Should I be doing more BMF intake testing?

[OmniLuvr]

The downside that I see right off the bat is making a "smaller" turbo working harder to fill the plenum size. I could really see a smaller turbo running out of breathe way before the 400+ range with this intake

Turbos arent sized according to intake tract volume, they're sized to mass air flow into the engine

the only difference would be the amount of pressure (psi) needed to meet the tq/hp # of the previous intake setup. a small turbo will make 250 hp, the only difference will be the psi needed to make it, unless the flow path is so restricted that it needs such a high psi to reach the number that its out of its pressure map. it would be the same thing as people adding 3" intercooler tubes that are 4 feet long (at least) to reach a large front mount intercooler, only problem might be "lag" which so far usually isn't the case.

there is also plenty of meat in the inj bore to be ported out to fit a heavily ported head like warrens that would reduce the "taper" point. again, this is why I opted for the unwelded version so I can port the intake flange to my head to have a nice flow path...

[Shadow]

there is also plenty of meat in the inj bore to be ported out to fit a heavily ported head like warrens that would reduce the "taper" point. again, this is why I opted for the unwelded version so I can port the intake flange to my head to have a nice flow path...

I don't want to beat this like a dead horse, but remember, that Taper Should follow all the way to the Valve seat! So there is No choke flow through that taper, Only Acceleration Too the Valve opening!

So the BMF gets the volume + pressure Too the opening of that inj flange and then the taper does the rest! Larger the port opening to the head, more gradual the taper But Still accelerating Too the valve opening!

[Reaper1]

You do NOT want maximum flow velocity AT the valve seat. The port will hit choked flow and the turbulence will KILL flow in the low lift areas. Maximum velocity, and the port choke point should be BEFORE the valve. Typically right around the STR (short turn radius).

A long time ago I did a lot of figuring on what size the port needed to be at the STR and I think I got right around 1.8sqin. (maybe is was 1.65...can't remember and the info is LONG gone, I'd have to re-do it all). This would be for an "ideal" situation based on a certain amount of flow required fro a certain amount of power. So, one size does NOT fit all (please keep that in mind).

[OmniLuvr]

I don't want to beat this like a dead horse, but remember, that Taper Should follow all the way to the Valve seat! So there is No choke flow through that taper, Only Acceleration Too the Valve opening!

I was basically just stating that the "taper" (in quotes) could be modified to suit other individuals needs, the taper that is put into it should be fine for a gasket matched head port job, but can be opened up much more if needed to suit other peoples needs for (much) larger ports.

[thedon809]

To sum this all up, I think we can all agree that having the large runners with a more gradual taper would be ideal, but whether it is actually worth the added cost is the question. The only true way to find out if the taper in the BMF intake hurts or doesn't would be a direct comparison with another BMF that had smaller runners instead of the taper, or the same size runners with a more gradual taper.

[acannell]

Heres what continuing the taper to the plenum would look like. Additional cost, probably $150. The cost is because the runners would have to be made from scratch and there would be alot more welding. I dont see what the big deal is. Its barely any different.

[OmniLuvr]

I think the "problem" in question about taper is in the manifold flange itself, because it starts at (?) size and ends at gasket size within a certain distance. so either the runner would have to be a smaller inside diameter (which I wouldnt want) or the intake port in the head would have to be larger than gasket with the intake flange being ported to suit.

personally, I don't think any of that is a problem with the intake, I don't think there is any "problems" at all, just certain tweaks they may want to be done to suit other peoples needs, but the whole point of "this" intake was to flow a crap load of air at a reasonable price, I mean, you are literally "giving" them away... well at cost anyways... and maybe not even that...

[Vigo]

a small turbo will make 250 hp, the only difference will be the psi needed to make it

I think most of the power differences between two turbos which are both capable of flowing X are firstly the pumping losses on the exhaust side, and much less significantly, changes in oxygen content in the air charge @ x psi due to differences in temperature from compressor adiabatic efficiency.

I guess one of the issues with this thread is that 'people' are asking other 'people' to hand out the equivalent of a high dollar education for free through what would probably be literally hours of typing, or just back away from using simplified analogies at all. Different people are talking on different levels, and i think there is a difference between someone being wrong, and someone just not being willing to dedicate a huge charity effort towards writing something that is complex out in a long and detailed enough form that it will be irrefutable. The internet has its limitations. One person can't and won't confer the learnings of an entire career out through a few posts, especially to a guy who is prickly about how he receives info.

Regarding water vs air (vaguely), here is a question: Doesnt air flow between the turbo and the intake valves SLOW as boost increases? Greater pressure potentially means moving a larger mass at a lower speed. I have an inkling that the boost number is actually a reflection of the fact that the intake charge CANT maintain the same speed as mass flow through the system goes up. Obviously the acceleration into the cylinder when the intake valve is open will be higher, but i wonder if the air transitioning from the throttle body to the plenum isnt actually slower than 'stock' at high boost pressures and whether this makes that transition area more forgiving.

