Butterfly Valves stuck?

[nocwage]

Weird experience..Just dyno'd my car and made 230 lb-ft.. which is great.. except that immedaitely after peaking at like 4700 rpm it just dropped like a SOHC..Do you think my butterfly valves are not opening?

[nocwage]

Did two pulls, different amount of boost, each time the exact same thing.. torque ramped up then peaked at 4500ish and then dropped..

Not like the nice curves I see everyone else with who's torque basically flattens at the point mine starts to fall

[nocwage]

Oh yea

Super-60 T3, 450cc injectors.. was around 10.5:1 about 1000 rpm before the peak and then right through it pretty much..Standard timing94 Octane gas

16psi of boost

Car runs fine otherwise.. no blow-by or smoking.

[nocwage]

I disconnected the vac line from the butterfly actuator.Should this make them OPEN all the time or be CLOSED all the time?Butt dyno says the car pulls way more above 5000rpm but I haven't drove the car for a while and I might just be comparing against my Sentra SE-R..

[biosehnsucht]

if they're not connected at all, or even straight connected, then they should open at atmospheric and above on their own, vacuum pulls them closed.

if they're not connected properly (vacuum check valve etc) then you might mess something up but I would expect them to fail open, not closed. If you have a check valve only, and no way to relieve the pressure, they'd get stuck closed.

[nocwage]

My car is an actual imported Silvia so it had everything in place, including what I'm guessing is the 'vacuum pump' I have a feeling though that the solenoid that is supposed to trigger them to open is dead (the car is from 1988 after all) in which case the butterfly valves were closed all the time..

I jsut disconnected the hose and plugged it so I would not have a boost leak.. seems okay so far, just not sure I want to go blow $85 on two pulls to fidn that it's still fubar'd, is there a way I can check?

[float_6969]

It's kinda hard to get to, but if you look at the intake manifold, near the head, you can kinda see that the sub-manifold that comes off of the runners of the plenum is 2 pieces. There is a weird spring loaded thing with a screw dead center of the motor on the sub manifold. The shaft of the valves are connected to this thing. With the line disconnected, or the car off, they should be UP. With the line conenected, they should be down at idle, and open up somewhere between 3K and 4K RPM. You don't need a special solenoid to turn them on and off. Anything from a junkyard will work.

[float_6969]

wow 10.5:1 is pretty rich, that could make it bog down as well.

[nocwage]

I agree, it's far too rich.But the torque curve is uncanny, it's just like a SOHC..It peaks at 4500 and then drops like a SOHC rather than a smooth plateau like all the other Dyno graphs people posted in the dyno thread.

I make the same amount of torque at 6500 rpm as I do at 2800..

I'm hoping someone has experienced the same issue so that I know it's not some other problem..

I don't think it's compression or anything else.. the car makes power nicely until the peak and then it just drops like the throttle was let off

[nocwage]

Sorry I don't have a scanner..

Green line is torque

[float_6969]

Did you read my post on the butterfly valves a couple of posts up?

[nocwage]

Yes, but it's not exactly easy to test.. How can I see that unless I'm lying underneath the car on jacks while someone revs it to 4000?

I've disconnected it and this week I'm going to jack it up and just make sure it's not seized and just leave them open all the time.

I won't miss the small amount of torque i'd get compared to the HUGE amount of HP I'm losing.

[float_6969]

Apparently I wasn't clear. Except for the 3-4K RPM change over, you can at least check that they are mechanically functional. This can all be done with the car at idle.

Connect the vac line back up to the actuator. Start the car. Remove the vac line from the actuator, and watch the middle of the intake manifold, down between the fuel rail and the head. You should see a little thing move up when it's disconnected, and down when it's connected. If that part of it works properly, then you've simply got a potentially free actuator that has failed. Go to the junkyard and pick one up. Put it in your pocket. Leave.

[nocwage]

Do you have a picture of where I should look? I was looking for a while yesterday and couldn't see anything on the top and assumed it was underneath..

Should it be dead center?I couldn't see anything

[rico05]

Is there supposed to be a check valve in the vac source line for the actuator? I just have mine hooked directly to the vac source on the back of the intake mani.

Good info. Ryan, you may want to clean this thread up and sticky it somehow. I dunno. Add butterfly info to the FAQ?

[float_6969]

No, there's not. At least not unless you hook it up so that it's controlled by the computer like it's supposed to be.

Here is the issue if it's not controlled by the computer. The whole purpose of the valve is to increase port velocity at low RPMS. This means that the actuator needs to be RPM sensitive. With it referenced to the manifold, it's load sensitive.

