Outer Limits 4x4 Board

HI,

After figuring out the limitations of pre combustion chambers on a boosted 1HZ head, I figured that high flowing or "porting" the pre combustion chamber so it created less resistance woudl be the go. Seeing how these create cracks in the head and issues all around...

Just wondering if anyone has had this done, thought of it or had toyota laugh at them... I'm going to buy 1 pre comp chamber, trial it with the machine shop and get the flow rates measured pre and post... I'd be keen to get a 20% improvement in flow which should help resistance and over heating....

Anyone? I have a mate who "apparently" had this done in his performance GQ diesel but he's a bit iffy on it...

I have wondered about this too after seeing the cracks in my head when I pulled it off. Could you actually run the 1hz without the precom cups altogether when it's turboed? As its when these crack that they crack the rest of the head. (I'm assuming its also because they are a different metal with different heat expansion properties to the cast iron head)

I'm no expert, but the shape of the precomp chamber is veeeery important - change the shape and ignition timing, burn rate and hot/cold spots could be all over the shop.

Would wanna really know what you were doing!

Doesn't adding a turbo change all that anyways???

short answer,

No

You cannot modify a precom in this manner.

Try getting them HPC coated....

The later model 1HZ has a bigger oulet in them which would flow better and that would be the best option. As for the cracks unless they go all the way to the edge they are not a concern the pre com wont fall into the cylinder.

Z()LTAN wrote:short answer,

No

You cannot modify a precom in this manner.

Try getting them HPC coated....

Nope - forget HPC as they will flow LESS as thats a build up...

I'm still keen to play with this idea - as It makes sense... Will let you know how I go.. Head may have to come off soon anyway - radiator died on a trip a while back and using water now (no milk in oil...)... Good opportunity to mess with it..

give it a shot, it's something I've wanted to do to see if there are performance gains to be had, but it's probably not such a hot idea. indirect injected diesels need high compression and high gas velocity to ensure good swirl and combustion, and although you will achieve that with boost and higher rpm, at idle you will lose, it will be nasty rough and may not run below say 1000rpm depending how much material you remove.

probably the best thing you can do for a turboed 1HZ is to install the 5 notch head gasket, and possibly skim the piston crowns a tiny amount, say half a mm to bring the compression down.

since there is a direct injected alternative in the 1HD-T, it doesn't really pay to go all out to try for a a super hipo 1HZ.

dumbdunce wrote:give it a shot, it's something I've wanted to do to see if there are performance gains to be had, but it's probably not such a hot idea. indirect injected diesels need high compression and high gas velocity to ensure good swirl and combustion, and although you will achieve that with boost and higher rpm, at idle you will lose, it will be nasty rough and may not run below say 1000rpm depending how much material you remove.

probably the best thing you can do for a turboed 1HZ is to install the 5 notch head gasket, and possibly skim the piston crowns a tiny amount, say half a mm to bring the compression down.

since there is a direct injected alternative in the 1HD-T, it doesn't really pay to go all out to try for a a super hipo 1HZ.

Looking for a 20% flow gain - which should equate to bugger all material removed. I already have 1HDT pistons/rods and lower compression due to different head gasket... 1HDT head can be grafted but have too much invested in the donk.

I run 12-13psi now and built the motor to take the 18psi - just these are the one thing I didn't consider whilst it was all apart! The pump and bottom end ae designed and built for 160+kw at the wheels... Turbo change will make the power but figured I'd look at this prior to opening up the wallet and boost controller!

Cheers guys - definitely looking at this - will see what hapens!

80diesel4play wrote:
I already have 1HDT pistons...

they will only work with a 1HD-T head.

Hi flowing precomps is only going to alter how quickly the flame front comes out into the top of the piston area. I don't think it will help with power but I am always open to new suggestions.

A better inlet manifold and bb turbo would give a better improvement than pre comps I think.



Andy

dumbdunce wrote:

80diesel4play wrote:
I already have 1HDT pistons...

they will only work with a 1HD-T head.

I think he meant the 1hdt rods and the 1hz pistons with the larger gugen pin holes, still a flat top piston.

horndog wrote:

dumbdunce wrote:

80diesel4play wrote:
I already have 1HDT pistons...

they will only work with a 1HD-T head.

I think he meant the 1hdt rods and the 1hz pistons with the larger gugen pin holes, still a flat top piston.

Yep - that I do...

Andy - BB and Exhaust manifold are on the cards as the Turbo in use is maxed out a 13psi (on your dyno!!) - what I'm referring to here is to manage the Pre comp chambers and reduce expansion within the head at higher boost pressures. Hopefully I can gain even a 10 reduction in heat transfer/improve flow rate as a minimum...

As dumbdance mentioned, and Gale Banks has proven, be careful about what you do, how you do and how much with diesel combustion chambers and pre combustions, as the best thing for diesels is swirl of the intake charge mixing with the fuel and having a good flame.