How much swirl is too much swirl

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Bryan Maloney
New Member
New Member
Posts: 34
Joined: Wed Feb 27, 2013 3:04 am
Location: Martinsville VA

Re: How much swirl is too much swirl

Post by Bryan Maloney »

maxracesoftware wrote: Sun Sep 19, 2021 4:41 pm
by Bryan Maloney » Sun Sep 19, 2021 2:53 pm
I observed almost the same thing years ago after adding reverse swirl fins to a pair of 18 degree Chevy heads on an open ARCA engine. Picked up 8-13 cfm on the bench, but no power increase on the Dyno.
was that on Race Gasoline ??
any Dyno Tests with Methanol w/Bowl Swirl Fin ??

here's Pics of ProAction 14 deg SBC Heads on 406cid
Looses 90+ HP @ 9400 RPM with Bowl-Swirl Fin only on "Methanol"
makes 1005 HP @ 9400 RPM "without" any Bowl Swirl Fins
and without anyother trick Fins :)
Runs quickest down the Dragstrip "without" any Trick Fins !

You can get away with "Trick Fins" with Gasoline
but Methanol is a different story !!!
On Year 2020 NHRA Comp Eliminator Champion Craig Bourgeois's A/ND 14deg=1024HP and B/ND 23deg=1005.2 HP Heads
( highest Tq and HP Curve is with 4.7 to 4.85:1 Air/Fuel Ratio on both 14deg and 23deg )
with Methanol ....there are no "Trick Fins" ... just straight forward Porting !

Note : the Chrysler ProStock Truck Heads Bowl Swirl-Fin were even a little more drastic than these Pics ... but were only run on Race Gas , no Methanol tests !

a Bowl Swirl-Fin is "worthless" on Methanol ,
also i always gain HP , as much as 40 HP so far ,
grinding away Swirl-Fins in various LS-type Heads + reworking Short turn Curve -to- Floor Apex area
to compliment me removing that Bowl-Fin !

pretty drastic when you see Piston's Gas-Port hole combustion so deep inside the Chamber
( on the Deck surface , yes, but so deep into the Chamber , no ! :evil: )
i doubt anyone seen anything like this before ???

"How to Lose 90+ HP on Methanol"

Hi_Vortex_Bowl_Fin_18.jpg
Hi_Vortex_Bowl_Fin_17.jpg
Hi_Vortex_Bowl_Fin_15.jpg
Hi_Vortex_Bowl_Fin_13.jpg
Hi_Vortex_Bowl_Fin_5.jpg
Larry, all of our testing was with gasoline.

The fins that are in your heads in the photos are really extreme. The siamese port wedge heads don't seem to run well with extreme fin trickery. I think any fin needs to be a smooth continuation of the port; not an extreme dam.
KIMG0043.jpg
You do not have the required permissions to view the files attached to this post.
maxracesoftware
Vendor
Posts: 3627
Joined: Sat Feb 14, 2004 4:04 pm
Location: Abbeville, LA
Contact:

Re: How much swirl is too much swirl

Post by maxracesoftware »

by Bryan Maloney » Tue Sep 21, 2021 9:05 am

Larry, all of our testing was with gasoline.
The fins that are in your heads in the photos are really extreme.
The siamese port wedge heads don't seem to run well with extreme fin trickery.
I think any fin needs to be a smooth continuation of the port; not an extreme dam.
Those Bowl Swirl Fins gained +15 CFM on the Flowbench ... basically same gains as Chrysler ProStock Truck Heads
and lost 90 HP on Methanol , and on the Dyno made way more HP on Race Gasoline than on Methanol, ( which is an opposite outcome ! )
but even on Race Gas was still down a bunch of HP compared to Bourgeois's Heads on Methanol ! ( which is as it should always be )
On the Chrysler ProStock Truck Heads , it didn't hurt anywhere , but didn't help out either, even though it gained +15 CFM !

