Cylinders: To hole or not to hole, that is the question.

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Guges Mk3
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Cylinders: To hole or not to hole, that is the question.

Post by Guges Mk3 » Tue Mar 08, 2011 12:51 pm

This came from a thread where some asked what type of Cylinder one should throw into a mechbox. I said just toss in a Type 0 and be done with it.

Another poster said this:
Simply throwing in a Type 0 cylinder regardless of the barrel length does not maximize efficiency of the system. The porting allows the piston to accelerate faster before it begins to compress the air (it can accelerate faster because there is no resistance from the compressing air, or the friction of the o-ring on the cylinder) This means when the piston hits the cylinder head (and when the bb should be leaving the barrel) it will be traveling at its fastest which will mean the bb will be traveling at its fastest for that particular system.

An under ported system means the force acting on the bb will stop before the bb leaves the barrel which leads to a decrease in velocity and could affect flight performance in other ways. An over ported (or lack of port) system means the bb will leave the barrel before the piston head hits the cylinder head traveling at its fastest, which means you are not optimizing the performance of your gun.

While over porting is better than under porting, it is not a good idea to just "throw the list out the window". If you want maximum performance, then that list is a very good start on how to do it.
Note this is the list:

Type 0 (No hole): 450-580mm
Type 1: Systema makes this one, it has a hole in the edge and is said to be for M4/M16/XM177/AK47. It is essentially a go between for the type 0 and type 2
Type 2 (4/5 hole): 364-460mm
Type 3 (3/4 hole): 227-430mm
Type 4 (1/2 hole): 110-170mm


This comment came about me saying OB parts are pretty much worthless for the price you pay. You get about a 2-3% increase for double the price in parts.
I agree that bore ups are pretty much worthless, but when you are talking about exceeding 580mm of barrel length, you need all the extra cylinder volume you can get. I also agree that there isn't really a need to go past 509mm barrels, but for the people out there, that still want the performance form the system, bore ups might be their answer.
However, what the internet is spreading around is only true for a "slow" blow system.

AEG’s work on the “fast” blow system and this is why:

Example: How fast does it take for a 15rps AEG to release the piston and have the head slam against the cylinder head?

~.0334 seconds.

There is no “major” time issue here for acceleration and ports.

AEGs are "Fast" blow systems.

And at 300fps how far has a bb traveled in that time?

10 feet

These effects reflect the totality of the system and again that is a fast blow system.

Most of us know that TM is the creator of the Modern AEG. In Japan they have a regulation they must follow. This is the ASGK Standard. Back in the 1990’s ASGK said you cannot have an AEG shoot a .20g bb faster than 300fps.

And the Japanese are the Japanese, very good engineers. All mechbox parts in an AEG is made to a standard and are ALL the same except the Nozzle and the Cylinder. The key is efficiency of mass production. If you keep all parts the same, you only need to modify one part to change the outcome.
Thus that is why there are holed cylinders.

If you put a non-holed Cylinder in a MP5K, velocity will go up. That will make them in violation of the ASGK standard. To counter the velocity increase, due to the shorter barrel. They used holed cylinders. This is the main reason why there are holed Cylinders.

So if you want a smarter upgrade that will not stress your mechbox. If it has a holed cylinder…upgrade to a non-holed one.
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Re: Cylinders: To hole or not to hole, that is the question.

Post by Irish » Tue Mar 08, 2011 2:26 pm

Great read. Thanks Guges
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Re: Cylinders: To hole or not to hole, that is the question.

Post by mau5 » Tue Mar 08, 2011 5:59 pm

Am I wrong in thinking that a non-holed cylinder would decrease the chance of a cracked front of a v2 gbx? I mean, wouldn't that extra seal create a kind of air cushion with the last bit of distance the piston travels instead of allowing air through and ramming straight on? I only ask because I've heard v2s have a problem with the front cracking. Also, you're basically saying that if your cylinder is ported you can downgrade your spring and get a type 0 and achieve the same FPS with a more efficient system, right?

Anyways, thanks for the post. It's really nice to have someone around here who really knows what they're talking about.

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Re: Cylinders: To hole or not to hole, that is the question.

