What causes swirl

[bob664spd]

Hi Everyone, I am the newest new guy. My name is Bob. I cant belive I was lucky enough to find this site. I have been reading and was wondering what causes swirl in the runner and if it can be measured? And if turbulance has anything to do with it? I havent built a bench yet but have been thinking about it for awhile and I think it is time. Thanks for any thoughts on this.

[maxracesoftware]

Inside Cylinder Swirl
or
Inside Bowl Swirl ? ( Bowl to Curtain Area )

[bob664spd]

I think I am talking about bowl swirl. I think this is what makes a good mixture. I have not done a lot of testing but am wondering if it is the shape of the runner approaching the bowl . How would you measure this?

[blaktopr]

Every time ( I ) see bowl swirl, ( so far ) I have an attachment problem.

[maxracesoftware]

[blaktopr]

Larry, the more heads I test, the more I learn. I have found in an aftermarket ported by other head, where velocities are high at the pinch and ssr, and flows an ok number with a large throat, that there is swirl in the chamber because of the air going right over the valve and exiting mostly on the long side. I personally don't like how uncontolled the air exits out through the seat. Plus the fact that the csa's and speeds are not where they should be. Reason for my thinking is because I shaped a few other heads to have a more uniform exit and a better distribution seen with liquid. Other thing I also notice with this air over valve is it happens with a separation over the ssr on low port (1/2 above seat to apex) type heads when trying to get locals "correct" for the flow. Your thoughts? I gotta stop before writing a novel.

Chris.

[maxracesoftware]

[Tony]

My understanding of this is that swirl is not a high rpm power producer.

What it does do, is promote better mixture distribution and combustion at lower rpm and smaller throttle openings. So high swirl may be of definite advantage in street engines where economy and lean running without misfire are fairly important.

At flat out power producing rpm, air velocities will always be high enough to give good mixture distribution, and break up with very little deliberate induced swirl.

The now ancient original six cylinder Jaguar engine had two very different cylinder heads available for it. The one fitted to most of their passenger cars had the curved offset inlet port to promote swirl. The E type Jaguar had perfectly straight inlet ports located right on the bore centres, and this cylinder head was always preferred for racing development because of this feature.

I have never seen a purpose built high rpm racing engine with offset swirl producing inlet ports. But mild production engines are very often built this way to produce a much more fuel efficient engine at the rpm and loads normally seen by a street engine.

[thomasvaught-1]

Swirl used to be the hot topic at one time. We tend to limit the swirl and concentrate more on the tumble ratio for current heads. I too remember the old swirl strain gages.

Tom Vaught

[Half-Inch Stud]

ER yeap: GM looked into the CYL for Swirl-inducing techniques (Piston top shapes & Chamber shapes). Basically concluded that kind of "Swirl Technology" had no advantage.

ER ah yes: Intake runner to Head runner to valve "Swirl" will DEFINITELY have an advantage. MY statement is foundational on; "The desire Propagation mode must be launched/induced for maximal mass air flow". <-- let's define "Swirl" as the Desired propagation mode to support our CYL Filling goals.

Definition of "optimal propagation mode": A well defined movement versus distance travelled that sustains the equation of Velocity & Mass = a constant.

Either SINGLE-Mode: a singular air movement behavior versus distance traveled.

[thomasvaught-1]

Mark, stick to English for the people here. There are a lot of different levels of knowledge here and everyone is trying to learn at their own pace. "NASA SPEAK" will impress some but will drive away many. You have 7 posts, start off slow.

Tom Vaught

[Half-Inch Stud]

Roger that Tom. I'm still in jack-rabbit start mode with the Flow Bench activity.