Bryan,
thanks a whole bunch for sharing all that nice Data + Pics
you've taken Swirl tests to a much higher Level :shock:

i just have Oz's Digital Swirl Torque Meter ... nothing anywhere as good as you or your Data !
i painted a thin bright radius line across the Honeycomb
so i could see "Swirl Jitter" during Flow testing by looking thru clear Plexiglass Flow Bore Fixture .
MaxRace Software
PipeMax and ET_Analyst for DragRacers
https://www.maxracesoftwares.com
Gobrdgo
New Member
New Member
Posts: 3
Joined: Fri Sep 17, 2021 3:19 pm
Location: Socal

Re: How much swirl is too much swirl

Post by Gobrdgo »

Thank you for all the great replies. Not gonna lie it’s a lot to wrap my head around. Need to spend some time studying my notes and see the patterns.
Bryan Maloney
New Member
New Member
Posts: 34
Joined: Wed Feb 27, 2013 3:04 am
Location: Martinsville VA

Re: How much swirl is too much swirl

Post by Bryan Maloney »

Gobrdgo wrote: Fri Sep 17, 2021 10:29 pm I thought tumble was a 4 valve only thing? Am I in correct on that?
Four valve heads will be no NET swirl unless inlet steering or staggered valve size/timing induce swirl.
Hemi heads will be no NET swirl unless the intake trajectory or pushrod tube staggering induce some swirl.

There can be small pockets of localized swirl, even though net swirl is zero.

Tumble is the primary mixture motion in the above types of heads. It can be hindered or helped depending on if the piston has a dome or dish.
Tumble characteristics can vary greatly depending upon port short-turn and "chimney" height.
Chopping the short-turn away, and making the roof line low, can create extreme in-cylinder tumble. We only did this for an experimental hybrid engine that was throttled by EGR percentage, and needed extreme in-cylinder mixing.
User avatar
Mummert
Expert
Expert
Posts: 692
Joined: Mon Aug 06, 2007 4:24 am
Location: El Cajon CA

Re: How much swirl is too much swirl

Post by Mummert »

Bryan Maloney wrote: Sun Sep 19, 2021 2:43 pm
hysteric wrote: Sun Sep 19, 2021 7:52 am
Bryan Maloney wrote: Sat Sep 18, 2021 11:20 pm If you can do some wet flow testing on your cylinder head, you will be mesmerized by what you see. It will tie in with your swirl and tumble observations.
Did you see a net gain in performance by improving swirl?
No, our goal was to prevent the swirl from ramping up so highly at high lift. When the goal is cylinder filling, we wanted the air column helix to chase the piston down the bore and not sling the fuel into the cylinder walls.
Sound about right.
Mummert Machine and Development 4 stroke hp
Mummert Y-blocks
hysteric
Pro
Pro
Posts: 222
Joined: Sat Apr 04, 2009 2:03 am
Location:

Re: How much swirl is too much swirl

Post by hysteric »

Bryan Maloney wrote: Tue Sep 21, 2021 9:37 am
hysteric wrote: Sun Sep 19, 2021 4:38 pm
Bryan Maloney wrote: Sun Sep 19, 2021 2:43 pm

No, our goal was to prevent the swirl from ramping up so highly at high lift. When the goal is cylinder filling, we wanted the air column helix to chase the piston down the bore and not sling the fuel into the cylinder walls.
Street engines with low valve lift may benefit at low RPM from additional swirl; the valve L/D never gets high enough to where the swirl naturally spikes.
The often maligned reverse-swirl "Elkins fin" behind the intake guides can be beneficial in moderation. Some OEM's take this feature to the extreme.
A "Glidden fin" along the centerline of the floor of the intake port can add flow stability and help limit high lift swirl.
Thanks Bryan, did you experiment with different droplet sizes? Also at what L/D's was it evident that spiking occurred?
We did not vary droplet size. The fluid was a mist leaving the booster. The swirl ramped up after .500 lift using a 2.170 valve.

