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

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

Post by af2 »

Why are people stuck on the short turn? The Velocity and fuel will go beyond and end up??? The given head has told you that? Just making sure you don't get stuck on 1 thing when there is more.
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Re: Porting the VW/Audi 8v head with port energy discussion

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Af2, have you seen the cutaway pictures of these ports? The ssr is by far passing the highest volume of air at the highest speed. Working on slowing them a bit and using the rest of the bowl. Thanks, Charlie
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Re: Porting the VW/Audi 8v head with port energy discussion

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Carnut1 wrote: Sat Nov 25, 2017 7:22 pm Af2, have you seen the cutaway pictures of these ports? The ssr is by far passing the highest volume of air at the highest speed. Working on slowing them a bit and using the rest of the bowl. Thanks, Charlie
Yes I saw that and thinking how you can make up for the speed over the ssr that's all.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by naukkis79 »

4vpc wrote: Sat Nov 25, 2017 1:10 pm
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.
With high angle ssr-heads the problem is how to get air turn past ssr side of valve. Lowering ssr as you suggest makes air not able to turn into ssr side of valve resulting that big part of valve don't flow.

What we need to do is to raise ssr floor and make turn radius longer with way that airflow has turned enough when meeting seat to flow past ssr side of valve. When done properly it's also need that port entrance has to be raised too.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by mag2555 »

X2 with the above!!!
Once tumble / sheer or whatever you care to call it sets in the air mass will bypass a certain area of the valve seat and you drop curtain area!

Since with any Head you can only have no more then a 90 degree short turn , once tumble locks in your bypass triangle will be 90 degrees minus whatever the heads valve inclination is in reaction to the piston top.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by mag2555 »

Charlie, from the looks of that short turn shot taken from the valve bowl side it looks like your now replicating the so called Intake Humber hump floor used in some post 69 Mopar heads, which by the way does work although when you first see it you wonder WTF they where thinking with this casting!
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by peejay »

naukkis79 wrote: Sun Nov 26, 2017 4:57 am
With high angle ssr-heads the problem is how to get air turn past ssr side of valve. Lowering ssr as you suggest makes air not able to turn into ssr side of valve resulting that big part of valve don't flow.
And suddenly it clicks in my head why opposed valve heads can work so well... that part of the valve is mostly dead anyway because of the cylinder wall.
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Re: Porting the VW/Audi 8v head with port energy discussion

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Sometimes the best way to work on a problem is step back and take a different view of the problem. I decided to dig out the dinosaur computer that had port flow analyzer v3.5b on it. Test report intake and exhaust calculated data.
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Re: Porting the VW/Audi 8v head with port energy discussion

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Engine performance estimate Port flow analyzer. Cam is what I feel this mill could use. Solid, 222 degrees @.05" intake 220 degrees@.05" exhaust. The exhaust is good for 150 cfm with pipe so with a well designed exhaust system I think it will need less duration even with poor exhaust port design. The cam is right out of my imagination and I am sure could be improved. I have not gotten feedback on maximum compression ratio so I am using a sad 9/1 compression ratio. As far as comparing intake flow numbers on Stan's site with simialar valve sizes high lift flow is with the competition and mine easily demolish the competition from .05" to .4" lift! Why? DV "inspired" valve job. Not the same angles he uses. This is a very lift limited application so low lift flow will be very important on these as will swirl for a torque improvement. Input welcome. Thanks, Charlie
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Re: Porting the VW/Audi 8v head with port energy discussion

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Should I mention the competition flows are measured with an unrealistic 3.95" bore? My block slice measures 3.22". Thanks, Charlie
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Re: Porting the VW/Audi 8v head with port energy discussion

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The stock throttle body is a nice piece of engineering, progressive two barrel with nice curves. Problem with such a nice design is it may be difficult to make airflow gains with porting of throttle body. I would say the most difficult t.b. I have ever worked on. Worth up to 2.1 cfm at every lift point. Shaft was left stock.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by MadBill »

Per David Vizard's Holley book, dressing the throttle screws ends and heads is worth 17 CFM and aero-contouring (not slabbing!) the throttle shafts 40 more for an 850 Holley. Modded per most of his recommendations, a pair I did up flowed ~1025 dry.
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Re: Porting the VW/Audi 8v head with port energy discussion

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I figured the stock VW intake may need the plenum enlarged but bone stock it takes a full 30 cfm intake flow off. It will need to be cut in three pieces and welded back just to port and keep some taper in the ports. It may be easier to build some nice stacks. Thanks, Charlie
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Smoke ring »

Here's a way to get that 30 cfm back.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 »

Smoke, is that a bolt on for VW RB head?
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