Is there a purpose to the dog-leg port on the Subaru heads?

Scubynubie · 12-11-2012, 10:17 PM

After reading Crawford's analysis of the new FA BRZ and hearing that even the new BRZ heads have a dog-leg port, I have really been wondering if there is a purpose to having them.

You have to figure that if they could have gained some efficiency, or a gain in power, they could have easily designed a head that didn't have them with the 2007 STI, the 2008+ STI with Dual AVCS, and especially the FA BRZ engine that is trying to make a lot of NA hp where I would assume that efficiency would be paramount.

Part of the purpose of this thread is that before this point, I have been thinking of porting a head only enough to match the flow of the dog-leg and straight port, and pairing that with an EL headder. But now I wonder if that would actually not be an ideal set-up compared to leaving the dog-leg port different.

In a nut shell, if the dog-leg port was bad/less efficient, wouldn't they have remove it by now?

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Storm · 12-12-2012, 12:05 PM

My understanding is a simple packaging restraint. The engine subframe occupies the space where the dogleg exhaust port would exit if it werent turned and routed closer to the other port.

Jay

CatfaceType-R · 12-12-2012, 12:24 PM

idk how we can match the ports with that dogleg...

matched airflow+matched (cc) injectors+matched gap in spark plugs in between cylinders=good. Ability for your tune to be pertinent...

tja1618 · 12-12-2012, 02:09 PM

Can someone point out what you mean by dog-leg ports? Does this refer to the shape of the ports as they curve up/down to the intake/header? As opposed to something straight up and down?

FuJi K · 12-12-2012, 02:12 PM

Quote:

Originally Posted by tja1618

Can someone point out what you mean by dog-leg ports? Does this refer to the shape of the ports as they curve up/down to the intake/header? As opposed to something straight up and down?

spoolinsti05 · 12-19-2012, 01:40 PM

Exactly how mine look^ Besides for the valve seat blend you had done.

The dog leg will always be their. Matching it's flow is what you need to aim for.

12-11-2012, 10:17 PM	#1
Scubynubie Scooby Newbie Member#: 103757 Join Date: Dec 2005	Is there a purpose to the dog-leg port on the Subaru heads? After reading Crawford's analysis of the new FA BRZ and hearing that even the new BRZ heads have a dog-leg port, I have really been wondering if there is a purpose to having them. You have to figure that if they could have gained some efficiency, or a gain in power, they could have easily designed a head that didn't have them with the 2007 STI, the 2008+ STI with Dual AVCS, and especially the FA BRZ engine that is trying to make a lot of NA hp where I would assume that efficiency would be paramount. Part of the purpose of this thread is that before this point, I have been thinking of porting a head only enough to match the flow of the dog-leg and straight port, and pairing that with an EL headder. But now I wonder if that would actually not be an ideal set-up compared to leaving the dog-leg port different. In a nut shell, if the dog-leg port was bad/less efficient, wouldn't they have remove it by now? * Registered users of the site do not see these ads.

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12-12-2012, 12:05 PM	#2
Storm Scooby Guru Member#: 5218 Join Date: Mar 2001 Chapter/Region: MWSOC Location: SAUL'S Motorsports Vehicle: 96L Most Over- Developed Beater	My understanding is a simple packaging restraint. The engine subframe occupies the space where the dogleg exhaust port would exit if it werent turned and routed closer to the other port. Jay

12-12-2012, 12:24 PM	#3
CatfaceType-R NASIOC Supporter Member#: 81102 Join Date: Feb 2005 Chapter/Region: MWSOC	idk how we can match the ports with that dogleg... matched airflow+matched (cc) injectors+matched gap in spark plugs in between cylinders=good. Ability for your tune to be pertinent...

12-12-2012, 02:09 PM	#4
tja1618 Scooby Newbie Member#: 181995 Join Date: Jun 2008 Chapter/Region: Tri-State Location: Rochester, NY Vehicle: 2003 WRX WRB	Can someone point out what you mean by dog-leg ports? Does this refer to the shape of the ports as they curve up/down to the intake/header? As opposed to something straight up and down?

12-19-2012, 01:40 PM	#6
spoolinsti05 Scooby Specialist Member#: 108051 Join Date: Feb 2006 Chapter/Region: Tri-State Location: NY Vehicle: 2005 TickingTimeBomb Jr tuned TT Sleeved	Exactly how mine look^ Besides for the valve seat blend you had done. The dog leg will always be their. Matching it's flow is what you need to aim for.