Note in the photo there are two vortices in the chamber; one above and to the left of the intake valve and one between the plug and the exhaust valve. Just as there can be tornadoes within a hurricane. Swirl testing rigs are only showing net swirl, wet flow shows the motion is much more complex.

This photo does not do justice to what you actually see in motion. Everyone that has seen this in action has been mesmerized.


Effect_20210921_091526.jpg
Thanks Bryan. Would be interesting to see what the chamber and piston look like after some runs to see how that corresponds to the data. Was the ramp up after .500 lift dramatic or a steady rise?

Also does the swirl testing allow for different piston top locations in relation to cam lift or is it just steady state testing with different valve lift?

Thanks gain.
hysteric
Pro
Pro
Posts: 222
Joined: Sat Apr 04, 2009 2:03 am
Location:

Re: How much swirl is too much swirl

Post by hysteric »

The piston and chamber coloring looked phenomenal after racing them.
Can you elaborate in the difference between the 2?
Bryan Maloney
New Member
New Member
Posts: 34
Joined: Wed Feb 27, 2013 3:04 am
Location: Martinsville VA

Re: How much swirl is too much swirl

Post by Bryan Maloney »

hysteric wrote: Wed Sep 22, 2021 12:14 am
Bryan Maloney wrote: Tue Sep 21, 2021 9:37 am
hysteric wrote: Sun Sep 19, 2021 4:38 pm

Thanks Bryan, did you experiment with different droplet sizes? Also at what L/D's was it evident that spiking occurred?
We did not vary droplet size. The fluid was a mist leaving the booster. The swirl ramped up after .500 lift using a 2.170 valve.

Note in the photo there are two vortices in the chamber; one above and to the left of the intake valve and one between the plug and the exhaust valve. Just as there can be tornadoes within a hurricane. Swirl testing rigs are only showing net swirl, wet flow shows the motion is much more complex.

This photo does not do justice to what you actually see in motion. Everyone that has seen this in action has been mesmerized.


Effect_20210921_091526.jpg
Thanks Bryan. Would be interesting to see what the chamber and piston look like after some runs to see how that corresponds to the data. Was the ramp up after .500 lift dramatic or a steady rise?

Also does the swirl testing allow for different piston top locations in relation to cam lift or is it just steady state testing with different valve lift?

Thanks gain.
The swirl torque is in the next to last column. The ramp up is fairly severe.
Effect_20210921_091526.jpg
The swirl measuring was with a one inch thick honeycomb in the flow adaptor of one of our SF 1020 benches. So no dome or dish simulation. This honeycomb knocked the raw airflow values in the right column down about 15 cfm from what recall.

We performed the wet flow testing at .400, .600, and .800 lift. The photo I attached previously was at .800 lift.
You do not have the required permissions to view the files attached to this post.
Bryan Maloney
New Member
New Member
Posts: 34
Joined: Wed Feb 27, 2013 3:04 am
Location: Martinsville VA

Re: How much swirl is too much swirl

Post by Bryan Maloney »

hysteric wrote: Wed Sep 22, 2021 12:24 am
The piston and chamber coloring looked phenomenal after racing them.
Can you elaborate in the difference between the 2?
Our long rod, gasoline fueled restrictor plate engine with moderate reverse-swirl fins had almost perfectly uniform carbon buildup and coloring in the chambers and on the piston domes. This was back around 1993.
BLSTIC
Expert
Expert
Posts: 869
Joined: Wed Dec 05, 2018 7:14 pm
Location:

Re: How much swirl is too much swirl

Post by BLSTIC »

Bryan Maloney wrote: Tue Sep 21, 2021 2:46 pm Chopping the short-turn away, and making the roof line low, can create extreme in-cylinder tumble. We only did this for an experimental hybrid engine that was throttled by EGR percentage, and needed extreme in-cylinder mixing.
What changes did you note from that experiment?

