Head flow testing.

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THIS is a Velocity Stack / Concentric

Head flow testing.


& Mk II

Head flow testing.


Particularly relephant for the Mk 1 otherwise theres trouble . :p

http://www.amalcarb.co.uk/ProductCatego ... arentId=28
 
comnoz said:
worntorn said:
If a screen does that, what happens with an air filter on the carb?

Glen
Click to expand...

An air filter hardly affects the flow- an air filter has a lot more area so the air velocity through the element stays low. A screen causes problems when you try to move the air through it at a high speed. A vortice is created at each wire and plugs the holes. Try holding a window screen out of you car window and going for a drive - it will act just like a piece of plywood when the wind hits it. Jim
Click to expand...

I know you have other priorities right now but did you flow test larger screens like this?

Head flow testing.
 
From what I`ve seen those wire-gauze flame traps are flow killers, better to try a correct K & N properly mounted, possibly even with a U-bend connecting them end-to-end so each cyl can breath through both [& collect/re-use over-lap blow-back].
 
Thats a nice anecdote, but numbers of independant flow tests [inc engines on dyno as well as air meters] show that a correctly sized K & N will flow as well [even when dirty ], as a new foam or paper element filter, factory riders get to toss their foam/paper filters out after every use, so it dont matter to them. Of course if you were running a 2- stroke, you would n`t even need to oil them either..
 
swooshdave said:
comnoz said:
worntorn said:
If a screen does that, what happens with an air filter on the carb?

Glen
Click to expand...

An air filter hardly affects the flow- an air filter has a lot more area so the air velocity through the element stays low. A screen causes problems when you try to move the air through it at a high speed. A vortice is created at each wire and plugs the holes. Try holding a window screen out of you car window and going for a drive - it will act just like a piece of plywood when the wind hits it. Jim
Click to expand...

I know you have other priorities right now but did you flow test larger screens like this?

Head flow testing.
Click to expand...

No I can't say as I have tried the coarse screen. I suspect it would be better than the fine screen but not as good as a real filter. Jim
 
Airbox , with a flat pare / fram filter at the junction into the plenum , with the carbs in the plenum , is theoretical satisfactory .
Ram Air tubes from high pressure area ( Like a F-750 Trident fairing , similar to JPS ) aft to the ' air box ' , no kinks or sudden
changes of direction .
 
Here's something else to ponder in intakes and corners. Mostly used to straighten air flow so more constant velocity across the diameter of intake passage. Screens also even flow speed across a tube d/t breaking up turbulence swirls to smaller size. Another turbulence vs resistance compromise of course.

http://navier.stanford.edu/bradshaw/tun ... ycomb.html
Head flow testing.
 
Yeah, some of that honey-comb matrix [dont mention the singularity- oops I think I just did, nevermind...]research was done back in the day when high-speed liquid-cooled aircraft designers were working on getting a net flow increase from radiators rather than a drag penalty.
 
From my work in the fire department, our training on ventilating buildings tells us that a screen over a window reduces flow by 50 percent. On the performance-engine side, David Vizard (author of many tuning books) showed drastic drops in power/flow with screens fitted over velocity stacks. I think I read that stuff in his Tuning BL A-Series book.

For what it's worth, I ran my 500cc MSS (with Venom head and the /8 cam, for those who care) on a Dynojet dyno both with and without an oiled-foam filter and it made the same curves from top to bottom. On a previous build of this engine, I had run it without an air filter for about 2000 miles. When I tore it down and saw the cylinder wear, I decided that any minor benefit I might get from running no filter in the short term was far outweighed by power loss from wear in the bore and from diminished valve sealing. I always filter my inlet air. But I'm not a racer. If I were a racer, I would run a filter to preserve that bitchin' 3.8 percent leakdown I would surely achieve through careful machining and assembly...

I'll add that the Venomized MSS is no fire-breather in the grand scheme and certainly not a high-compression, high(er) rpm, flow-optimized engine. But it has a great valve job, Nikasil bore and a Carillo rod.
Mark
 
Those Nikasil bores are worth protecting, all it takes is a spray of hard [sand,metal & etc] debris which could pass a gauze screen, I note too, that NASCAR utilize wire-gauze screens over air vents to preserve aero-dynamic flow by preventing excess air entry drag penalties at high speed.
 
Honey comb and Screens only keep stones out not grit and are only used in air streams to even the velocity better across a port diameter and can be made up for by more fan power in stationary wind tunnels. Honeycomb evens up the major turbulence swirls but tend to leave smaller ones further down stream than screens, which are place after to finish the smoothing task.

Size of surface area is the major factor in good filters, bigger is better no matter the filter element. If can be constructed to even flow into intake all the better, ie: least penalty for protective resistance.

I was recently informed Ms Peel's early CHO head has such sharp bend not even worth setting up to measure flow, it won't be good news.
 
J.A.W. said:
Those Nikasil bores are worth protecting, all it takes is a spray of hard [sand,metal & etc] debris which could pass a gauze screen, I note too, that
NASCAR utilize wire-gauze screens

over air vents to preserve aero-dynamic flow by preventing excess air entry drag penalties at high speed.
Click to expand...

Wire Gauze is also a FLAME TRAP . 8) this can be quite usefull , at times . :shock: :mrgreen:
 
Here is a test on a head Ken Canaga sent me some time ago. [bet he was thinking he would never get it back].

It is an Axtel modified 750 head. The intake ports are at 30 mm with stock sized valves. I was impressed with what I saw. After testing it I can see why Axtel's motors were good ones.

The blue line is the Axtel head. The green line is a RH4 head that someone polished up a bit. Not a big increase in numbers but remember the port is smaller.

Head flow testing.


Here is the big difference. Just a little smaller port and a little more airflow does great things to the velocity. This is among the highest velocity numbers I have seen for a stock casting. The colors are reversed with the green line being the Axtel head. Jim

Head flow testing.
 
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