Well, that still doesn't necessarily mean that the supercharger ONLY comes into play at WOT, but that IS the reason everyone is so SURE that the truck is so much faster at part throttle. I posted that thing from C & D way back on page one. Nissan isn't the first to do it. It used to be a common trick that GM did to make people think their cars were more powerful than they actually were. The car magazines used to joke about it. My guess is that Nissan did it so that uninformed people who test drove an SC and a non SC felt like there was a huge difference right off the line. Nissan could have made the SC to operate at all throttle positions, but then the gas mileage would have been horrible. This way, it "feels" faster all the time, and they get to put a sticker in the window that only shows a 1 MPG hit on fuel economy. I'd say given the defensiveness of certain posters, Nissan was successful in their ploy.

Hey, guys, I got this from a site called 'fc3spro':
"WOT "Wide Open Throttle" - term used to describe the throttle (plates) being fully open or the gas pedal being fully depressed"

Sounds to me like the definition of the term itself indicates 'pedal to the metal'.

The supercharger kicks in well before that.

Sorry guys....you lose.

I agree that the linkages are different. I also agree that there will be a difference between pedal position and trottle position between the SC and NA engines. Hello I've known this all along, and I wasn't arguing about that issue.

I guess until someone with money to blow on dyno runs comes along there really isn't going to be a happy party in this debate. Someone will have to strap onto a dyno and monitor the TPS voltage at part-throttle, then do another dyno run with a truck with the other engine and the same drivetrain, set the TPS to output the same voltage, and see what comes up.

I'm bored of this topic. Hell I'm arguing the SC side of things and I don't even own one. I'm sorry I can look at the diagrams for the SC and "see" how it (and the bypass) works without having to put my hands on it or run it on a dyno. I noticed that ILUVMYX worked for Roush (finally checked your site). I cannot understand why he cannot understand this.

Over and out.

It's simple, iluvmyx is an idiot. He's trying to sound educated about something he knows nothing about. Darwin award candidate.

Why I can't understand what? Look, I don't own a supercharged Xterra. So the only evidence I have to form an opinion is what I've read in magazines and web site reviews and what owners have to say. Given that I've found three sources that all say the SC only works at WOT and that Eaton themselves imply that by saying the supercharger only works 5% of the time and that Car & Driver pointed out what you just did about the throttle linkage... well, let's just say I'm pretty convinced of what the story really is. Yes, the only way to test for sure would be to do as you said: measure the voltage at the TPS while comparing the output on the dyno. But that's not going to happen. Since that's not going to happen, and since everyone else's "proof" amounts to "it feels faster at all throttle positions", I've come to my conclusion as best I can given the information I have.

Based on Eaton's claim that the supercharger is operating 5% of the time, I'll concede that there's a possibility that the SC begins to supply power just shy of WOT. But the evidence is quite overwhelming that the people who think the supercharger is operational accross all throttle positions were nicely taken by Nissan's throttle linkage trick.

As a side note since you mentioned Roush: My comment about Engineers comes largely from my engine development experience at Roush. I knew a lot of Dyno Techs whose knowlege and understanding of engines was far greater than some of the engineers. Not to say we didn't have some great Engineers--we did--but we also had some very shitty ones. So when I hear "but I'm an Engineer" it brings back some bad memories.

Are you 14 years old? Do you know what a Darwin Award is? Do I jump from tall buildings without a parachute? Do I strap rockets to my car? Do I play Russian Roulette? Do I juggle grenades? Do I smoke in an oxygen tent? No, I don't. And even if I did, you wouldn't know it from this thread. So you saying I'm a Darwin Award Candidate just shows what a moron you are.

Wow, what a thread! Lots of 'knots' along the way.
I installed(meaning with my own hands) an Eaton SC from a kit provided by the Downing-Atlanta race shop in my car. After nine years and 50,000 miles I'm still happy.
Too much of this thread is based on (mis)information, speculation, opinion and bullshit. So I'll provide some links that may help.

How about Eaton, the company that makes the SC:
http://automotive.eaton.com/product/engine_controls/supercharger.html

Magnuson is the offical aftermarket supplier. Spend some time at their site - lots of information.
http://www.magnusonproducts.com/

From a typical aftermarket kit vendor(there are many):
http://www.jacksonracing.com/pages/sprchrgrhnd.html#

A TC and SC article in an industry mag:
http://www.autofieldguide.com/articles/050103.html (SC in the shaded section)

I'll let you guys spin things however you like.

dave and xtoy and miatank(with the SC)

Is this definition of the bypass the same as that applied to the Eaton SC used on the Xterra?

