CSA in dual planes ?

[BOOT]

Dual planes smaller higher velocity runners is only part of it and yes the length part is overblown.

from this article https://www.motortrend.com/news/0601em-intake/

"A V-8 engine fires a cylinder every 90 degrees of crank rotation, and the induction cycle of any given cylinder will greatly overlap the induction cycle of the next cylinder in the firing order. The two-plane design isolates each side of the manifold and connects the cylinders in a sequence in which each isolated plenum is connected to every other cylinder in the firing order. Plumbed as such, each side "sees" only every other firing pulse. Rather than having overlapping intake pulses coming into the plenum every 90 degrees as with a single-plane, each side of a dual-plane gets a much cleaner induction pulse every 180 degrees of crank rotation. That's why a dual-plane intake is often referred to as a 180-degree manifold. With the induction pulses coming into the carb every 180 degrees (or actually only one-half of the carb in a divided plenum two-plane), the induction pulse seen at the carb is greatly enhanced, especially at low air speed. This translates to further improved lower-rpm carb booster function and atomization, resulting in better low-end output, enhanced drivability, and economy.

Perhaps the greatest benefit to lower rpm and part-throttle operation with the 180-degree design is that it also largely separates the communication of the induction pulse from the exhaust system. With a single-plane, the wide-open intake valve of a cylinder at peak piston speed on the intake stroke is communicated directly into the plenum, as it should be. At the same time, another cylinder in the overlap phase is also open to the same plenum. At low speed, especially with high-overlap cams, and most acutely at part throttle, this tends to draw exhaust gasses into the cylinder in the overlap phase. This reversion causes rougher low-rpm running and a penalty in torque production until the air speed and overlap tuning effect overcomes the tendency towards reversion at higher rpm. With the 180-degree system, this pathway is greatly reduced, improving idle quality, vacuum, and part-throttle responsiveness."

There is more in the article but I'm not gonna copy n paste it all. Another point I've read somewhere is how a true dual plane is like two 4 cylinders with different peaks and that broadens the power band.

[BOOT]

And of course the 23 dual plane comparison https://www.motortrend.com/how-to/dual- ... mparisons/

Not a huge spread and if you cleaned up each intake, it would narrow it I'd bet.

Also think all(most) the ones tested were modern design and close to same style plenum/runners, unlike older design in the OP post.

[bobmc]

has anyone ever put tumbler type media inside a dual plane and shook it with something like a paint shaker?

[1980RS]

My NHRA A/stocker friend can run either the 163 intake or the GM performance Bowtie intake as per NHRA. He uses the GM one with the smaller runners because the engine they run made 12hp better than the 163 intake did.

[Tom68]

Dual planes smaller higher velocity runners is only part of it and yes the length part is overblown.

from this article https://www.motortrend.com/news/0601em-intake/

Yer that's a funny article, lots of truths, some errors and some omissions.

If their comments on single planes providing bad low speed performance due to exhaust dilution is true (not saying it's not) how do they think all the single plane EFI manifolds (almost all EFI cars for the last two decades) get on. Anything with two or more cylinders has manifold vacuum pulling on overlap if using a plenum connected to three or more cylinders.

If they think a dual plane gets a stronger signal because one cylinder is pulling on half a carby (actually more than one cylinder), how do they justify that against a single plane that has 2 cylinders (actually more than 2 cylinders) pulling on a whole carby.

[BOOT]

Overlap, fuel puddling/dropout & plenum size

Look at factory cams, check out the factory TPI cam or any non variable timing cam. The plenum on a 2.2L that I had was small and long runners. Still it's well know that plenum size impacts carbs more than EFI OR that carb size effects velocity.

The engine works in pulses, no 2 cylinders pull at the same time. It's similar as how a longer runner keeps the flow in one direction longer and that makes it have a stronger signal, 180 degs instead of 90 allows the flow in one direction longer. At some point a single plane will even rob other runners to fill a cylinder, that's part of the reason to use firing order swap cams. Most people just say it's plenum size that hurts single plane carb signal low end, I felt that article explained it in a better way that cams & other parts also effect them. It's a mess in there! https://youtu.be/7Iq1B-2paCs

Modern heads, intake & exhaust manifold design, even for a common 4 cylinder(designed to operate at higher RPM kinda like a single plane) is much better than the SBC, just look at the LS The better your design(aftermarket), the less sensitive it is to some changes. Apples to Oranges That's part of why the LS is so popular, it's much harder to screw up than older V8's Also then lets look at the LS dual plane, I hear it's not popular and most just use a single plane or make better power with one. Cause it's totally a diff engine and much better deign in countless ways. But that's a diff topic and yes blah blah blah older V8 with 100% aftermarket parts that totally change/correct the original old deign n so on.....

