[Land-speed] Intake Manifold Question(s)

[Larry Mayfield]

Plenum is to be made from 4 in sq tube, 1/8 wall for a 3.75 sq inside 
dim. and about 14 inches long. That covers all the runners and provides 
about 196 cubic inches. Plus the TB mount on the side will hang out a 
couple of inches for a few more cubic inches. And the motor will have a 
new smaller displacement. Will come pretty close to 2/3 displacement 
size. Important? I don't know. Wont be the first thing I have tried that 
didn't pan out, lol.

Curious as to the technical aspect of why some roughness or smoothness 
is needed. Seems to me that the smoother the walls the smoother the flow 
because of boundary layer thniness, ie velocity profile is improved.  
Again, I have no real insight to this though.

______________________________
drmayf
Worlds Fastest Sunbeam, period.
204.913 mph flying mile
210.779 mph exit speed


On 6/5/2011 9:24 AM, Dave Dahlgren wrote:
> 36 to no finer than 60 grit is just fine.
> You will be hard pressed to build a 200 cu in plenum...
> 10 X 5 X 4 =200 and will not reach the end runners very well.
> ----- Original Message ----- From: "Larry Mayfield" <drmayf at mayfco.com>
> To: <land-speed at autox.team.net>
> Sent: Sunday, June 05, 2011 11:48 AM
> Subject: [Land-speed] Intake Manifold Question(s)
>
>
>> Ok, those of you who consider me a crank can hit delete now, lol....
>>
>> I am making or revising an old manifold for use on the Sunbeam. I 
>> notice that the runners are pretty dog gone rough and I want to do 
>> port matching and polishing.  My questions have to do with the 
>> smoothness of the air flow in the runners.  This is an EFI manifold 
>> so it is what I would call dry. No fuel in the manifold. So do I want 
>> a really smooth runner wall or rough? If smooth just how smooth? 
>> Should I have it extrude honed for smoothness and removal of any 
>> small turbulence generators? If really smooth would coating the 
>> runner walls with glyptol be a good thing? That stuff drys to a hard 
>> finish and is pretty slippery and dang near impervious to oils and 
>> anything else.
>>
>> The manifold will be a short runner box with a plenum about 2/3 size 
>> of the engine displacement (an old rule of thumb I once heard and 
>> maybe be invalid) for use with my HP72 turbo(s).
>>
>> Thoughts, comments, ideas? I'll listen to them all....
>>
>> Just going to try and increase the Sunbeams speed over the old first 
>> Sunbeam top speed.  Class record speeds are way beyond my 
>> capabilities and pockets, lol...
>>
>> --