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  #46  
Old 11-30-2008, 09:54 PM
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interesting...

I imagine this would coincide with a complete removal of the end of the tube with the holes in it?

If this were the case then the PC just became a swirl chamber.

Would this put the piston/rings/etc at risk from shocks, or something?

...I wonder if you couldn't achieve a similar thing more simply with a series of pins offset from eachother stuck through the tube...
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  #47  
Old 11-30-2008, 11:12 PM
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Quote:
Originally Posted by GREASY_BEAST View Post
interesting...

I imagine this would coincide with a complete removal of the end of the tube with the holes in it?

If this were the case then the PC just became a swirl chamber.

Would this put the piston/rings/etc at risk from shocks, or something?

...I wonder if you couldn't achieve a similar thing more simply with a series of pins offset from eachother stuck through the tube...
My thought was to leave the bottom and cut a horizontal slot (burn hole to burn hole) that will allow for a higher flow rate, allow the exiting gasses to fan out into the main chamber parallel to the piston and the head, and keep the heat from concentrating on one location of the piston, ( if the tube bottom was removed).
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  #48  
Old 12-01-2008, 02:13 AM
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The ID of the turbo PC is 8mm.
The upper and lower part is screwed together and secured (welded or 2x5mm pin) before the outside was grinded. This should be the location for opening.
There is a risk for loosing the lower part when you cut it and re-weld. At least when you pull it after a certain time.
I will provide the 616 angled PC part number tonight.

Tom
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  #49  
Old 12-01-2008, 02:16 AM
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The purpose of the holes is to direct jets of partially burned fuel through out the cylinder. The jets allow more fresh air to surround the unburnt fuel and promote mixing and thus better combustion. It also allows the heat to be more evenly distributed. This means less heat lost to the walls. A sheet of of fuel mixture won't mix as well and will lead to less fuel burning and less power due to less mixing and lower in cylinder turbulence.
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  #50  
Old 12-01-2008, 03:11 PM
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part number of 616 angled PC:

616 010 0752

Tom
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  #51  
Old 12-02-2008, 02:59 PM
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Originally Posted by ConnClark View Post
The purpose of the holes is to direct jets of partially burned fuel through out the cylinder. The jets allow more fresh air to surround the unburnt fuel and promote mixing and thus better combustion. It also allows the heat to be more evenly distributed. This means less heat lost to the walls. A sheet of of fuel mixture won't mix as well and will lead to less fuel burning and less power due to less mixing and lower in cylinder turbulence.

I would imagine that the gasses reach near supersonic speeds going through those little holes, which create some +s and -s.


Forgive me here, I am going to attempt to reference my theory bases. I might get lost.

My thinking is that what is called the PC, should be called the "combustion chamber", and what is commonly called the combustion chamber should be called the "main chamber, pressure chamber or just cylinder". Both PC and swirl chamber (SC) engines, IMO, are like steam engines, in that combustion creates pressure in a vessel separate from the cylinder, (boiler / PC / SC). The pressure travels through passageways to the cylinder, (steam pipes/ burn tube/ SC port) the pressure then raises in the cylinder and pushes against the piston. In this steam engine scenario, no combustion is taking place in the cylinder.

I think EGTs get high when unburnt fuel is sent into the cylinder. My thinking is the cylinder pressure is most likely higher than the PC pressure during the compression stroke and is lower than the PC pressure after ignition due to the restrictive holes, and the lower pressure cylinder air would be at a lower temp than the post ignition PC air/ fuel temp. This may sound absurd, but since fuel evaporates, would it feel a wind chill (assuming the cylinder air temp is below ignition temp) when a single stream (created by the small holes) of air and partially atomized fuel was shot into the cooler cylinder air at really high speeds? The cooled fuel would tend to condense until the cylinder pressure is raised enough to raise the air temp enough to ignite the unburt fuel and then "BANG" the nailing sound is created?

If that is plausible, a slit ( or other orifice shape), that flowed more air in less time, could not only create a potential for increasing the air content of the PC during the compression stroke, but the PC / cylinder pressure differential could potentially be reduced. The higher cylinder air temp, caused by the faster equalization of the cylinder / PC pressures, would not cool the PC gasses as much, and a sheet of hot gasses might tend to retain heat better and keep the fuel gaseous. My understanding is that a single controlled flame front is better than multiple flame fronts colliding.
Now if the fuel was still not burned in the cylinder, then it would burn in the exhaust. NOT GOOD.


IMO, all the combustion needs / should take place in the PC / SC, and the increase in combustion efficiently resulting from MB improving the PC swirl quality (latest PC design) supports that theory.

I think it is safe to say that the PC is less efficient, power wise, than a SC. Now, that being said, there is a point were the power / over all fuel efficiency becomes less than ideal, as in a prostock car. If there is lots of unburnt fuel that is pushed into the cylinder then there is not enough air in the PC and boost will need to be increased to increase the air content in the PC for more complete combustion.