Yes plenty of people run a single plane on the street and I bet those cars aren't huge tanks with stock stalls n those guys have better than average tuning skills.

If throttle plate size didn't matter, you'd see us all running mono blades(SV1) like TB's But area change does impact a draw thru fuel design. Look at the quadrajets.

I'm no expert and explained it the best I can atm, others I'm sure could do better.

[Tom68]

So to me the much overstated long runner was the key to better low end torque is false. It is the smaller CSA than the single planes that makes better low end toque. just my .02 cents

They work better than all the Torkers that have ever been made to though.

I think if as simple as the reversion pulse frpm a closing valve bouncing back to an opening valve. 180 degree separation supports this. A 90 degree single plane has too many valves open at once for the reversion pulses to give a direct hit onto a filling cylinder until speeds are higher, of course then the dual plane lays down because the runners are crap.

[BOOT]

single plane has too many valves open at once for the reversion pulses to give a direct hit onto a filling cylinder until speeds are higher, of course then the dual plane lays down because the runners are crap.

Exactly! Just like the TPI suffers from a 180 turn low max RPM, even the dual plane runners turn too much at a point for the air, for their size. Straighter runner single planes or tunnel rams beat them with RPM! Sure runner size could help some(older dual planes) but it's a double edge sword at those low RPM's

Again the best I understand it, at this time.

[Tom1500]

Dual planes smaller higher velocity runners is only part of it and yes the length part is overblown.

from this article https://www.motortrend.com/news/0601em-intake/

Yer that's a funny article, lots of truths, some errors and some omissions.

If their comments on single planes providing bad low speed performance due to exhaust dilution is true (not saying it's not) how do they think all the single plane EFI manifolds (almost all EFI cars for the last two decades) get on. Anything with two or more cylinders has manifold vacuum pulling on overlap if using a plenum connected to three or more cylinders.

If they think a dual plane gets a stronger signal because one cylinder is pulling on half a carby (actually more than one cylinder), how do they justify that against a single plane that has 2 cylinders (actually more than 2 cylinders) pulling on a whole carby.

I would think that the less cylinders pulling at once, the greater the 'strength' of the pulse that the carby sees, but shorter the duration.

The competing intake valves are open at differing points of their intake cycles. This results in the intake valve that is opening to rob the intake valve that is closing, and I would think decrease the strength of the pulse the carby sees.

[Tom68]

I would think that the less cylinders pulling at once, the greater the 'strength' of the pulse that the carby sees, but shorter the duration.

The competing intake valves are open at differing points of their intake cycles. This results in the intake valve that is opening to rob the intake valve that is closing, and I would think decrease the strength of the pulse the carby sees.

For sure, should have clarified in my posts when we're talking about what.

When you say cylinders pulling, that implies (in my mind) throttled low speed operation/drivability.

Obviously there's a big difference in what's happening between throttled driving and WOT, especially WOT at higher than 3500 rpm.

[Tuner]

So to me the much overstated long runner was the key to better low end torque is false. It is the smaller CSA than the single planes that makes better low end toque. just my .02 cents

They work better than all the Torkers that have ever been made to though.

I think it is as simple as the reversion pulse from a closing valve bouncing back to an opening valve. 180 degree separation supports this. A 90 degree single plane has too many valves open at once for the reversion pulses to give a direct hit onto a filling cylinder until speeds are higher, of course then the dual plane lays down because the runners are crap.

"it is as simple as the reversion pulse from a closing valve bouncing back to an opening valve."

this ^^^^ in the SAE paper GM presented 60 years ago describing the new BBC this effect and the influence of port and manifold volume for the desired RPM range, therefor the large port and small port engines. This is described on page 7 of the first edition of the HP book "How to Hot Rod Big Block Chevys"

[Tom68]

"it is as simple as the reversion pulse from a closing valve bouncing back to an opening valve."

this ^^^^ in the SAE paper GM presented 60 years ago describing the new BBC this effect and the influence of port and manifold volume for the desired RPM range, therefor the large port and small port engines. This is described on page 7 of the first edition of the HP book "How to Hot Rod Big Block Chevys"

I've never owned a dedicated BBC Book, have one on the way now though.

[EDC]

Played with a bunch of dual plane intakes from the Edelbrock C3BX to a semi-dual plane Holley Z manifold and the original DZ 302 Z28 dual plane always came out on top. Runner layout seemed to be the priority over cross section.

[Dave B]

Just get your miller out and get creative.Dual planes can be improved a ton.They are not rpm limited if you get after them.

[BOOT]

The dual plane intake I just bought is on the larger side compared to others I have https://youtu.be/bWHINmJNP68

I know some still praise old design intakes But then why aren't any still making them? Why have all the dual planes by several CO's turned into pretty much the same design with minor differences?