I wanted to do this to a quenched hemi that had more airflow than it needed for the valvetrain restricted RPM it could reach (and sensible street duties). The lower 'before' picture was after someone cut the inlet port with some kind of ball mill apparently. Green in the upper picture is roughly where I think the stock port would be. Blue is fill, red is cut. The plan was to add tumble, velocity, and boost. The engine stock was only using 210hp of its "330hp" head potential, so there's a lot of excess flow to play with.



proposedport.jpg
You do not have the required permissions to view the files attached to this post.
hysteric
Pro
Pro
Posts: 222
Joined: Sat Apr 04, 2009 2:03 am
Location:

Re: How much swirl is too much swirl

Post by hysteric »

Bryan Maloney wrote: Wed Sep 22, 2021 2:17 am
hysteric wrote: Wed Sep 22, 2021 12:24 am
The piston and chamber coloring looked phenomenal after racing them.
Can you elaborate in the difference between the 2?
Our long rod, gasoline fueled restrictor plate engine with moderate reverse-swirl fins had almost perfectly uniform carbon buildup and coloring in the chambers and on the piston domes. This was back around 1993.
Thanks Bryan, I appreciate the replies as its a very interesting subject indeed.
hoffman900
HotPass
HotPass
Posts: 3445
Joined: Sat Feb 23, 2013 5:42 pm
Location:

Re: How much swirl is too much swirl

Post by hoffman900 »

Bryan Maloney wrote: Sat Sep 18, 2021 11:20 pm We had swirl, tumble, and wet flow test equipment available as part of Dodge's Nascar effort from 2000 to 2012.
We measured swirl as rotational torque with a honeycomb insert and a rotary strain gauge. Tumble was measured on another fixture with a perforated plate and three load cells. Data from the three load cells gave us total combined tumble torque, and more importantly, the force location defined as distance from the bore center and clocking in degrees.
We found that the swirl and tumble combined define the helix of the incoming air column in a two-valve chamber.
As Mummert stated, the swirl tends to jump up at low lift, lag behind in the mid-lift, and ramp up again at high lift. The tumble curve tends to do the same. The tumble force location (we called it "moment arm") moved closer to the bore center as the intake valve opened, and moved away from the bore center rapidly at high lift, when the swirl was spiking.
Our conclusion was we needed a smooth, linear increase in the swirl as the valve opened; not a set value.
To manage the swirl, we worked with chamber containment of the flow cone, runner trajectory, and some slight steering with the fin behind the guide. The flow must stay attached to the short-turn; swirl and tumble go out of control if there is separation. The modern steep seat and top angles really helped.
Reverse swirl fins behind the intake guides can improve burn uniformity, BSFC, and help prevent the swirl from spiking at high lift.
If you can do some wet flow testing on your cylinder head, you will be mesmerized by what you see. It will tie in with your swirl and tumble observations.
Bryan

What did you guys see by focusing on tumble after the swirl intensity was contained? Improved BSFC? Did you guys every get as far as getting the tumble portion modeled in a CFD program with a modeled piston top? How did you guys go about managing tumble short of moving the entire intake port angle?

Thanks
-Bob
hoffman900
HotPass
HotPass
Posts: 3445
Joined: Sat Feb 23, 2013 5:42 pm
Location:

Re: How much swirl is too much swirl

Post by hoffman900 »

