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

Posted: Sat Nov 04, 2017 9:00 pm
by Carnut1
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Three counterflow 8v heads and one later crossflow head a 2" slice of a 1.8l block. This is a port and chamber developement project for an ST member who would like to remain annonymous. This project actually started months ago but these parts arrived recently. Project outline develope an intake, exhaust and chamber with the idea of max usable output in a full body street ride. Max rpm is only 7000 rpm looking at the vertical sohc design layout the guides and valves are very short and the spring package is very short. Hydraulic buckets directly act on valves buckets can be upgraded for solid buckets and save some weight and increase rpm. The stock rods and cast pistons are very robust for a small engine. I would feel comfortable spinning the stock rotating kit to 8000 but the customer isn't.

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

Posted: Sat Nov 04, 2017 9:04 pm
by Carnut1
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some internet pics of my challenge. Cutaway exhaust and intake port.

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

Posted: Sat Nov 04, 2017 9:16 pm
by Carnut1
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gasket, 2" block slice, cylinder head clamped. I am not a fan of clamping heads but I need to buy some hardware to be able to bolt this whole assembly together. Swirl meter still mounted under bore adapter. I couldn't wait to get started so this was first up.

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

Posted: Sat Nov 04, 2017 9:22 pm
by Carnut1
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Stock 2 angle valve job 1.57" and 1.3" valve seats. This may go from 8mm stems to 7mm stems possibly offset valve centers, possible welded chambers, possible oversized valves. All dependant on how responsive these heads are and projected output. We will see the customer is interested in pushing limits so everything is on the table.

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

Posted: Sat Nov 04, 2017 9:28 pm
by Carnut1
1104170925.jpg[/attachment]Customer designed custom plugs to fill injector holes.
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Plug blended into port

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

Posted: Sat Nov 04, 2017 9:34 pm
by peejay
Would there be a point to offsetting the valves given that they're already on-center and the bores are tiny?

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

Posted: Sat Nov 04, 2017 9:59 pm
by Carnut1
peejay wrote:
Sat Nov 04, 2017 9:34 pm
Would there be a point to offsetting the valves given that they're already on-center and the bores are tiny?
I get the feeling it would not be worth the effort. Even oversized valves are only 1mm larger.

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

Posted: Sun Nov 05, 2017 1:30 am
by cgarb
Do you typically see an increase of swirl in a totally round port? A square port I would think the air is kept more straight with the flat side walls. In the pump hydraulics world we use vanes in places to keep the fluid from creating a vortex and that will cause cavitation. We even have honeycomb looking "flow straighteners" integrated into some large piping.

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

Posted: Sun Nov 05, 2017 2:37 am
by MTENGINES
Unless you plan on putting a different camshaft to this and spinning 7500rpm+. Nothing more than a bowl blend is needed. That head flows more than the engine will take in stock form even with a mild camshaft valve event. I see this too often. People want me to port heads and throw a stock camshaft in the mix. And are pissed because they didn't pick up 100hp. Meanwhile other forums insure customers this unobtainable to gain with stock configuration.

I applause your work in the speed community. But there needs to be a blunt truth to some of these people in what they want. Sometimes a performance cam. Will offset any portwork period!

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

Posted: Sun Nov 05, 2017 2:40 am
by MTENGINES
cgarb wrote:
Sun Nov 05, 2017 1:30 am
Do you typically see an increase of swirl in a totally round port? A square port I would think the air is kept more straight with the flat side walls. In the pump hydraulics world we use vanes in places to keep the fluid from creating a vortex and that will cause cavitation. We even have honeycomb looking "flow straighteners" integrated into some large piping.
I have seen swirl kill horsepower big. And I have seen swirl improve brake specifics. Dependant upon what the goal is, more swirl is not an indicator of more hp.

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

Posted: Sun Nov 05, 2017 3:25 am
by Carnut1
cgarb wrote:
Sun Nov 05, 2017 1:30 am
Do you typically see an increase of swirl in a totally round port? A square port I would think the air is kept more straight with the flat side walls. In the pump hydraulics world we use vanes in places to keep the fluid from creating a vortex and that will cause cavitation. We even have honeycomb looking "flow straighteners" integrated into some large piping.
I do not have lots of experience with round ports. What I do like about them is they have the best surface to volume ratio you can get. They also have less places to create eddy currents which would increase the Reynolds number. In theory this should give a lower turbulence air stream and the porter should be able to push the speed of the air higher than a rectangular port of the same mcsa. This should improve the engines ability to produce lower rpm torque and not fall off as fast in upper rpm. So far stock these do not have a high swirl at the lifts this valve layout can accomodate. Thanks, Charlie

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

Posted: Sun Nov 05, 2017 3:38 am
by Carnut1
MTENGINES wrote:
Sun Nov 05, 2017 2:37 am
Unless you plan on putting a different camshaft to this and spinning 7500rpm+. Nothing more than a bowl blend is needed. That head flows more than the engine will take in stock form even with a mild camshaft valve event. I see this too often. People want me to port heads and throw a stock camshaft in the mix. And are pissed because they didn't pick up 100hp. Meanwhile other forums insure customers this unobtainable to gain with stock configuration.

I applause your work in the speed community. But there needs to be a blunt truth to some of these people in what they want. Sometimes a performance cam. Will offset any portwork period!
Mt, I don't disagree with you a bit. The customer is set on 7000 rpm as of now. The stock components are well designed and I feel with some prep and balancing could easily go 8000 rpm. I am more worried about the short valve train and bucket arrangement as far as rpm. There has already been the camshaft discussion with the customer and DV and Mike Jones names were mentioned. A quick ratio proportion equation with stock airflows are similar to a 370cfm head on a 306 Ford. So it does sound a bit silly working to increase cfm on such a design. So, cfm, port energy, turbulence, swirl, tumble, chamber design will all need a good look at. MT, it is high performance engine design, anyone can do it! Thanks, Charlie

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

Posted: Sun Nov 05, 2017 3:48 am
by Carnut1
MTENGINES wrote:
Sun Nov 05, 2017 2:40 am
cgarb wrote:
Sun Nov 05, 2017 1:30 am
Do you typically see an increase of swirl in a totally round port? A square port I would think the air is kept more straight with the flat side walls. In the pump hydraulics world we use vanes in places to keep the fluid from creating a vortex and that will cause cavitation. We even have honeycomb looking "flow straighteners" integrated into some large piping.
I have seen swirl kill horsepower big. And I have seen swirl improve brake specifics. Dependant upon what the goal is, more swirl is not an indicator of more hp.
MT, as of what I have seen so far on this head I have worked on flow increases from .05" lift to .5" lift which I feel is about all the stock valve train is capable of. I would like to keep as much llf as possible even though many believe to just work on hlf. As of now swirl was about 1500 rpm at .5" lift stock and after about 5 cut and try flowtests the swirl has increased to about 2000 rpm. This was with Pitot work and no port biasing to increase swirl. Someone else wrote at some point just work on flow quantity and quality and let the swirl fall where it may. Or something very similar. Thanks, Charlie

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

Posted: Sun Nov 05, 2017 1:47 pm
by cgarb
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.

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

Posted: Mon Nov 06, 2017 6:45 pm
by Carnut1
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Exhaust and intake bowl work. With some more Pitot work I expected more flow improvements but seems the bowl ratio needed adjustment.