26 replies to this topic

[speedster]

So, when your designing your intake manifold runners consider how you like the needle to behave in your revcounter. The dbilas runners are about approximately 15cm in lenght hence the improvement in mid to high RPM power, which works well with my driving style

Edited by speedster, 12 April 2007 - 03:13 PM.

[luna_s]

overall question, is it worth doing ? seeing as the plastic manifold apparently does a good job ? eg a load of work for little to no gains ? would look a lot nicer tho , shouldn't be too hard to make and maybe cost 50 quid in materials

[rabidh]

So what does everyone think is the real-life difference in performance between: a.) Long, tuned intake pipes b.) The old approach of getting the butterfly as close to all cylinders as possible, keeping the cross-sectional area high but the volume low B is definitely a whole load easier to do, but i guess with a single butterfly its hard to keep all runners short and the distance from each runner to the TB the same, which could be one of the reasons for the crazty shape on the Z22SE? The other thought I had was whether the long runners (as well as for tuning obviously) are to allow slightly harsher cams to be used without a risk of blowback into other cylinders?

Edited by rabidh, 12 April 2007 - 05:17 PM.

[speedster]

I love the change pulling out the plastic made to my machine! If you have access to all the materials, a workshop, the skill to make one, or those all important helping heads and hand, I'd go ahead. Been interesting to see how you fair. You can always bolt the OEM item back on if the results don't improve your lot. Results can be compared with clipping_points mani too.

[luna_s]

heh i lack the first three but i'm always keen, i've never welded aluminium before or worked with it, welded enough steel tho, and i've only got access to a mig. think i just want my car back on the road asap, missing it terribly heh might make the flange before the car gets put back together.

[mandarinvx]

They have a flange too for £45 + post, Here, at the bottom

PS, has anyone got either Of These?or know if there's a copy online somewhere? - Is the book just the same as the GM PDF tuning file

Edited by mandarinvx, 13 April 2007 - 12:33 AM.

[SteV6]

PS- I can't get my head around this bit:

Resonance tuning occurs in the following manner. During an intake valve opening, air is drawn into the engine at very high speed and therefore, has a good deal of momentum. When the intake valve shuts abruptly, the air in the runner continues to move down the runner, creating a high-pressure area on top of the intake valve. This high-pressure zone will travel up the runner until it comes into contact with the dense, slow moving air in the plenum. This collision causes a hard reflection and a high-pressure wave to travel back down the runner to the intake valve. If the runner is the correct length, the intake valve opening will coincide with the high-pressure wave’s arrival. This will force more air into the cylinder, allowing for volumetric efficiencies over 1.0 (Winterbone).

Surely this could only apply if the engine were set at a given rpm, but as soon as the speed increases or decreases the valves will operate at a different frequency so the return air 'reflection' timing would be out, or is it because the velocity of the air is increased in proportion to the engine speed or am I missing something

This is exactly what VW uses for their VR6 engines! The 2.8, 3.2 and new 3.6L narrow angle V6 engines have a resonancechamber for this purpose. The chamber is open up to 900 rpm and above 4400 rpm. Believe it or not, but you can feel the "boost" when the valve opens!

Instead of using high velocity air flow in a long narrow manifold duct to ram more air into an engine at low rpm and then opening a short, large diameter duct for high rpm, the 3.2-liter V6 engine takes advantage of the pressure wave created by the pressure differential that exists between the combustion chamber and the intake manifold. All air enters the intake manifold plenum and torque port, then is drawn down the long intake ducts to the cylinders. Variable Path Intake Manifold The variable path intake manifold design increases low rpm torque and high rpm power by taking advantage of the selfcharging or “ram effect” that exists at some engine speeds. By “tuning” the intake manifold air duct length, engineers can produce this ram effect for a given rpm range. A manifold that has two different lengths of air ducts can produce the ram effect over a broader rpm range. The 3.2-liter V6 engine uses two lengths of air ducts but not in the same way as the dual path manifolds used on other engines.

A second plenum called the performance port, which is attached to a set of short manifold ducts, joins the long intake ducts near the cylinder head. A performance port valve, similar in design to a throttle valve, separates the performance port from the short ducts. Note that the performance port does not have any other passages to the intake manifold other than through the performance port valve. It does not have access to the torque port and does not admit any more air into the cylinders than what is already drawn down the long intake ducts. At engine speeds below 900 rpm the performance port is open for idling. The performance port valve is actuated. At engine speeds between 900 rpm and 4100 rpm the performance port is closed and the engine produces its maximum low end torque (the performance port valve is not actuated). At engine speeds above 4100 rpm the performance port is open (the performance port valve is actuated).

In the 3.2-liter V6 engine, the performance port valve turns to the performance position at engine speeds below 900 rpm and above 4100 rpm. This opens up the path to the performance port. The performance port is designed so that the intake and pressure waves will have a shorter path back to the intake valve ports. The performance port is filled with air when the intake valve ports are closed. When the intake valves open, the intake wave moves up both manifold intake ducts toward the torque port and the performance port at the same speed. Because the distance it must travel is shorter, the intake wave reaches the open end of the intake duct at the performance port before it reaches the open end of the intake duct at the torque port.

The performance port pressure wave is reflected back toward the intake valve ports, and that air is forced into the combustion chamber before the intake valves close. The pressure wave arriving too late from the torque port is reflected by the closed intake valves and pushes its air charge up the intake duct, filling the performance port in preparation for the next cycle.

At an optimal intake manifold length, the maximum pressure reaches the intake valve ports shortly before the valves close. By this time the piston has started back up the cylinder, compressing the air/fuel mixture. The pressure wave forces more air into the cylinder against this rising compression pressure, filling the cylinder with more air/ fuel mixture than would be possible from just the piston moving downward on the intake stroke alone. This adds to what is called self-charging or “ram effect.” As engine speed increases, the high pressure wave will have less time to reach the inlet port. Because the pressure wave is only able to move at the speed of sound, it will reach the intake valve ports too late. The valves will already be closed, and the “ram effect” cannot take place. This problem can be solved by shortening the intake manifold.

so basically the rearward part of the intake mani by the tb is always open and feeds the runners. the performance port is the frontward chamber of the intake mani. Having it open at certain rpms increases the ramming and sucking effect of the airflow and engine cycle.

so removing it or leaving it open would most likely decrease your low end while doing nothing else. I am unaware of how this is changed with FI programming. Probably leave it since both the VF and EIP kits for the 24v are fairly high rpm systems and kick in when the port opens anyway. if they made more boost at lower rpms you wouldn't need the help from the manifold design.

For picture see: http://www.seat-onli....html#msg386652


SteV6

Edited by SteV6, 13 April 2007 - 12:51 AM.