Author Topic: Pre combustors (new manufacturing) (Read 9425 times)

jimfoo · « **Reply #15 on:** August 20, 2008, 08:39:42 am »

When I was going to try to sell an old head(no one bought it so it went for scrap) I had a loose PC on it. Using a press and a socket, I was able to expand it enough for a very tight fit. I did keep 3 of the PC's but they are 1.9 so wouldn't work in a 1.6.

Jet A · « **Reply #16 on:** August 20, 2008, 10:02:13 am »

Mine has substantally cracking.

To much to risk the engine. Going to have the alloy analysed then try to get them turned. Getting test pieces made from 4041 today.

Still looking for a supplier.

zukgod1 · « **Reply #17 on:** August 20, 2008, 10:30:10 am »

I was unable to find that link last night, The link posted earlier (in German) looks like the one I had as well.
There has to be someone on this board that speaks German so you could communicate with them.

Jet A · « **Reply #18 on:** August 20, 2008, 12:45:50 pm »

Actually ended up doing 2 in 4140 and 4 in 304ss. they are gunna be my test pieces. Once i get the hole correctly in place, i am going to have them cast in stellite...which is a chromium cobalt alloy. Havent got a firm price on casting, but sounds like approx $20 per piece

gigaz2 · « **Reply #19 on:** August 20, 2008, 02:35:32 pm »

this is a interesting topic, if you can make new inserts, why not make one that goes all the way, like including the roof.
having 3 holes, the stock transfer port, one for the plug, and another for the injector.

that would provide another thermal barrier, increasing the efficiency of the engine, am I right?

Jet A · « **Reply #20 on:** August 20, 2008, 03:01:50 pm »

Quote from: "gigaz2"

this is a interesting topic, if you can make new inserts, why not make one that goes all the way, like including the roof.
having 3 holes, the stock transfer port, one for the plug, and another for the injector.

that would provide another thermal barrier, increasing the efficiency of the engine, am I right?

You lost me....

3 holes where? one in the top, one in the side and one in the bottom? I cant picture what your thinking.

gigaz2 · « **Reply #21 on:** August 20, 2008, 04:30:11 pm »

exactly, including the top part of the prechamber into the insert, probably the head would have to be machined to make some clearance.

EDIT: now that I visualized it in my mind, a ceramic upper insert would be better, so the air would heat by passing trough the transfer port (inconel would be hot) and there would be less thermal loss to the head material on the upper part (more than 50% of the prechamber surface)

subsonic · « **Reply #22 on:** August 20, 2008, 08:14:56 pm »

The prechamber is actually a two piece deal. The sweet graphics you did show the bottom half.

Jet A · « **Reply #23 on:** August 20, 2008, 08:30:20 pm »

Quote from: "subsonic"

The prechamber is actually a two piece deal. The sweet graphics you did show the bottom half.

To be honest i havent seen the upper half. Isnt it part of the head, as in not removable?

That is actually the same model i sent to 3d printer and the cnc machine.

CoolAirVw · « **Reply #24 on:** August 20, 2008, 09:35:45 pm »

Also you may want to make some that are slightly oversized.

That way if stock size fits loose you can mill the hole slightly bigger and install the oversized chambers.

jackbombay · « **Reply #25 on:** August 20, 2008, 11:29:57 pm »

Quote from: "Jet A"

To be honest i havent seen the upper half. Isnt it part of the head, as in not removable?

Yes, it is part of the head, I have a head that the pre chamber fell out of, I can get a pic if you want...

gigaz2 · « **Reply #26 on:** August 22, 2008, 03:05:47 am »

it is in the vw design

take a look at these Renault:

EDIT: just realised that as they are much bigger theres less chance that they fall into the cylinder as the VW ones do.

arb · « **Reply #27 on:** August 22, 2008, 06:27:17 am »

Some aircraft engine builders I know use JB weld in an aluminum "head" to hold a stainless steel port tube in the coolant jacket of the combustion chamber (Mazda rotary). Since JB Weld is a thick epoxy, I would think your machine shop's approach is sound.

http://rotaryeng.net/Welded-steel-p-port.html

jimfoo · « **Reply #28 on:** August 22, 2008, 07:09:55 am »

Quote from: "arb"

Some aircraft engine builders I know use JB weld in an aluminum "head" to hold a stainless steel port tube in the coolant jacket of the combustion chamber (Mazda rotary). Since JB Weld is a thick epoxy, I would think your machine shop's approach is sound.

http://rotaryeng.net/Welded-steel-p-port.html

You lost me with this comment. What does JB weld have to do with a pre chamber?

gigaz2 · « **Reply #29 on:** August 22, 2008, 07:40:27 am »

Quote from: "myke_w"

I don't sell them either. I have no idea how you'd get them to stay in and trust them once they are out. My machine shop says they epoxy the ford truck ones in, but that's steel in cast iron, not aluminum like our setups.

FYI, many TD PC's I see have hairline cracks from heat, and as long as they aren't cracked all the way to the outside they are generally considered reusable. Though I always have them peened in anymore, just too many horror stories to take a risk.

I guess ARB is quoting this, I guess applying some kind of glue that can whit stand the heat wont hurt.