From Magnuson:

The best kept secret in forced induction is the little known bypass valve. This small valve, when properly installed between the supercharger and the air throttle body, allows the supercharger to become extremely efficient in terms of economy and parasitic power loss. Our M90 supercharger uses less than 1/3 of 1 HP at 60 MPH cruising. The bypass is operated by a vacuum actuator control unit that is normally closed. When vacuum is high (idle-cruising) the actuator opens the bypass valve, equalizing the vacuum pressure throughout the system. When boost is required (accelerating) the vacuum is decreased and the bypass valve instantly closes, causing pressure to increase into the cylinders. This equalized vacuum condition virtually eliminates the normal parasitic power loss of a forced induction system.

If so, it would seem that the SC supplies pressure during acceleration regardless of throttle position. The bypass then dumps during idle or crusing (maintaining steady throttle).

Yes, the Nissan application uses a bypass valve. There is one difference between the X and the install in my car. The X has an on-off solenoid valve that controls the action of the bypass valve. The ECU controls the solenoid. Kind of a way to idiot-proof the system. For example; low octane gas is added to the tank. The knock sensor will signal the ECU and boost can be 'shut off' by activating the solenoid which will block the vacuum line that activates the bypass valve. For those that don't know, sustained detonation will turn a forced induction engine into a boat anchor in no time. There are also other emissions related conditions when the ECU is programed to prevent boost. Of course bypassing the solenoid has been documented and doing so is up to the owner.

dave and xtoy - mistakes are expensive

Man, I wish you would, Darwin. You don't own an SC so why don't you move along and show your intellect on another thread or better yet another forum. For your information, Darwin, I have an AS and BS degree. Done with you Darwin.

Wow, you've just proven yourself to be even dumber than I thought. Calling someone Darwin isn't an insult. He was the one with the theory, remember? He was a brilliant man. Thanks for the compliment, dumb ass. And you're just more proof that getting a degree doesn't mean you're smart.

Thanks DatsunDave, for providing some real information, with absolutely no childish insults! I love learning, and you have helped me do that. And what a pleasure to get facts from an adult.

Looks like there is boost all the time, except when the bypass is activated at low vacuum (idle & cruising). I'm still not sure why the talk/literature about WOT needed. That doesn't jive with Dave's references:

From Eaton:
"The Eaton supercharger increases torque across the entire operating range without compromising driveability or emissions. ... Additionally, the supercharger incorporates a bypass system to reduce air handling losses when boost is not required, resulting in better fuel economy."

From Jackson Racing:
"The Jackson Racing Supercharger gives you a 40% boost in power. Instantly. From off-idle to max rpm, with no spiking and no hesitation."

I'm convinced there is always boost unless bypassed.

Now for the next lesson, how does the Engine Mgmt System interface vacuum demand of the SC and of the auto tranny? Does the EMS have a specific action at WOT? What besides low vacuum (and possibly low octane) opens the bypass valve? How low is low - at what vacuum pressure?

I really think that you will get a better understanding if you install a boost gauge in your truck. Granted, it won't exact in helping you determine your throttle postiion, but, you will get a better understanding at what is going on by watching the needle in vacuum and under boost.

The ECU (EMS if you prefer) uses a computer controlled solenoid that is plumbed in series from the vacuum signal port on the intake to the vacuum supply port of the bypass valve. The computer controls the opening and closing of this solenoid - controlling how much vacuum the supercharger bypass valve sees.

Someone else may answer this better but the only thing I have seen at WOT is lowering boost when low octane fuel is used, or lowering boost when under high loads at high ambient temperatures. Both are indicitave of being triggered by the knock sensor.

Presumably any other knock condition. High load and high ambient temperature...

I have no clue what you are asking here.

. For your information, Darwin, I have an AS and BS degree. Done with you Darwin.

So you have a degree. What was your GPA? How long did it take you? I went to college got my AS I also got my BS and I got my Mr. My wife has her AS her BS and her Mrs. People now refer to us as Mr. and Mrs. brings a smile to my face every time Since I own my own business I've used my degree 0 (zero) times but I use my common sense everyday. The only people that care about your degree are those that paid for it.

I almost died laughing when I saw that! SWEET!

I'm no engineer, but I feel my SC kick in at a certain speed/RPM and NOT when I have it floored. It gives me a little extra boost to pass on the road or splash through a bog. Nothing "super" about it other than a shot in the arm but I like it.