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Old 08-31-2007, 10:40 AM   #1
Wrinkleboi
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Default Photos of 2007 USDM STi Intake Ports compared to v7 JDM STi Intake Ports... wow

Doing a TGV delete to my 07 STi motor now and I was surprised to see how small and rough the intake ports look, figured I'd take a couple photos to just show everyone...
Also took a photo of a v7 JDM Big Port for comparison... there is a 19mm Craftsman deep socket in both of them for scale... there was plenty of side to side room in the JDM ports, but pretty much none in the USDM. The knife edged divider was a lot thicker in the USDM motor as well. Also, it looks like they crinkle coated the inside of the USDM engine too!!!

2007 USDM STi Heads


v7 JDM Big Port Heads


texture
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Old 08-31-2007, 12:16 PM   #2
modaddict
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Casting differences are huge.

Hey, can you do me a favor? Can you post a picture of the JDM heads without the socket in the port? And can you post of a tape measure showing the overall length of the JDM port? Does the port taper from the top edge where the intake bolts up....downward deeper into the port? maybe take a pic the exhaust differences too?

It would be interesting to see how a USDM gasket lines up on the JDM head.

Im curious as I am thinking about port work for my heads....and want the JDM flow out of a USDM head....so i want to port it like the JDM BIG PORT heads. i appreciate you help!


This is good info with nice pics! thanks!
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Old 08-31-2007, 03:15 PM   #3
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my OEM 05 heads were new and looked just like that, with the crinkled texture. We ported them during assembly and did a lot of smoothing to the divider area. seems to help a ton, simply from the butt dyno perspective!
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Old 09-01-2007, 01:34 PM   #4
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yeah i'll take a couple photos of the jdm v7 ports without the socket when i have some time
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Old 09-01-2007, 05:27 PM   #5
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Hey just be careful with those version 7 heads man

cheers

poorman
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Old 09-01-2007, 06:25 PM   #6
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I have a UK V7sti.. is there any casting numbers on the JDMs that would tell me if i had the big port heads or not?
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Old 09-01-2007, 07:17 PM   #7
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oh dang....
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Old 09-02-2007, 12:18 AM   #8
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Quote:
Originally Posted by poormansporsche View Post
Hey just be careful with those version 7 heads man

cheers

poorman
haha busted. i thought you might be observant enough to catch this. anyway, your new heads look a whole lot more badass than my new heads... ah well. dont worry though, being very careful with them and they'll be on the way asap.

as for the guy with the UK heads... are they assembled so you cannot look at the ports? if you can look at the ports then if they are small port they'll look more like a O (almost totally round), whereas with the big ports it looks like a wide D like you can see in the photo.
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Old 09-02-2007, 03:55 AM   #9
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You should see my JDM Spec C heads!

THe Crinkle finish is on purpose. Air flows easier over the rough surface vs the smooth surface. THis is why a Golf ball has Dimples.

CLark
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Old 09-02-2007, 03:57 AM   #10
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so why are the jdm heads smooth, and why are the spec c heads even smoother?
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Old 09-02-2007, 07:50 AM   #11
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Clark is right. The dimples on the golf ball cause the flow to stay attached longer and reduce the pressure drag on the ball. I would assume the same applies to the heads, keep the flow attached to the wall/surface and it would reduce the boundary layer.

Think of it like this; with a smooth surface the air just ricochets off of it and sqeezes the air into the middle of the pipe, with the rough surface it grabs the air and keeps it towards the edge effectively increasing the flow diameter of the air through the pipe.

The rough surface actually causes the flow to stay attached longer and have a lower reynolds number. even though the flow is turbulent it becomes turbulent later with the rough surface.

I would assume the reason most companies stay away from this is because of the "frag" that can result from such a surface. If you have a rough surface like that it is way more likely to have debris coming off the walls than that of a nice smooth surface.
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Old 09-02-2007, 11:52 AM   #12
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well subaru clearly does both because my jdm v7 heads are much smoother and i know that the spec c heads are even smoother than that. and when you have porting work done on heads they get it very smooth as well.
so whats the verdict considering all of that?
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Old 09-02-2007, 02:48 PM   #13
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The JDM V7 heads are older. We only see this new finish on the 07 and later cars.

The reason you dont see this on hand ported heads such as my JDM SPec C heads is simple.. How in the hell are you going to get that finish after you ground the ports larger? I have seen some high end race shops bead blast the ports after enlarging them but that is not nearly as severe as the 07 ports. This finish must be cast in.

In short.. THe 07 heads have small ports with high velocity and less drag. THis helps emissions and response. The JDM heads flow alot more air but have a much lower velocity. For HP the larger port is going to win everytime. Smooth or not.