[black86glhs]

Rob, you are correct and I should have clarified "stockish" in my previous posts. Someone might have a ported head but not making major HP(like me). The intake will fit on it, but isn't really designed for something like that. That makes sense.

[acannell]

Rob, you are correct and I should have clarified "stockish" in my previous posts. Someone might have a ported head but not making major HP(like me). The intake will fit on it, but isn't really designed for something like that. That makes sense.

I didnt see any negative effects using it on my stock unported swirl head at stock boost levels. I saw minor improvements but I have alot of other things done to the car so I cant really attribute that to the BMF.

Its not so much that the BMF wont work on a stock engine, its just being wasted, thats all. Like buying forged pistons but keeping everything else stock.

Also, Im pretty sure that the stock intakes and the head dont line up either unport-matched, so whatever kind of mismatch you get with the BMF is probably not much different than a stock intake. Or probably doesn't matter that much anyway at stock power levels.

[black86glhs]

I didnt see any negative effects using it on my stock unported swirl head at stock boost levels. I saw minor improvements but I have alot of other things done to the car so I cant really attribute that to the BMF.

Its not so much that the BMF wont work on a stock engine, its just being wasted, thats all. Like buying forged pistons but keeping everything else stock.

Also, Im pretty sure that the stock intakes and the head dont line up either unport-matched, so whatever kind of mismatch you get with the BMF is probably not much different than a stock intake. Or probably doesn't matter that much anyway at stock power levels.

Agreed. That is the translation of my post.

[5DIGITS]

I don't want to beat this like a dead horse, but remember, that Taper Should follow all the way to the Valve seat!
So there is No choke flow through that taper, Only Acceleration Too the Valve opening!
So the BMF gets the volume + pressure Too the opening of that inj flange and then the taper does the rest!
Larger the port opening to the head, more gradual the taper But Still accelerating Too the valve opening!

You do NOT want maximum flow velocity AT the valve seat.
The port will hit choked flow and the turbulence will KILL flow in the low lift areas.
Maximum velocity, and the port choke point should be BEFORE the valve. Typically right around the STR (short turn radius).

Great point - you are not alone on this one.
It's agreed within and outside this forum that this a poor place to accelerate something that does like to turn.
Consider that the bowl area increases in volume to reduce velocity, aid in short side flow while targeting a uniform turn into the seat area.

You brought up a second point that's worth recognizing - low lift flow.
While many target the greatest CFM # at peak lift, it typically comes at the cost of low lift flow.
The game of area under the curve is certainly a better approach when porting a head and your point was well placed.

[Shadow]

I was basically just stating that the "taper" (in quotes) could be modified to suit other individuals needs, the taper that is put into it should be fine for a gasket matched head port job, but can be opened up much more if needed to suit other peoples needs for (much) larger ports.

My dead horse comment wasn't directed at you Just an opportunity to state something that I believed people were missing

You do NOT want maximum flow velocity AT the valve seat. The port will hit choked flow and the turbulence will KILL flow in the low lift areas. Maximum velocity, and the port choke point should be BEFORE the valve. Typically right around the STR (short turn radius).

A long time ago I did a lot of figuring on what size the port needed to be at the STR and I think I got right around 1.8sqin. (maybe is was 1.65...can't remember and the info is LONG gone, I'd have to re-do it all). This would be for an "ideal" situation based on a certain amount of flow required fro a certain amount of power. So, one size does NOT fit all (please keep that in mind).

Yeah, this is where trying to explain things on the net becomes a lesson in futility! lol I was simply trying to get people to "see" the intake tract as a Whole. To Remove the "tunnel vision" of just seeing the 1.8" taper in the manifold.

I Didn't mean that the taper actually goes Right to the seat, as that would be impossible. (the factory valve throat is already too big! lol) This is where I Expect people to read between the lines and use some Common sense, but my bad for wording it Wrong.

So, the taper is going to continue past the head flange area, and reach right down to the throat. (how's that?)

[5DIGITS]

Yeah, this is where trying to explain things on the net becomes a lesson in futility! lol
I was simply trying to get people to "see" the intake tract as a Whole.
To Remove the "tunnel vision" of just seeing the 1.8" taper in the manifold.
I Didn't mean that the taper actually goes Right to the seat, as that would be impossible. (the factory valve throat is already too big! lol)
This is where I Expect people to read between the lines and use some Common sense, but my bad for wording it Wrong.
So, the taper is going to continue past the head flange area, and reach right down to the throat. (how's that?)

Certainly easier to understand.
Much like a valve to seat ratio is desired (the seat ID should support 85% of the valve OD - a slightly higher ratio will work depending on the surrounding port work), the bowl area should exceed the area of the upstream port area.
Great care should be considered during the porting process to insure that the port enlargement is not extended to the point just prior to the bowl area.
Generally speaking, the air requires a 3/16" - 1/4" (Even wider on high RPM/high boost applications) to realize a reduction of velocity before the short side turn - not at the turn.
If the port area is opened too far and too late in the port (too close to the turn) it will be identified as audible "sputtering or air spitting" during flow bench testing with flow numbers that will go flat, regardless of increased valve opening/lift.