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michael1968
Samba Member
Joined: August 17, 2007
Posts: 36
Location: Newcastle, Australia
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 Posted: Tue Sep 04, 2007 4:56 am Post subject: twin cam aircooled heads |
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Hi, new to this but anyway,
Below are some jpgs of the twin cam head I designed last year for my engineering thesis.
It's meant to run on a type1 case, it uses Subaru EJ25 valve gear. It's just a model (proE) at the moment, it'll take a bit of cash to get going. I did do a 3D print of half of the head and flow tested it. With the stock EJ25 cam and valves it had half the pressure drop as my slightly ported twin port at big lift.
In the pics it's sitting on stock 1600 barrels, the valves just fit.
Any Comments/advise?
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BugUser
Samba Member
Joined: March 02, 2007
Posts: 29
Location: Stuttgart/Germany
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| Posted: Tue Sep 04, 2007 6:03 am Post subject: |
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Nice 3D model, and nice effort, too.
...but...
all previous efforts of creating 4-valve heads for a/c engines I know of suffered the same fundamental problem:
They all smoked their exhaust valves & seats! With the exhaust side facing downwards, that area of the head could never be cooled sufficient enough.
I think there's a reason not even Porsche got 4 valves going on an aircooled basis...
But, as I already stated, nice approach!
BugUser |
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bpritchert87
The Idea Man
Joined: February 26, 2007
Posts: 1507
Location: Wisconsin
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| Posted: Tue Sep 04, 2007 7:47 am Post subject: |
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very nice indeed.... im currently going to school to become an engineer and that is one kick ass modeling...... damn i wish i could design like that.... (maybe someday i will) .... but anyways a few questions for ya
what will time the cams?? i dont see anything connecting to the crank.. maybe just missed it....
maybe a stupid question but what will be the major benifit of 4 vavles versus the standard 2.....
oo anther thing.. what about lubing those cams?
either way great job and great idea.... im hoping when i finish school that i can design something vw type1 related....
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Stripped66
Samba Member
Joined: May 31, 2005
Posts: 3509
Location: Charleston, SC
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| Posted: Tue Sep 04, 2007 8:28 am Post subject: Re: twin cam aircooled heads |
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| michael1968 wrote: |
Any Comments/advise?
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If this is something you plan on actually creating, and not just a design project, optimize the combustion chamber, valve size and valve location for a 94mm cylinder (if you haven't already) and larger displacements (2.2L+), not an 85.5mm cylinder.
_________________
| 66brm wrote: |
| Bodacious wrote: |
| Why not just make a custom set of wires with a Y splice in them. Then you could just run one distributor. |
I don't think electrickery works that way |
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juki48
Samba Member
Joined: March 07, 2007
Posts: 602
Location: Upstate NY
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| Posted: Tue Sep 04, 2007 9:16 am Post subject: |
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| looks pretty good. you might try making the heads water cooled. then you could really control the head temps. |
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bpritchert87
The Idea Man
Joined: February 26, 2007
Posts: 1507
Location: Wisconsin
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| Posted: Tue Sep 04, 2007 10:18 am Post subject: |
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its also looks like the studs are in the way of the valves... or is just that the angle in which it is presented?? im talking about the studs used to torque the head to the jugs.....
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Knowledge is Power Read and Learn !!!
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Banzai KG
Samba Member
Joined: April 10, 2004
Posts: 2992
Location: Sunnyvale, CA
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| Posted: Tue Sep 04, 2007 10:36 am Post subject: |
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Nice CAD drawing there Michael1968.
| BugUser wrote: |
I think there's a reason not even Porsche got 4 valves going on an aircooled basis...
But, as I already stated, nice approach!
BugUser |
Eh? Where have you been?
Porsche did make an aircooled 4-cam engine in the 904 Spyders and 356 Carrera.
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Sunnyvale (near San Jose), CA
1964 Karmann Ghia coupe
V.V.W.C.A. - Golden Gate Chapter: http://www.ggcvvwca.org/
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Banzai KG
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GDOG57
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Joined: March 19, 2006
Posts: 1066
Location: Gilbert,Arizona
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| Posted: Tue Sep 04, 2007 11:47 am Post subject: |
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| Banzai KG wrote: |
Nice CAD drawing there Michael1968.
| BugUser wrote: |
I think there's a reason not even Porsche got 4 valves going on an aircooled basis...
