Some Nice 8 port info…
Basic Theory of Operation of the 8 Port
The amount of fuel and air sucked/forced into a cylinder is dictated by several factors, one of which is charge velocity. Higher velocity means more gets in. At low RPMs, you usually aren't generating much boost, and since you don't have much displacement, you're not sucking much either. A larger opening lets the charge in slower, a smaller one faster. Think of a garden hose: just holding the hose out, the water comes out at a decent rate, but it's in no real hurry. Press your thumb over the opening to restrict the exit area, and flow velocity must increase, for flow to be maintained. At some point, you are restricting total theoretical flow, but at lower flow levels, this will cause a higher exit velocity. The same is true with the CA18DET's secondary butterfly system. At lower airflow points (i.e. RPM), the butterflies are closed, forcing nearly all intake charge to go through half the space, increasing its velocity into the cylinder and therefore the rate at which the cylinder fills. More charge = more power, all else being equal.
CA18DET Secondary Butterflies Control System
The secondary butterflies are controlled via a vacuum operated actuator that sits on the back end of the intake manifold. When there is a vacuum, the butterflies are closed, and when there is no vacuum, are allowed to open. When correctly hooked up, this is controlled via the ECU for (presumably) optimal operation. The stock system uses a fairly complicated arrangement of gizmos, which I will cover towards the end. There are many ways to hook up this system. I'll start with the simplest.
Method 0: Do Nothing (WRONG way)
This is the worst method, i.e. not hooking it up at all. You get no benefits at all, and potentially some losses vs. not having the butterflies at all.
Method 1: The Simple way
This is the bare minimum anyone should do, and is very straightforward. Basically, you connect it to the intake manifold such that it sees vacuum and boost directly. As described above, when there's vacuum it'll pull the butterflies closed, and when there's no vacuum or boost, it'll let them open. This is not necessarily optimal, and from multiple accounts, is nowhere near as good as the correct way of hooking it up. You can either dedicate one of the vacuum ports to this, or T it in with something else (i.e. the FPR).
Method 2: The Stock ("Correct") Way
This is how it should be done, if you're running a stock ECU. By stock I mean OEM type engine control, retuned ECUs inclusive. This is quite complicated. The ECU controls the butterflies by turning a solenoid on and off. When on, they close, and when off, they open. This is achieved by connecting (when on) the butterflies to a vacuum source, and then when off, connecting them to a vent to ambient air pressure.
In detail, the vacuum source comes off the intake manifold, goes through a vacuum delay valve (possibly check valve), into a vacuum tank, then to the solenoid, then another vacuum delay valve (they’re to smooth the on/off transition) and finally into the actuator. The solenoid also has a connection running around to the intake side of the engine, behind the MAF, before the turbo, where it "dumps" the vacuum when the butterflies are switched off. The first valve may be a check valve (makes more sense), but the parts catalog in all regions has it listed "delay", whilst the FSM says "check" - and "check" also for the other valve, which can't be right or it would never release the actuator! Use the OEM parts and you won't have to care.
What happens is that due to the vacuum check valve built into the vacuum tank, the engine is always pulling a vacuum, or at least, not "venting" the vacuum, from the vacuum tank. This keeps it ready to go, all the time, in theory. After the tank, we have the solenoid. This is the one the ECU controls. When the solenoid is on, the butterflies are continuously held in vacuum by the vacuum tank. When off, the solenoid shunts the vacuum in the actuator and it's vacuum hose to the ambient air pressure by the intake, which releases the vacuum and opens the butterflies. Between the manifold and the vacuum tank, and also between the actuator and the solenoid, are vacuum delay valves. You could live without the valves, they’re just there to smooth things out. They merely restrict airflow to make the pressure changes in the system less sudden..
Like I said, it's complicated. It also takes up a lot of space in the engine bay...
Thank you to biosehnsucht and the NICO Club
Now this sounds really great doesn’t it, Higher port velocity increased “VE” everyone’s happy but there are two problems first off , I have personally seen around six “8 port CA18DET” swaps but I have never seen the control solenoid for the Butterfly’s also above this in order to use the Solenoids you will need the “jap” harness and ECU.
Now don’t get me wrong, I’m not attacking anyone. I have come to accept that I will also not win the 8 Port Vs 4 port debut, yes in theory you can gain extra low to maybe midrange torque but how much? And at what loss on the top-end?
Also now if the system was so great why wasn’t it more widely spread? Why Didn’t the RB or SR20 OR hell even the Sr16 use the same system?
Yes! Toyota used the system in the 4age but it’s the first thing they disable when pushing for ponies and its not used in the 20 Valves.
It’s not used in the 4G63 or in the 13B /12a that could use some low down torque
Because restricting intake flow and long runners work great on truck motor or pulling motor, to increase your port speeds and VE at a RPM. For example a bakkie for towing, my dad has the same system on his 1300 cc rustler but that thing can’t really rev past 5500rpm
It all because as soon as you revs climb past 5000 RPM the small ports and the butterflies (even when up) act like a restriction now why would you want this on a motor with a 7200 RPM ceiling?
But Now I hear you say, in theory small intake ports assist in VE and cylinder fill!
Yes! Small port designs are used in high performance N/A motors , Like Bikes and B16 (Vtec) and the S2000 where you want to keep the port speed up and growing as you climb into the higher RPM bands to increase VE but these motors can REV to 8000 RPM without batting an eye and that where they make there power.
But our cars are “boosted”, We don’t need to try and keep the ports speed up, The air is there with more pressure then any Honda could dream of about 0,5 bars of it. We just need to force as much of this air through the small ports we have into the Cylinder.
Now really it all boils down to what you fell and think is best, I have left some thing out of this because I’m to lazy to type anymore.
But I’m not attacking anyone just my point of view…
, now the motor is an import 8 port. Everyone says the 4 port has better flow, does anyone have anything to back this up?? Remember I am not looking peak power (Im not a dyno junky, number mean nothing to me), but more midrange torque. This is my everyday car so lowdown - midrange torque is what I am after, but I also dont want to restrict the motor at higher rpm. Would the 8 port be a restriction over 1 Bar??
