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Port volume dyno testing

General engine tech -- Drag Racing to Circle Track

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pastry_chef
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Port volume dyno testing

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Mike R
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Re: Port volume dyno testing

Post by 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.
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Re: Port volume dyno testing

Post by 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.
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Re: Port volume dyno testing

Post by maxracesoftware »

pastry_chef wrote: Wed Oct 07, 2020 1:51 pm 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 .
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MadBill
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Re: Port volume dyno testing

Post by MadBill »

David Redszus wrote: Wed Oct 07, 2020 8:38 pm 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.
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Re: Port volume dyno testing

Post by 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.
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Re: Port volume dyno testing

Post by 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.
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Re: Port volume dyno testing

Post by Orr89rocz »

BOOT wrote: Wed Oct 07, 2020 7:10 pm 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
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Re: Port volume dyno testing

Post by 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).
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Re: Port volume dyno testing

Post by 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
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Re: Port volume dyno testing

Post by 289nate »

Would have been nice to see a ported intake tested on the larger engines with the larger heads.
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Re: Port volume dyno testing

Post by BOOT »

Orr89rocz wrote: Mon Oct 12, 2020 8:37 amHis 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?
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