new design for precups

[NintendoKD]

I was thinking about the new design for the precups and thought about dual ports, the reason is is to have one inlet and one outlet for passive turbulence.  The current design is a straight single inlet/outlet.  I want to have a tool and die cut me one that has dual ports on the combustion side as well as putting a slight curve in the port to produce a vortex, therefore mixing air and fuel that much better.   The idea is similar to connecting two bottles together in science class if you flip them upside down then the air has to slowly reach a pressure breaking point so that the water can blub blub into th4e bottom bottle, this is inefficient, if you cut a small hole in the top bottle air pressure can equalize and the water flows esily into the bottom bottle.  Or there is always a vortex, give the bottles a slight swirl and VIOLA! the water esily flows and equalizes air pressure through the hole created in he center of the vortex.  A single centrally located hourglass shaped port could also be used, but there is another change I wanted to make to the swirl chamber.  I also thought that it would be a good idea to have a cone inside the swirl chamber to help create this vortex, similar to the cone inside the tdi pistons, or in the front of a jet engine for example.  I think that the dual port option is the way to go because the precup is offset inside the combustion area and would make it more difficult to create a sideways topsy turvy spiral.  Just some musings from Afghanistan, hope all is well with you my friends.  Should be home in about four months.

god bless, semper fi,

Sgt Kevin A. Davies, USMC

[Mark(The Miser)UK]

Interesting idea Kevin, but alas Andrew is spot on in this case.  Your idea will not improve economy, or even performance I suspect.
All flow is either into, presumably a brief stationary point at the entrance, and then a flow reversal.
Merely enlarging the opening won’t help, as part of the research done by H Ricardo, the originator [main developer] of this design of swirl chamber [Comet MkV], was to create a swirl that rotated at about 8 times that of the engine.
Enlarging would reduce this ratio.
The SAE paper on the early development of the VW engine did experiment with the entrance size.

 IMO, changing the shape away from an ovoid, towards a slot would add to the passage resistance.
The injector fires the fuel into the swirl, and combines the atomisation, with shear from the swirl to mix the fuel.
It is thought that over atomisation, with higher ‘bars’ can lead to reduced mixing due to the reduced  momentum of the smaller droplets penetrating the swirl less.

…I’m actually experimenting with improved fuel economies, using only 125bar at the moment…  

I think research may remain in radiussing the entrance, to reduce resistive turbulance, and perhaps the inner exit also.
More on the use of ceramic coatings too, as some practical attempts on this forum have not produced the anticipated improvements.
Maybe combining lowering bars, and extending burn time thus lowering peak temperatures, and the use of ceramics and coatings to increase average temps can produce something…

Keep the ideas flowing… It only takes one good one to advance science!

[Aki-76]

here's something odd happening in Finaldn 

http://aki76.kuvat.fi/kuvat/Caddy+Mk+I/caddyn+tekniikka/30122010955.jpg

http://aki76.kuvat.fi/kuvat/Caddy+Mk+I/caddyn+tekniikka/R12+kaari.jpg

shape is not ready yet

[R.O.R-2.0]

I don't mean to rain on your parade, but I don't think there is an issue with the existing pre-cups and your analogy doesn't really apply.  There is not a situation where one fluid is displacing another such as in your analogy, but rather there are times when there is air being pushed into the pre-chambers and other times when the expanding gases are pushing back out.  IMO, a second opening, if optimized, would perform the same as the existing pre-cups and simply mean that the gases were sometimes flowing in both at the same time and sometimes flowing out both at the same time.  If not optimized (how much time and money do you have for R+D?  how many different types/experiments are you willing to try?) then you will destroy the turbulence/swirl of the existing chamber and the result will be a big loss of efficiency.  

when the piston is at TDC, theres like a hair between the head and the piston, right? and doesnt the actual turbulance and burn happen on top of the piston in the clover leaf?

i would think it would be easier to re-shape that, than re-design the pre cups.

but are you gonna see gains from either?

i know how we fix pre-cups, GO TDI!!!

[rabbitman]

when the piston is at TDC, theres like a hair between the head and the piston, right? and doesnt the actual turbulance and burn happen on top of the piston in the clover leaf?
but are you gonna see gains from either?

It's more than a hair, I was trying to change valve adjust shims a while back and forgot to put the piston before TDC and with the valve hitting the piston I could almost get the shim out. I thought something was reall y wrong until I figured that out .