But, as I already stated, nice approach!
BugUser |
Eh? Where have you been?
Porsche did make an aircooled 4-cam engine in the 904 Spyders and 356 Carrera.
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Those porsche 4 cams are sweet,but they are not 4 valves per cylinder.Ever have one apart?If you don't have a book your screwed.The cam timing gears are tricky.
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akokarski
Samba Member
Joined: May 24, 2004
Posts: 2098
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| Posted: Tue Sep 04, 2007 12:16 pm Post subject: |
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wouldn't t1 case need some modifications in order to support side loads from the belts? I remember reading about people attaching propellers to the back side of the engine (crankshaft pulley) in the AV applications and destroying bearings. This was also the case with superchargers as well...
Anton |
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Stripped66
Samba Member
Joined: May 31, 2005
Posts: 3509
Location: Charleston, SC
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| Posted: Tue Sep 04, 2007 12:31 pm Post subject: |
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| akokarski wrote: |
wouldn't t1 case need some modifications in order to support side loads from the belts? I remember reading about people attaching propellers to the back side of the engine (crankshaft pulley) in the AV applications and destroying bearings. This was also the case with superchargers as well...
Anton |
Probably not; any side-loading to drive the cams is going to be minor in comparison to a supercharger or a propellor.
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| 66brm wrote: |
| Bodacious wrote: |
| Why not just make a custom set of wires with a Y splice in them. Then you could just run one distributor. |
I don't think electrickery works that way |
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grimace007
Samba Member
Joined: August 30, 2006
Posts: 2673
Location: swampville, florida
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| Posted: Tue Sep 04, 2007 1:28 pm Post subject: |
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| Banzai KG wrote: |
Oh yeah...BTW Michael1968, have you seen the VW/Subaru hybrid engine project which utilizes a VW engine case, internals, and cylinders while using a Suby heads?
Hybrid Engine Project - http://www.shoptalkforums.com/viewtopic.php?t=93249
edit out photos for space
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wow thats gnarly man!
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68 sedan
Dallas Air Coolers
| perrib wrote: |
Hey It is The Samba where well thought out rational answers can take a while and getting side tracked is normal. I was just lucky this time.  |
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gears
Samba Member
Joined: October 28, 2002
Posts: 4411
Location: Tamarack, Bend, Kailua
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| Posted: Tue Sep 04, 2007 3:34 pm Post subject: |
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A lot simpler option to going water-cooled is to box the head fins in, and run a separate oil supply over them, utilizing the common automatic Bug's oil pump. Jon Karcey did a couple engines like this, commenting how cool the valves ran. The valve lash never required regapping.
4 valves per cylinder of course yields great low end torque with sufficient flow for high rpm. |
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michael1968
Samba Member
Joined: August 17, 2007
Posts: 36
Location: Newcastle, Australia
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| Posted: Tue Sep 04, 2007 11:54 pm Post subject: |
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OK, lots of questions.
| Quote: |
They all smoked their exhaust valves & seats! With the exhaust side facing downwards, that area of the head could never be cooled sufficient enough.
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Yeah, this is a bit of a concern, but 2 exhaust valves do run cooler than 1, I was looking into ceramic coating the exhaust ports to keep temps down.
| Quote: |
| what will time the cams?? |
I haven't modeled the cam pulleys(subaru), I'm trying to use as many ready made parts as possible.
| Quote: |
| major benifit of 4 vavles versus the standard 2 |
You can get a lot more effective valve area for the same or less mass ie less power loss.
| Quote: |
| If this is something you plan on actually creating, and not just a design project, optimize the combustion chamber, valve size and valve location for a 94mm cylinder (if you haven't already) and larger displacements (2.2L+), not an 85.5mm cylinder. |
It's a long term project, this is only the first stage. The whole point of the project was to increase the efficency of the engine not the capacity. It was kind of concieved to run in an under 1600cc unlimited hill climb class we have over here.
| Quote: |
| its also looks like the studs are in the way of the valves... |
They would be, they are designed to bolt into threaded holes in the heads, just like in a normal case.
I've heard of the hybrid but hadn't seen any pics, nice. It would be easier in some respects to just bolt on a set of sub heads but where's the fun in that.
