Engine/Transmission (1994 - 1998) porting turbos?

[dlefebvre]

Have been away from the forums for a while now - busy at the new place and at work. I see new threads about porting the 12 cm housing. Have no idea about this. I am ready to put my non wastegated 16 on, but want to learn about this porting. Is this something new? thanks, Dean

 

[Matthug]

I just ported out my 12 as an experiment to compare to the 16. I cut the center divider out about 1. 5'' back and also ported the wastegate hole along with port matching to the gasket at the flange. A ported 12 spools about the same as the 16, but actually feels like it has more top end. Probably because the wastegate flows more now and it's venting all 6 cylinders. The gain is minimal and not worth the work, I have 2 hours into porting the housing. I would just slap on the 16 and call it a day.

 

[Joseph Donnelly]

Several years ago Mark Chapple (TST), 33 years with Cummins/12 on turbo development, told me every year one of the newly hired engineers spent a day or so porting a turbine housing to improve it. No change. When you consider the turbulence and restriction elsewhere, porting doesn't make much sense. In fact, the point of most restriction (as noted by the housing size) is inherent to its function.

 

[Forrest Nearing]

also, you can't port the inside of the scroll...



if you have a port mismatch entering the housing, yes, open it up to remove that mismatch...



the only thing I would CONSIDER would be extrude honing the housing which would polish the entire inside portion of the scroll... this would keep more heat in the exhaust.

 

[BPonci]

Porting seems to work ok for me. To each there own.

 

[Matthug]

Several years ago Mark Chapple (TST), 33 years with Cummins/12 on turbo development, told me every year one of the newly hired engineers spent a day or so porting a turbine housing to improve it. No change. When you consider the turbulence and restriction elsewhere, porting doesn't make much sense. In fact, the point of most restriction (as noted by the housing size) is inherent to its function.

95% of the gain in flow is through making the wastegate hole bigger then cutting out the center divider so it wastes all 6 cylinders, and of course the port matching helps so you don't have the exhaust hitting a wall on it's way into the housing.

 

[Forrest Nearing]

exactly, opening up the wastegate orifice and allowing both sides of the engine to breathe through the wastegate is going to help a LOT, but I wouldn't consider that "porting" the turbine housing... maybe we're all on different pages here?



I would call that opening up the wastegate and letting both sides of the engine breathe

 

[Matthug]

''opening'' would be another word for porting. Also I used the same tool to port manifolds as I did to cut out the center divider and same tool used to port match the housing, an air die grinder with carbide bits.

 

[thekidfan]

Porting seems to work ok for me. To each there own.

I was going to stay out of this but since you opened the door... .

YES, it does work/help to what degree well that all depends, some would say a ported head doesn't help on a turbocharged engine either odds are they didn't do it right

 

[Matthug]

Whoever said porting a head doesn't help on a turbocharged engine has their head up their ***.

 

[pwerwagn]

Whoever said porting a head doesn't help on a turbocharged engine has their head up their ***.

Not necessarily. I know quite a few guys that think porting the head costs power. There are 2 guys I know of that ported their own head, and felt they lost power. Chances are they did it wrong. They pulled the ported head off and put a stocker back on.

so they truly do believe porting didnt help on a turbocharged engine.



Plus, I think they both ported the exhaust side way to much for their application. One of them was running a B-1 steroid, with not enough fuel for it to begin with. I think that when he created the extra volume in the exhaust, he cause the spool to be far worse than what it was.

Now maybe if he would have added more fuel along with the porting, he woulda liked it. who knows.

 

[BPonci]

Porting a head is not for everybody. When you do this you lose bottom end exhaust velosity (turbo spool). But you do gain in the mid range and the top end.

 

[Matthug]

Porting a head is not for everybody. When you do this you lose bottom end exhaust velosity (turbo spool). But you do gain in the mid range and the top end.

Not if you do it right. I've seen ported heads that flow more AND have more velocity than stock even at low lift and RPM's, velocity is actually more important than flow for any vehicle thats not drag/race only. I think the problem is here that 99% of people with a ported head also replace the cam moving the power band up.

Now the ones I've seen were gas applications (BB chrysler), but it's still internal combustion turbo engine I don't think diesel has anything to do with it.