[NintendoKD]

I guess it is difficult to convey here without pictures and hand motions.  Perhaps a skype meeting would be more conclusive LOL.  yes I believe a reduction in individual inlet outlet size would improve things quite a bit leave it in a round shape "ovoid?" , not really sure which would be better.  The use of an all ceramic swirl chamber would be ideal I think, just a coating isn't going to help much, I think one of the toyota designs even had ceramic piston tops.  The fundemental principles behind how an tdi and idi works are totally different.  we have slow moving fuel and fast moving air, which is where the idi advantage comes from, more mixing can occur to a much greater degree, I really do believe that there is a better design for a swirl chamber and turbulence/vortex is the key here.  This model is represented in nature and is known as one of the more powerful forces on the planet.  This is a passive movement that creates a void in the center and created an excellent colloidal mixture of various things ex. cows fences cars people houses LOL  but seriously, I think that this is the key and modeling from existing designs such as jet turbine "vortex" or jet nozzle "mixture" is an excellent way to at least make some headway.  some problems air/ fuel has to move both in and out of the swirl chamber "remember: some of the combustion surface is in between the piston and head" we have to find a way to optimize this process if we are to succeed.  creating a vortex I really believe that creating turbulence via a vortex is the best way to go, the fuel pressure is going to provide some of the push but what about the air? is there a more efficient way to make the air coming in behave in a vortex fashion with out much loss of momentum when fuel is introduced?  there is more but I really have to go.  good stuff so far very informative, thanks guys.

[R.O.R-2.0]

im sorry kevin, dont mean this bad, but why do you always try and make a great design even better?

wouldnt the germans have used 2 holed pre cups had they worked better? or used ceramic precups had they worked better for longer?

i really dont think were gonna see gains from different precups, like we would see gains from a cast iron head.. there is a mod that would see a direct improvement in how much boost we can run, and in turn make more power.. we know that one is going to work right.

[NintendoKD]

true and I'm still working to that end   the germans at the time didn't have some of the materials and technology that we do now, that is yet another reason why idi went to the wayside.  There are all of these great advantges to idi, over di, not many see that.  Don't get me wrong here, german engineering is the best, but there is always room for improvement.  I was also thinking about the piston modification as well, but I want to concentate on one variable at a time.  I also think that using the dual breaking pressure aaz injectors is worth loking into because of the effect that it has on combustion.  Once again, need to focus on one variable at a time.  When I return stateside I will continue negotiations with the vietnamese contact I know so that we can all have 50+ psi capable heads "whatever that means"

thanks,

Kevin

[monkey magic]

There are all of these great advantges to idi, over di,

Don't take this the wrong way, but what are these advantages?

As far as reasons for going to DI, surely the central factor is they were approaching the limits of IDI technology? Agreed we have different technologies available now, but the IDI system (like any other system) still has its limits, and the gains from applying tech like this will only ever be minimal, as ROR-20 implied.

Not knocking IDI's by the way, before anyone gets too excited... 

[R.O.R-2.0]

IDI engines are almost not even produced anymore.. i was VERY surprised to find out that they still actually build IDI engines..

but its just because they burn cleaner. and its a damn tractor. we dont need lots of power..

that being said, direct injection is far superior to IDI..

look at all the IDI truck engines in the late 80s.. you dont see many of those running around still.

IDI has one downfall.. the precup. and not being able to get all the heat out of the head..

[ShoulderMan]

Well, one nice advantage of the older IDI engines with pre cups are that if your ever in an area that gets hit with a EMP, the IDI will still start and run, while the TDI wont be going anywahere.

[coke]

Alas, the tdi with the mechanical pump will.

[rallydiesel]

An advantage of the idi is that it can run on almost anything, including used motor oil.

[R.O.R-2.0]

Well, one nice advantage of the older IDI engines with pre cups are that if your ever in an area that gets hit with a EMP, the IDI will still start and run, while the TDI wont be going anywahere.

only if its a freshly run IDI diesel, cause if its cold, you aint getting it to run!

but the mechanically controlled DI engines will still be able to run, because 99% of the time, a DI engine will start with no glow plugs.

[monkey magic]

Well, one nice advantage of the older IDI engines with pre cups are that if your ever in an area that gets hit with a EMP, the IDI will still start and run, while the TDI wont be going anywahere.

Youre comparing electronic with non electronic, not idi with tdi. my tdi will run post EMP no problem.

Ref glow plugs, havent connected mine yet, been running 18 months without no problem, even down to -7C..

And ref running on anything, fair comment, but the early tdi's run on veg just fine. Im sure they can tolerate a lot.