AFR220 port swirl?

highVE · Post by **highVE** » Sat Jul 30, 2005 6:37 pm

I"m wondering if anyone has any info. on the port swirl characteristics of AFR 220 racing heads cnc'd (sbc) i'm only asking cause to my surprise of how much power the made. I'ts a 434ci 13.4:1 static cr, unported dart intake w/a 950cfm 4150 HP. i'd rather not type all the specs of the engine do to it's to much to type. it made 689 hp. i flow tested the heads after purchasing them for the customer, i got close to what AFR advertises (308 cfm @.700 int. 236 @.700 exh) good numbers but what i thought was hardly enough to fill those big cylinders at 7500rpm. any thoughts?

Mike

www.mikesportingservice.com

highVE · Post by **highVE** » Sat Jul 30, 2005 6:39 pm

Of course i will remove the intake and to work to the plenum. i would like the see the 725hp mark,

cboggs · Post by **cboggs** » Sat Jul 30, 2005 6:53 pm

Mike,

The CnC AFR stuff can benift from some hand work, ..
short turns, .. etc. I've had those heads flow over 320's.

I did some swirl meter tests early in my development of
their ports, .. don't show anything more then other ported heads, ..
they just have a decent cross section.

Curtis

Joe Mendelis · Post by **Joe Mendelis** » Sat Jul 30, 2005 8:03 pm

Why do you think swirl is the reason that engine made power?

highVE · Post by **highVE** » Sat Jul 30, 2005 8:16 pm

The reason i considered these heads possilbley having a highly port swirl charachterisitcs. is the lack of flow numbers . granted 308 isn't bad, and they had very strong mid lift numbers as well. however port swirl makes incredable hp. in some cases more important than just cfm. a freind of mine ported heads for steve shcmidt (some pro-stock stuff) and a couple of years back they were doing some R&D on some ports, and they came across a port that flowed 12cfm less @.900, but had better port swirl and made 9 hp @9100rpm. Again, different applications react differently to engine dynamics. but it was just a thought. i don't have a swirl meter on my bench, so i can not measure it.

cboggs · Post by **cboggs** » Sat Jul 30, 2005 8:54 pm

Joe, let's see if you agree, ..

I think too much swirl is a bad thing, .. I don't like a bunch of swirl
in my ports.

Wet flow & air speed however is important and would be my guess
why the pro stock port made more power then the better flowing port.

Overall there's much more to this then just a cfm number or a bunch of swirl
etc, .. it's also the proper cross section for the combination, .. air speed, ..
overall mixture motion and wet flow.

Again I've tested the AFR ports on a swirl meter, .. I wouldn't say they
have a large amount of swirl type mixture motion.

Curtis

Joe Mendelis · Post by **Joe Mendelis** » Sun Jul 31, 2005 3:21 pm

cboggs wrote:Joe, let's see if you agree, ..

I think too much swirl is a bad thing, .. I don't like a bunch of swirl
in my ports.
Curtis

I think you want enough mixture motion to stabilize combustion. You want similar mixture motion in every cylinder. The higher peak pressure the cylinder sees, and the shorter effective burn angle the engine has, the less mm you need.
Too much swirl will hurt flow. It takes energy to make swirl. So yes, I definitely agree that too much swirl is bad.

cboggs · Post by **cboggs** » Sun Jul 31, 2005 4:39 pm

Joe,

Do you think the current trend in small chambers, .. lots of "squish" area,
is enough mixture motion in the chamber to stabilize combustion?
Does this allow us to reduce swirl and gain flow & power?

I tend to look for mixture motion in other ways then swirl, .. like the velocities
exiting the valve / curtain area, .. and the effects of the mixture motion
exiting the valve on wet flow in the chamber.

I think you do need a little swirl, .. but with current design cylinder heads
I'm starting to "like" less & less.