Thanks for your comments guys. |
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BugUser
Samba Member
Joined: March 02, 2007
Posts: 29
Location: Stuttgart/Germany
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| Posted: Wed Sep 05, 2007 3:41 am Post subject: |
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| Banzai KG wrote: |
Nice CAD drawing there Michael1968.
| BugUser wrote: |
I think there's a reason not even Porsche got 4 valves going on an aircooled basis...
But, as I already stated, nice approach!
BugUser |
Eh? Where have you been?
Porsche did make an aircooled 4-cam engine in the 904 Spyders and 356 Carrera.
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Eh? Where have You been?
4 cams don't equate 4 valves per cylinder... |
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Jake Raby
Samba Member
Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Wed Sep 05, 2007 6:40 am Post subject: |
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| Quote: |
| They all smoked their exhaust valves & seats! With the exhaust side facing downwards, that area of the head could never be cooled sufficient enough. |
Absolutely incorrect.
The 4 cam Carrera engine has underside exhaust ports, so does the Porsche 911 and the Type 4 engine, Corvairs and Pinzgauers as well..
Placing the exhaust port under the head is a MORE EFFECTIVE means of positioning a cooling charge around it- IF the head is designed to allow this, as all the aforementioned examples I posted were. Side mounted exhaust ports like the TI and the Porsche 356 have great flow characteristics, but horrible cooling characteristics as a sold 1/4 of the port is incapable of being exposed to the cooling charge.
If you need any assistance let me know, I have more experience than I'd like to have with challenges like yours having taken a solid works model of a cylinder head and manipulating it into a working piece.....
This
to this
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Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
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BugUser
Samba Member
Joined: March 02, 2007
Posts: 29
Location: Stuttgart/Germany
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| Posted: Wed Sep 05, 2007 8:18 am Post subject: |
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| Jake Raby wrote: |
| Quote: |
| They all smoked their exhaust valves & seats! With the exhaust side facing downwards, that area of the head could never be cooled sufficient enough. |
Absolutely incorrect.
The 4 cam Carrera engine has underside exhaust ports, so does the Porsche 911 and the Type 4 engine, Corvairs and Pinzgauers as well..
Placing the exhaust port under the head is a MORE EFFECTIVE means of positioning a cooling charge around it- IF the head is designed to allow this, as all the aforementioned examples I posted were. Side mounted exhaust ports like the TI and the Porsche 356 have great flow characteristics, but horrible cooling characteristics as a sold 1/4 of the port is incapable of being exposed to the cooling charge.
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Dear Mr. Raby,
I very well know the underside exhaust ports of those engines and I never negated their cooling capabilites in a SINGLE exhaust valve scenario...
From my own experience in creating watercooled 4-valve head designs (and following mandatory logic), the highest thermal stresses occur in the web between both exhaust valve seats and the area where the discrete exhaust ports merge together. THIS is the crucial area that makes the 4-valve underside exhaust incommensurable to the well-known and proven 2-valve exhaust...
If You find a solution of striking simplicity to this issue, You'll surely take credit for its development throughout the whole aircooled world...
BTW...
in 1980's Group C series, Porsche "cheated" around that issue by putting watercooled 4-valve heads on their otherwise aircooled Flat-6' in the 956 and 962 series race cars...
Cheers,
BugUser |
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Jake Raby
Samba Member
Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Wed Sep 05, 2007 8:26 am Post subject: |
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Multiple exhaust valves CAN cause over temp issues, just as a single exhaust valve can that is too big too be suported by the port or exhaust system.
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Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
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aawright18
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Joined: June 13, 2012
Posts: 39
Location: Riverside
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| Posted: Mon Jun 02, 2014 8:34 pm Post subject: |
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Hey i know this post is long dead but maybe the op will see.
I like that Cad image is that solid works you used?
Did you ever try creating a usable prototype?
I am in school for Mechanical engineering and am thinking some something similar but for a cam-less servo motor valve actuation.
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VWporscheGT3
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Joined: September 01, 2006
Posts: 2180
Location: Gardnerville, NV
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| Posted: Tue Jun 03, 2014 9:53 am Post subject: |
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| BugUser wrote: |
BTW...
in 1980's Group C series, Porsche "cheated" around that issue by putting watercooled 4-valve heads on their otherwise aircooled Flat-6' in the 956 and 962 series race cars...
Cheers,
BugUser |
they were also Dual Turbocharged... more heat/strain on the cooling system, at that point it was more effective to water-cool the heads.... that is a point I think you are missing.
lmao... i just realized his post was in 2007 ... lol sorry 
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