Extrude honing two part manifold?

[gliding_serpent]

For those who had their intake manifolds extrude honed, do you know if it was done with the two haves pf the manifold connected?

Also, i see flow measurements pre and post. Did you get flow curves? Just wondering what flow rate was put "in" to get the initial and final flow rates... Or are those max rates?

Thanks for any help.

[stownsen914]

I'll be curious to hear what people have to say. When I looked into extrude honing a long time ago, I think it was more about polishing and taking the edges off, as opposed to making any significant enlargement to the passages.

[mrm930]

I had my "pancake" manifold done for my 78 Turbo. All the extruded honing does - is polish and de-bur the interior ports. If you need the intakes larger - these need to be ported prior to the extruded process.

From what I understand it does increase HP a bit. Better and smoother air movement.

[gliding_serpent]

Extrude honing polishes and flow balances each runner. You polish the lower flowing runners to bring their flow equal to the better flowing runners. Some were as far as 30% off from the factory... Not good. I have a 8% dpread between my best and worst.

It does not significantly increase the diameter, but the smoothness reduces turbulance, and increases flow.

My question relates to how they extrude hone a two piece manifold like ours. I can't see the oem rubber seal holding to the pressure of the process, but you would want to flow the system when connected. I assume they join them with something more robust with their process. Just wanted to verify.

[911pcars]

Not sure about the process Extrude Hone uses to treat a 3.2 2-piece manifold, but as long as the flow characteristics between left and right side match, why not treat them separately? AFAIK, the process still forces abrasive material through the runners to arrive at a "maximum" flow rate - restrictive passages receive more abrasive flow. The procedure continues until the flow levels are optimized and matched as close as possible.

Reports describe minimal increase for the cost, but if one is looking for every advantage, then one goes for it. YMMV.

Sherwood

[Tippy]

Originally Posted by mrm930

I had my "pancake" manifold done for my 78 Turbo. All the extruded honing does - is polish and de-bur the interior ports. If you need the intakes larger - these need to be ported prior to the extruded process.

From what I understand it does increase HP a bit. Better and smoother air movement.

I never seen an EH done where it didn't significantly "port" the ports.

[gliding_serpent]

Originally Posted by 911pcars

Not sure about the process Extrude Hone uses to treat a 3.2 2-piece manifold, but as long as the flow characteristics between left and right side match, why not treat them separately? AFAIK, the process still forces abrasive material through the runners to arrive at a "maximum" flow rate - restrictive passages receive more abrasive flow. The procedure continues until the flow levels are optimized and matched as close as possible.

Reports describe minimal increase for the cost, but if one is looking for every advantage, then one goes for it. YMMV.

Sherwood

My issue is that if they were flow tested/matched as separate pieces, the flows measured would not represent the true path of the air from the throttle body port. Thus there would be a discrepancy in flows from the cylinders 1-3, compared to 4-6. I am sure they account for this, but just wanted to be sure, otherwise the process is in error in my mind. I don't want half of my engine running more lean (and that would be 1-3 if they flowed/honed the sides separately).

My understanding was that you could also get them to flow your head to a specific spec. Someone advised me to have them take my best flowing runner, and increase that by 25% (about the power I am increasing my engine from a euro spec) and match the rest to that. Or maybe I am mistaken. I will speak with them Monday, but was just curious.

[911pcars]

Originally Posted by gliding_serpent

My issue is that if they were flow tested/matched as separate pieces, the flows measured would not represent the true path of the air from the throttle body port. Thus there would be a discrepancy in flows from the cylinders 1-3, compared to 4-6. I am sure they account for this, but just wanted to be sure, otherwise the process is in error in my mind. I don't want half of my engine running more lean (and that would be 1-3 if they flowed/honed the sides separately).

My understanding was that you could also get them to flow your head to a specific spec. Someone advised me to have them take my best flowing runner, and increase that by 25% (about the power I am increasing my engine from a euro spec) and match the rest to that. Or maybe I am mistaken. I will speak with them Monday, but was just curious.

Pretty sure any common manifold would suffer that potential discrepancy in uneven flow. The manifold is just a passage for air, not air/fuel and it seems that variations in cam timing, rocker arm ratio, exhaust tube dimension are elements that may make a difference.

One solution would be to provide a specifically-szed plenum, surge or reservoir chamber after the throttle body that supplies air to the next opening intake runner; enough air volume to not disturb the airflow to the next cylinder in the firing order. Either that or provide one standalone induction throat per intake port - aka ITBs (individual or independent throttle bodies).

IMHO, one would have to reserve plenty of engine dyno time to optimize a particular intake manifold and shape to react to the needs of the engine.

Sherwood

[gliding_serpent]

Ahhh... I think i get what you are saying sherwood.

I have been thinking of this as one system... When my intake runners were flowed they were attached, 5 ports were blocked, and air was run from the throttle body opening. Flows took into account the entire path. I assumed, or wanted to confirm that this is how extrude hone did it. In my mind, extrude honing by this method would solve the air flow discrepancy issues (which to me is why you extrude hone).

Now you have me rethinking how air behaves in a common air resevoir chamber. does the general shape of the chamber, or even location of the throttle body (assuming it is not overly offset) not matter so much? Is the part of the design to balance these issues?

I will do some more reading.

[gliding_serpent]

Good description here. I have been misusing the term plenum. I was interchanging it with intake runners.

https://en.m.wikipedia.org/wiki/Inlet_manifold

They seem to suggest that the distance from the throttle body to each intake runner is important. Also note of discussions on turbulance and rough surfaces. An engineer told me not to polish my manifold for this reason. He felt that flow benefits might be offset by reduced air fuel mixing. I opted to this year as my car will run modern injectors used with Sal Carcellers maf setup, which have far better spray patterns and atomization than older injector designs that came with our cars.

On the other hand... Maybe microturbulance is not as important in the design of our intakes... Circa 2002

Originally Posted by Steve W

For a FI intake, smoother results in bigger intake manifolds. One of the basic things I learned from studies in fluid flow and thermodynamics is that the rough casting surfaces inside the Carrera manifolds create eddy currents which are microswirls of air currents along the entire inside surface of the manifold created by the rough surface. These eddy currents do not contribute to the straight flow of air towards the intake port, and because they take up the entire inner circumference of the intake port, the effective diameter of the manifold is reduced significantly. Polishing the intake manifold port minimizes this turbulence, so that when air velocity is high, the effective diameter is maintained. A straight polish of the intake ports of the heads though is not desirable. A swirl polish is prefered because the swirling turbulence helps to atomize and mix the air/fuel mixture better prior to it entering the combustion chamber. Since the fuel injectors are mounted right before the intake ports at the head, a swirl finish is not necessary on the manifolds of a FI vehicle. However on carbed motors, the opposite is desirable. On those vehicles, ultra polished surfaces would most likely cause fuel droplets to cluster.

[gliding_serpent]

Here is an answer from a faq i found:

I want my parts to be flow matched. Can my parts be bolted together while they are Extrude Honed?
Fixturing assembled parts is physically impossible; but mating part can still be easily matched for flow. What we do, is we the match parts to the gasket. This way they will have the same dimensions post process.

But now that I think about it, the manifold plenums (air resevoir) between the throttle body and each intake runner is quite large diameter. Thus it is not a significant restriction in its own right. The only restriction would be distance, and that is not a big factor in our case. So as long as they flow match each runner, the rest should be a non issue.

Thanks again sheerwood! Good to think about, and now i can incorperate the vacuum of the intake manifold into my understanding of the system.