hoffman900 wrote: Wed Sep 22, 2021 7:14 pm
Bryan Maloney wrote: Sat Sep 18, 2021 11:20 pm We had swirl, tumble, and wet flow test equipment available as part of Dodge's Nascar effort from 2000 to 2012.
We measured swirl as rotational torque with a honeycomb insert and a rotary strain gauge. Tumble was measured on another fixture with a perforated plate and three load cells. Data from the three load cells gave us total combined tumble torque, and more importantly, the force location defined as distance from the bore center and clocking in degrees.
We found that the swirl and tumble combined define the helix of the incoming air column in a two-valve chamber.
As Mummert stated, the swirl tends to jump up at low lift, lag behind in the mid-lift, and ramp up again at high lift. The tumble curve tends to do the same. The tumble force location (we called it "moment arm") moved closer to the bore center as the intake valve opened, and moved away from the bore center rapidly at high lift, when the swirl was spiking.
Our conclusion was we needed a smooth, linear increase in the swirl as the valve opened; not a set value.
To manage the swirl, we worked with chamber containment of the flow cone, runner trajectory, and some slight steering with the fin behind the guide. The flow must stay attached to the short-turn; swirl and tumble go out of control if there is separation. The modern steep seat and top angles really helped.
Reverse swirl fins behind the intake guides can improve burn uniformity, BSFC, and help prevent the swirl from spiking at high lift.
If you can do some wet flow testing on your cylinder head, you will be mesmerized by what you see. It will tie in with your swirl and tumble observations.
Bryan

What did you guys see by focusing on tumble after the swirl intensity was contained? Improved BSFC? Did you guys every get as far as getting the tumble portion modeled in a CFD program with a modeled piston top? How did you guys go about managing tumble short of moving the entire intake port angle?

Thanks
Also, how did you guys target a tumble value? Here is what LoganD said about tumble. At the time he worked for AVL. He works for Ilmor now:
Well, I guess it depends on what you consider "old". You have to be careful because an engine released in 2005 had the combustion system designed at least 5 years earlier, so there's a time lag. Basically any engine with the combustion system designed in the last 15 years is going to have very high tumble due to shallow valve angles. So that would basically be any production engine after 2010. In the late 90's and very early 2000's high end CFD was still so expensive that it was being used sparingly and time-dependent CFD was virtually impossible with automotive development budgets. It was also pretty impractical from a time perspective, what used to take 6 months to run now takes 2 weeks and can be done on computers that are 1/100th the cost you would have paid 20 years ago.

I guess what I'm saying is that the drastic increase in speed and drastic reduction in cost for high end CFD has caused us to change a lot of our previous perceptions about engine design. The new Mercedes M139 is a perfect example, 20 years ago if someone were going to design a 2.0 turbo 4-cyl to make over 400 hp on pump fuel they wouldn't make it heavily undersquare (83x92) with almost no valve angle. That engine revs to 7400 RPM and makes 370 lb-ft from 121 ci.

It makes a lot of sense if you think about it. If you're knock limited and not airflow limited, which most is the case for most heavily turbocharged engines, it makes sense to design the entire engine around reducing knock instead of just trying to make it flow more. This is where the aftermarket is behind, a Coyote or LS head doesn't need more flow to make 1000 hp on pump fuel, it needs more knock resistance.

This thinking spilled over into naturally aspirated engine design. They now give the engine just enough airflow to make the RPM/power target, and then they design the rest of the engine around maximizing efficiency and cylinder pressure. That's why the new GT3 engine has 13.5:1 compression and pretty shallow valve angles for an engine that revs to 9000 RPM. They spent a great deal of time making the large bore engine very knock resistant, and that's a hard thing to do.
To piggy back on my other post, have you worked with tumble specifically on hemi's? What have you found if so.

Sorry for all the questions, but I'm starved (and I think the forum is too) for a good conversation on this topic
-Bob
Bryan Maloney
New Member
New Member
Posts: 34
Joined: Wed Feb 27, 2013 3:04 am
Location: Martinsville VA

Re: How much swirl is too much swirl

Post by Bryan Maloney »

BLSTIC wrote: Wed Sep 22, 2021 5:50 am
Bryan Maloney wrote: Tue Sep 21, 2021 2:46 pm Chopping the short-turn away, and making the roof line low, can create extreme in-cylinder tumble. We only did this for an experimental hybrid engine that was throttled by EGR percentage, and needed extreme in-cylinder mixing.
What changes did you note from that experiment?

