New (old?) Idea.

[2006eg33]

basically its just like this


thats from a 96 mustang cobra. basically it has 16 runners, 8 long, 8 short. in low rpms the short runners are closed, so air is forced to travel the long runners with good low end driveability, great low end torque. At the proper rpm it opens the short runners and the air passes through the short runners taking the path of least resistance. making power to 6500rpm

[oab_au]

Originally Posted by BRZCory

TireIron, that sounds like a BEAST!

Also guys, FWIW, I bought a Ford supercoupe M90. It's a LOT smaller externally, so it should be easier to mount/fabricate flanges for.

Getting back on topic, a couple of extranious theories:

From what I've read I understand it thusly: The stock system at low RPM uses an inertia system. This is the same as most other "Tuned" intake system whereby the runner length and diameter are tuned so that the inertia of the air flowing into the cylinder is at it's greatest. Too big and you don't build inertia, too small and it's restrictive, much like exhaust header tuning.

Am I on topic here or completely off my rocker?

(Also, I'm still trying to figure out why they need a small port beside the IRIS valve, and then open the valve for a big port. Unless I've got my systems mixed, and the resonance (sound) tuning is for lower-RPM, while the inertia tuning is for high-rpm)

That small port is the PCV outlet. When the valve closes it has to connect to both sides, the EGR also.

Originally Posted by 2006eg33

basically, it starts with a long runner intake for torque development, and switches to short runner intake for power development.

it's basically an IMRC, but with a single valve in the middle.

You both are looking at the type of inertia system that everyone else uses. The Subaru inertia is completely different to the type that uses an inlet tract for each cylinder, that changes length, like the 96 mustang cobra you show.
Subaru uses the valve, to divide the inlet manifold into two separate systems, that has the three cylinders on each side, breathing through its own throttle body to work independently.
If you look under the manifold, you can see that the three inlets open into a fat log chamber, fed by a throttle body.



The three cylinders pull air into the chamber, one after the other, every 240*. As one inlet valve closes the next cylinder opens its inlet valve to pull its air into the chamber. This has air pulsing into the chamber every 240* causing a rise in pressure, as each piston accelerates down the bore. As the piston slows, to stop, at the bottom of the stroke, the air keeps rushing into the chamber, increasing the pressure. As the pressure reaches its maximum, that inlet valve closes to trap about a 7psi. pressure in the cylinder. At the same time the next inlet valve opens, and the rest of the pressure blows through the combustion chamber to clear the exhaust gas. Then its piston starts to pull its air into the chamber to increase the pressure for its inlet valve to close on.

The cycle goes on reaching its maximum pressure at 3200rpm, which depends on the chamber volume, throttle opening and the valve duration of 240*.

This is the pumping action of the Helmholtz chamber that is used on many inlets to produce an opposite pressure to control induction sound. I don’t know of any other engines that use the chamber to power the inlet pressure as succesfully as this one does.
Yamaha use a version on their exhaust (EXUP) that uses the exhaust pulses to power the chamber, but they use the negative pressure to start the inlet..


Harvey.

[BackWoodsBob]

Originally Posted by BRZCory

I was under the impression that the stock manifold makes it's power via intake resonance tuning (IRIS valve). And that boost of any type would cancel out the effects of such (hence why turbocharged/supercharged cars don't have variable length intakes, because the pressure wave is a minimal factor compared to the charged intake air).

Processengr, it's an M90. I'd need twin M62's on an EG! which would allow you to retain the stock manifold if you could find room for all of that, but then you'd probably need a 12" cowl hood!

I told you like 100000x's to keep the iris valve operating when going boosted. y u no listen NOOB

[BRZCory]

Originally Posted by BackWoodsBob

I told you like 100000x's to keep the iris valve operating when going boosted. y u no listen NOOB

Because no room MR. PVC INTAKE!

