Dual Plane vs Single Plane Intakes

[redshift96]

Two manifolds, both from non-egr 6.2 motors.

This open plenum unit is from a 1990 J code:




This dual plane unit came off of a 1985 J code Sub with a 1999 GM crate motor:



When and why were each type used on which motors? Any idea?

Thoughts on which might be better for a Banks-turbo'd 6.2/6.5 hybrid?

I'm inclined to use the dual-plane (which is why it's all spiffed up), but wonder if there's any reason to think the open plenum unit might benefit the turbo motor more.

Thanks in advance for any hints or opinions.

 

[EWC]

Single plane is worth 20 CFM over the dual plane .

 

[just a number]

that's a big difference.

 

[ak diesel driver]

My understanding in gassers dual plan manifolds kept the airflow at a higher velocity so the fuel mist would stay in suspension at a low rpm but it also limited airflow for topend power. be interesting to see what it would do for WMI

 

[just a number]

interesting idea.....

 

[WarWagon]

Suppose there is a reason turbo 6.5's have a single plane intake...

 

[redshift96]

Yep.

Suppose there is a reason turbo 6.5's have a single plane intake...

My thinking exactly.

Yet, these both came off 6.2NA motors. And while I understand the general thinking behind each type, I have NO idea what the general may have had in mind when deciding to use one or the other at different times.

Did any 6.5TD's ever use a dual plane?

 

[great white]

Hmmm, I essentially have a gasser background and dual plane intakes only have significant benefits in a wet manifold design for keeping velocities up.

The 6.5 is a dry manifold with IDI, so I'm not sure what benefits a dual plane would have. Maybe velocity and cylinder turbulence? Dunno...

I do know this: with a pressurized manifold, there aren't any real benefits to a dual plane intake. If anything, it becomes a restriction in my way of thinking...I could be wrong though....

 

[redshift96]

Hmmm, I essentially have a gasser background and dual plane intakes only have significant benefits in a wet manifold design for keeping velocities up.

The 6.5 is a dry manifold with IDI, so I'm not sure what benefits a dual plane would have. Maybe velocity and cylinder turbulence? Dunno...

I do know this: with a pressurized manifold, there aren't any real benefits to a dual plane intake. If anything, it becomes a restriction in my way of thinking...I could be wrong though....

I believe that the other potential benefits of using a dual plane have to do with lengthening the runners overall, and equalizing the lengths between them somewhat.

Isn't there some buffering acheived between adjacent cylinders drawing from a common plenum as well ?

Does anyone know which vehicles got the dual plane in which years?

 

[WarWagon]

Gassers have sweet spots for the RPM band with dual plane being ideal for lower RPM ranges. Longer runners tend to put more air in the cylinder at low RPM from inertia of the air. Thus getting more torque. The dual plane runs out of air at higher RPM. A Jegs catalog for 454 intakes give an RPM band of 3000 - 7000 RPM for a single plane as I recall - You need a well built 454 to spin that high or boat application sitting at 5000 RPM redline all day...

So perhaps the single plane was for a high RPM engine like 4.10 gears or heavy tow rig option?

I think 6.5 Non turbo have a dual plane.

 

[turbovanman]

I don't see how a dual plane would work on a diesel, there is no tuning per say. They have no throttle blade so ANY restriction before the valve will cost power, especially on an N/A. I would say go single or open plenum, the more open it is, the more power it will make.

Are the floors in your "dual plane" at the same level, if so, its not a dual plane but just a split plenum which they could have done for noise control.

 

[redshift96]

Are the floors in your "dual plane" at the same level, if so, its not a dual plane but just a split plenum which they could have done for noise control.

Nope, it's truly dual plane, which you can just make out if you look closely at the photo.

 

[WarWagon]

Same applies for a gasser as a diesel. Gassers on a dyno at WOT where the manifolds are tested would be the same. Light throttle gasser is different only for air pressure. Air at any pressure still has mass.

Given this the runners on the open plenum manifold are uneven lengths. So when the piston stops moving on the intake stroke with the valve open air continues to enter the cylinder from it's own inertia. Longer runner means more air will enter. So low RPM has more air in some cylinders than in others on the open plane manifold. Till you run out of air at higher RPM for the dual plane manifold. This uneven air could unbalance the engine and be felt by vibration - maybe.

So smooth engine operation and a specific cam shaft for intake valve duration may also be paired with the manifold. Check GM part numbers by VIN for camshafts if you can.

I would think a 6PSI+ turbo overcomes any benefit from air's inertia in the runners. Thus an open plane not running out of air is the better choice.

 

[iamdave0887]

When i went from the dual plane EGR intake(EGR non-functional) to the single plane 6.5 NA intake on my blazer it made a world of difference.

Much less smoke from the exhaust and more power to boot.

I don't know of any 6.2 NAs that had the single plane intakes from the factory. That was a 6.5 NA thing. All non-EGR 6.2s came factory w/ the dual plane intake I believe. Even my friends Ex-Military 6.2 Blazer has the Dual plane non EGR intake.

 

[redshift96]

Really great feedback

When i went from the dual plane EGR intake(EGR non-functional) to the single plane 6.5 NA intake on my blazer it made a world of difference.

Much less smoke from the exhaust and more power to boot.

I don't know of any 6.2 NAs that had the single plane intakes from the factory. That was a 6.5 NA thing. All non-EGR 6.2s came factory w/ the dual plane intake I believe. Even my friends Ex-Military 6.2 Blazer has the Dual plane non EGR intake.

Thanks Dave.

Pretty sure that the 1990 3/4t J-code 6.2NA Sub's open plenum intake was OE. That thing was rock stock under the hood from what I could tell. Sure wish I understood which manifolds were used where and when by GM.

 

[Acesneights1]

Now you guys have me curious. I'll have to do some lookin tommorow. I have 3 6.2s all different. I have a c, j and mil j.

 

[buddy]

You have to look at the 6.2 upper plenum. it comes in from the passenger side, 90 degrees into the engine. It could be that they were trying to prevent turbulence in the intake from the air on the outer part of the bend moving faster than the air on the inner bend. For a turbo application it wouldnt matter as much. And then what was mentioned about which cylinders valves were opening in relation to eachother.

even if EGR isnt functioning, an EGR intake is way more restrictive with all the nonsense extra material in there. So going from an EGR to non-EGR is a good change.