Port volume dyno testing

[pastry_chef]

Dyno testing different size ports.
https://www.youtube.com/watch?v=PZSQ5Kd ... e=youtu.be

[BOOT]

Read the comments, there is a good one somewhere. After the vid was posted, I went to comment myself and saw one that pretty much covered it. Basically says testing nothing but port size is not ideal when other things would be changed to make the most of different size ports.

For example if you took all the SBC dart pro1 heads and test them on the same combo the 230 has a larger valve.

[David Redszus]

I have often wondered why the concern over port volume.

A short, large diameter port can have exactly the same volume as a long smaller diameter port.
Which will perform better? I don't know. It would seem to me that several other factors would have a much
more significant impact on performance and especially on low end performance.

Air flow is a function of piston speed (and displacement). At low piston speeds, neither the valve curtain nor port
cross section have reached their flow limits.

A mentioned earlier, for low end performance get a bigger engine or raise the compression.

[maxracesoftware]

Dyno testing different size ports.
https://www.youtube.com/watch?v=PZSQ5Kd ... e=youtu.be

various Legal maximum Port Volume CC's on NHRA SuperStockers Cylinder Heads
on the same Cubic Inch engines show different HP and RPM ranges

example :
all the same exact Valves + Flowbench CFM Numbers + Legal engine combination specs :
#462 SBC 162.0 CC Intake Port
-vs-
#041X SBC 165.0 CC Intake Port ... this casting will be +10 to as much as +20 HP better than #462 casting ,
and have a higher RPM Range ... just 3.0 CC's has this effect on a relatively restricted SuperStock engine

the #462 casting goes into pumping choke deeper and sooner in the RPM Range
( a Pitot Probe shows exact same problem with #462 -vs- #041x )

the #041x is quicker down the Dragstrip as well .

[MadBill]

I have often wondered why the concern over port volume...

I think it's just an easy way of comparing average cross section areas, based on the assumption that most heads for a given engine will have roughly the same port lengths, but of course this would mean that comparing port volume of say a BBF to an LS would be an exercise in futility.

[David Redszus]

Volume is a function of area x length.

The area will determine the mass flow limit, which is a function of displacement and rpm.
Flow co-efficients, density, and sonic velocity must be considered as well.

The length will determine the arrival time of pressure waves, which is a function of sonic velocity.
Sonic velocity is a function of inlet air composition, and temperature.
Centerline lengths do not consider the effects of pipe bends; it only works for straight pipes.

In addition, there is a large difference between pressure wave velocity and particle velocity.

[induction apprentice]

I would have liked to see that testing done comparing heads with larger CSA and more taper. While keeping the valve sizes, throats and valve jobs all the same.
Then try it again each time enlarging the intake manifold runners.

[Orr89rocz]

Read the comments, there is a good one somewhere. After the vid was posted, I went to comment myself and saw one that pretty much covered it. Basically says testing nothing but port size is not ideal when other things would be changed to make the most of different size ports.

For example if you took all the SBC dart pro1 heads and test them on the same combo the 230 has a larger valve.

His tests are mainly for average hot rod guys who buy off the shelf parts and bolt them on. Tests like this are good enough to show differences in bolt on parts if a guy was considering between two different head sizes from a given manufacturer. Would have been nice to show valve sizes and flow number differences tho

[PRH]

If you gave a set of Dart 200 SBC heads to pretty much any of the guys on this forum who do porting and told them to do some port work to the intake ports, but not to go over whatever the actual runner volume was of a Dart 215 head, and used the same size intake valve as the 215....... and tested them on a suitable combination that could exploit the better flow of the ported 200 vs the unported 215........ I would expect the ported 200’s to be superior.

So, then you’d have equal runner volume, but different power output.
How does that fit into the “runner volume” debate.

I seem to recall Larry testing some SS heads where the volumes were very equal, but there was a rather large difference in power(like close to 100hp iirc).

[Orr89rocz]

The volume itself is meaningless without other data to go with it. Its a system Of components, so without the information of all components you cant make a reasonable guess on what the results will look like

[289nate]

Would have been nice to see a ported intake tested on the larger engines with the larger heads.

[BOOT]

His tests are mainly for average hot rod guys who buy off the shelf parts and bolt them on. Tests like this are good enough to show differences in bolt on parts if a guy was considering between two different head sizes from a given manufacturer. Would have been nice to show valve sizes and flow number differences tho

I agree his test are for off the shelf parts, those 230cc off the shelf heads have larger valves as is. Also if your considering larger heads you often look at larger cams n so on. So did he start with a cam better for the smaller or larger heads?