I will order the new off set ball PC and a 617.95 PC and build a flow bench for them. This will allow for a means of measuring any increases in flow and calculating velocity. The flow would be measured in both directions. I would also like to take the PC injector end off and force air in the cylinder end to try to see any kind of swirl. If it can be done, any changes like adding a helical insert, a series of pins or what ever could be evaluated.

The basic reality is I want the performance of a swirl chamber and I will accept the downsides of that.

Again, any thoughts or comments…
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  #52  
Old 12-02-2008, 04:19 PM
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You probably realize that starting will become more difficult for two reasons. Static compression ratio will decrease due to loss of material, and second heating of the air will decrease due to less friction. Hopefully, startability will not decrease too drastically. The other concern is that the gasses accelerate well tangential to the piston to prevent isolated heating (hole in piston). Most SC have the outlet angled such that the gasses exiting the SC spread out across the face of the piston, and the piston may have a recess machined into it to facilitate mixture.

I think that you are mistaken in the assumption that all of the combustion occurs in the PC. The holes in the PC would be useless if they weren't incorporated to continue mixing as the fuel air mixture enters the combustion chamber.

One more area in which the PC design can affect engine performance is in burn rate. Obviously the PC enables the fuel to be burned quicker, else how could the engine obtain rpms near 5K vs 3K common in DI engines. This is further shown in the difference in start of injection timing. IDI engines commonly inject at 20+ degrees BTDC whereas the Cummins 6bt as an example is somewhere around 15*. Again the PC allows the fuel to be injected earlier and the pressure rise is delayed apparently via the PC. Just some thoughts to add to the mix
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  #53  
Old 12-02-2008, 06:27 PM
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You know cutting a PC might be pretty difficult but what about turning the ball at a slight angle. That would be much more easily achieved.
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  #54  
Old 12-02-2008, 09:48 PM
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I've wanted to toy with the PC's too, Great thread, keep it goin!
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  #55  
Old 12-02-2008, 10:07 PM
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Originally Posted by winmutt View Post
You know cutting a PC might be pretty difficult but what about turning the ball at a slight angle. That would be much more easily achieved.
I have been trying to figure out a way of doing this for a while. I thought about trying to modify an existing impingement pin but doing so with out weakening it is a problem. I have also thought about trying to come up with a new pin but this is an expensive proposition without access to a machine shop. Also finding the right angle might take quite a few tries and some careful measuring on a dyno.
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  #56  
Old 12-02-2008, 10:13 PM
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Originally Posted by ConnClark View Post
I have been trying to figure out a way of doing this for a while. I thought about trying to modify an existing impingement pin but doing so with out weakening it is a problem. I have also thought about trying to come up with a new pin but this is an expensive proposition without access to a machine shop. Also finding the right angle might take quite a few tries and some careful measuring on a dyno.

Sorry, did I not mention I have a full machine shop? All manual, but I have access to CNC for a slightly discounted rate.
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  #57  
Old 12-03-2008, 01:39 AM
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Originally Posted by winmutt View Post
You know cutting a PC might be pretty difficult but what about turning the ball at a slight angle. That would be much more easily achieved.
this can be done, but without angling the injector you don't get the defined swirl.
"Cutting" is not so difficult. Open them where they are screwed together. You can see the threat, it is in the upper part of the GP opening.
Then exchange the the complete upper part. The result will be: Lower part form 617a with upper part of 616 angled version. Then turn the ball.

Tom
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  #58  
Old 12-03-2008, 11:58 AM
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I think the safest bet would be to enlarge each PC hole by the same percentage. That way, you hopefully won't negate any distribution effects the engineers designed into it. By incrementally enlarging them, and meaningfully measuring the change in engine characteristics, you can home in on an optimal value.
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  #59  
Old 12-03-2008, 12:43 PM
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Quote:
Originally Posted by Bajaman View Post
Obviously the PC enables the fuel to be burned quicker, else how could the engine obtain rpms near 5K vs 3K common in DI engines. This is further shown in the difference in start of injection timing. IDI engines commonly inject at 20+ degrees BTDC whereas the Cummins 6bt as an example is somewhere around 15*. Again the PC allows the fuel to be injected earlier and the pressure rise is delayed apparently via the PC. Just some thoughts to add to the mix
Some people rev the Cummins to ~7000RPM.
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  #60  
Old 12-03-2008, 01:46 PM
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Originally Posted by tomnik View Post
this can be done, but without angling the injector you don't get the defined swirl.
"Cutting" is not so difficult. Open them where they are screwed together. You can see the threat, it is in the upper part of the GP opening.
Then exchange the the complete upper part. The result will be: Lower part form 617a with upper part of 616 angled version. Then turn the ball.

Tom
I think the injector was angled to put the ball back in the spray pattern after the ball was offset from the tube centerline. The ball was off set, per patent doc, to increase the swirl in the chamber.

I have attempted to attach the actual patent drawings. (sometimes you have to order the patent to see the drawings)

They are not in order, but the patent numbers are on each page. If you have the patent claims text you can use the drawings to get an idea of what they did. All the changes were for improved emissions, but there was also a power benefit side effect.

I think if the angled injector holder is put on a centered ball then the ball will not act as an atomizer. The result could be like an injector with a bad spray pattern.
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