get a little braver and do 1.0,1.0,2.0 with a real good pan and vac pump.

Here is one thing i don't understand
If the oil ring is a 3 piece,there would basically be no difference in resistance since it is the same 2 rings touching the wall no matter if it's a 2 or 3mm tall ring package

With the 2mm package, both the rails and the expander are downsized. The axial and radial dimensions of the rail and expander are much smaller and delicate. Installation can be a challenge for someone with fat fingers or if the top of bores have anything more than a minimal chamfer.

[NORSK]

.043, .043, 3.0mm would be my normal choice for the typical street driver. Track only car I would get a little braver and do 1.0,1.0,2.0 with a real good pan and vac pump.

Here is one thing i don't understand
If the oil ring is a 3 piece,there would basically be no difference in resistance since it is the same 2 rings touching the wall no matter if it's a 2 or 3mm tall ring package

With the 2mm package, both the rails and the expander are downsized. The axial and radial dimensions of the rail and expander are much smaller and delicate. Installation can be a challenge for someone with fat fingers or if the top of bores have anything more than a minimal chamfer.

If the rails are different i can see the point
A few weeks back i had 3 different piston sets in my hand
They had 3mm-2.8mm and 2mm oil ring packages.
The rails on all 3 was 100% identical in both height and depth
The expander was ofcourse different to suit the grooves,but the design of the expander was identical
I had no way to measure the difference in tension the expanders made,but i doubt it can be much

A taller oil ring package also works better for oil control

[MadBill]

Sometimes that 1 mm can be the difference between needing an oil ring support rail (which not everyone loves) and not.

[NORSK]

Sometimes that 1 mm can be the difference between needing an oil ring support rail (which not everyone loves) and not.

Sure.
However a support rail does not add any ring drag either

[digger]

Sometimes that 1 mm can be the difference between needing an oil ring support rail (which not everyone loves) and not.

Sure.
However a support rail does not add any ring drag either

i guess that means not everyting is about reducing drag

[jed]

[quote=NORSK post_id=788616 time=1551426373 user_i



A taller oil ring package also works better for oil control

How have you qualified this statement???
John

[NORSK]

[quote=NORSK post_id=788616 time=1551426373 user_i



A taller oil ring package also works better for oil control

How have you qualified this statement???
John

How do i get qualified to make such a statement in your opinion?

What i mean by better oil control,is more for the street higher mileage engines
In my 28 years experience as a engine mechanic/builder i have seen countless oil ring issues with thinner oil rings AKA 2mm and smaller
Just look at the hilarious vw/Audi 1.8-2.0 engines that run 1.5mm oil rings,hundreds of thousands of cars were called back
Same thing with the smaller 1.4 liter VAG engines,same stupid thin oil ring same problem
Older VAG engines with 3mm rings went on forever with no issues

[Momus]

A taller oil ring package also works better for oil control

How is this conclusion arrived at? Data from ring manufacturers or testing?

Low height oil rings offer obvious packaging advantages and less chance of flutter.

I have smaller bore stuff here with 3 piece oil rings that are 1.5 mm high.

[NORSK]

A taller oil ring package also works better for oil control

How is this conclusion arrived at? Data from ring manufacturers or testing?

Low height oil rings offer obvious packaging advantages and less chance of flutter.

I have smaller bore stuff here with 3 piece oil rings that are 1.5 mm high.

Did you read my previous comments?

[Mark O'Neal]

A taller oil ring package also works better for oil control

How is this conclusion arrived at? Data from ring manufacturers or testing?

Low height oil rings offer obvious packaging advantages and less chance of flutter.

I have smaller bore stuff here with 3 piece oil rings that are 1.5 mm high.

The correct answer for almost all questions about engine design is "it depends"...and this is no exception.

Efficient oil control requires exactly two things. They are tension and area. Remove one, and you have to add the other. So you can reduce tension by adding split radius oil returns, more drainback holes in the back of the oil groove, use lugs instead of drilled holes. However you choose to do it, you're just manipulating those two things.