Secondaries... What exactly do they do?

[Camarok]

I've been putzing around and i happend to find the connector that connects to the secondaries diaphrams. As i unhooked it, they opened up. They stay open. I've heard that "you lose low end torque and power", "loss of gas milage" and other things. I've noticed no loss in power, and actually it is more responsive/less jerky when you slam on it at low revs. Also when I hit 3k rpms, it seems to pull harder then. SO instead now i have a sho that will pull harder at 3k insetad of it kicking in at 4k. What am I losing in this.

~~FYI I do have the secondaries connected factory style now so as not to potentially ruin something.

THANKS GUYS!

 

[DHMag]

Camarok:
I've been putzing around and i happend to find the connector that connects to the secondaries diaphrams. As i unhooked it, they opened up. They stay open. I've heard that "you lose low end torque and power", "loss of gas milage" and other things. I've noticed no loss in power, and actually it is more responsive/less jerky when you slam on it at low revs. Also when I hit 3k rpms, it seems to pull harder then. SO instead now i have a sho that will pull harder at 3k insetad of it kicking in at 4k. What am I losing in this.

~~FYI I do have the secondaries connected factory style now so as not to potentially ruin something.

THANKS GUYS!

the secondaries operate on vacuum. when the engine is off, they are open. when sufficient engine vacuum is aquired, they snap closed. at 3950 RPMs, they open fully, giving you that extra boost of HP. more often than not, youll hear the secondaries open up. as far as the accusations of loss power and low fuel mileage, im unsure of. if your secondaries are opening at 3K, there is something wrong electronically.

 

[reags8]

Define "As i unhooked it, they opened up". I think you might have closed the secondaries. Are the tabs just behind the actuators up or down when the car idles ?
Check out this post for a picture of what I'm talking about :
http://www.shoforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=17;t=005650#000010
Reags

 

[93EmeraldMTX]

reags8:
Define "As i unhooked it, they opened up". I think you might have closed the secondaries. Are the tabs just behind the actuators up or down when the car idles ?
Check out this post for a picture of what I'm talking about :
http://www.shoforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=17;t=005650#000010
Reags

im pretty sure he means he unhooked the vacumn lines going to them. they will open if he does this.

 

[SHOZ123]

Go here if you are wanting to know what secondaries do. Secondary Intake Runner Explanation

Go here for more in depth stuff. Secondary Intake Runner Math

 

[olympic]

Yamaha did not spend tens of thousands of dollars designing those secondaries just to look cool, they're there for a reason. Your car will feel like it's picking up power at 3K RPM now because you lost so much low end torque. At 3k RPM, the engine is finally requiring enough air to get some descent velocity going.

Take your car to the strip, you probably won't be able to break 15's with the secondairies open all the time. It's been proven time and again that opening the secondaries earlier will cost you performance.

 

[jelloslug]

When I bough my '90 the connector for the secondaries was unhooked. After driving around like this for a week or two I found out they were unhooked and reconnected them. That made a wold of differance. I would not say that the fuel mileage changed that much but low end torque was much differant.

 

[sdpatt]

DHMag:
the secondaries operate on vacuum. when the engine is off, they are open. when sufficient engine vacuum is aquired, they snap closed. at 3950 RPMs, they open fully, giving you that extra boost of HP.

Just to clarify, the secondary butterflies are closed by vacuum applied to the vacuum actuators (diaphragm valves) and allowed to open when the vacuum is vented to atmosphere by the electrical solenoid that was mentioned earlier in this topic. Allowing the larger diameter secondary runners to be used prior to about 3,950 rpm will slow the intake charge and reduce the cylinder filling ram effect from the longer, smaller diameter intake runners. The result is not positive for power output or engine efficiency. A butt dyno may not detect it, but a DynoJet will show you how much power you have prevented your engine from making in the lower rpm range.

 

[autobahnsho]

Ditto the other guys. There are some dyno pics floating around that compared leaving them open all the time to closing them before 3600rpms. The difference is drastic!!

 

[Camarok]

K cool guys. I just wanted to know. I know that they were there for a reason, just curious. Crazy engines these are!

 

[SHO4CY]

The longer intake runners promote more turbulence during the intake process due to more surface area causing more friction. At low rpm's there is not as much air being drawn in so by making the air travel a longer distance through smaller diameter pipes this makes more turbulence which give you a better stoichiometric (even) mixture of air and fuel, thus giving you better power. At higher rpm's since the engine is sucking in more air, the extra distance and friction are not needed because it actually hinders the ability of the motor to get air to itself, kind of a choking effect. Therefore having shorter, larger intake runners allows more air in and since it is coming in at a much higher velocity turbulence is created much easier.
On a side note I'm sure you've heard of honda's vtec or variable valve timing. This works on a similar concept to that of the dual intake runners on the sho. At low engine speeds the intake valves are not lifted very high so this makes the air flow more turbulent by increasing the air speed by the valve since it has such a small area to flow into. This creates a better stoichiometric (even) mixture of air and fuel. At higher rpm's the valve lifts up higher, since the velocity of the air is higher it does not need to be sucked through such a small area because it becomes turbulent easier.
Hope this helps some. thumb

 

[yamahaSHO]

It's not so much the turbulance, it is the pulse matching. That is how tuning works.