The follow is an example of what should happen.You're going along at 2000RPM (nice round number). The butterfly valves are shut. You punch it and the volume of air in the intake increases. The increased volume means that the RPMS increase (providing you have sufficient fuel) as does the port velocities, this increases the volume of air, which increases the RPMS and port velocities, etc, etc. The will continue until the point that the computer opens the valves. The exact point this happens I'm not sure of (peak torque?) but will occur at whatever RPM is associated with a lack of increase in the volume of air, even though the RPMS are increasing. (At some point the fact that the opening into the motor is small will not allow enough air to enter the motor and power will fall off) The opening of the valve will now allow a larger volume of air to enter the motor, the RPMS will increase, etc, until peak HP is reached at which point the cams/plenum/exhaust/something doesn't allow the motor to breath well anymore and the power falls off.

With the line hooked up to vacuum the actuator opens the valves when you step on it because there isn't any vacuum to keep them shut. The same happens as above, but because the valves are open, the total intake area is greater and able to flow a greater volume at a given port speed. Because of this the port speeds are lower at a given RPM. Low port speeds = poor torque.

This is why 8 and 12V motors have really good low end power. Their small port volumes allow for really got port speeds down low and good torque. The problem is that the small volume of inlet area eventually poses enough of a restriction to the air flow that power starts to fall off as the air can only move so fast. With the butterfly system you are basically putting a 12V and a 16V in one motor. The best of both worlds.

What isn't definitive is HOW much increase in torque it makes. I KNOW it's noticeable, but does it increase the are under the curve enough to compensate for it's potentially poorer high end power abilities?

THAT'S what I hope to find out...

[dattodude]

Yes, and to expand on floats description. The vaccuum canister is installed to allow for on/off throttle actuation of the power valve. Without it installed, it is possible there won't be any vaccuum for the power valve to pull the butterflies shut. This will result in flat spots and less responsive performance at sub 4000rpm. It just happens that most of your city driving will be done in this rev range..so you'll think your CA is less of a monster than it really is.

Remember the butterflies are all open by default.

The 'ms paint' diagrams I've seen on this site are ok to get the car running, but not the way the factory intended it to be installed.

The flow diagram is this:

(1) strong vaccuum source -> (2) one way valve -> (3) vaccuum canister -> (4) three port solenoid valve -> (5) one way + restrictor valve -> (6) power valve

1. Back of the plenum for vaccuum, generally spliced into the fuel reg vaccuum source.2. one way valve to only allow airflow towards engine so boost doesn't break things. Also allows the vaccuum canister to 'fill up with vaccum equal to manifold vaccuum'.3. black plastic canister the size of a beer can, 2 connections, one to the one way valve (3), and one to the solenoid valve (4) 4. this solenoid valve is controlled by the ECU, it determines when all 16 valves are flowing. It is normally on, and flips the power valve side to atmosphere.5. This valve allows the air to quickly flow towards the vaccuum canister (via the valve), but it slowly flows towards the engine. This slow flow of air, is the vaccuum draining from the power valve to atmosphere (or back to low pressure intake) via the power valve. This slower flow means the power valve opens slowly at the pre-defined 4000rpm, it doesn't flip open.6. The power valve does the work of opening and closing the butterflies.

Because I know the CA18 ECU will open the valves with the car in neutral, I reckon it's not 'load dependent', just revs dependant, as explained in the 1990 N13 EXA Pulsar Workshop Manual.

Hope this helps.

ps. I have all this vaccuum stuff under my dash, and it sounds like an iron lung when I'm going through the gears. :-)
Modified by dattodude at 3:26 AM 1/8/2007

[float_6969]

So yours does change over at 4K? I knew it was somewhere between 3K & 4K, but not exactly sure where, and since I was connecting a standalone, I had to decide where to open it by my "butt dyno", and I ended up settling on 4K. It also took me a little while to figure out that I needed them to open slowly. If they don't, you get an odd hiccup in the power as the port velocities suddenly drop and the intake volume suddenly increases. I couldn't find the inline bleeder, so I just capped the outlet port on the solenoid and then put a very small hole in it so that they opened slowly. It works like a champ now!

[rico05]

I knoe the therory of the purpose of the multiport design, I am just having a hard time visualizing how to get them to operate as functionally as possible. If someone could get a pic of their setup (on a swapped car, preferrably), I would be very appreciative.

[nocwage]

Hah I think my dyno graph shows EXACTLY what float was describing..If mine never opened then the car just choked itself after 4500 which is around where they should have opened.

Should sticky this thread, it's good info and I couldn't find anything like it anywhere.

[nocwage]

Do you guys want a picture of the stock vacuum pump stuff?I didn't remove any of it, just disconnected the hose from the butterfly valve actuator and plugged it.

[davidricardo86]

Here i took these last night. They are on my build up page(my ca18det...!) and thought maybe they might be useful to you nocwage.

[dattodude]

Those pictures should be a good help.

Good work DR86.

[nocwage]

AWESOME! Thanks a lot!

[nocwage]

Thanks again, those pics made it really easy to find what I was looking for!

[dattodude]

..and what did you find? :-)