Post by Guges Mk3 » Tue Mar 08, 2011 7:16 pm

Am I wrong in thinking that a non-holed cylinder would decrease the chance of a cracked front of a v2 gbx?
Yes, your wrong in this application. There is no air cushion that forms in .0334 second to mitigate the impact force of the piston on the cylinder head.
I mean, wouldn't that extra seal create a kind of air cushion with the last bit of distance the piston travels instead of allowing air through and ramming straight on?
It would, but your thinking like other people where you think this is a "slow" blow system. The piston hits the cylinder head in a hundredth of a second, a hundredth. There is also no opportunity for an air cushion to form either due to the hole in the cylinder head that ducts the pressure out from the cylinder to "blow" the bb down the barrel.
I only ask because I've heard v2s have a problem with the front cracking. Also, you're basically saying that if your cylinder is ported you can downgrade your spring and get a type 0 and achieve the same FPS with a more efficient system, right?
Yes.
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Re: Cylinders: To hole or not to hole, that is the question.

Post by Irish » Thu Mar 10, 2011 8:11 pm

If you put a non-holed Cylinder in a MP5K, velocity will go up. That will make them in violation of the ASGK standard. To counter the velocity increase, due to the shorter barrel. They used holed cylinders. This is the main reason why there are holed Cylinders.
Have you done this?
What's the fps difference?
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Re: Cylinders: To hole or not to hole, that is the question.

Post by Guges Mk3 » Thu Mar 10, 2011 10:28 pm

For a short barrel like a MP%K..you will only get a small amount. About 8-10fps.
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Re: Cylinders: To hole or not to hole, that is the question.

Post by IsparkTheLa » Wed Mar 16, 2011 10:50 am

Guges Mk3 wrote: So if you want a smarter upgrade that will not stress your mechbox. If it has a holed cylinder…upgrade to a non-holed one.
I tested this theory in my PDW and with my set up was given the following results:

Barrel length: 228 mm
Cylinder: ¾ ported
Spring: PDI 170%
Velocity with .2g bb: 380 fps

I then switched the ported cylinder to a non ported one while everything else remained the same:
Velocity with .2g bb: 340 fps
~11% loss in velocity

I wish I had more data to back up my theory, but I don’t. That is why it is simply theory…

An AEG is a system of pneumatics, not hydraulics. The BB does not begin to move as soon as the piston moves forward. At what point does the BB enter motion? I have no idea, but we know that air is very compressible. The piston enters motion and air begins to fill the cylinder. As pressure rises in the cylinder the kinetic energy from the spring/piston is then transferred to the BB and it begins its motion.
Guges Mk3 wrote:If you put a non-holed Cylinder in a MP5K, velocity will go up. That will make them in violation of the ASGK standard. To counter the velocity increase, due to the shorter barrel. They used holed cylinders. This is the main reason why there are holed Cylinders.
This is where my theory gets heavy…
After seeing my results, I think it is exactly the opposite which leads back to the original topic: matching cylinder to barrel volume. In a short barrel with a ported cylinder situation, like you said, it’s a “fast blow” system. The piston moves forward rather quickly because air is bleeding from the cylinder port resulting in minimal resistance on the piston. Once the piston head has passed the port, compression occurs quickly because of the piston speed. The BB is in motion and due to the decreased cylinder volume from the port; the piston has slammed into the cylinder head and is now at rest BEFORE the BB has left the barrel. Meaning, the piston/spring has transferred all of it’s kinetic energy to the BB.

In a short barrel NON ported cylinder, my guess is exactly the opposite occurs. The piston begins motion and compression begins sooner because of the absence of porting. Due to the shortness of the barrel, the BB has left the barrel before the piston is at rest. So the BB was not able to absorb all of the energy from the full piston stroke.
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Guges Mk3
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Re: Cylinders: To hole or not to hole, that is the question.

Post by Guges Mk3 » Wed Mar 16, 2011 12:55 pm

Hah, I am going to use you as a test subject!

With additional testing lately, I am finding that moving to a full cylinder has less of a negative effect on barrels that are under 8". Yours being 228mm is roughly 9" My threshold tests are with barrels around 300mm ~12"and 363mm ~14".

Also bb weight is a factor. Can you rerun the test with .25 and .28 bbs?
I rather use a "nightmare" that shoots like a dream over something that looks like a "dream" but shoots like a nightmare.

Don't fear the gun...fear the one that's wielding it!

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