[BackWoodsBob]

Mount the SC on the side of the engine, use the intake runner bolts for the mounting points. It's been done on rs25 for the ej25 SC'er projects...

And besides, harvey, at 8psi the m90 is going to be CRANKING heat to keep up with the eg33's taste for oxygen.

Hell, 10psi on an ej25 had intake temps well over 130f post TMIC. At the higher volume the EG33 eats it's going to make even more heat, which is why cory, I recommended you going with the m112

[BRZCory]

Originally Posted by BackWoodsBob

Mount the SC on the side of the engine, use the intake runner bolts for the mounting points. It's been done on rs25 for the ej25 SC'er projects...

And besides, harvey, at 8psi the m90 is going to be CRANKING heat to keep up with the eg33's taste for oxygen.

Hell, 10psi on an ej25 had intake temps well over 130f post TMIC. At the higher volume the EG33 eats it's going to make even more heat, which is why cory, I recommended you going with the m112

I'd go twin screw before paying for an M112.

And I don't have a *good* way to route the belt around the side of the engine with my radiator placement. Nor do I have enough length between the headlight and strut tower for either of my M90's. Nor do I like how it looks.

So I'm gonna DIY my own intake. If it doesn't work well, I'll just bolt the stock one back on. I'm starting to put more faith in the practice of not discussing things to death.

[2006eg33]

Originally Posted by oab_au

That small port is the PCV outlet. When the valve closes it has to connect to both sides, the EGR also.



You both are looking at the type of inertia system that everyone else uses. The Subaru inertia is completely different to the type that uses an inlet tract for each cylinder, that changes length, like the 96 mustang cobra you show.
Subaru uses the valve, to divide the inlet manifold into two separate systems, that has the three cylinders on each side, breathing through its own throttle body to work independently.
If you look under the manifold, you can see that the three inlets open into a fat log chamber, fed by a throttle body.



The three cylinders pull air into the chamber, one after the other, every 240*. As one inlet valve closes the next cylinder opens its inlet valve to pull its air into the chamber. This has air pulsing into the chamber every 240* causing a rise in pressure, as each piston accelerates down the bore. As the piston slows, to stop, at the bottom of the stroke, the air keeps rushing into the chamber, increasing the pressure. As the pressure reaches its maximum, that inlet valve closes to trap about a 7psi. pressure in the cylinder. At the same time the next inlet valve opens, and the rest of the pressure blows through the combustion chamber to clear the exhaust gas. Then its piston starts to pull its air into the chamber to increase the pressure for its inlet valve to close on.

The cycle goes on reaching its maximum pressure at 3200rpm, which depends on the chamber volume, throttle opening and the valve duration of 240*.

This is the pumping action of the Helmholtz chamber that is used on many inlets to produce an opposite pressure to control induction sound. I don’t know of any other engines that use the chamber to power the inlet pressure as succesfully as this one does.
Yamaha use a version on their exhaust (EXUP) that uses the exhaust pulses to power the chamber, but they use the negative pressure to start the inlet..


Harvey.

i took this and did some non svx reading about using intake manifold tuning to get a positive pressure in the cylinder. it's very cool stuff. free boost almost.

now would this intake tuning be accentuated by boost? or hampered by it?

also it seems to me that cam's could severely alter this effect if the valve over lap is played with. possibly for the better, or the worse.

[BackWoodsBob]

Be a man, mount that **** on TOP of the stock intake and run a hood cowl! And by 'hood cowl' I mean throw a plastic storage tote upside down over it. Walmart has them for 15$!

[icingdeath88]

Originally Posted by 2006eg33

i took this and did some non svx reading about using intake manifold tuning to get a positive pressure in the cylinder. it's very cool stuff. free boost almost.

now would this intake tuning be accentuated by boost? or hampered by it?

also it seems to me that cam's could severely alter this effect if the valve over lap is played with. possibly for the better, or the worse.