On a small block Chevy conventional style head, .. it seems like too much
swirl will toss the fuel out of suspension and cause raw fuel to run around
the cylinder wall.
Have you seen this?????

My wet flow equipment IS rather crude, .. I'm hoping to by a unit from
Mondello soon.

Curtis

Joe Mendelis · Post by **Joe Mendelis** » Sun Jul 31, 2005 6:19 pm

cboggs wrote:Joe,

Do you think the current trend in small chambers, .. lots of "squish" area,
is enough mixture motion in the chamber to stabilize combustion?
Does this allow us to reduce swirl and gain flow & power?

Yes, and with shallow valve heads with high ports the distribution of air and fuel is better so wetflow is better. Then the engine takes less timing and can be run with more compression, further enhancing combustion.

I tend to look for mixture motion in other ways then swirl, .. like the velocities
exiting the valve / curtain area, .. and the effects of the mixture motion
exiting the valve on wet flow in the chamber.

That sounds like a good idea. Do you use a magnehelic gauge to check velocity around the valve?

I think you do need a little swirl, .. but with current design cylinder heads
I'm starting to "like" less & less.
I agree there too.

On a small block Chevy conventional style head, .. it seems like too much
swirl will toss the fuel out of suspension and cause raw fuel to run around
the cylinder wall.
Have you seen this?????
I have seen that in the chamber. How far down the wall do the marks go past where the first ring land is positioned when the piston is at TDC?

My wet flow equipment IS rather crude, .. I'm hoping to by a unit from
Mondello soon.
Crude equipment is way better than NO equipment.
Curtis

Thank you for your opinion Curtis.

Joe Mendelis · Post by **Joe Mendelis** » Sun Jul 31, 2005 6:21 pm

Sorry about the above post. I didn't realize you wouldn't be able to distinguish what I wrote from yours Curtis.

cboggs · Post by **cboggs** » Sun Jul 31, 2005 6:49 pm

Joe,

I'll see if I can make heads or tails of the above post, ..

Looking at velocity out of the valve / curtain area, ..
I turn the head around on the bench so it blows into the intake port
and exposes the chamber so I can probe with a pitot tube.

As for "tossing" the fuel out of suspension, .. the more swirl there is
the less distance down the chamber it seems to go, .. and concentrate
more at the top of the bore and in the chamber.

Joe, .. your thoughts on this??, .. have you done the same tests
and seen the same things??

Curtis

Post by **ou812** » Sun Jul 31, 2005 7:50 pm

how do you adapt the intake to the bench Curt???

Brian

cboggs · Post by **cboggs** » Sun Jul 31, 2005 9:05 pm

ou812 wrote:how do you adapt the intake to the bench Curt???

Brian

Yea, just like Mondello's wet flow system, .. mount the intake face to the
bench, .. chamber faces out away from the bench. I then clamp
my bore adaptor to the head so I have a bore but can get to the valve
to probe with a Pitot.

Curtis

Joe Mendelis · Post by **Joe Mendelis** » Sun Jul 31, 2005 9:53 pm

cboggs wrote:Joe,

I'll see if I can make heads or tails of the above post, ..

Looking at velocity out of the valve / curtain area, ..
I turn the head around on the bench so it blows into the intake port
and exposes the chamber so I can probe with a pitot tube.

As for "tossing" the fuel out of suspension, .. the more swirl there is
the less distance down the chamber it seems to go, .. and concentrate
more at the top of the bore and in the chamber.

Joe, .. your thoughts on this??, .. have you done the same tests
and seen the same things??

Curtis

Curtis, what type of pitot tube do you use to get near the valve with a bore adapter on there? Is it just straight?
I haven't done tests like that. I have just seen 23 degree heads that have problems like that.
That would make sense that the more swirl you had the fuel would be moving laterally with even greater force so the helix angle would be lessened.

cboggs · Post by **cboggs** » Sun Jul 31, 2005 10:52 pm

Joe,

yes I just use a strait pitot tube, ..

Curtis