Any real value to porting for FI?

[Coldswede]

I keep looking at the b35 head, manifolds and gaskets, to my eyes there is nothing to be gained by porting these, especially for a FI set up.

The runners are as straight and clean as a factory can make them, the seat areas are clean, the valve guide boss is not enough of a protrusion to matter.

While searching I did find one reference to smoothing the injector area, but I suspect that is done purposely to create some turbulence to help load the incoming charge with fuel.

Anyway like I said, Search didn't really answer the question, so what do you guys think or what have you done?

[turbodan]

Porting is just as beneficial for a turbo motor as it is for a NA motor. The thing is that its just not necessary for most cars. There is also a lot to lose with a bad port job.

There are other things to spend your money on before you go there.

[Brad D.]

Dan makes a very good point. Airflow increases help any engine regardless of how it is aspirated. He also is right about a bad port job doing more harm than good. If I had a head off the car I would do a mild cleanup and guide blend but would probably leave the CC alone even though there are probably small gains to be had here as well. Wait until Todd posts his dyno numbers with his sweet new head.

[turbodan]

I did a bit of work on my combustion chambers. There are things you can do in there to improve flow and resistance to detonation. Stock porting though...

[Brad D.]

Valve deshrouding can really help as can properly modifying the quench regions of the head if you know what you are doing.

[Murfinator]

I feel port matching the intake manifold to the head is beneficial. As is smoothing the radius of bends the intake/exhaust charge takes as it makes its way through the system. This is extremely beneficial to any engine since the more air you can pull in and push out, the more potential power may be produced.

I've heard there may be some benefit to smoothing/removing the protrusions just downstream of the injectors in the intake manifold. I assume these were designed to create some turbulence to improve mixing of fuel/air prior to entering the combustion chamber.

[turbodan]

Port matching is generally a good idea, though gains are slight if you get anything at all. You'd better know what you're doing if you're going to do anything more than that.

[Scottinva]

I heard the rough casting I believe on the intake side helps scavenging, and unless you know what you are doing, by making it smooth, it can hurt flow. Learned that in an ASE training class.

[Murfinator]

I heard the rough casting I believe on the intake side helps scavenging, and unless you know what you are doing, by making it smooth, it can hurt flow. Learned that in an ASE training class.

So I assume that would explain why machine work such as port matching, porting and polishing is typically done only on the head and the intake is left alone?

[Coldswede]

Dan, you mentioned doing some work to help prevent detonation.

I know about removing any sharp edges, corners or protruding bits to prevent detonation, is there something else that can be done? Would you elaborate or is it a secret?

[turbodan]

I heard the rough casting I believe on the intake side helps scavenging, and unless you know what you are doing, by making it smooth, it can hurt flow. Learned that in an ASE training class.

Helps scavenging huh? Thats new...

[Jeremy]

I heard the rough casting I believe on the intake side helps scavenging, and unless you know what you are doing, by making it smooth, it can hurt flow. Learned that in an ASE training class.

Helps scavenging huh? Thats new...

I've heard that before. Something to do with laminar flow and boundary layers. Creating a boundary layer with the rough casting results in better flow than polishing a port of the same area. However, since you're generally increasing the port size when you do such work, I'm not sure how the math works out.

Jeremy

[Scottinva]

I heard the rough casting I believe on the intake side helps scavenging, and unless you know what you are doing, by making it smooth, it can hurt flow. Learned that in an ASE training class.

Helps scavenging huh? Thats new...

I've heard that before. Something to do with laminar flow and boundary layers. Creating a boundary layer with the rough casting results in better flow than polishing a port of the same area. However, since you're generally increasing the port size when you do such work, I'm not sure how the math works out.

Jeremy

Thats more of the engineering side of what I heard. I don't know if its true or not. I may pull out my ase book later on, to find an exact quote.

[turbodan]

"Smooth" and "rough" dont sufficiently detail the kinds of finishes involved. The 100+ HP/L ///M engines all have a very finely machined finish all the way through the head. Smooth, but not polished. Stock cast ports have a relatively smooth but uneven surface finish. As long as you dont go through it with polishing compound and remove all the texture from the ports you're probably fine.

The differences in flow between the different finishes are probably extremely small. The one thing you want to avoid is leaving a finish smooth enough to encourage the pooling of fuel. Intake ports should wet with fuel while the engine is running. Some texture allows the fuel to cling. Too little texture causes pooling and liquid fuel dribbling into the cylinders. It probably wont cost any power but it wont run as well under low speed/low load conditions.

[mooseheadm5]

^-- This.

Scott- you took a class for the ASE tests?

[Scottinva]

Well i'm at TCC automotive, which is a NATEF certified program. So we learn the necessary things to pass the correseponding ASE tests. So all the books we must purchase, help you study for the ase tests, and such.

[Rich Euro M5]

I heard the rough casting I believe on the intake side helps scavenging, and unless you know what you are doing, by making it smooth, it can hurt flow. Learned that in an ASE training class.

Helps scavenging huh? Thats new...

I've heard that before. Something to do with laminar flow and boundary layers. Creating a boundary layer with the rough casting results in better flow than polishing a port of the same area. However, since you're generally increasing the port size when you do such work, I'm not sure how the math works out.

Jeremy

It's actually gets more complicated as it involves reynolds number. The reynolds number determines whether flow will be laminar or turbulant. If you can achieve laminar flow in the port, then the port casting roughness will be negated by the boundary layer. However if you get it wrong, then you'll lose the boundary layer and the result is turbulant flow and the resultant eddy currents which can restrict flow. To get it right you need to know what you're doing. There are computational modeling programs which can help determine the port shhape, but a flow bench with a capability to see if the flow is staying laminar at various velocities is needed to confirm the results when put in practice. This is why porting heads is such an art.

My casual observation is most porting work done on the M30 head is to unshroud the valve stem and to help the intake charge make the turn from the port into the combustion chamber. The 4 valve ///M heads don't have this abrupt turn, when the valves are out of the head you can see directly through the intake ports and out of the exhaust ports.


Just my $.02.

Rich

[mooseheadm5]

^--- this too, but it is pretty technical and math intensive and only engineering geeks really care about it (like me.) Most people learn on a flow bench what works and skip much of the theory.

Scott,
Have you taken the ASE tests yet? If not, don't sweat it. The 6 I have taken were pretty easy.

[George]

Its not that technical.

There's a good bit of multi-variable calculus though

[mooseheadm5]

Its not that technical.

There's a good bit of multi-variable calculus though

Says one engineer to another (well, I count at least 3 here.)

[Scottinva]

^--- this too, but it is pretty technical and math intensive and only engineering geeks really care about it (like me.) Most people learn on a flow bench what works and skip much of the theory.

Scott,
Have you taken the ASE tests yet? If not, don't sweat it. The 6 I have taken were pretty easy.

I took one 2 years ago, when I was only 17 so I knew a lot less than now. I attempted the brakes one, the ABS questions had me, I plan to take them soon enough.

[Brad D.]

I do think it would be interesting to evaluate the surface roughness and its effect on boundary layer size in an M30 intake using some sort of CFD. I just don't have the time to model the the intake manifold or I would take on the task. I don't know what you guys typically use but I usually use Floworks. If anyone has an M30 intake modeled, I'd give some analysis a go.

[turbodan]

Might be a lot of work for what its worth.

[Brad D.]

Might be a lot of work for what its worth.

I agree, but sometimes my geeky nature finds amusement in doing things like that. I do intend to do a full CFD analysis on my sheetmetal plenum I plan on building though to ensure good airflow distribution.