flow theory

[mercrazy]

what do you motor wizards think about putting a ripple effect on the air flow passages in an engine?
doesn't 'moving air' cling to the adjacent surfaces?
i guess it has to be high speed before the cling effect will develop.
helmuts with ridges are designed to break surface tension.
if the engine had ridges like that only smaller, wouldn't the air pass through more easily?
they should be sized according to flow velocity.
what is the typical flow velocity range around 7-8000rpm?
is the velocity high enough to develop the cling effect?

[Mark75H]

Any ripples or bumps are detours that slow down flow. A straight shot with no ripples or bumps flows more than a polished passage full of ripples, dips and doglegs arranged in a pattern or random.

Ripples arranged parallel to the flow direction would just be minor intrusions into the path. Little arrows painted to show the air molecules which way to go would work just as well or better. ;)

I haven't done any speed calculations on intake velocity, but I have a theory that the reason you hear a really tremendous intake roar at low/mid-range speeds is that the intake velocity is below the speed of sound. As a motor speeds up and the deafening intake roar decreases my theory is this is because the intake roar is actually being sucked in faster than the speed of sound.

Actual intake velocity probably varies quite a bit from motor to motor. I don't think it would be too much of a problem to calculate an estimated intake velocity based on carb/inlet horn size, rpm and motor displacement. Velocity will vary through the intake system. It will be highest where the passage is smallest and lower where the passage is bigger.

[gtsmpuc]

but when you polish the intakes on car motors I believe they use 80 grit wheels because if oiu get hem to smooth it takes a way from the atomization process. It keps teh air jsut slightly disturbed. Jay will porbably know more about this.

[Greg Moss]

I just installed a set of CNC ported heads on a 598 Big block that had slight wash board look to the intake. I think that the ripples do keep the air from sticking to the walls of the ports and slowing the volocity of the charge. I know all the top porters tell you not to polish the intake to smooth. when I port a motor I always polish the intake with the sanding grooves at 90 degrees to the flow of air. Sam I am not so sure about the sonic volicity of the air in a motor but I don't think it is above the speed of sound. I think the reason that the top end motor sound may not be so load to you is the air rushing past you ears is louder than the noicwe behind you. I have run motors on my dyno at WOT and they are Loud SOBs. At WOT running the wind noise will drown out the motor noise just like in a airplane all the noise you hear in a airliner is wind against the outside of the plane not the motors.

[T-REX]

They both have thier place in tha route to tha exhaust exit!!!...Polish the inlets to the point of the gas entering the picture...from there to tha point of entering the cyl, ripple or heavy bbead blasting iz tha way to go...exhaust port outward should be az smooth az possible...I will probablly git arguements about this, but It haz always worked for me...the ripples work the same way as the steps in the bottom of a boat, and keeps the gas from dropping, or clinging to the intake walls...Thats my story,, and I'm stick'in to it...REX:cool:

[KeninSC]

The Rex is right. Dry = polished, Wet = rough.

[B.Leonard]

Mark;

Interesting theory on the sound effect. I remember in my hot roddinng days as a kid flipping the lids on air cleaners just to hear the howl at WOT!

Some of the most stock motors sounded the meanest! I think the restrictive exhaust (and everything else) really slowed the flow down to where you could hear everything.

I remember one stock 2bbl 350ci MonteCarlo that had the lowest meanest howl you have ever heard! It was a dog but sounded so mean at WOT! Gotta love the learning process :)

The more hopped up the motor, the howl gradually turned into a scream where you were probably hearing the increased air flow over the deep vacuum howl.

-BL

[Craig Knight]

Any body know the real story on bored out air horns vs. stock Merc air horn. I have a 2.5 drag with a bored horn and it seems a little lazy!

[laser]

John Tiger Jr had an article a while back in hot boat concerning SVS vs Stock Merc Horn vs Bored Merc Horn. The results were:


SVS kicked ass - 1 second quicker in 1/4 mile
Stock Horn - Baseline
Bored Horn - Slower than stock, poor response


I can try and find the issue if your interested.

[Craig Knight]

Hey Laser,

Must be my lucky day, some real data to look at!
Please find that for me. I will be gone over the weekend so if I dont catch you tonight it will be monday.

>>>>>>>thanks<<<<<<<<<

[Jay Smith]

And with my cuts to the Plenium and reed plates it picks up even more !


And T-Rex you old fart go back to sleepyou know it past bed check at the home !! :)


( but he is correct , wet needs rough, dry needs smooth,and exhaust needs chrome slick or at least thats what works for me )!

Jay @ JSRE

[laser]

Craig, here is the data I mentioned. I could scan the whole article and then send you a link. It would be far to large to post the images here.

http://www.me.mygarage.com/hb2.JPG

[Tony Brucato]

Craig,

I've got the reprint of that article on my website.
The link is http://brucatosvs.com/hp_sept.html

[laser]

Good job, keep up the good work.

[imq707s]

Usually on hi-po automotive heads, that intake ports are smoothed out with 80-grit paper so you end up with a slightly rough finish. This not only keeps the fuel atomized, it keeps that fuel from puddling. Then on the exhasut ports, you want to polish them up as slick and shiny as possible to aid in exhasust flow. I think and kind of ripples or ridges in the intake would just disturb the flow, and probably collect puddles of fuel.

[T-REX]

Are U gunna make it to Jasper??? That Hydro spote would raelly look good and will pick up about 10mph if dat stripe wuz ORANGE!!!!;) , Later REX

[BilDewey]

It is not as crucial on a 4 stroke to have the swirl marks or flapper wheel marks as it is with a two stroke. The intake valve has a tendancy to add to the swirl effect which keeps the fuel/air in suspension. All of the heads I've proted I still leave it a little rougher than the exhaust and finish with an 80 grit flapper wheel. I try to get the exhaust as smooth and polished as possible.

Bill

[Tony Brucato]

Hey T-Rex,

http://www.brucatosvs.com/Zoom1orange.jpg

It looks faster. Will I have to re-prop?

I'll be in Jasper as a spectator, see ya there!

[T-REX]

I kan tell it's faster...I don't know bout tha prop though...kan't expect me ta solve all ya problems:D See ya @ Jasper, REX