I'd bet that the RPM ranges that the effect works at will will move either up or down. Pressure is a factor in Heimholtz resonance: http://www.phys.unsw.edu.au/jw/Helmholtz.htm

[oab_au]

Originally Posted by icingdeath88

I'd bet that the RPM ranges that the effect works at will will move either up or down. Pressure is a factor in Heimholtz resonance: http://www.phys.unsw.edu.au/jw/Helmholtz.htm

Link no work.

Harvey.

[oab_au]

Originally Posted by 2006eg33

i took this and did some non svx reading about using intake manifold tuning to get a positive pressure in the cylinder. it's very cool stuff. free boost almost.

now would this intake tuning be accentuated by boost? or hampered by it?

also it seems to me that cam's could severely alter this effect if the valve over lap is played with. possibly for the better, or the worse.

Boost won't change how the pressure works in the inertia system, just add about 7psi pressure to it.
The Resonate system will change a bit, due to the increase in pressure, to increase, and the temp to reduce, the speed of sound. So have to do it to see.

The inlet cam duration for the Inertia to work, has to be no longer than 240*. If you look at what I said, 'about one valve closing on the high pressure, and the rest of the high pressure, blowing through the next valve to open, blowing the chamber clean'.
You can see that if the duration is increased to 250* the second valve opens 10* before the first has captured the high pressure, so all the pressure went out the seconds valve overlap,and out the exhaust.

Harvey.

[Tireiron]

Yea my setup has the IRIS valve removed and just an open plenum for the intake after the supercharger, however it also has custom ground cams that change the overlap BIG time to better suit a S/C setup which needs almost no overlap in the valves. Once I get the Hydra tuning sorted out this spring I will be able to post up some results from driving and dyno time.

[oab_au]

Originally Posted by Tireiron

Yea my setup has the IRIS valve removed and just an open plenum for the intake after the supercharger, however it also has custom ground cams that change the overlap BIG time to better suit a S/C setup which needs almost no overlap in the valves. Once I get the Hydra tuning sorted out this spring I will be able to post up some results from driving and dyno time.

Yes I am very familiar with that set-up, though don't really know what the cams ended up being. I don't think that they had less overlap, maybe a bit more.
Be good to see you get it going.

Harvey.

[EdWindows]

Originally Posted by BackWoodsBob

Mount the SC on the side of the engine, use the intake runner bolts for the mounting points. It's been done on rs25 for the ej25 SC'er projects...

This is what I'm planning on doing, but I'm not sure if there's enough room. I need to go pull one off a dead Buick and do a test fit.

Btw, you have an EG33 swapped Legacy, right? I believe you mentioned that in your looong DIY port polish thread on RS25 (a lot of threads there are 100+ pages ) I read a while ago. I'm helping my friend upgrade his 97 2.5GT and was wondering how much it cost you to swap in the EG33, as it seems to be a more realistic option than a EJ257 swap given his budget.

Originally Posted by BackWoodsBob

Be a man, mount that **** on TOP of the stock intake and run a hood cowl! And by 'hood cowl' I mean throw a plastic storage tote upside down over it. Walmart has them for 15$!

+1

[2006eg33]

Originally Posted by oab_au

Boost won't change how the pressure works in the inertia system, just add about 7psi pressure to it.
The Resonate system will change a bit, due to the increase in pressure, to increase, and the temp to reduce, the speed of sound. So have to do it to see.

The inlet cam duration for the Inertia to work, has to be no longer than 240*. If you look at what I said, 'about one valve closing on the high pressure, and the rest of the high pressure, blowing through the next valve to open, blowing the chamber clean'.
You can see that if the duration is increased to 250* the second valve opens 10* before the first has captured the high pressure, so all the pressure went out the seconds valve overlap,and out the exhaust.

Harvey.

240 at .050 right?


this intake system is making sense to me.

do you happen to have the stock camshaft specs? advertised duration, duration at .050, lobe seperation angle and lift?