I wanted to do this to a quenched hemi that had more airflow than it needed for the valvetrain restricted RPM it could reach (and sensible street duties). The lower 'before' picture was after someone cut the inlet port with some kind of ball mill apparently. Green in the upper picture is roughly where I think the stock port would be. Blue is fill, red is cut. The plan was to add tumble, velocity, and boost. The engine stock was only using 210hp of its "330hp" head potential, so there's a lot of excess flow to play with.




proposedport.jpg
The shallow "line of sight" port I did was for an engine that was projected for a hybrid car. The existing Tiger Shark engine made about 160 hp if I recall. They wanted the new engine to only make 120 hp max. It's job was to run the generator, and be a backup.
The engine was to be throttled by EGR percentage, so it needed extreme mixture motion in cylinder.

If you have excessive airflow capabilities, it may benefit to trade off some of the airflow for increased mixture motion in the form of tumble. Chopping the short-turn away will definitely reduce the mid lift flow as it increases the tumble moment arm. On that hybrid project, I believe I got the moment arm value up to 1.3 inches away from the bore center. On all of our race heads previously, we had always worked towards keeping the moment arm value low (.390-.420 inches from bore center).

So much of the motion characteristics are locked into the valve placement and runner trajectories. After a head is designed, we realized we could only make relatively minor mixture motion and wet flow improvements.
Bryan Maloney
New Member
New Member
Posts: 34
Joined: Wed Feb 27, 2013 3:04 am
Location: Martinsville VA

Re: How much swirl is too much swirl

Post by Bryan Maloney »

hoffman900 wrote: Wed Sep 22, 2021 7:14 pm
Bryan Maloney wrote: Sat Sep 18, 2021 11:20 pm We had swirl, tumble, and wet flow test equipment available as part of Dodge's Nascar effort from 2000 to 2012.
We measured swirl as rotational torque with a honeycomb insert and a rotary strain gauge. Tumble was measured on another fixture with a perforated plate and three load cells. Data from the three load cells gave us total combined tumble torque, and more importantly, the force location defined as distance from the bore center and clocking in degrees.
We found that the swirl and tumble combined define the helix of the incoming air column in a two-valve chamber.
As Mummert stated, the swirl tends to jump up at low lift, lag behind in the mid-lift, and ramp up again at high lift. The tumble curve tends to do the same. The tumble force location (we called it "moment arm") moved closer to the bore center as the intake valve opened, and moved away from the bore center rapidly at high lift, when the swirl was spiking.
Our conclusion was we needed a smooth, linear increase in the swirl as the valve opened; not a set value.
To manage the swirl, we worked with chamber containment of the flow cone, runner trajectory, and some slight steering with the fin behind the guide. The flow must stay attached to the short-turn; swirl and tumble go out of control if there is separation. The modern steep seat and top angles really helped.
Reverse swirl fins behind the intake guides can improve burn uniformity, BSFC, and help prevent the swirl from spiking at high lift.
If you can do some wet flow testing on your cylinder head, you will be mesmerized by what you see. It will tie in with your swirl and tumble observations.
Bryan

What did you guys see by focusing on tumble after the swirl intensity was contained? Improved BSFC? Did you guys every get as far as getting the tumble portion modeled in a CFD program with a modeled piston top? How did you guys go about managing tumble short of moving the entire intake port angle?

Thanks
The swirl control was tied in with keeping the tumble moment arm value low. I don't recall the BSFC being improved much, but the engines seemed to better utilize the .894 net intake valve lift we were running at the time.

We didn't see any CFD modeling on our race engines back in 2004, but later I saw a simulation on a production engine that showed a dished piston allowed better tumble continuation after BDC. We ended up running a small chamber and a shallow spherical dish in our race engines; as many others had.

Tumble management boiled down to chamber containment, and runner short-turn/ roofline height. Twist in the intake port floor can have some affect, too.
Post Reply