Porting the VW/Audi 8v head with port energy discussion

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mag2555
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by mag2555 » Tue Nov 21, 2017 9:34 am

That's good advise , but mod it / rework it to a D shape slowly , real slowly as with so little short turn height you will find yourself eating into low lift flow for the sake of high lift flow.

There's nothing worse to have in a port like that then no Venturi shape going on!

As you rework it I would start to do flow test in steps of .025" from .050" up to .250" so that regressive grinding trends can be spotted sooner!

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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Tue Nov 21, 2017 8:30 pm

1114171912.jpg
Thanks guys, I have hone fairly radical on the ssr intake and exhaust. Small gains, tough little customers these VW heads. This pic is a squared up ssr cut right to the seat angle.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Tue Nov 21, 2017 8:43 pm

1114171821.jpg
Not a great pic but the ssr has a deep cut intersecting right where the floor of the ssr should be. Limits what can be done.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Tue Nov 21, 2017 8:47 pm

1121171959_HDR.jpg
Since the architecture of this exhaust is not spectacular I need to look everywhere for gains. The machined stem was worth 6 cfm at certain lift points.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Fri Nov 24, 2017 8:56 am

1121171940.jpg
Intake port #4 , tighter throat ratio, smaller bowl, less aggressive ssr, chamber deshrouded, 7mm valve. This design gives stronger cfm and port energy up to .4" lift. The clay blob on floor adds 4 cfm. Taller fin design loses cfm. What does the blob tell us the port would like?
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by mag2555 » Fri Nov 24, 2017 9:33 am

I can't fully say without velocity probing it , but I would venture a guess that the half round / oval floor leading up to the short turn is feeding too much air at too high of a speed over the center of the short turn.
I guess you could somewhat prove this out using the clay and making the floor flat from the flange to about half way down the floor, if you then see no flow gain that would point me to what I posted as taking place.

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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Fri Nov 24, 2017 9:46 am

Mag, the ssr is interesting. The more radical I make it the faster the airspeeds on the ssr get and the less flow you get at the back of the bowl. Yet the mass flow really doesn't change which tells me the restriction moves at that point. Port is quite fast about 350ft/sec 1/2" in centered. Thanks, Charlie
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Sat Nov 25, 2017 9:20 am

20171124_144159.jpg[/attachment]
20171124_144159.jpg
Angled ssr experiment.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by 4vpc » Sat Nov 25, 2017 1:10 pm

naukkis79 wrote:
Sun Nov 12, 2017 3:00 am
4vpc wrote:
Sat Nov 11, 2017 1:03 pm
Why not simply round off the short side to give a better radius and blend the bit on the roof just before the guide?
Disadvantages of a better SSR?
We want to turn flow to flow past SSR part of valve, what you supposed to SSR will do exact opposite.

For better SSR turn flow that port entry has to be raised, both floor and roof.
Sorry I don't understand, can you explain? To me rounding the SSR to a bigger radius means the air can stay attached to it.
It seems to be working ok here from what I have gathered.

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Re: Porting the VW/Audi 8v head with port energy discussion

Post by 4vpc » Sat Nov 25, 2017 1:16 pm

Carnut1 wrote:
Fri Nov 24, 2017 8:56 am
1121171940.jpg Intake port #4 , tighter throat ratio, smaller bowl, less aggressive ssr, chamber deshrouded, 7mm valve. This design gives stronger cfm and port energy up to .4" lift. The clay blob on floor adds 4 cfm. Taller fin design loses cfm. What does the blob tell us the port would like?
Try shaping it more aerodynamically and putting it on the roof inline with the valve guide.

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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Sat Nov 25, 2017 1:45 pm

Interesting idea.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Sat Nov 25, 2017 1:49 pm

1113171955.jpg
I have tried this, not great.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Sat Nov 25, 2017 5:44 pm

20171124_150305.jpg
Angled ssr experiment .35" lift string held top left intake port.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Sat Nov 25, 2017 5:45 pm

20171124_150347.jpg
Angled ssr experiment string held center roof intake at .35" lift.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Sat Nov 25, 2017 5:52 pm

2017112495150412.jpg
Angled ssr experiment string held top right roof intake .35" lift. Notice all three string pics show very steady high speed airflow. Strings did not change position at higher lifts. The angled ssr may not show higher cfm but I believe the smoother the string the more laminar the flow and I feel that is worth power. Input welcome. Thanks, Charlie
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