[NewbVetteGuy]

Resurrecting this thread...

*Zombie Thread: Go eat brains!*

It just seems like there's way too much to be learned from the tests in that video to not dive into it deeper..


What if we do the typical head sizing calculations for each of those 3 engines and see how the various heads port sizes compare?
Which tests involved a head that was the most significantly oversized vs. undersized and what does the dyno tell us about that?


-I don't know the typical intake port centerline length for a small block Ford to do the conversion from min CSA sizing to actual port volumes; anyone have a good enough number to use for an SBF head?


For the SBC 372: 4.125 bore x 3.48, if we use the 6,200 RPM hp peak of the smallest head tested in the sizing formula, I get:
2.2043" min CSA
Using 5.45" as a generic SBC intake port centerline length: 196.5cc port volume estimation
-The traditional sizing yields a result in the middle between the two heads tested, basically. The small head is like 15cc too small; the big head is 15cc too big... Neither one is OVERLY large or OVERLY small to see much... A 165cc and a 226cc head with a 30cc under and over sizing and a 60cc diff would've been more interesting, IMHO.

For the 5.0 Ford 305 4.030 bore x 3" stroke; if we use the 6,500 rpm peak of the smallest head tested in the sizing formula, I get:
1.82" min CSA
-I don't know a good intake port centerline length to use to convert to CC; reusing the SBC stat I get 162.5cc

Ford 363 4.125" bore x 3.4" stroke; if we use the 6,500 rpm peak of the smallest head tested in the sizing formula, I get:
2.21" min CSA
-I don't know a good intake port centerline length to use to convert to CC; reusing the SBC stat I get 192cc



What was consistent across the dyno results?:
Bigger Heads made more power at the top of the RPM range (not much to learn there..)
Bigger heads really didn't lose much down low -more interesting
-Would they have if the dyno started at a lower RPM? -Guesses?
With one exception, the larger heads seemed to lose a SOME torque around the engine's torque peak: WHY?
-The 195cc head on the 363 Ford had better peak torque vs the 170cc head on the same engine.
Is this because the 195cc head was the "best sized for the engine" (doubt it)? Or because this head's ports were simply BETTER than the
170cc head? (more CFM / avg csa)

Why do the bigger heads give up torque around the peak in almost all instances? (Is this where the velocity "really matters"? As you try to get more than 100% VE around the torque peak while the piston is going up the bore, the only way to do it is with the extra pressure from high velocity otherwise the pressure in the cylinder from the rising piston is higher than that in the intake port so the air flows backwards there?)




Is torque @ WoT more driven by the amount of CFM / CSA than just the simple port volume?


What would have changed if the same test looked at part throttle at low RPM and the transition to WOT?
(Isn't this what would suffer the most with a "too large" port on a given engine?) -I'm asking a question we'll outside of my area of understanding, but isn't this why the circle track guys are all obsessed with high velocity to have snappy performance from part to full throttle?




This stupid Richard Holdner video has broken my brain and I keep oscillating from the extremes of "size everything for the cubic inches, RPM, and intended use" now to "intake port size doesn't matter / go big/ it's only a dumb air pump"... It can't be both.

The stupid giant CSAs of the LS and LT engines also have me wondering if port size matters any more or whether that's just some old thinking or a "wet flow world only" consideration...

Too many questions. Apologies.

Adam

[modok]

The tests are with the same intake manifold. If an ideal intake manifold was designed to match each head used, then the best sized head would win.
I think it is unfortunate he didn't mention what exact intake manifold was used. not much was said about valve size either. i guess you could figure it out if you wanted.
MORe volume in the port, ALL else the same, would just get less peak torque in the powerband, but possibly better torque below above and below the tuned points of the intake.
Placing additional volume at the END of the runner softens the ramming or weakens the tuned effect of the intake....so where in the RPM range the intake tuning is HURTING ve, then softening it improves torque. But evidently the heads also flow more and/or have larger valves because the peak power is higher....and/or this improvement is outside the range of where that intake works best.
If you just dremeled out your ports in ways that don't improve flow and tested again I don't think you'll see any REAL improvement to anything useful, but it may CHANGE the intake tuning one way or another. if enlarging the port in a way that does not improve flow DID produce the type of results you were looking for.....I'd be pretty sure dremeling out some other area of the intake would probably be even better.

[AA Performance]

They were going from an as cast cylinder head to CNC hi flowing cylinder heads and still using a manifold that suited the cast heads. The ford had an issue in the 4300 - 5000 rpm as the dip in power was there in all tests. I'm sure it was something that could be cleaned up.