People have purchased new Spec C heads and found them to be exactly the same as the V7's. Its like the Type R head for the honda. Buy the vehicle and you get Hand ported head. Buy the head and you dont get that hand porting. When mine come out they will be enlarged even more with bigger valves and cams. I want ports that you could stick your mushroom into and not touch the walls.. LOL


Clark
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Old 09-02-2007, 07:08 PM   #14
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Having the rough surface also helps the fuel/air to mix. I have seen shops chisel in dimples to achieve this effect.
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Old 09-02-2007, 08:43 PM   #15
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maybe its just me, but my 06 wrx head ports look bigger to me than that of the 07 STI

here is the link below:



Last edited by need2boost; 09-02-2007 at 08:55 PM.
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Old 09-02-2007, 08:47 PM   #16
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still got it apart? get some more light on that engine bay and snap some closer photos... if you can, take a craftsman deep 19mm socket and lower it into one of the ports to see how tight of a fit it is so we can have a side by side comparo.
did you notice any texture or are they smooth?
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Old 09-02-2007, 08:57 PM   #17
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these pics were taken when i had my TGV's deleted, i wish i could help more. I have one more photo which i just added to the list.
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Old 09-02-2007, 09:37 PM   #18
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I think the 06 are a bit larger and smoother than the 07s Rough castings.

Clark
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Old 09-02-2007, 10:05 PM   #19
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Quote:
Originally Posted by AZScoobie View Post
You should see my JDM Spec C heads!

THe Crinkle finish is on purpose. Air flows easier over the rough surface vs the smooth surface. THis is why a Golf ball has Dimples.

CLark
Yeah Laminar flow...
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Old 09-03-2007, 01:22 AM   #20
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While I certainly understand the dimpled golf ball/Reynolds number argument, are you asserting that the casting sands are engineered and constructed to a certain surface finish rather than the surface simply being a result of the casting process itself?
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Old 09-03-2007, 01:47 AM   #21
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How many diff. Mani's are there?

USDM, JDM, and SpecC?
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Old 09-03-2007, 01:56 AM   #22
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I was under the impresson that the dimples on a golf-ball CAUSED drag, and from the backwards spin imparted on the ball from the club's horizontal grooves, it created LIFT.

Without the dimples, the ball doesn't create enough high-pressure resistance on the bottom of the ball and it drops quicker than a dimpled ball....decreasing distance.

I am not an engineer, didn't stay at a Holiday Inn last night, and have never built an engine...must be why I can't wrap my head around the reason to make an intake port ROUGH, instead of the smooth ports I've always seen on race engines.

If the dimples/rough surface allowed air to flow faster or with less resistance, then why is every aerodynamic vehicle (bike/car/plane/rocket) made smooth?
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Old 09-03-2007, 02:55 AM   #23
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Just bustin your chops! Feelin pretty good about the purchase now. It's also nice to have these comparisons documented. I love it when I'm looking for something like this and the nasioc query returns a link like this thread. Good thinkin.

cheers

poorman


Quote:
Originally Posted by Wrinkleboi View Post
haha busted. i thought you might be observant enough to catch this. anyway, your new heads look a whole lot more badass than my new heads... ah well. dont worry though, being very careful with them and they'll be on the way asap.
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Old 09-03-2007, 09:12 AM   #24
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Quote:
Originally Posted by Phatron View Post
Having the rough surface also helps the fuel/air to mix. I have seen shops chisel in dimples to achieve this effect.
Kinda like mini TGVs. Of course, many people remove these restrictions.
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Old 09-03-2007, 01:10 PM   #25
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Quote:
Originally Posted by ace996 View Post
I was under the impresson that the dimples on a golf-ball CAUSED drag, and from the backwards spin imparted on the ball from the club's horizontal grooves, it created LIFT.

Without the dimples, the ball doesn't create enough high-pressure resistance on the bottom of the ball and it drops quicker than a dimpled ball....decreasing distance.

I am not an engineer, didn't stay at a Holiday Inn last night, and have never built an engine...must be why I can't wrap my head around the reason to make an intake port ROUGH, instead of the smooth ports I've always seen on race engines.

If the dimples/rough surface allowed air to flow faster or with less resistance, then why is every aerodynamic vehicle (bike/car/plane/rocket) made smooth?

The golf ball example can be a bit misleading. As the air moves around the sphere it separates from the surface & creates a turbulent/low-pressure wake behind it. With a thicker boundary layer of turbulent air, the airstream will be drawn farther around the back of the ball before separating. The net effect is a smaller wake/low-pressure zone.

The golf ball's dimples are a band-aid for it's relatively poor shape in regards to aerodynamics. Similarly, if a port needs to be significantly roughed up in testing to prevent separation/turbulence then perhaps it's shape is far from ideal.

As it pertains to ports, the smoother port will technically have more effective crossection. However, of all the port's characteristics, surface finish typically has very little effect on performance provided it's within a normal range. The vast majority of the time surface finish considerations are due to any effect it may have on fueling, not airflow.
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