Frezny

Maybe we should start a Pay-Don-to-Research pool. We know he loves the work. If enough of us chip in, he can go further... I've already done my part, its your turn now guys.

SleeperSE

- First, a message for Daniel B. Martin: you're right on the square thing. I got my engine's mixed up and lost the numbers for the VQ. Although, this still makes me wonder why we (4th Generation Maxima's, Don) can't rev since the stroke is less than the bore. Some parts of this engine just don't make sense.

- I'd like to express how tired I am of hearing how the only people that matter are the ones who rip their engine's apart every weekend just to go fast in a straight line for a 1/4 mile. You people STILL haven't answered my questions concerning the intake manifold. All you said was that it was not worth your time.
- Is that because there are systems involved that are beyond your capabilities, or is it because YOU DON'T KNOW THE ANSWER?

- The question still stands: Does the 5th generation dual-stage intake manifold operate based upon the physical (air-flow, etc.) or the electrical (ECU controlled)?

bigtexan7

no clue, why don't you buy one and try to put it on your car and then report back to all of us?

SleeperSE

- OK. I was already planning on putting in an inquiry to my dealer today (if they're still open) or Monday. I'll post back later.

Daniel B. Martin

I inquired about this with an E-mail pal who works at a Nissan dealership in a distant city. His answer was "The valve is controlled through a solenoid that is controlled by the ECU in the 2000 and 2001 Maxima."

MardiGrasMax

iTrader: (14)

It is vacum actuated, but controlled (switched open and closed) by the ECU. Paramaters are engine load, engine rpm, throttle position etc.

ZuMBLe

iTrader: (1)

It would be really cool if we could control the runners with a switch in the car. We don't even have to use the ECU. If you know you're gonna be racing. Keep the switch off (long runners) while launching. Once you get up past 3500rpm. Flip the switch and go to short runners. If you're racing you won't use the bottom end of the band anyways. But for better driveability you can turn the switch off and go back to long runners for torque. That would be great! =) I hope this mod works and its not too expensive. It would be a very good mod.

ZuM

mzmtg

iTrader: (11)

You're missing the point. The car does that anyway. On the 5th gen its done automatically, and if put on a 4th gen a simple RPM activated switch would be ideal.

It already switches when it needs to. There's no situation where you would want it to stay at the same setting for all RPMs.

You would never want long runners at high RPM and short ones at low RPMs (given the choice). That's why the 5th gen (and all cars with this system) do it by themselves.

Jeff92se

iTrader: (82)

Well you wouldn't want it to engage when the car is in neutral or how about when the car is downshifted but the gas pedal is not pressed?? Both cases would not be ideal for the 2nd runners to engage because there is no load on the engine to warrant the 2ndary runners. But still, a strick rpm switch would engage them. Might create surging or other drivibilty problems. I would bet the 2k runners are actived not only by rpm, but tp position, gear (N or in gear), and vacuum activated through the ecu. That is how the 3-gen VTC assemblies are handled.

mzmtg

iTrader: (11)

I found some info in one of my books about how this all works for ya. This came form Advanced Engine Technology by Heinz Heisler. (Incidently the book has a cutaway of the SR20DE on the front)

"This system has a plenum chamber positioned alongside the engine with the throttle valve situated in its entrance to control the air flow. Long curved ram pipes supply air from the plenum chamber to the individual inlet ports and a secondary short pipe, also supllied form the plenum chamber, intersects the long pipe further downstream. Each short high-speed pipe has its own butterfly power valve to close off the secondary passageway at low engine speeds.

Low engine speeds

At low engine speeds the power valves are closed, and therefore air can only flow from the plenum chamber to the valve port through the tuned long ram pipes. The dimensions of the long pipes maximize the inertial pile-up of the charge in the engine's speed range and also tune the reflected pressure-waves to reach their peaks just before the effective closure point of the inlet vlaves at some critical engine speed. On either side of this critical engine speed, the phasing of the pressure-wave relative to the closing point of the inlet vlave will have shifted and thus reduced the effectiveness of the pressure-wave.

High engine speeds

As the engine speed rises beyond [the critical speed], the power valves open so that the inlet valve ports now draw charge from both the long and short branch pipes. Accordingly, there is now a much shorter tuned ram pipe length which requires a much higher engine speed for the first reflected pressure-wave peak to align with the inlet valve closure point. Thus, the volumetric efficiency curve will have two peaks, and hence this secind stage tuned system upholds the engine's torque in the upper speed range."

MardiGrasMax

iTrader: (14)

Acording to the FSM it uses...
MAF
CAMSHAFT REF
CAMSHAFT POS
ENGINE COOLANT
THROTTLE POSITION
THROTTLE CLOSED
IGNITION ON

Why do you think it uses engine coolant? So it dosent switch over until the motor is warmed up? Curious!!!

There is also a diagnostic procedure that says you need to rev the motor above 5k and see if the Variable Air Control Induction System (VACIS) power chamber actuator moves. So 5k is the setting for the RPM switch

I think a WOT and and 5k RPM should be good enough. Or just a 5k RPM switch, but you may get some surging.

If I can find some one to go in with on a 2k motor I'll do it. I might just buy the motor and hold the block, heads, etc. till someone needs them.

Loren00Miata

First, this shows the benefit of a flow bench. The most likely reason for the nominal difference is that the exhaust manifolds already outflow the exhaust ports in the heads. Headers are a waste of money at this point. In addition, if the Y-pipe is equal length and has tubing at least as large as the manifold exits, there is simply no benefit in going larger. Unequal length pipes may benefit with larger tubing due to exhaust pulses colliding together, but will not produce the velocity of the smaller tubing and reducing torque. A good example of this is an equal length 1 1/2" header will product more HP and torque than an unequal length 1 5/8" header on a Mustang(dyno proven). Opening the exhaust up too much will also lose velocity and cause turbulence.

This is why before porting any parts, I would have them flow benched. This is very significant. It will give the best indications of gains without bolting everything together. This is especially true for doing it for the first time. If the numbers between the exhaust ports are very close to the stock manifolds, then there will be gains with porting the heads.

The same goes for the intake. Before making any changes to the intake, get the intake ports in the heads flow benched. Then flow bench both a 4th gen and a 5th gen intake. See where the flow bench numbers are in reference to the heads. If the numbers are close between the 2, you may be better off porting or extrude honing the 4th gen intake than going to the 5th gen intake.

As far as the 5th gen butterflies go, just do what the hybrid Honda guys do. A lot of DOHC VTEC swaps are done using the non-VTEC computers. They simply put an external rpm switch in. This is much simplier than having to worry about the computer.

ZuMBLe

iTrader: (1)

You are right. A RPM switch would be much easier. =) But flipping a switch seems cooler.. =) haha.

ZuM