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

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Carnut1
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Sat Dec 02, 2017 1:45 pm

1202171028.jpg[/attachment]Smoke, we are on the same page. I am thinking I can get to all the areas of the runners with one cut and then enlarge the plenum. I will need to do some calculations on plenum size and figure the tapee. Stock runners have a taper and would probably work well if they were straighted and a bit larger. I was also thinking of just building a flange at the cut with 3/8" aluminum plate. Bolt on the plenum for street or bolt on the stacks for racing. Just an idea, customer has the say. Thanks, Charlie
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Mon Dec 04, 2017 6:41 am

1203171110c.jpg
Since the stock intake knocks a full 30 cfm off a modified intake port I wanted to see what could be done without welding and cutting, I was able to slightly enlarge and reduce taper 6.25" into the flange. This was worth 6 cfm. A discussion about anti reversion (a.r.) and subsequent mods lost about 1cfm at high lift and low lift flow took a hit. Now llf will be important on this build due to the engine design restrictions. I will need to consider the advantages of a.r. vs. The llf loss. Thanks, Charlie
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by mag2555 » Mon Dec 04, 2017 6:58 am

Treat it some what like a short turn Charlie!

Widen out and flatten it little by little for a distance of half way thru that 90 degree bend and then switch off to widening the long side of the bend on the other half of the 90 as it approaches the head.

I guess your next issue even if you only pick up 15 cfm per runner is the restriction the throttle body may become now?

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

Post by Carnut1 » Fri Oct 26, 2018 8:41 pm

1026181922.jpg
This project has been near dead for a year but is back with my international customer doing lots of prep, design and fabrication work. Check out the 2mm offset plate that is reversable and custom built (and honed to size) bore adapter. We decided the stock block bores are thick enough to offset bore 2mm safely. I will be posting more soon. The custom intake looks really good. Thanks, Charlie
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by David Vizard » Sat Oct 27, 2018 12:46 pm

cgarb wrote:
Sun Nov 05, 2017 1:47 pm
I can very well see where too much swirl will go from keeping fuel suspended to slinging it to the edges of the chamber and creating a dead spot in the center. Maybe that's not what too much swirl does but it makes sense by my logic.
cgarb,

Too much swirl and a carb that delivers insufficient atomization will do just as you describe. Saw this on many cup car and similar engines back in the late 90's.

By the time we got to 2005 it did not seem to be a problem as most setups had veered away for high swirl ports and chambers.

It appears from my experience testing swirl that if you are targeting power up in the 9 -10,000 rpm range that swirl is unnecessary as having any motion stagnation would be very unlikely. On the other hand at 1000 - 5000 rpm swirl is an aid. I have a swirl test graph in my cylinder head book I can poach and post if anyone is interested.

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

Post by Carnut1 » Sat Oct 27, 2018 7:36 pm

Resized_20181027_190724_2077.jpeg
2mm bore shift on old test head. This head has a bit too much deshrouding on intake. This mod makes easy 10 cfm on the intake vs. -2mm.. Thanks,Charlie
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Kbails » Sat Oct 27, 2018 9:43 pm

what about extrude honing for the intake?
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Sat Oct 27, 2018 10:13 pm

Kbails wrote:
Sat Oct 27, 2018 9:43 pm
what about extrude honing for the intake?
You will like the intake. I will be able to port it now.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by JoePorting » Sun Oct 28, 2018 12:50 am

Have you thought of putting in a larger intake valve? Should respond good with that open chamber.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Sun Oct 28, 2018 7:49 am

I have Joe, The valves that he bought for testing are 7mm stem which we are going to use. But a much longer stem. The customer was even thinking of changing the cam perches and lifting the cam higher. I feel like that is just an insane amount of work for an unknown amount of performance. He wants to keep the rpm to 7000. The 7mm stem valves that are pictured are from a crossflow VW head. Thanks, Charlie
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Sun Oct 28, 2018 8:42 pm

Resized_20181028_181750_2631~2.jpeg
2mm shift with stock head gasket. This gasket's fire ring is not wide enough to survive. That would mean custom gaskets. A 1mm offset may be wiser.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Sun Oct 28, 2018 8:51 pm

Resized952018102895185108953720.jpg
Modified VW manifold bottom. Flowing each section to see where the restrictions are. Clay radius on unported botton half.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Sun Oct 28, 2018 8:53 pm

Resized952018102895191247952151.jpg
Modified VW intake top runner section.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Sun Oct 28, 2018 8:58 pm

Resized952018102895191809954382.jpg
Trumpet that will need to be epoxied in place.
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Re: Porting the VW/Audi 8v head with port energy discussion

Post by Carnut1 » Sun Oct 28, 2018 9:00 pm

Resized_20181028_193556_6087.jpeg
Throttle body view of custom plenum with trumpet placed for quick flow testing.
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