Cylinder leakage test

[Kirk Morgan]

Will a gas ported piston and ring package leak the same as a conventional piston and ring package?

[Henrys Toy]

Originally Posted by Kirk Morgan

Will a gas ported piston and ring package leak the same as a conventional piston and ring package?

Good morning Kirk and to all,
Are you using a leak down tester to quantify this ? A cylinder pressure transducer would probably be the best choice to be sure. What dynamics that actually happens during combustion and the resulting pressures will be much different then we can simulate with a compressed air leak down tester.
The leak down testers vary for tester to tester, the various temperatures while the test is being done and other factors will lead to variation.
If you use the same leak down tester the same way, might give you a reasonable answer, but it will still vary.
If someone on here has a better solution for testing this, I hope you will chime in here.

Respectfully,
Henry Kunz 1534 H/SA

[Lenny5160_v2]

While not an answer to the question, when I use a leak-down tester I'm mainly looking for consistent results from all cylinders.

[Ralph A Powell]

You can also listen for intake and exhaust valve leakage. When I tested at TDC then I would let the piston roll over to BDC and with a long beaker bar pull the piston toward TDC and watch tester to see if it is holding pressure.

[Kirk Morgan]

Here is some detail to my findings. This is a Nitrous engine which was chirping out of the left bank after a run. Iam not a Nitrous person but a N/A engine person. Ran the valves all was good. Ran a compression test not good. The compression was a roller coaster from 200 PSI to 50 PSI. Un adjusted all the valves and removed the rocker arms. The 50 PSI was a exhaust valve leak with 80% leakage and the 200 PSI is 20% leakage. I have a cylinder leakage tester and they way i use it i turn the pressure on one side to 100PSI and read the other gauge to see how much leakage there is. To me the 20% leakage on the 200 PSI cylinder is to much i was always trying to get in the 10% or less leakage range on engines i have built. I have never built a engine with gas ported pistons. BTW i always spin the engine over 5 revolutions when checking static compression.
Thanks

[Jeff Stout]

Exhaust valves leaking I wonder why, they run away from each other. Low valve spring pressure or broken spring.Any of the low

cylinders measurements next to each other? What did plugs look
like? Asking as I have had all these problems on nitrous plus more.

[Mike Pearson]

A leak down checker is just a tool. It is mostly used to diagnose an issue in the cylinders of the engine. its a comparison tool. If you have a baseline for the engine when it is performing properly then you have something to compare it to down the road if you are having issues with performance. Typically anything better than 10 percent is considered good. Leakage by the intake valve is the worst and even a small leakage past the intake valve will effect the performance of the engine. The exhaust is typically not as sensitive.

[340Cuda]

Originally Posted by Kirk Morgan

Will a gas ported piston and ring package leak the same as a conventional piston and ring package?

That has been my experience over they years even though the engines could be very different.

I could have very good or not so good readings on any piston configurations.

[Cglrcng]

Originally Posted by Kirk Morgan

Will a gas ported piston and ring package leak the same as a conventional piston and ring package?

Am no expert here (call Ed Ercis at Ross, or anyone at Total Seal and they will explain it in simple terms)...But logic says the gas ported piston ring package is a historically recent modification beyond the normal piston/ring usage (though now widely used), and using a tiny bit of cylinder pressure on the way up, and the same in exhaust gasses on the way down (to expand the top or top 2 rings outward against the cylinder walls for better compression ring to cylinder wall sealing, has to without a
doubt in my mind also allow a certain amount of those gasses/pressure to bypass the compression rings and escape to the pan due to the gaps below, unless maybe in the use of a gap less ringset (don't know, and my logical mind says that is also a further modification that may change the equation).

Now add in that a leak test is usually done static (without piston and ringset movement in the up/down directions so it (the air pressure, that you are introducing during the leakdown testing process would still be pushing the compression ringsets against the cylinder walls, but some leakage is bound to be present, just not in the
same exact manner as actual running of the engine uses it.

Who was it long ago that was actually knurling the piston skirts? It was beyond a novel concept and gave birth I think I read many years later to the gas ported piston/ringset idea.

My bet is the Guys in Lake Havasu City at EFI University having a Spintron machine, probably have tested the exact question you posed in a non-static (and an actual engine spinning but not actuallt running condition). The Spintron is an expensive yet amazing test machine. They have done testing there as a learning institution that nobody has ever attempted (like running an engine on the dyno full throttle open plenum intake without a throttle body or carb, just to see what happens)...it ran...wide open w/zero restrictions. A super crazy test for sure. No throttle blades to close off airflow. Ever seen a runaway diesel on a dyno explosion? Think ok it runs perfectly...Now how do we shut it off without intentionally going full lean by simply shutting off the fuel flow? Will the clipboard in his hand be big enough to choke off that airflow, and who would be crazy enough to enter a dyno room and approach that engine at full throttle....all on camera and uploaded to YouTube for our viewing pleasure.

Pose the question to them, my bet is they know the answer.